Uneven Concrete Correction Crystal Lake

Uneven Concrete Correction Crystal Lake

Concrete Pressure Injection

It's a win-win situation where safety meets aesthetics. You're not just choosing a more efficient method; you're opting for a sustainable solution. Learn more about Uneven Concrete Correction Crystal Lake here In recent years, the field of concrete raising has seen significant advancements, introducing more effective and lasting solutions than ever before. Garage Apron Repair Concrete Contractors Crystal Lake So, when you weigh the benefits, it's clear why Acme's innovative approach is outshining traditional methods in the Crystal Lake area.
It's not magic-it's our expertise in action. It's no wonder it's rising in popularity. This innovative approach involves injecting a high-density foam beneath the concrete slab.

Concrete Leveling

  1. Concrete Grinding
  2. Cracked Driveway Repair
  3. Uneven Concrete Repair
  4. Soil Erosion Under Slab
  5. Trip Hazard Removal
  6. Commercial Concrete Services
  7. Precision Concrete Leveling
  8. Concrete Lifting
  9. Residential Concrete Services
  10. Concrete Floor Leveling Contractors
  11. Driveway Settling Solutions
  12. Concrete Preservation
  13. Concrete Foundation Settlement
  14. Garage Slab Settlement
  15. Sidewalk Leveling
  16. Backyard Patio Repair

With its blend of cutting-edge technology and user-friendly features, Acme's system not only promises to raise the bar but also to redefine it. Homeowners across Crystal Lake are enjoying smoother driveways, revitalized sidewalks, and sturdy patios, thanks to Acme's innovative approach. Learn more about Acme Concrete Raising & Repair here. Cracks or uneven sections not only detract from your walkway's appearance but can also pose safety hazards.
Addressing sinking concrete sooner rather than later is crucial. When you choose us, you're opting for a team that's committed to excellence at every turn. Sidewalks round out the list of common areas needing attention.

This approach not only saves you money but also time, as repair work is typically completed much faster than full replacements. They're in and out before you know it, leaving behind nothing but excellent results. Then, they drill small, strategically placed holes into the slab. This foam expands, gently lifting the concrete back to its original level. Fix Uneven Driveway Crystal Lake

This technique, centered around polyurethane foam, offers numerous benefits that extend beyond mere aesthetics to include environmental advantages, something that's increasingly important in today's world. So, if you're facing sinking concrete, Acme's Smart Lift could be the smart solution you're looking for. Another highlight includes lifting a large patio that had settled over time, causing water to pool and creating potential foundation issues.

This material is less invasive and requires fewer resources, reducing the impact on surrounding landscapes.

Concrete Leveling

  1. Concrete Leveling
  2. Concrete Repair Estimate Crystal Lake
  3. Garage Apron Repair
  4. Sunken Concrete
  5. Crystal Lake IL Contractors
  6. Concrete Waterproofing
  7. Sidewalk Leveling Experts
  8. Concrete Raising Reviews
  9. Soil Stabilization
  10. Chicagoland Concrete Solutions
  11. Concrete Pressure Grouting
  12. Foam Injection Contractors
  13. Fast Dry Concrete Lifting
  14. Level Concrete Surfaces
  15. Foundation Leveling Services
  16. Local Concrete Leveling Services
You'll find that it's a cost-effective solution compared to complete concrete replacement, saving you both time and money. Sensors embedded within concrete will monitor its health in real-time, alerting you to potential issues before they become major problems.

After the lifting is complete, we seal any cracks or joints to prevent water from seeping underneath the concrete again. Their joy was palpable, sharing how the Smart Lift not only restored their outdoor space but also prevented potential injuries. You won't have to worry about mismatched concrete patches disrupting your home's overall look.

Citations and other links

Sidewalk Trip Hazard Repair Crystal Lake

Over time, this causes them to sink and shift, creating hazards and unsightly areas around your home. This project not only enhanced the property's curb appeal but also increased its overall value. Concrete raising, also known as slab jacking, is a cost-effective method to repair uneven concrete surfaces by lifting the slab back to its original position. Residential Concrete Services We're also proud to say our materials are made from recycled and eco-friendly components.
Choosing Acme means you're not just getting a service provider; you're gaining a partner dedicated to enhancing your property's value and appeal. You won't have to deal with a large crew trampling through your property or a long, drawn-out process. By choosing to repair rather than replace, you're not just avoiding the immediate higher costs of new concrete, but you're also dodging the associated demolition and disposal fees.
Moreover, the energy consumption involved in producing the cement used in mudjacking can't be ignored. It's not just an eyesore; it can also lead to more serious problems if you don't address it quickly. The system uses a polyurethane foam, which is more durable and stable than the materials used in traditional concrete raising methods. Read more about Uneven Concrete Correction Crystal Lake here
With Acme Concrete's advanced repair system, you're not just fixing a problem. But with Acme's Smart Lift System, that's not your reality. When you're facing sunken or uneven concrete, it's not just an eyesore; it's a trip hazard that can lead to injuries or liability issues.

Concrete Floor Leveling Contractors

  1. Concrete Settling
  2. Garage Floor Lifting
  3. Crystal Lake Mudjacking Company
  4. Residential Driveway Leveling
  5. Concrete Leveling Companies
  6. Concrete Grinding
  7. Cracked Driveway Repair
  8. Uneven Concrete Repair
  9. Soil Erosion Under Slab
  10. Trip Hazard Removal
  11. Commercial Concrete Services
  12. Precision Concrete Leveling
  13. Concrete Lifting
  14. Concrete Leveling
  15. Concrete Repair Estimate Crystal Lake
  16. Garage Apron Repair
  17. Sunken Concrete
  18. Crystal Lake IL Contractors

Sidewalk Trip Hazard Repair Crystal Lake
Concrete Crack Leveling Crystal Lake

Concrete Crack Leveling Crystal Lake

Before jumping to replacement, it's worth exploring repair and resurfacing options. Moreover, the industry's focus on sustainability is driving the development of green concrete repair materials. During this meeting, they'll assess the current state of your walkways, listen to your concerns, and discuss the most effective solutions tailored to your specific needs. Concrete Floor Leveling Contractors If you've noticed sinking driveways, walkways, or patios around your home, you're witnessing a common issue that affects many properties. As the material expands, it raises the slab back to its original level.

Instead, you'll enjoy a uniform appearance that enhances your property's overall aesthetics. This durability translates into fewer repairs and replacements down the line. Hearing directly from satisfied customers offers the best insight into the quality and impact of our concrete raising services. They use state-of-the-art equipment and the latest techniques to ensure the job is done right the first time.

Concrete Contractors Crystal Lake

  1. Concrete Waterproofing
  2. Sidewalk Leveling Experts
  3. Concrete Raising Reviews
  4. Soil Stabilization
  5. Chicagoland Concrete Solutions
  6. Concrete Pressure Grouting
  7. Foam Injection Contractors
  8. Fast Dry Concrete Lifting
  9. Level Concrete Surfaces
  10. Foundation Leveling Services
  11. Local Concrete Leveling Services
  12. Concrete Settling
  13. Garage Floor Lifting
  14. Crystal Lake Mudjacking Company
  15. Residential Driveway Leveling


This proactive approach means you're less likely to face cracking, scaling, or other common issues that can shorten a surface's life. You might be wondering what causes this frustrating issue. This speed doesn't compromise its strength; in fact, it ensures a stronger bond with the existing concrete, enhancing its stability and longevity. The traditional fix often involves a noisy, disruptive process of breaking up and pouring new concrete.

Having covered the common areas for repair, let's hear directly from customers who've experienced Acme Concrete's exceptional service firsthand. Here's how it works: small holes are drilled into the affected concrete, through which a high-density foam is injected.

Residential Concrete Services

  1. Garage Slab Settlement
  2. Sidewalk Leveling
  3. Backyard Patio Repair
  4. Slab Leveling Solutions
  5. Concrete Contractors Crystal Lake
  6. Quick Concrete Lifting Service
  7. Sunken Walkway Fix
  8. Concrete Leveling
  9. Concrete Repair Estimate Crystal Lake
  10. Garage Apron Repair
  11. Sunken Concrete
  12. Crystal Lake IL Contractors
  13. Concrete Waterproofing
  14. Sidewalk Leveling Experts
  15. Concrete Raising Reviews
  16. Soil Stabilization
These case studies highlight not just the immediate improvements in appearance and safety but also the long-term benefits of choosing modern concrete raising methods. They use techniques that make repairs almost invisible, blending seamlessly with the original concrete.

Local Concrete Contractors Crystal Lake

You're actively choosing a greener alternative to traditional concrete replacement methods. By choosing Acme's system, you're not just repairing the concrete; you're investing in the safety and well-being of your employees and customers. It's a win-win situation for both you and the planet. Driveway Settling Solutions It's about making informed decisions that reflect your values and the kind of world you want to live in.

Moreover, digital tools and software are set to revolutionize how assessments are done. But what exactly sets Acme apart in the realm of concrete repair, and how have Crystal Lake residents benefited from their unique approach? The transformation is evident neighborhood-wide, proving that Acme Concrete isn't just about preserving concrete; it's about enhancing community well-being.

We understand that keeping your family, friends, and visitors safe is a top priority, and that's why we're dedicated to not only fixing the underlying issues but also ensuring the aesthetics are up to par. This technique isn't only efficient but also cost-effective, saving you from the hassle and expense of complete slab replacement. Mudjacking, while less expensive upfront, often leads to higher costs over time.

The foam cures quickly, creating a strong, stable base that prevents future sinking or shifting. Polyurethane foam, already known for its efficiency, is getting greener, reducing its carbon footprint without compromising on quality. These aren't just eyesores; they're trip hazards and can lower your home's value.



Quick Concrete Lifting Service

  • Concrete Pressure Grouting
  • Foam Injection Contractors
  • Fast Dry Concrete Lifting
  • Level Concrete Surfaces
  • Foundation Leveling Services
  • Local Concrete Leveling Services
  • Concrete Settling
  • Garage Floor Lifting
  • Crystal Lake Mudjacking Company
  • Residential Driveway Leveling
  • Concrete Leveling Companies
  • Concrete Grinding
  • Cracked Driveway Repair
  • Uneven Concrete Repair
  • Soil Erosion Under Slab
Local Concrete Contractors Crystal Lake
Walkway Concrete Repair Crystal Lake
Walkway Concrete Repair Crystal Lake

This rapid turnaround minimizes downtime for businesses and inconvenience for homeowners, making it a more practical choice for busy lives. Moreover, Acme's customer service is top-notch. My driveway looks brand new, and they finished it so quickly,' she marvels. The city's decision to use modern concrete raising solutions transformed this once dangerous walkway into a safe, smooth path for pedestrians.

She couldn't believe the transformation of her sunken patio back to its original glory. 'Acme's team was professional, quick, and the results were beyond my expectations,' she raves. Stick around to discover the impact of their work on the community and the environment, and why this might just be the solution you didn't know you were looking for. They've literally raised the bar for home services,' he admits with a chuckle.

Here's where Acme steps in with its innovative Smart Lift System, revolutionizing the way concrete is raised and repaired. This means you're not just getting a facelift for your walkways; you're investing in the longevity and safety of your property.

Concrete Foundation Settlement

  1. Trip Hazard Removal
  2. Commercial Concrete Services
  3. Precision Concrete Leveling
  4. Concrete Lifting
  5. Concrete Contractors Crystal Lake
  6. Quick Concrete Lifting Service
  7. Sunken Walkway Fix
  8. Concrete Leveling
  9. Concrete Repair Estimate Crystal Lake
  10. Garage Apron Repair
  11. Sunken Concrete
  12. Crystal Lake IL Contractors
  13. Concrete Waterproofing
  14. Sidewalk Leveling Experts
  15. Concrete Raising Reviews
  16. Soil Stabilization
  17. Chicagoland Concrete Solutions
  18. Concrete Pressure Grouting
  19. Foam Injection Contractors
In Crystal Lake, where appearances matter, this could be a deciding factor for someone considering your home. Concrete Pressure Injection

It involves drilling large holes in the concrete and pumping a slurry underneath to raise it. Trust us to keep your walkways safe, ensuring peace of mind for you and your community. The process is precise, allowing for targeted lifting that repairs your concrete without the need for replacement.

Sunken Concrete Leveling Crystal Lake

They've seen their property's aesthetics and value soar without breaking the bank. Sidewalk Leveling Garage Slab Settlement Now that you understand how Acme Concrete raises and stabilizes your concrete with polyurethane foam, let's explore what makes this material so effective. Plus, the material's lightweight nature means less burden on the soil, reducing the risk of future settlement. First impressions matter, and well-maintained premises reflect positively on your business.
You've likely walked through areas where the ground feels like a patchwork of repairs, distracting from the environment's natural beauty. These before and after snapshots not only highlight the aesthetic improvement but also underscore the importance of safety and accessibility enhancements provided by our concrete raising services. One standout technique they use is polyurethane foam injection, a method far superior to traditional mudjacking.
The longer you wait, the more complicated and expensive the repairs can become. You'll hear about how quick and efficient our team is, turning what seemed like daunting repairs into seamless fixes. Concrete Repair Estimate Crystal Lake Plus, the environmental impact is minimal compared to traditional concrete replacement methods.
Choosing Acme means opting for reliability, quality, and unparalleled service. They're essential for safe pedestrian movement and, when maintained, boost your property's curb appeal. They appreciated not only the high-quality work but also the way our team took the time to explain the process, ensuring they understood every step.

Explore Uneven Concrete Correction Crystal Lake here Concrete Preservation
Sunken Concrete Leveling Crystal Lake
Polyurethane synthesis: the urethane groups −NH−(C=O)−O− link the molecular units, resulting in a polymer consisting of an alternating chain of two monomers.
A kitchen sponge made of polyurethane foam

Polyurethane (/ËŒpÉ’liˈjÊŠÉ™rəˌθeɪn, -jʊəˈrÉ›θeɪn/;[1] often abbreviated PUR and PU) is a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane does not refer to a single type of polymer but a group of polymers. Unlike polyethylene and polystyrene, polyurethanes can be produced from a wide range of starting materials, resulting in various polymers within the same group. This chemical variety produces polyurethanes with different chemical structures leading to many different applications. These include rigid and flexible foams, and coatings, adhesives, electrical potting compounds, and fibers such as spandex and polyurethane laminate (PUL). Foams are the largest application accounting for 67% of all polyurethane produced in 2016.[2]

A polyurethane is typically produced by reacting a polymeric isocyanate with a polyol.[3] Since a polyurethane contains two types of monomers, which polymerize one after the other, they are classed as alternating copolymers. Both the isocyanates and polyols used to make a polyurethane contain two or more functional groups per molecule.

Global production in 2019 was 25 million metric tonnes,[4] accounting for about 6% of all polymers produced in that year.

History

[edit]
Otto Bayer in 1952 demonstrating his creation

Otto Bayer and his coworkers at IG Farben in Leverkusen, Germany, first made polyurethanes in 1937.[5][6] The new polymers had some advantages over existing plastics that were made by polymerizing olefins or by polycondensation, and were not covered by patents obtained by Wallace Carothers on polyesters.[7] Early work focused on the production of fibers and flexible foams and PUs were applied on a limited scale as aircraft coating during World War II.[7] Polyisocyanates became commercially available in 1952, and production of flexible polyurethane foam began in 1954 by combining toluene diisocyanate (TDI) and polyester polyols. These materials were also used to produce rigid foams, gum rubber, and elastomers. Linear fibers were produced from hexamethylene diisocyanate (HDI) and 1,4-Butanediol (BDO).

DuPont introduced polyethers, specifically poly(tetramethylene ether) glycol, in 1956. BASF and Dow Chemical introduced polyalkylene glycols in 1957. Polyether polyols were cheaper, easier to handle and more water-resistant than polyester polyols. Union Carbide and Mobay, a U.S. Monsanto/Bayer joint venture, also began making polyurethane chemicals.[7] In 1960 more than 45,000 metric tons of flexible polyurethane foams were produced. The availability of chlorofluoroalkane blowing agents, inexpensive polyether polyols, and methylene diphenyl diisocyanate (MDI) allowed polyurethane rigid foams to be used as high-performance insulation materials. In 1967, urethane-modified polyisocyanurate rigid foams were introduced, offering even better thermal stability and flammability resistance. During the 1960s, automotive interior safety components, such as instrument and door panels, were produced by back-filling thermoplastic skins with semi-rigid foam.

In 1969, Bayer exhibited an all-plastic car in Düsseldorf, Germany. Parts of this car, such as the fascia and body panels, were manufactured using a new process called reaction injection molding (RIM), in which the reactants were mixed and then injected into a mold. The addition of fillers, such as milled glass, mica, and processed mineral fibers, gave rise to reinforced RIM (RRIM), which provided improvements in flexural modulus (stiffness), reduction in coefficient of thermal expansion and better thermal stability. This technology was used to make the first plastic-body automobile in the United States, the Pontiac Fiero, in 1983. Further increases in stiffness were obtained by incorporating pre-placed glass mats into the RIM mold cavity, also known broadly as resin injection molding, or structural RIM.

Starting in the early 1980s, water-blown microcellular flexible foams were used to mold gaskets for automotive panels and air-filter seals, replacing PVC polymers. Polyurethane foams are used in many automotive applications including seating, head and arm rests, and headliners.

Polyurethane foam (including foam rubber) is sometimes made using small amounts of blowing agents to give less dense foam, better cushioning/energy absorption or thermal insulation. In the early 1990s, because of their impact on ozone depletion, the Montreal Protocol restricted the use of many chlorine-containing blowing agents, such as trichlorofluoromethane (CFC-11). By the late 1990s, blowing agents such as carbon dioxide, pentane, 1,1,1,2-tetrafluoroethane (HFC-134a) and 1,1,1,3,3-pentafluoropropane (HFC-245fa) were widely used in North America and the EU, although chlorinated blowing agents remained in use in many developing countries. Later, HFC-134a was also banned due to high ODP and GWP readings, and HFC-141B was introduced in early 2000s as an alternate blowing agent in developing nations.[8]

Chemistry

[edit]

Polyurethanes are produced by reacting diisocyanates with polyols,[9][10][11][12][13][14] often in the presence of a catalyst, or upon exposure to ultraviolet radiation.[15] Common catalysts include tertiary amines, such as DABCO, DMDEE, or metallic soaps, such as dibutyltin dilaurate. The stoichiometry of the starting materials must be carefully controlled as excess isocyanate can trimerise, leading to the formation of rigid polyisocyanurates. The polymer usually has a highly crosslinked molecular structure, resulting in a thermosetting material which does not melt on heating; although some thermoplastic polyurethanes are also produced.

 
Carbon dioxide gas and urea links formed by reacting water and isocyanate

The most common application of polyurethane is as solid foams, which requires the presence of a gas, or blowing agent, during the polymerization step. This is commonly achieved by adding small amounts of water, which reacts with isocyanates to form CO2 gas and an amine, via an unstable carbamic acid group. The amine produced can also react with isocyanates to form urea groups, and as such the polymer will contain both these and urethane linkers. The urea is not very soluble in the reaction mixture and tends to form separate "hard segment" phases consisting mostly of polyurea. The concentration and organization of these polyurea phases can have a significant impact on the properties of the foam.[16]

The type of foam produced can be controlled by regulating the amount of blowing agent and also by the addition of various surfactants which change the rheology of the polymerising mixture. Foams can be either "closed-cell", where most of the original bubbles or cells remain intact, or "open-cell", where the bubbles have broken but the edges of the bubbles are stiff enough to retain their shape, in extreme cases reticulated foams can be formed. Open-cell foams feel soft and allow air to flow through, so they are comfortable when used in seat cushions or mattresses. Closed-cell foams are used as rigid thermal insulation. High-density microcellular foams can be formed without the addition of blowing agents by mechanically frothing the polyol prior to use. These are tough elastomeric materials used in covering car steering wheels or shoe soles.

The properties of a polyurethane are greatly influenced by the types of isocyanates and polyols used to make it. Long, flexible segments, contributed by the polyol, give soft, elastic polymer. High amounts of crosslinking give tough or rigid polymers. Long chains and low crosslinking give a polymer that is very stretchy, short chains with many crosslinks produce a hard polymer while long chains and intermediate crosslinking give a polymer useful for making foam. The choices available for the isocyanates and polyols, in addition to other additives and processing conditions allow polyurethanes to have the very wide range of properties that make them such widely used polymers.

Raw materials

[edit]

The main ingredients to make a polyurethane are di- and tri-isocyanates and polyols. Other materials are added to aid processing the polymer or to modify the properties of the polymer. PU foam formulation sometimes have water added too.

Isocyanates

[edit]

Isocyanates used to make polyurethane have two or more isocyanate groups on each molecule. The most commonly used isocyanates are the aromatic diisocyanates, toluene diisocyanate (TDI) and methylene diphenyl diisocyanate, (MDI). These aromatic isocyanates are more reactive than aliphatic isocyanates.

TDI and MDI are generally less expensive and more reactive than other isocyanates. Industrial grade TDI and MDI are mixtures of isomers and MDI often contains polymeric materials. They are used to make flexible foam (for example slabstock foam for mattresses or molded foams for car seats),[17] rigid foam (for example insulating foam in refrigerators) elastomers (shoe soles, for example), and so on. The isocyanates may be modified by partially reacting them with polyols or introducing some other materials to reduce volatility (and hence toxicity) of the isocyanates, decrease their freezing points to make handling easier or to improve the properties of the final polymers.

MDI isomers and polymer
MDI isomers and polymer

Aliphatic and cycloaliphatic isocyanates are used in smaller quantities, most often in coatings and other applications where color and transparency are important since polyurethanes made with aromatic isocyanates tend to darken on exposure to light.[page needed][18] The most important aliphatic and cycloaliphatic isocyanates are 1,6-hexamethylene diisocyanate (HDI), 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), and 4,4′-diisocyanato dicyclohexylmethane (H12MDI or hydrogenated MDI). Other more specialized isocyanates include Tetramethylxylylene diisocyanate (TMXDI).

Polyols

[edit]

Polyols are polymers in their own right and have on average two or more hydroxyl groups per molecule. They can be converted to polyether polyols by co-polymerizing ethylene oxide and propylene oxide with a suitable polyol precursor.[19] Polyester polyols are made by the polycondensation of multifunctional carboxylic acids and polyhydroxyl compounds. They can be further classified according to their end use. Higher molecular weight polyols (molecular weights from 2,000 to 10,000) are used to make more flexible polyurethanes while lower molecular weight polyols make more rigid products.

Polyols for flexible applications use low functionality initiators such as dipropylene glycol (f = 2), glycerine (f = 3), or a sorbitol/water solution (f = 2.75).[20] Polyols for rigid applications use higher functionality initiators such as sucrose (f = 8), sorbitol (f = 6), toluenediamine (f = 4), and Mannich bases (f = 4). Propylene oxide and/or ethylene oxide is added to the initiators until the desired molecular weight is achieved. The order of addition and the amounts of each oxide affect many polyol properties, such as compatibility, water-solubility, and reactivity. Polyols made with only propylene oxide are terminated with secondary hydroxyl groups and are less reactive than polyols capped with ethylene oxide, which contain primary hydroxyl groups. Incorporating carbon dioxide into the polyol structure is being researched by multiple companies.

Graft polyols (also called filled polyols or polymer polyols) contain finely dispersed styrene–acrylonitrile, acrylonitrile, or polyurea (PHD) polymer solids chemically grafted to a high molecular weight polyether backbone. They are used to increase the load-bearing properties of low-density high-resiliency (HR) foam, as well as add toughness to microcellular foams and cast elastomers. Initiators such as ethylenediamine and triethanolamine are used to make low molecular weight rigid foam polyols that have built-in catalytic activity due to the presence of nitrogen atoms in the backbone. A special class of polyether polyols, poly(tetramethylene ether) glycols, which are made by polymerizing tetrahydrofuran, are used in high performance coating, wetting and elastomer applications.

Conventional polyester polyols are based on virgin raw materials and are manufactured by the direct polyesterification of high-purity diacids and glycols, such as adipic acid and 1,4-butanediol. Polyester polyols are usually more expensive and more viscous than polyether polyols, but they make polyurethanes with better solvent, abrasion, and cut resistance. Other polyester polyols are based on reclaimed raw materials. They are manufactured by transesterification (glycolysis) of recycled poly(ethyleneterephthalate) (PET) or dimethylterephthalate (DMT) distillation bottoms with glycols such as diethylene glycol. These low molecular weight, aromatic polyester polyols are used in rigid foam, and bring low cost and excellent flammability characteristics to polyisocyanurate (PIR) boardstock and polyurethane spray foam insulation.

Specialty polyols include polycarbonate polyols, polycaprolactone polyols, polybutadiene polyols, and polysulfide polyols. The materials are used in elastomer, sealant, and adhesive applications that require superior weatherability, and resistance to chemical and environmental attack. Natural oil polyols derived from castor oil and other vegetable oils are used to make elastomers, flexible bunstock, and flexible molded foam.

Co-polymerizing chlorotrifluoroethylene or tetrafluoroethylene with vinyl ethers containing hydroxyalkyl vinyl ether produces fluorinated (FEVE) polyols. Two-component fluorinated polyurethanes prepared by reacting FEVE fluorinated polyols with polyisocyanate have been used to make ambient cure paints and coatings. Since fluorinated polyurethanes contain a high percentage of fluorine–carbon bonds, which are the strongest bonds among all chemical bonds, fluorinated polyurethanes exhibit resistance to UV, acids, alkali, salts, chemicals, solvents, weathering, corrosion, fungi and microbial attack. These have been used for high performance coatings and paints.[21]

Phosphorus-containing polyols are available that become chemically bonded to the polyurethane matrix for the use as flame retardants. This covalent linkage prevents migration and leaching of the organophosphorus compound.

Bio-derived materials

[edit]

Interest in sustainable "green" products raised interest in polyols derived from vegetable oils,[22][23][24] fatty acids,[25] lignin, sorbitol,[26] etc. These are mostly contributing to polyol part. There are attempts made to prepare isocyanate part using bio-derived material. However, as far as commercialization is concern, polyol part is more targeted being easy and required in more quantity than isocyanate part. Various oils used in the preparation polyols for polyurethanes include soybean oil, cottonseed oil, neem seed oil, algae oil,[27][28] and castor oil. Vegetable oils are functionalized in various ways and modified to polyetheramides, polyethers, alkyds, etc. Renewable sources used to prepare polyols may be fatty acids or dimer fatty acids.[29] Some biobased and isocyanate-free polyurethanes exploit the reaction between polyamines and cyclic carbonates to produce polyhydroxyurethanes.[30]

Chain extenders and cross linkers

[edit]

Chain extenders (f = 2) and cross linkers (f ≥ 3) are low molecular weight hydroxyl and amine terminated compounds that play an important role in the polymer morphology of polyurethane fibers, elastomers, adhesives, and certain integral skin and microcellular foams.

The elastomeric properties of these materials are derived from the phase separation of the hard and soft copolymer segments of the polymer, such that the urethane hard segment domains serve as cross-links between the amorphous polyether (or polyester) soft segment domains. This phase separation occurs because the mainly nonpolar, low melting soft segments are incompatible with the polar, high melting hard segments. The soft segments, which are formed from high molecular weight polyols, are mobile and are normally present in coiled formation, while the hard segments, which are formed from the isocyanate and chain extenders, are stiff and immobile. As the hard segments are covalently coupled to the soft segments, they inhibit plastic flow of the polymer chains, thus creating elastomeric resiliency. Upon mechanical deformation, a portion of the soft segments are stressed by uncoiling, and the hard segments become aligned in the stress direction. This reorientation of the hard segments and consequent powerful hydrogen bonding contributes to high tensile strength, elongation, and tear resistance values.[12][31][32][33][34] The choice of chain extender also determines flexural, heat, and chemical resistance properties.

The most important chain extenders are ethylene glycol, 1,4-butanediol (1,4-BDO or BDO), 1,6-hexanediol, cyclohexane dimethanol and hydroquinone bis(2-hydroxyethyl) ether (HQEE). All of these glycols form polyurethanes that phase separate well and form well defined hard segment domains, and are melt processable. They are all suitable for thermoplastic polyurethanes with the exception of ethylene glycol, since its derived bis-phenyl urethane undergoes unfavorable degradation at high hard segment levels.[10] Diethanolamine and triethanolamine are used in flex molded foams to build firmness and add catalytic activity. Diethyltoluenediamine is used extensively in RIM, and in polyurethane and polyurea elastomer formulations.

Table of chain extenders and cross linkers[35]
Compound type Molecule Mol.
mass
Density
(g/cm3)
Melting
pt (°C)
Boiling
pt (°C)
Hydroxyl compounds – difunctional molecules Ethylene glycol 62.1 1.110 −13.4 197.4
Diethylene glycol 106.1 1.111 −8.7 245.5
Triethylene glycol 150.2 1.120 −7.2 287.8
Tetraethylene glycol 194.2 1.123 −9.4 325.6
Propylene glycol 76.1 1.032 Supercools 187.4
Dipropylene glycol 134.2 1.022 Supercools 232.2
Tripropylene glycol 192.3 1.110 Supercools 265.1
1,3-Propanediol 76.1 1.060 −28 210
1,3-Butanediol 92.1 1.005 207.5
1,4-Butanediol 92.1 1.017 20.1 235
Neopentyl glycol 104.2 130 206
1,6-Hexanediol 118.2 1.017 43 250
1,4-Cyclohexanedimethanol
HQEE
Ethanolamine 61.1 1.018 10.3 170
Diethanolamine 105.1 1.097 28 271
Methyldiethanolamine 119.1 1.043 −21 242
Phenyldiethanolamine 181.2 58 228
Hydroxyl compounds – trifunctional molecules Glycerol 92.1 1.261 18.0 290
Trimethylolpropane
1,2,6-Hexanetriol
Triethanolamine 149.2 1.124 21
Hydroxyl compounds – tetrafunctional molecules Pentaerythritol 136.2 260.5
N,N,N′,N′-Tetrakis
(2-hydroxypropyl)
ethylenediamine
Amine compounds – difunctional molecules Diethyltoluenediamine 178.3 1.022 308
Dimethylthiotoluenediamine 214.0 1.208

Catalysts

[edit]

Polyurethane catalysts can be classified into two broad categories, basic and acidic amine. Tertiary amine catalysts function by enhancing the nucleophilicity of the diol component. Alkyl tin carboxylates, oxides and mercaptides oxides function as mild Lewis acids in accelerating the formation of polyurethane. As bases, traditional amine catalysts include triethylenediamine (TEDA, also called DABCO, 1,4-diazabicyclo[2.2.2]octane), dimethylcyclohexylamine (DMCHA), dimethylethanolamine (DMEA), Dimethylaminoethoxyethanol and bis-(2-dimethylaminoethyl)ether, a blowing catalyst also called A-99. A typical Lewis acidic catalyst is dibutyltin dilaurate. The process is highly sensitive to the nature of the catalyst and is also known to be autocatalytic.[36]

Another class of catalysts was published in a study in May 2024. In this study, polyurethane synthesis was investigated in the presence of acid catalysts, namely dimethylphosphite (DMHP), methanesulfonic acid (MSA), and trifluoromethanesulfonic acid (TFMSA). The thermodynamic profile was examined and described in detail through computational tools, showing that TFMSA had the best catalytic properties. The study aimed to open the door to a new class of catalysts.[37]

Factors affecting catalyst selection include balancing three reactions: urethane (polyol+isocyanate, or gel) formation, the urea (water+isocyanate, or "blow") formation, or the isocyanate trimerization reaction (e.g., using potassium acetate, to form isocyanurate rings). A variety of specialized catalysts have been developed.[38][39][40]

Surfactants

[edit]

Surfactants are used to modify the characteristics of both foam and non-foam polyurethane polymers. They take the form of polydimethylsiloxane-polyoxyalkylene block copolymers, silicone oils, nonylphenol ethoxylates, and other organic compounds. In foams, they are used to emulsify the liquid components, regulate cell size, and stabilize the cell structure to prevent collapse and sub-surface voids.[41] In non-foam applications they are used as air release and antifoaming agents, as wetting agents, and are used to eliminate surface defects such as pin holes, orange peel, and sink marks.

Production

[edit]

Polyurethanes are produced by mixing two or more liquid streams. The polyol stream contains catalysts, surfactants, blowing agents (when making polyurethane foam insulation) and so on. The two components are referred to as a polyurethane system, or simply a system. The isocyanate is commonly referred to in North America as the 'A-side' or just the 'iso'. The blend of polyols and other additives is commonly referred to as the 'B-side' or as the 'poly'.[citation needed] This mixture might also be called a 'resin' or 'resin blend'. In Europe the meanings for 'A-side' and 'B-side' are reversed.[citation needed] Resin blend additives may include chain extenders, cross linkers, surfactants, flame retardants, blowing agents, pigments, and fillers. Polyurethane can be made in a variety of densities and hardnesses by varying the isocyanate, polyol or additives.

Health and safety

[edit]

Fully reacted polyurethane polymer is chemically inert.[42] No exposure limits have been established in the U.S. by OSHA (Occupational Safety and Health Administration) or ACGIH (American Conference of Governmental Industrial Hygienists). It is not regulated by OSHA for carcinogenicity.

Open-flame test. Top: untreated polyurethane foam burns vigorously. Bottom: with fire-retardant treatment.

Polyurethanes are combustible.[43] Decomposition from fire can produce significant amounts of carbon monoxide and hydrogen cyanide, in addition to nitrogen oxides, isocyanates, and other toxic products.[44] Due to the flammability of the material, it has to be treated with flame retardants (at least in case of furniture), almost all of which are considered harmful.[45][46] California later issued Technical Bulletin 117 2013 which allowed most polyurethane foam to pass flammability tests without the use of flame retardants. Green Science Policy Institute states: "Although the new standard can be met without flame retardants, it does NOT ban their use. Consumers who wish to reduce household exposure to flame retardants can look for a TB117-2013 tag on furniture, and verify with retailers that products do not contain flame retardants."[47]

Liquid resin blends and isocyanates may contain hazardous or regulated components. Isocyanates are known skin and respiratory sensitizers. Additionally, amines, glycols, and phosphate present in spray polyurethane foams present risks.[48]

Exposure to chemicals that may be emitted during or after application of polyurethane spray foam (such as isocyanates) are harmful to human health and therefore special precautions are required during and after this process.[49]

In the United States, additional health and safety information can be found through organizations such as the Polyurethane Manufacturers Association (PMA) and the Center for the Polyurethanes Industry (CPI), as well as from polyurethane system and raw material manufacturers. Regulatory information can be found in the Code of Federal Regulations Title 21 (Food and Drugs) and Title 40 (Protection of the Environment). In Europe, health and safety information is available from ISOPA,[50] the European Diisocyanate and Polyol Producers Association.

Manufacturing

[edit]

The methods of manufacturing polyurethane finished goods range from small, hand pour piece-part operations to large, high-volume bunstock and boardstock production lines. Regardless of the end-product, the manufacturing principle is the same: to meter the liquid isocyanate and resin blend at a specified stoichiometric ratio, mix them together until a homogeneous blend is obtained, dispense the reacting liquid into a mold or on to a surface, wait until it cures, then demold the finished part.

Dispensing equipment

[edit]

Although the capital outlay can be high, it is desirable to use a meter-mix or dispense unit for even low-volume production operations that require a steady output of finished parts. Dispense equipment consists of material holding (day) tanks, metering pumps, a mix head, and a control unit. Often, a conditioning or heater–chiller unit is added to control material temperature in order to improve mix efficiency, cure rate, and to reduce process variability. Choice of dispense equipment components depends on shot size, throughput, material characteristics such as viscosity and filler content, and process control. Material day tanks may be single to hundreds of gallons in size and may be supplied directly from drums, IBCs (intermediate bulk containers, such as caged IBC totes), or bulk storage tanks. They may incorporate level sensors, conditioning jackets, and mixers. Pumps can be sized to meter in single grams per second up to hundreds of pounds per minute. They can be rotary, gear, or piston pumps, or can be specially hardened lance pumps to meter liquids containing highly abrasive fillers such as chopped or hammer-milled glass fiber and wollastonite.[citation needed]

The pumps can drive low-pressure (10 to 30 bar, 1 to 3 MPa) or high-pressure (125 to 250 bar, 12.5 to 25.0 MPa) dispense systems. Mix heads can be simple static mix tubes, rotary-element mixers, low-pressure dynamic mixers, or high-pressure hydraulically actuated direct impingement mixers. Control units may have basic on/off and dispense/stop switches, and analogue pressure and temperature gauges, or may be computer-controlled with flow meters to electronically calibrate mix ratio, digital temperature and level sensors, and a full suite of statistical process control software. Add-ons to dispense equipment include nucleation or gas injection units, and third or fourth stream capability for adding pigments or metering in supplemental additive packages.

Tooling

[edit]

Distinct from pour-in-place, bun and boardstock, and coating applications, the production of piece parts requires tooling to contain and form the reacting liquid. The choice of mold-making material is dependent on the expected number of uses to end-of-life (EOL), molding pressure, flexibility, and heat transfer characteristics.

RTV silicone is used for tooling that has an EOL in the thousands of parts. It is typically used for molding rigid foam parts, where the ability to stretch and peel the mold around undercuts is needed. The heat transfer characteristic of RTV silicone tooling is poor. High-performance, flexible polyurethane elastomers are also used in this way.

Epoxy, metal-filled epoxy, and metal-coated epoxy is used for tooling that has an EOL in the tens of thousands of parts. It is typically used for molding flexible foam cushions and seating, integral skin and microcellular foam padding, and shallow-draft RIM bezels and fascia. The heat transfer characteristic of epoxy tooling is fair; the heat transfer characteristic of metal-filled and metal-coated epoxy is good. Copper tubing can be incorporated into the body of the tool, allowing hot water to circulate and heat the mold surface.

Aluminum is used for tooling that has an EOL in the hundreds of thousands of parts. It is typically used for molding microcellular foam gasketing and cast elastomer parts, and is milled or extruded into shape.

Mirror-finish stainless steel is used for tooling that imparts a glossy appearance to the finished part. The heat transfer characteristic of metal tooling is excellent.

Finally, molded or milled polypropylene is used to create low-volume tooling for molded gasket applications. Instead of many expensive metal molds, low-cost plastic tooling can be formed from a single metal master, which also allows greater design flexibility. The heat transfer characteristic of polypropylene tooling is poor, which must be taken into consideration during the formulation process.

Applications

[edit]

In 2007, the global consumption of polyurethane raw materials was above 12 million metric tons, and the average annual growth rate was about 5%.[51] Revenues generated with PUR on the global market are expected to rise to approximately US$75 billion by 2022.[52] As they are such an important class of materials, research is constantly taking place and papers published.[53]

Degradation and environmental fate

[edit]

Effects of visible light

[edit]
Polyurethane foam made with an aromatic isocyanate, which has been exposed to UV light. Readily apparent is the discoloration that occurs over time.

Polyurethanes, especially those made using aromatic isocyanates, contain chromophores that interact with light. This is of particular interest in the area of polyurethane coatings, where light stability is a critical factor and is the main reason that aliphatic isocyanates are used in making polyurethane coatings. When PU foam, which is made using aromatic isocyanates, is exposed to visible light, it discolors, turning from off-white to yellow to reddish brown. It has been generally accepted that apart from yellowing, visible light has little effect on foam properties.[54][55] This is especially the case if the yellowing happens on the outer portions of a large foam, as the deterioration of properties in the outer portion has little effect on the overall bulk properties of the foam itself.

It has been reported that exposure to visible light can affect the variability of some physical property test results.[56]

Higher-energy UV radiation promotes chemical reactions in foam, some of which are detrimental to the foam structure.[57]

Hydrolysis and biodegradation

[edit]

Polyurethanes may degrade due to hydrolysis. This is a common problem with shoes left in a closet, and reacting with moisture in the air.[58]

Microbial degradation of polyurethane is believed to be due to the action of esterase, urethanase, hydrolase and protease enzymes.[59] The process is slow as most microbes have difficulty moving beyond the surface of the polymer. Susceptibility to fungi is higher due to their release of extracellular enzymes, which are better able to permeate the polymer matrix. Two species of the Ecuadorian fungus Pestalotiopsis are capable of biodegrading polyurethane in aerobic and anaerobic conditions such as found at the bottom of landfills.[60][61] Degradation of polyurethane items at museums has been reported.[62] Polyester-type polyurethanes are more easily biodegraded by fungus than polyether-type.[63]

See also

[edit]
  • Botanol, a material with higher plant-based content
  • Passive fire protection
  • Penetrant (mechanical, electrical, or structural)
  • Polyaspartic
  • Polyurethane dispersion
  • Thermoplastic polyurethanes
  • Thermoset polymer matrix

References

[edit]
  1. ^ "polyurethane". Dictionary.com Unabridged (Online). n.d.
  2. ^ Gama, Nuno; Ferreira, Artur; Barros-Timmons, Ana (27 September 2018). "Polyurethane Foams: Past, Present, and Future". Materials. 11 (10): 1841. Bibcode:2018Mate...11.1841G. doi:10.3390/ma11101841. PMC 6213201. PMID 30262722.
  3. ^ "Polyurethane". American Chemistry Council. Retrieved 2022-09-19.
  4. ^ "Polyurethane global market volume 2015-2026". Statista. Retrieved 23 July 2021.
  5. ^ Bayer, Otto (1947). "Das Di-Isocyanat-Polyadditionsverfahren (Polyurethane)". Angewandte Chemie. 59 (9): 257–72. Bibcode:1947AngCh..59..257B. doi:10.1002/ange.19470590901.
  6. ^ DE 728981, I.G. Farbenindustrie A.G., "Verfahren zur Herstellung von Polyurethanen bzw. Polyharnstoffen [Process for the production of polyurethanes or polyurea]", published 1942-12-07 
  7. ^ a b c Seymour, Raymond B.; Kauffman, George B. (1992). "Polyurethanes: A class of modern versatile materials". Journal of Chemical Education. 69 (11): 909. Bibcode:1992JChEd..69..909S. doi:10.1021/ed069p909.
  8. ^ Feske, Bert (October 2004). "The Use of Saytex RB-9130/9170 Low Viscosity Brominated Flame Retardant Polyols in HFC-245fa and High Water Formulations" (PDF). Polyurethanes Expo 2004. Las Vegas, NV: Alliance for the Polyurethane Industry Technical Conference. p. 309. Retrieved 2007-08-01.
  9. ^ n ≥ 2
  10. ^ a b Gum, Wilson; Riese, Wolfram; Ulrich, Henri (1992). Reaction Polymers. New York: Oxford University Press. ISBN 978-0-19-520933-4.
  11. ^ Harrington, Ron; Hock, Kathy (1991). Flexible Polyurethane Foams. Midland: The Dow Chemical Company.
  12. ^ a b Oertel, Gunter (1985). Polyurethane Handbook. New York: Macmillen Publishing Co., Inc. ISBN 978-0-02-948920-8.[page needed]
  13. ^ Ulrich, Henri (1996). Chemistry and Technology of Isocyanates. New York: John Wiley & Sons, Inc. ISBN 978-0-471-96371-4.[page needed]
  14. ^ Woods, George (1990). The ICI Polyurethanes Book. New York: John Wiley & Sons, Inc. ISBN 978-0-471-92658-0.[page needed]
  15. ^ Soto, Marc; Sebastián, Rosa María; Marquet, Jordi (2014). "Photochemical Activation of Extremely Weak Nucleophiles: Highly Fluorinated Urethanes and Polyurethanes from Polyfluoro Alcohols". The Journal of Organic Chemistry. 79 (11): 5019–27. doi:10.1021/jo5005789. PMID 24820955.
  16. ^ Kaushiva, Byran D. (August 15, 1999). Structure-Property Relationships of Flexible Polyurethane Foams (Ph.D.). Virginia Polytechnic Institute.
  17. ^ "Technical data sheet from Dow Chemical". Archived from the original on 2007-10-13. Retrieved 2007-09-15.
  18. ^ Randall, David; Lee, Steve (2002). The Polyurethanes Book. New York: Wiley. ISBN 978-0-470-85041-1.
  19. ^ Petrović, Zoran S. (2008). "Polyurethanes from Vegetable Oils". Polymer Reviews. 48 (1): 109–155. doi:10.1080/15583720701834224. S2CID 95466690.
  20. ^ EP 0755955, Hager, Stanley L.; Knight, James E. & Helma, Gregory F. et al., "Polyether polyols suitable for flexible polyurethane foam prepared by co-initiation of aqueous solutions of solid polyhydroxyl initiators", published 1997-01-29, assigned to ARCO Chemical Technology 
  21. ^ Bob Parker. "FEVE Technology for Higher Performance Coating Systems on Bridges" (PDF). Paintsquare.com. Archived from the original (PDF) on 15 August 2021. Retrieved 5 March 2022.
  22. ^ Khanderay, Jitendra C., and Vikas V. Gite. "Vegetable oil-based polyurethane coatings: recent developments in India." Green Materials 5.3 (2017): 109-122.
  23. ^ Niemeyer, Timothy; Patel, Munjal; Geiger, Eric (September 2006). A Further Examination of Soy-Based Polyols in Polyurethane Systems. Salt Lake City, UT: Alliance for the Polyurethane Industry Technical Conference.
  24. ^ "New Twist on Green: 2008 Ford Mustang Seats Will Be Soy-Based Foam". Edmunds inside line. July 12, 2007. Archived from the original on 2008-05-31. Retrieved 2010-06-15.
  25. ^ SD Rajput, PP Mahulikar, VV Gite, Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings, Progress in Organic Coatings 77 (1), 38-46 https://doi.org/10.1016/j.porgcoat.2014.04.030
  26. ^ A Anand, RD Kulkarni, VV Gite, Preparation and properties of eco-friendly two pack PU coatings based on renewable source (sorbitol) and its property improvement by nano ZnO, Progress in Organic Coatings 74 (4), 764-767, https://doi.org/10.1016/j.porgcoat.2011.09.031
  27. ^ Chandrashekhar K Patil, Harishchandra D Jirimali, Jayasinh S Paradeshi, Bhushan L Chaudhari, Prakash K Alagi, Pramod P Mahulikar, Sung Chul Hong, Vikas V Gite, Chemical transformation of renewable algae oil to polyetheramide polyols for polyurethane coatings, Progress in Organic Coatings 151, 106084, https://doi.org/10.1016/j.porgcoat.2020.106084
  28. ^ CK Patil, HD Jirimali, JS Paradeshi, BL Chaudhari, VV Gite, Functional antimicrobial and anticorrosive polyurethane composite coatings from algae oil and silver doped egg shell hydroxyapatite for sustainable development, Progress in Organic Coatings 128, 127-136, https://doi.org/10.1016/j.porgcoat.2018.11.002
  29. ^ Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings, SD Rajput, PP Mahulikar, VV Gite, Progress in Organic Coatings 77 (1), 38-46
  30. ^ Nohra, Bassam; Candy, Laure; Blanco, Jean-François; Guerin, Celine; Raoul, Yann; Mouloungui, Zephirin (2013). "From Petrochemical Polyurethanes to Biobased Polyhydroxyurethanes" (PDF). Macromolecules. 46 (10): 3771–92. Bibcode:2013MaMol..46.3771N. doi:10.1021/ma400197c. Archived (PDF) from the original on 2017-09-22.
  31. ^ Blackwell, J.; Nagarajan, M. R.; Hoitink, T. B. (1981). "The Structure of the Hard Segments in MDI/diol/PTMA Polyurethane Elastomers". ACS Symposium Series. 172. Washington, D.C.: American Chemical Society: 179–196. doi:10.1021/bk-1981-0172.ch014. ISBN 978-0-8412-0664-9. ISSN 0097-6156.
  32. ^ Blackwell, John; Gardner, Kenncorwin H. (1979). "Structure of the hard segments in polyurethane elastomers". Polymer. 20 (1): 13–17. doi:10.1016/0032-3861(79)90035-1. ISSN 0032-3861.
  33. ^ Grillo, D. J.; Housel, T. L. (1992). "Physical Properties of Polyurethanes from Polyesters and Other Polyols". Polyurethanes '92 Conference Proceedings. New Orleans, LA: The Society of the Plastics Industry, Inc.
  34. ^ Musselman, S. G.; Santosusso, T. M.; Sperling, L. H. (1998). "Structure Versus Performance Properties of Cast Elastomers". Polyurethanes '98 Conference Proceedings. Dallas, TX: The Society of the Plastics Industry, Inc.
  35. ^ A Guide to Glycols. Midland, Mich.: The Dow Chemical Co., Chemicals and Metals Department. 1992. Brochure 117-00991-92Hyc.
  36. ^ Adam, Norbert; Avar, Geza; Blankenheim, Herbert; Friederichs, Wolfgang; Giersig, Manfred; Weigand, Eckehard; Halfmann, Michael; Wittbecker, Friedrich-Wilhelm; Larimer, Donald-Richard; Maier, Udo; Meyer-Ahrens, Sven; Noble, Karl-Ludwig; Wussow, Hans-Georg (2005). "Polyurethanes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a21_665.pub2. ISBN 978-3-527-30673-2.
  37. ^ Waleed, H. Q.; Viskolcz, B.; Fiser, B. (2024). "Urethane Synthesis in the Presence of Organic Acid Catalysts—A Computational Study". Molecules (Basel, Switzerland). 29 (10): 2375. doi:10.3390/molecules29102375. PMC 11123846. PMID 38792235.
  38. ^ "Jeffcat Amine Catalysts for the Polyurethane Industry" (PDF). 2006. Archived from the original (PDF) on 2007-11-29. Retrieved 2007-10-23.
  39. ^ "Building quality with Air Products trimerisation catalysts" (PDF). 2003. Archived from the original (PDF) on 2007-11-29. Retrieved 2007-10-23.
  40. ^ "FOMREZ Specialty Tin Catalysts for Polyurethane Applications". 120-074-10. January 2001.
  41. ^ Randall, David; Lee, Steve, eds. (2002). "10". The Polyurethanes Book. The United Kingdom: Huntsman International LLC, Polyurethanes business. pp. 156–159. ISBN 978-0470850411. Archived from the original on 2018-05-24. Retrieved 2018-05-23.
  42. ^ Dernehl, C. U. (1966). "Health hazards associated with polyurethane foams". Journal of Occupational Medicine. 8 (2): 59–62. PMID 5903304.
  43. ^ "Health Alert: Polyurethane exposure" (PDF). Archived from the original (PDF) on 2004-10-19. Retrieved 2009-12-19.
  44. ^ McKenna, Sean Thomas; Hull, Terence Richard (2016). "The fire toxicity of polyurethane foams". Fire Science Reviews. 5 (1): 3. doi:10.1186/s40038-016-0012-3.
  45. ^ "Environmental Profiles of Chemical Flame-Retardant Alternatives for Low-Density Polyurethane Foam". United States Environmental Protection Agency. September 2005.
  46. ^ "Flame Retardants Used in Flexible Polyurethane Foam – Draft Update to a 2005 Alternatives Assessment". United States Environmental Protection Agency. June 2014. Archived from the original on November 21, 2014.
  47. ^ "Manufacturers" (PDF). greensciencepolicy.org. 2015. Archived (PDF) from the original on 2015-12-19.
  48. ^ "Help Wanted: Spray Polyurethane Foam Insulation Research". NIOSH Science Blog. CDC. 21 March 2012.
  49. ^ "Quick Safety Tips for Spray Polyurethane Foam Users". United States Environmental Protection Agency. 4 August 2015.
  50. ^ "Home : ISOPA". www.isopa.org.
  51. ^ Avar, G. (October 2008). "Polyurethanes (PU)". Kunststoffe International (10/2008): 123–7.
  52. ^ "Market Study: Polyurethanes and Isocyanates". Ceresana. July 2013.
  53. ^ Jakhmola, Swati; Das, Sonalee; Dutta, Kingshuk (2023-10-31). "Emerging research trends in the field of polyurethane and its nanocomposites: Chemistry, Synthesis, Characterization, Application in coatings and Future perspectives". Journal of Coatings Technology and Research. 21 (1): 137–172. doi:10.1007/s11998-023-00841-z. ISSN 1935-3804. S2CID 264908475.
  54. ^ "Discoloration of polyurethane foam" (PDF). Foamex Information sheet. Archived from the original (PDF) on 2010-09-24. Retrieved 2010-09-26.
  55. ^ Valentine, C.; Craig, T.A.; Hager, S.L. (1993). "Inhibition of the Discoloration of Polyurethane Foam Caused by Ultraviolet Light". Journal of Cellular Plastics. 29 (6): 569–88. doi:10.1177/0021955X9302900605. S2CID 208363195.
  56. ^ Blair, G. Ron; Dawe, Bob; McEvoy, Jim; Pask, Roy; de Priamus, Marcela Rusan; Wright, Carol (2007). The Effect of Visible Light on the Variability of Flexible Foam Compression Sets (PDF). Orlando, FL: Center for the Polyurethane Industry. Retrieved 2008-01-26.
  57. ^ Newman, Christopher R.; Forciniti, Daniel (2001). "Modeling the Ultraviolet Photodegradation of Rigid Polyurethane Foams". Industrial & Engineering Chemistry Research. 40 (15): 3346–52. doi:10.1021/ie0009738.
  58. ^ "Hydrolysis, The Crumbling of Shoe Soles explained | Safety Shoes and Gloves". www.safetyjogger.com.
  59. ^ Toward, Gary T. (June 2002). "Biodegradation of polyurethane: a review". International Biodeterioration & Biodegradation. 49 (4): 245–252. Bibcode:2002IBiBi..49..245H. doi:10.1016/S0964-8305(02)00051-3.
  60. ^ Russell, J. R.; Huang, J.; Anand, P.; Kucera, K.; Sandoval, A. G.; Dantzler, K. W.; Hickman, D.; Jee, J.; Kimovec, F. M.; Koppstein, D.; Marks, D. H.; Mittermiller, P. A.; Nunez, S. J.; Santiago, M.; Townes, M. A.; Vishnevetsky, M.; Williams, N. E.; Vargas, M. P. N.; Boulanger, L.-A.; Bascom-Slack, C.; Strobel, S. A. (2011). "Biodegradation of Polyester Polyurethane by Endophytic Fungi". Applied and Environmental Microbiology. 77 (17): 6076–84. Bibcode:2011ApEnM..77.6076R. doi:10.1128/AEM.00521-11. PMC 3165411. PMID 21764951.
  61. ^ "Could Plastic-Eating Mushrooms Solve mankind's Plastic Problem?". Sciencemint. 2021-04-14. Archived from the original on 2021-07-09. Retrieved 2021-07-02.
  62. ^ Cappitelli, F.; Sorlini, C. (2007). "Microorganisms Attack Synthetic Polymers in Items Representing Our Cultural Heritage". Applied and Environmental Microbiology. 74 (3): 564–9. Bibcode:2008ApEnM..74..564C. doi:10.1128/AEM.01768-07. PMC 2227722. PMID 18065627.
  63. ^ Tokiwa, Yutaka; Calabia, Buenaventurada P.; Ugwu, Charles U.; Aiba, Seiichi (2009). "Biodegradability of Plastics". International Journal of Molecular Sciences. 10 (9): 3722–42. doi:10.3390/ijms10093722. PMC 2769161. PMID 19865515.
[edit]
  • Center for the Polyurethanes Industry: information for EH&S issues related to polyurethanes developments
  • Polyurethane synthesis, Polymer Science Learning Center, University of Southern Mississippi
  • Polyurethane Foam Association: Industry information, educational materials and resources related to flexible polyurethane foam
  • PU Europe: European PU insulation industry association (formerly BING): European voice for the national trade associations representing the polyurethane insulation industry
  • ISOPA: European Diisocyanate & Polyol Producers Association: ISOPA represents the manufacturers in Europe of aromatic diisocyanates and polyols

 

Polyurethane synthesis: the urethane groups −NH−(C=O)−O− link the molecular units, resulting in a polymer consisting of an alternating chain of two monomers.
A kitchen sponge made of polyurethane foam

Polyurethane (/ËŒpÉ’liˈjÊŠÉ™rəˌθeɪn, -jʊəˈrÉ›θeɪn/;[1] often abbreviated PUR and PU) is a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane does not refer to a single type of polymer but a group of polymers. Unlike polyethylene and polystyrene, polyurethanes can be produced from a wide range of starting materials, resulting in various polymers within the same group. This chemical variety produces polyurethanes with different chemical structures leading to many different applications. These include rigid and flexible foams, and coatings, adhesives, electrical potting compounds, and fibers such as spandex and polyurethane laminate (PUL). Foams are the largest application accounting for 67% of all polyurethane produced in 2016.[2]

A polyurethane is typically produced by reacting a polymeric isocyanate with a polyol.[3] Since a polyurethane contains two types of monomers, which polymerize one after the other, they are classed as alternating copolymers. Both the isocyanates and polyols used to make a polyurethane contain two or more functional groups per molecule.

Global production in 2019 was 25 million metric tonnes,[4] accounting for about 6% of all polymers produced in that year.

History

[edit]
Otto Bayer in 1952 demonstrating his creation

Otto Bayer and his coworkers at IG Farben in Leverkusen, Germany, first made polyurethanes in 1937.[5][6] The new polymers had some advantages over existing plastics that were made by polymerizing olefins or by polycondensation, and were not covered by patents obtained by Wallace Carothers on polyesters.[7] Early work focused on the production of fibers and flexible foams and PUs were applied on a limited scale as aircraft coating during World War II.[7] Polyisocyanates became commercially available in 1952, and production of flexible polyurethane foam began in 1954 by combining toluene diisocyanate (TDI) and polyester polyols. These materials were also used to produce rigid foams, gum rubber, and elastomers. Linear fibers were produced from hexamethylene diisocyanate (HDI) and 1,4-Butanediol (BDO).

DuPont introduced polyethers, specifically poly(tetramethylene ether) glycol, in 1956. BASF and Dow Chemical introduced polyalkylene glycols in 1957. Polyether polyols were cheaper, easier to handle and more water-resistant than polyester polyols. Union Carbide and Mobay, a U.S. Monsanto/Bayer joint venture, also began making polyurethane chemicals.[7] In 1960 more than 45,000 metric tons of flexible polyurethane foams were produced. The availability of chlorofluoroalkane blowing agents, inexpensive polyether polyols, and methylene diphenyl diisocyanate (MDI) allowed polyurethane rigid foams to be used as high-performance insulation materials. In 1967, urethane-modified polyisocyanurate rigid foams were introduced, offering even better thermal stability and flammability resistance. During the 1960s, automotive interior safety components, such as instrument and door panels, were produced by back-filling thermoplastic skins with semi-rigid foam.

In 1969, Bayer exhibited an all-plastic car in Düsseldorf, Germany. Parts of this car, such as the fascia and body panels, were manufactured using a new process called reaction injection molding (RIM), in which the reactants were mixed and then injected into a mold. The addition of fillers, such as milled glass, mica, and processed mineral fibers, gave rise to reinforced RIM (RRIM), which provided improvements in flexural modulus (stiffness), reduction in coefficient of thermal expansion and better thermal stability. This technology was used to make the first plastic-body automobile in the United States, the Pontiac Fiero, in 1983. Further increases in stiffness were obtained by incorporating pre-placed glass mats into the RIM mold cavity, also known broadly as resin injection molding, or structural RIM.

Starting in the early 1980s, water-blown microcellular flexible foams were used to mold gaskets for automotive panels and air-filter seals, replacing PVC polymers. Polyurethane foams are used in many automotive applications including seating, head and arm rests, and headliners.

Polyurethane foam (including foam rubber) is sometimes made using small amounts of blowing agents to give less dense foam, better cushioning/energy absorption or thermal insulation. In the early 1990s, because of their impact on ozone depletion, the Montreal Protocol restricted the use of many chlorine-containing blowing agents, such as trichlorofluoromethane (CFC-11). By the late 1990s, blowing agents such as carbon dioxide, pentane, 1,1,1,2-tetrafluoroethane (HFC-134a) and 1,1,1,3,3-pentafluoropropane (HFC-245fa) were widely used in North America and the EU, although chlorinated blowing agents remained in use in many developing countries. Later, HFC-134a was also banned due to high ODP and GWP readings, and HFC-141B was introduced in early 2000s as an alternate blowing agent in developing nations.[8]

Chemistry

[edit]

Polyurethanes are produced by reacting diisocyanates with polyols,[9][10][11][12][13][14] often in the presence of a catalyst, or upon exposure to ultraviolet radiation.[15] Common catalysts include tertiary amines, such as DABCO, DMDEE, or metallic soaps, such as dibutyltin dilaurate. The stoichiometry of the starting materials must be carefully controlled as excess isocyanate can trimerise, leading to the formation of rigid polyisocyanurates. The polymer usually has a highly crosslinked molecular structure, resulting in a thermosetting material which does not melt on heating; although some thermoplastic polyurethanes are also produced.

 
Carbon dioxide gas and urea links formed by reacting water and isocyanate

The most common application of polyurethane is as solid foams, which requires the presence of a gas, or blowing agent, during the polymerization step. This is commonly achieved by adding small amounts of water, which reacts with isocyanates to form CO2 gas and an amine, via an unstable carbamic acid group. The amine produced can also react with isocyanates to form urea groups, and as such the polymer will contain both these and urethane linkers. The urea is not very soluble in the reaction mixture and tends to form separate "hard segment" phases consisting mostly of polyurea. The concentration and organization of these polyurea phases can have a significant impact on the properties of the foam.[16]

The type of foam produced can be controlled by regulating the amount of blowing agent and also by the addition of various surfactants which change the rheology of the polymerising mixture. Foams can be either "closed-cell", where most of the original bubbles or cells remain intact, or "open-cell", where the bubbles have broken but the edges of the bubbles are stiff enough to retain their shape, in extreme cases reticulated foams can be formed. Open-cell foams feel soft and allow air to flow through, so they are comfortable when used in seat cushions or mattresses. Closed-cell foams are used as rigid thermal insulation. High-density microcellular foams can be formed without the addition of blowing agents by mechanically frothing the polyol prior to use. These are tough elastomeric materials used in covering car steering wheels or shoe soles.

The properties of a polyurethane are greatly influenced by the types of isocyanates and polyols used to make it. Long, flexible segments, contributed by the polyol, give soft, elastic polymer. High amounts of crosslinking give tough or rigid polymers. Long chains and low crosslinking give a polymer that is very stretchy, short chains with many crosslinks produce a hard polymer while long chains and intermediate crosslinking give a polymer useful for making foam. The choices available for the isocyanates and polyols, in addition to other additives and processing conditions allow polyurethanes to have the very wide range of properties that make them such widely used polymers.

Raw materials

[edit]

The main ingredients to make a polyurethane are di- and tri-isocyanates and polyols. Other materials are added to aid processing the polymer or to modify the properties of the polymer. PU foam formulation sometimes have water added too.

Isocyanates

[edit]

Isocyanates used to make polyurethane have two or more isocyanate groups on each molecule. The most commonly used isocyanates are the aromatic diisocyanates, toluene diisocyanate (TDI) and methylene diphenyl diisocyanate, (MDI). These aromatic isocyanates are more reactive than aliphatic isocyanates.

TDI and MDI are generally less expensive and more reactive than other isocyanates. Industrial grade TDI and MDI are mixtures of isomers and MDI often contains polymeric materials. They are used to make flexible foam (for example slabstock foam for mattresses or molded foams for car seats),[17] rigid foam (for example insulating foam in refrigerators) elastomers (shoe soles, for example), and so on. The isocyanates may be modified by partially reacting them with polyols or introducing some other materials to reduce volatility (and hence toxicity) of the isocyanates, decrease their freezing points to make handling easier or to improve the properties of the final polymers.

MDI isomers and polymer
MDI isomers and polymer

Aliphatic and cycloaliphatic isocyanates are used in smaller quantities, most often in coatings and other applications where color and transparency are important since polyurethanes made with aromatic isocyanates tend to darken on exposure to light.[page needed][18] The most important aliphatic and cycloaliphatic isocyanates are 1,6-hexamethylene diisocyanate (HDI), 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), and 4,4′-diisocyanato dicyclohexylmethane (H12MDI or hydrogenated MDI). Other more specialized isocyanates include Tetramethylxylylene diisocyanate (TMXDI).

Polyols

[edit]

Polyols are polymers in their own right and have on average two or more hydroxyl groups per molecule. They can be converted to polyether polyols by co-polymerizing ethylene oxide and propylene oxide with a suitable polyol precursor.[19] Polyester polyols are made by the polycondensation of multifunctional carboxylic acids and polyhydroxyl compounds. They can be further classified according to their end use. Higher molecular weight polyols (molecular weights from 2,000 to 10,000) are used to make more flexible polyurethanes while lower molecular weight polyols make more rigid products.

Polyols for flexible applications use low functionality initiators such as dipropylene glycol (f = 2), glycerine (f = 3), or a sorbitol/water solution (f = 2.75).[20] Polyols for rigid applications use higher functionality initiators such as sucrose (f = 8), sorbitol (f = 6), toluenediamine (f = 4), and Mannich bases (f = 4). Propylene oxide and/or ethylene oxide is added to the initiators until the desired molecular weight is achieved. The order of addition and the amounts of each oxide affect many polyol properties, such as compatibility, water-solubility, and reactivity. Polyols made with only propylene oxide are terminated with secondary hydroxyl groups and are less reactive than polyols capped with ethylene oxide, which contain primary hydroxyl groups. Incorporating carbon dioxide into the polyol structure is being researched by multiple companies.

Graft polyols (also called filled polyols or polymer polyols) contain finely dispersed styrene–acrylonitrile, acrylonitrile, or polyurea (PHD) polymer solids chemically grafted to a high molecular weight polyether backbone. They are used to increase the load-bearing properties of low-density high-resiliency (HR) foam, as well as add toughness to microcellular foams and cast elastomers. Initiators such as ethylenediamine and triethanolamine are used to make low molecular weight rigid foam polyols that have built-in catalytic activity due to the presence of nitrogen atoms in the backbone. A special class of polyether polyols, poly(tetramethylene ether) glycols, which are made by polymerizing tetrahydrofuran, are used in high performance coating, wetting and elastomer applications.

Conventional polyester polyols are based on virgin raw materials and are manufactured by the direct polyesterification of high-purity diacids and glycols, such as adipic acid and 1,4-butanediol. Polyester polyols are usually more expensive and more viscous than polyether polyols, but they make polyurethanes with better solvent, abrasion, and cut resistance. Other polyester polyols are based on reclaimed raw materials. They are manufactured by transesterification (glycolysis) of recycled poly(ethyleneterephthalate) (PET) or dimethylterephthalate (DMT) distillation bottoms with glycols such as diethylene glycol. These low molecular weight, aromatic polyester polyols are used in rigid foam, and bring low cost and excellent flammability characteristics to polyisocyanurate (PIR) boardstock and polyurethane spray foam insulation.

Specialty polyols include polycarbonate polyols, polycaprolactone polyols, polybutadiene polyols, and polysulfide polyols. The materials are used in elastomer, sealant, and adhesive applications that require superior weatherability, and resistance to chemical and environmental attack. Natural oil polyols derived from castor oil and other vegetable oils are used to make elastomers, flexible bunstock, and flexible molded foam.

Co-polymerizing chlorotrifluoroethylene or tetrafluoroethylene with vinyl ethers containing hydroxyalkyl vinyl ether produces fluorinated (FEVE) polyols. Two-component fluorinated polyurethanes prepared by reacting FEVE fluorinated polyols with polyisocyanate have been used to make ambient cure paints and coatings. Since fluorinated polyurethanes contain a high percentage of fluorine–carbon bonds, which are the strongest bonds among all chemical bonds, fluorinated polyurethanes exhibit resistance to UV, acids, alkali, salts, chemicals, solvents, weathering, corrosion, fungi and microbial attack. These have been used for high performance coatings and paints.[21]

Phosphorus-containing polyols are available that become chemically bonded to the polyurethane matrix for the use as flame retardants. This covalent linkage prevents migration and leaching of the organophosphorus compound.

Bio-derived materials

[edit]

Interest in sustainable "green" products raised interest in polyols derived from vegetable oils,[22][23][24] fatty acids,[25] lignin, sorbitol,[26] etc. These are mostly contributing to polyol part. There are attempts made to prepare isocyanate part using bio-derived material. However, as far as commercialization is concern, polyol part is more targeted being easy and required in more quantity than isocyanate part. Various oils used in the preparation polyols for polyurethanes include soybean oil, cottonseed oil, neem seed oil, algae oil,[27][28] and castor oil. Vegetable oils are functionalized in various ways and modified to polyetheramides, polyethers, alkyds, etc. Renewable sources used to prepare polyols may be fatty acids or dimer fatty acids.[29] Some biobased and isocyanate-free polyurethanes exploit the reaction between polyamines and cyclic carbonates to produce polyhydroxyurethanes.[30]

Chain extenders and cross linkers

[edit]

Chain extenders (f = 2) and cross linkers (f ≥ 3) are low molecular weight hydroxyl and amine terminated compounds that play an important role in the polymer morphology of polyurethane fibers, elastomers, adhesives, and certain integral skin and microcellular foams.

The elastomeric properties of these materials are derived from the phase separation of the hard and soft copolymer segments of the polymer, such that the urethane hard segment domains serve as cross-links between the amorphous polyether (or polyester) soft segment domains. This phase separation occurs because the mainly nonpolar, low melting soft segments are incompatible with the polar, high melting hard segments. The soft segments, which are formed from high molecular weight polyols, are mobile and are normally present in coiled formation, while the hard segments, which are formed from the isocyanate and chain extenders, are stiff and immobile. As the hard segments are covalently coupled to the soft segments, they inhibit plastic flow of the polymer chains, thus creating elastomeric resiliency. Upon mechanical deformation, a portion of the soft segments are stressed by uncoiling, and the hard segments become aligned in the stress direction. This reorientation of the hard segments and consequent powerful hydrogen bonding contributes to high tensile strength, elongation, and tear resistance values.[12][31][32][33][34] The choice of chain extender also determines flexural, heat, and chemical resistance properties.

The most important chain extenders are ethylene glycol, 1,4-butanediol (1,4-BDO or BDO), 1,6-hexanediol, cyclohexane dimethanol and hydroquinone bis(2-hydroxyethyl) ether (HQEE). All of these glycols form polyurethanes that phase separate well and form well defined hard segment domains, and are melt processable. They are all suitable for thermoplastic polyurethanes with the exception of ethylene glycol, since its derived bis-phenyl urethane undergoes unfavorable degradation at high hard segment levels.[10] Diethanolamine and triethanolamine are used in flex molded foams to build firmness and add catalytic activity. Diethyltoluenediamine is used extensively in RIM, and in polyurethane and polyurea elastomer formulations.

Table of chain extenders and cross linkers[35]
Compound type Molecule Mol.
mass
Density
(g/cm3)
Melting
pt (°C)
Boiling
pt (°C)
Hydroxyl compounds – difunctional molecules Ethylene glycol 62.1 1.110 −13.4 197.4
Diethylene glycol 106.1 1.111 −8.7 245.5
Triethylene glycol 150.2 1.120 −7.2 287.8
Tetraethylene glycol 194.2 1.123 −9.4 325.6
Propylene glycol 76.1 1.032 Supercools 187.4
Dipropylene glycol 134.2 1.022 Supercools 232.2
Tripropylene glycol 192.3 1.110 Supercools 265.1
1,3-Propanediol 76.1 1.060 −28 210
1,3-Butanediol 92.1 1.005 207.5
1,4-Butanediol 92.1 1.017 20.1 235
Neopentyl glycol 104.2 130 206
1,6-Hexanediol 118.2 1.017 43 250
1,4-Cyclohexanedimethanol
HQEE
Ethanolamine 61.1 1.018 10.3 170
Diethanolamine 105.1 1.097 28 271
Methyldiethanolamine 119.1 1.043 −21 242
Phenyldiethanolamine 181.2 58 228
Hydroxyl compounds – trifunctional molecules Glycerol 92.1 1.261 18.0 290
Trimethylolpropane
1,2,6-Hexanetriol
Triethanolamine 149.2 1.124 21
Hydroxyl compounds – tetrafunctional molecules Pentaerythritol 136.2 260.5
N,N,N′,N′-Tetrakis
(2-hydroxypropyl)
ethylenediamine
Amine compounds – difunctional molecules Diethyltoluenediamine 178.3 1.022 308
Dimethylthiotoluenediamine 214.0 1.208

Catalysts

[edit]

Polyurethane catalysts can be classified into two broad categories, basic and acidic amine. Tertiary amine catalysts function by enhancing the nucleophilicity of the diol component. Alkyl tin carboxylates, oxides and mercaptides oxides function as mild Lewis acids in accelerating the formation of polyurethane. As bases, traditional amine catalysts include triethylenediamine (TEDA, also called DABCO, 1,4-diazabicyclo[2.2.2]octane), dimethylcyclohexylamine (DMCHA), dimethylethanolamine (DMEA), Dimethylaminoethoxyethanol and bis-(2-dimethylaminoethyl)ether, a blowing catalyst also called A-99. A typical Lewis acidic catalyst is dibutyltin dilaurate. The process is highly sensitive to the nature of the catalyst and is also known to be autocatalytic.[36]

Another class of catalysts was published in a study in May 2024. In this study, polyurethane synthesis was investigated in the presence of acid catalysts, namely dimethylphosphite (DMHP), methanesulfonic acid (MSA), and trifluoromethanesulfonic acid (TFMSA). The thermodynamic profile was examined and described in detail through computational tools, showing that TFMSA had the best catalytic properties. The study aimed to open the door to a new class of catalysts.[37]

Factors affecting catalyst selection include balancing three reactions: urethane (polyol+isocyanate, or gel) formation, the urea (water+isocyanate, or "blow") formation, or the isocyanate trimerization reaction (e.g., using potassium acetate, to form isocyanurate rings). A variety of specialized catalysts have been developed.[38][39][40]

Surfactants

[edit]

Surfactants are used to modify the characteristics of both foam and non-foam polyurethane polymers. They take the form of polydimethylsiloxane-polyoxyalkylene block copolymers, silicone oils, nonylphenol ethoxylates, and other organic compounds. In foams, they are used to emulsify the liquid components, regulate cell size, and stabilize the cell structure to prevent collapse and sub-surface voids.[41] In non-foam applications they are used as air release and antifoaming agents, as wetting agents, and are used to eliminate surface defects such as pin holes, orange peel, and sink marks.

Production

[edit]

Polyurethanes are produced by mixing two or more liquid streams. The polyol stream contains catalysts, surfactants, blowing agents (when making polyurethane foam insulation) and so on. The two components are referred to as a polyurethane system, or simply a system. The isocyanate is commonly referred to in North America as the 'A-side' or just the 'iso'. The blend of polyols and other additives is commonly referred to as the 'B-side' or as the 'poly'.[citation needed] This mixture might also be called a 'resin' or 'resin blend'. In Europe the meanings for 'A-side' and 'B-side' are reversed.[citation needed] Resin blend additives may include chain extenders, cross linkers, surfactants, flame retardants, blowing agents, pigments, and fillers. Polyurethane can be made in a variety of densities and hardnesses by varying the isocyanate, polyol or additives.

Health and safety

[edit]

Fully reacted polyurethane polymer is chemically inert.[42] No exposure limits have been established in the U.S. by OSHA (Occupational Safety and Health Administration) or ACGIH (American Conference of Governmental Industrial Hygienists). It is not regulated by OSHA for carcinogenicity.

Open-flame test. Top: untreated polyurethane foam burns vigorously. Bottom: with fire-retardant treatment.

Polyurethanes are combustible.[43] Decomposition from fire can produce significant amounts of carbon monoxide and hydrogen cyanide, in addition to nitrogen oxides, isocyanates, and other toxic products.[44] Due to the flammability of the material, it has to be treated with flame retardants (at least in case of furniture), almost all of which are considered harmful.[45][46] California later issued Technical Bulletin 117 2013 which allowed most polyurethane foam to pass flammability tests without the use of flame retardants. Green Science Policy Institute states: "Although the new standard can be met without flame retardants, it does NOT ban their use. Consumers who wish to reduce household exposure to flame retardants can look for a TB117-2013 tag on furniture, and verify with retailers that products do not contain flame retardants."[47]

Liquid resin blends and isocyanates may contain hazardous or regulated components. Isocyanates are known skin and respiratory sensitizers. Additionally, amines, glycols, and phosphate present in spray polyurethane foams present risks.[48]

Exposure to chemicals that may be emitted during or after application of polyurethane spray foam (such as isocyanates) are harmful to human health and therefore special precautions are required during and after this process.[49]

In the United States, additional health and safety information can be found through organizations such as the Polyurethane Manufacturers Association (PMA) and the Center for the Polyurethanes Industry (CPI), as well as from polyurethane system and raw material manufacturers. Regulatory information can be found in the Code of Federal Regulations Title 21 (Food and Drugs) and Title 40 (Protection of the Environment). In Europe, health and safety information is available from ISOPA,[50] the European Diisocyanate and Polyol Producers Association.

Manufacturing

[edit]

The methods of manufacturing polyurethane finished goods range from small, hand pour piece-part operations to large, high-volume bunstock and boardstock production lines. Regardless of the end-product, the manufacturing principle is the same: to meter the liquid isocyanate and resin blend at a specified stoichiometric ratio, mix them together until a homogeneous blend is obtained, dispense the reacting liquid into a mold or on to a surface, wait until it cures, then demold the finished part.

Dispensing equipment

[edit]

Although the capital outlay can be high, it is desirable to use a meter-mix or dispense unit for even low-volume production operations that require a steady output of finished parts. Dispense equipment consists of material holding (day) tanks, metering pumps, a mix head, and a control unit. Often, a conditioning or heater–chiller unit is added to control material temperature in order to improve mix efficiency, cure rate, and to reduce process variability. Choice of dispense equipment components depends on shot size, throughput, material characteristics such as viscosity and filler content, and process control. Material day tanks may be single to hundreds of gallons in size and may be supplied directly from drums, IBCs (intermediate bulk containers, such as caged IBC totes), or bulk storage tanks. They may incorporate level sensors, conditioning jackets, and mixers. Pumps can be sized to meter in single grams per second up to hundreds of pounds per minute. They can be rotary, gear, or piston pumps, or can be specially hardened lance pumps to meter liquids containing highly abrasive fillers such as chopped or hammer-milled glass fiber and wollastonite.[citation needed]

The pumps can drive low-pressure (10 to 30 bar, 1 to 3 MPa) or high-pressure (125 to 250 bar, 12.5 to 25.0 MPa) dispense systems. Mix heads can be simple static mix tubes, rotary-element mixers, low-pressure dynamic mixers, or high-pressure hydraulically actuated direct impingement mixers. Control units may have basic on/off and dispense/stop switches, and analogue pressure and temperature gauges, or may be computer-controlled with flow meters to electronically calibrate mix ratio, digital temperature and level sensors, and a full suite of statistical process control software. Add-ons to dispense equipment include nucleation or gas injection units, and third or fourth stream capability for adding pigments or metering in supplemental additive packages.

Tooling

[edit]

Distinct from pour-in-place, bun and boardstock, and coating applications, the production of piece parts requires tooling to contain and form the reacting liquid. The choice of mold-making material is dependent on the expected number of uses to end-of-life (EOL), molding pressure, flexibility, and heat transfer characteristics.

RTV silicone is used for tooling that has an EOL in the thousands of parts. It is typically used for molding rigid foam parts, where the ability to stretch and peel the mold around undercuts is needed. The heat transfer characteristic of RTV silicone tooling is poor. High-performance, flexible polyurethane elastomers are also used in this way.

Epoxy, metal-filled epoxy, and metal-coated epoxy is used for tooling that has an EOL in the tens of thousands of parts. It is typically used for molding flexible foam cushions and seating, integral skin and microcellular foam padding, and shallow-draft RIM bezels and fascia. The heat transfer characteristic of epoxy tooling is fair; the heat transfer characteristic of metal-filled and metal-coated epoxy is good. Copper tubing can be incorporated into the body of the tool, allowing hot water to circulate and heat the mold surface.

Aluminum is used for tooling that has an EOL in the hundreds of thousands of parts. It is typically used for molding microcellular foam gasketing and cast elastomer parts, and is milled or extruded into shape.

Mirror-finish stainless steel is used for tooling that imparts a glossy appearance to the finished part. The heat transfer characteristic of metal tooling is excellent.

Finally, molded or milled polypropylene is used to create low-volume tooling for molded gasket applications. Instead of many expensive metal molds, low-cost plastic tooling can be formed from a single metal master, which also allows greater design flexibility. The heat transfer characteristic of polypropylene tooling is poor, which must be taken into consideration during the formulation process.

Applications

[edit]

In 2007, the global consumption of polyurethane raw materials was above 12 million metric tons, and the average annual growth rate was about 5%.[51] Revenues generated with PUR on the global market are expected to rise to approximately US$75 billion by 2022.[52] As they are such an important class of materials, research is constantly taking place and papers published.[53]

Degradation and environmental fate

[edit]

Effects of visible light

[edit]
Polyurethane foam made with an aromatic isocyanate, which has been exposed to UV light. Readily apparent is the discoloration that occurs over time.

Polyurethanes, especially those made using aromatic isocyanates, contain chromophores that interact with light. This is of particular interest in the area of polyurethane coatings, where light stability is a critical factor and is the main reason that aliphatic isocyanates are used in making polyurethane coatings. When PU foam, which is made using aromatic isocyanates, is exposed to visible light, it discolors, turning from off-white to yellow to reddish brown. It has been generally accepted that apart from yellowing, visible light has little effect on foam properties.[54][55] This is especially the case if the yellowing happens on the outer portions of a large foam, as the deterioration of properties in the outer portion has little effect on the overall bulk properties of the foam itself.

It has been reported that exposure to visible light can affect the variability of some physical property test results.[56]

Higher-energy UV radiation promotes chemical reactions in foam, some of which are detrimental to the foam structure.[57]

Hydrolysis and biodegradation

[edit]

Polyurethanes may degrade due to hydrolysis. This is a common problem with shoes left in a closet, and reacting with moisture in the air.[58]

Microbial degradation of polyurethane is believed to be due to the action of esterase, urethanase, hydrolase and protease enzymes.[59] The process is slow as most microbes have difficulty moving beyond the surface of the polymer. Susceptibility to fungi is higher due to their release of extracellular enzymes, which are better able to permeate the polymer matrix. Two species of the Ecuadorian fungus Pestalotiopsis are capable of biodegrading polyurethane in aerobic and anaerobic conditions such as found at the bottom of landfills.[60][61] Degradation of polyurethane items at museums has been reported.[62] Polyester-type polyurethanes are more easily biodegraded by fungus than polyether-type.[63]

See also

[edit]
  • Botanol, a material with higher plant-based content
  • Passive fire protection
  • Penetrant (mechanical, electrical, or structural)
  • Polyaspartic
  • Polyurethane dispersion
  • Thermoplastic polyurethanes
  • Thermoset polymer matrix

References

[edit]
  1. ^ "polyurethane". Dictionary.com Unabridged (Online). n.d.
  2. ^ Gama, Nuno; Ferreira, Artur; Barros-Timmons, Ana (27 September 2018). "Polyurethane Foams: Past, Present, and Future". Materials. 11 (10): 1841. Bibcode:2018Mate...11.1841G. doi:10.3390/ma11101841. PMC 6213201. PMID 30262722.
  3. ^ "Polyurethane". American Chemistry Council. Retrieved 2022-09-19.
  4. ^ "Polyurethane global market volume 2015-2026". Statista. Retrieved 23 July 2021.
  5. ^ Bayer, Otto (1947). "Das Di-Isocyanat-Polyadditionsverfahren (Polyurethane)". Angewandte Chemie. 59 (9): 257–72. Bibcode:1947AngCh..59..257B. doi:10.1002/ange.19470590901.
  6. ^ DE 728981, I.G. Farbenindustrie A.G., "Verfahren zur Herstellung von Polyurethanen bzw. Polyharnstoffen [Process for the production of polyurethanes or polyurea]", published 1942-12-07 
  7. ^ a b c Seymour, Raymond B.; Kauffman, George B. (1992). "Polyurethanes: A class of modern versatile materials". Journal of Chemical Education. 69 (11): 909. Bibcode:1992JChEd..69..909S. doi:10.1021/ed069p909.
  8. ^ Feske, Bert (October 2004). "The Use of Saytex RB-9130/9170 Low Viscosity Brominated Flame Retardant Polyols in HFC-245fa and High Water Formulations" (PDF). Polyurethanes Expo 2004. Las Vegas, NV: Alliance for the Polyurethane Industry Technical Conference. p. 309. Retrieved 2007-08-01.
  9. ^ n ≥ 2
  10. ^ a b Gum, Wilson; Riese, Wolfram; Ulrich, Henri (1992). Reaction Polymers. New York: Oxford University Press. ISBN 978-0-19-520933-4.
  11. ^ Harrington, Ron; Hock, Kathy (1991). Flexible Polyurethane Foams. Midland: The Dow Chemical Company.
  12. ^ a b Oertel, Gunter (1985). Polyurethane Handbook. New York: Macmillen Publishing Co., Inc. ISBN 978-0-02-948920-8.[page needed]
  13. ^ Ulrich, Henri (1996). Chemistry and Technology of Isocyanates. New York: John Wiley & Sons, Inc. ISBN 978-0-471-96371-4.[page needed]
  14. ^ Woods, George (1990). The ICI Polyurethanes Book. New York: John Wiley & Sons, Inc. ISBN 978-0-471-92658-0.[page needed]
  15. ^ Soto, Marc; Sebastián, Rosa María; Marquet, Jordi (2014). "Photochemical Activation of Extremely Weak Nucleophiles: Highly Fluorinated Urethanes and Polyurethanes from Polyfluoro Alcohols". The Journal of Organic Chemistry. 79 (11): 5019–27. doi:10.1021/jo5005789. PMID 24820955.
  16. ^ Kaushiva, Byran D. (August 15, 1999). Structure-Property Relationships of Flexible Polyurethane Foams (Ph.D.). Virginia Polytechnic Institute.
  17. ^ "Technical data sheet from Dow Chemical". Archived from the original on 2007-10-13. Retrieved 2007-09-15.
  18. ^ Randall, David; Lee, Steve (2002). The Polyurethanes Book. New York: Wiley. ISBN 978-0-470-85041-1.
  19. ^ Petrović, Zoran S. (2008). "Polyurethanes from Vegetable Oils". Polymer Reviews. 48 (1): 109–155. doi:10.1080/15583720701834224. S2CID 95466690.
  20. ^ EP 0755955, Hager, Stanley L.; Knight, James E. & Helma, Gregory F. et al., "Polyether polyols suitable for flexible polyurethane foam prepared by co-initiation of aqueous solutions of solid polyhydroxyl initiators", published 1997-01-29, assigned to ARCO Chemical Technology 
  21. ^ Bob Parker. "FEVE Technology for Higher Performance Coating Systems on Bridges" (PDF). Paintsquare.com. Archived from the original (PDF) on 15 August 2021. Retrieved 5 March 2022.
  22. ^ Khanderay, Jitendra C., and Vikas V. Gite. "Vegetable oil-based polyurethane coatings: recent developments in India." Green Materials 5.3 (2017): 109-122.
  23. ^ Niemeyer, Timothy; Patel, Munjal; Geiger, Eric (September 2006). A Further Examination of Soy-Based Polyols in Polyurethane Systems. Salt Lake City, UT: Alliance for the Polyurethane Industry Technical Conference.
  24. ^ "New Twist on Green: 2008 Ford Mustang Seats Will Be Soy-Based Foam". Edmunds inside line. July 12, 2007. Archived from the original on 2008-05-31. Retrieved 2010-06-15.
  25. ^ SD Rajput, PP Mahulikar, VV Gite, Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings, Progress in Organic Coatings 77 (1), 38-46 https://doi.org/10.1016/j.porgcoat.2014.04.030
  26. ^ A Anand, RD Kulkarni, VV Gite, Preparation and properties of eco-friendly two pack PU coatings based on renewable source (sorbitol) and its property improvement by nano ZnO, Progress in Organic Coatings 74 (4), 764-767, https://doi.org/10.1016/j.porgcoat.2011.09.031
  27. ^ Chandrashekhar K Patil, Harishchandra D Jirimali, Jayasinh S Paradeshi, Bhushan L Chaudhari, Prakash K Alagi, Pramod P Mahulikar, Sung Chul Hong, Vikas V Gite, Chemical transformation of renewable algae oil to polyetheramide polyols for polyurethane coatings, Progress in Organic Coatings 151, 106084, https://doi.org/10.1016/j.porgcoat.2020.106084
  28. ^ CK Patil, HD Jirimali, JS Paradeshi, BL Chaudhari, VV Gite, Functional antimicrobial and anticorrosive polyurethane composite coatings from algae oil and silver doped egg shell hydroxyapatite for sustainable development, Progress in Organic Coatings 128, 127-136, https://doi.org/10.1016/j.porgcoat.2018.11.002
  29. ^ Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings, SD Rajput, PP Mahulikar, VV Gite, Progress in Organic Coatings 77 (1), 38-46
  30. ^ Nohra, Bassam; Candy, Laure; Blanco, Jean-François; Guerin, Celine; Raoul, Yann; Mouloungui, Zephirin (2013). "From Petrochemical Polyurethanes to Biobased Polyhydroxyurethanes" (PDF). Macromolecules. 46 (10): 3771–92. Bibcode:2013MaMol..46.3771N. doi:10.1021/ma400197c. Archived (PDF) from the original on 2017-09-22.
  31. ^ Blackwell, J.; Nagarajan, M. R.; Hoitink, T. B. (1981). "The Structure of the Hard Segments in MDI/diol/PTMA Polyurethane Elastomers". ACS Symposium Series. 172. Washington, D.C.: American Chemical Society: 179–196. doi:10.1021/bk-1981-0172.ch014. ISBN 978-0-8412-0664-9. ISSN 0097-6156.
  32. ^ Blackwell, John; Gardner, Kenncorwin H. (1979). "Structure of the hard segments in polyurethane elastomers". Polymer. 20 (1): 13–17. doi:10.1016/0032-3861(79)90035-1. ISSN 0032-3861.
  33. ^ Grillo, D. J.; Housel, T. L. (1992). "Physical Properties of Polyurethanes from Polyesters and Other Polyols". Polyurethanes '92 Conference Proceedings. New Orleans, LA: The Society of the Plastics Industry, Inc.
  34. ^ Musselman, S. G.; Santosusso, T. M.; Sperling, L. H. (1998). "Structure Versus Performance Properties of Cast Elastomers". Polyurethanes '98 Conference Proceedings. Dallas, TX: The Society of the Plastics Industry, Inc.
  35. ^ A Guide to Glycols. Midland, Mich.: The Dow Chemical Co., Chemicals and Metals Department. 1992. Brochure 117-00991-92Hyc.
  36. ^ Adam, Norbert; Avar, Geza; Blankenheim, Herbert; Friederichs, Wolfgang; Giersig, Manfred; Weigand, Eckehard; Halfmann, Michael; Wittbecker, Friedrich-Wilhelm; Larimer, Donald-Richard; Maier, Udo; Meyer-Ahrens, Sven; Noble, Karl-Ludwig; Wussow, Hans-Georg (2005). "Polyurethanes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a21_665.pub2. ISBN 978-3-527-30673-2.
  37. ^ Waleed, H. Q.; Viskolcz, B.; Fiser, B. (2024). "Urethane Synthesis in the Presence of Organic Acid Catalysts—A Computational Study". Molecules (Basel, Switzerland). 29 (10): 2375. doi:10.3390/molecules29102375. PMC 11123846. PMID 38792235.
  38. ^ "Jeffcat Amine Catalysts for the Polyurethane Industry" (PDF). 2006. Archived from the original (PDF) on 2007-11-29. Retrieved 2007-10-23.
  39. ^ "Building quality with Air Products trimerisation catalysts" (PDF). 2003. Archived from the original (PDF) on 2007-11-29. Retrieved 2007-10-23.
  40. ^ "FOMREZ Specialty Tin Catalysts for Polyurethane Applications". 120-074-10. January 2001.
  41. ^ Randall, David; Lee, Steve, eds. (2002). "10". The Polyurethanes Book. The United Kingdom: Huntsman International LLC, Polyurethanes business. pp. 156–159. ISBN 978-0470850411. Archived from the original on 2018-05-24. Retrieved 2018-05-23.
  42. ^ Dernehl, C. U. (1966). "Health hazards associated with polyurethane foams". Journal of Occupational Medicine. 8 (2): 59–62. PMID 5903304.
  43. ^ "Health Alert: Polyurethane exposure" (PDF). Archived from the original (PDF) on 2004-10-19. Retrieved 2009-12-19.
  44. ^ McKenna, Sean Thomas; Hull, Terence Richard (2016). "The fire toxicity of polyurethane foams". Fire Science Reviews. 5 (1): 3. doi:10.1186/s40038-016-0012-3.
  45. ^ "Environmental Profiles of Chemical Flame-Retardant Alternatives for Low-Density Polyurethane Foam". United States Environmental Protection Agency. September 2005.
  46. ^ "Flame Retardants Used in Flexible Polyurethane Foam – Draft Update to a 2005 Alternatives Assessment". United States Environmental Protection Agency. June 2014. Archived from the original on November 21, 2014.
  47. ^ "Manufacturers" (PDF). greensciencepolicy.org. 2015. Archived (PDF) from the original on 2015-12-19.
  48. ^ "Help Wanted: Spray Polyurethane Foam Insulation Research". NIOSH Science Blog. CDC. 21 March 2012.
  49. ^ "Quick Safety Tips for Spray Polyurethane Foam Users". United States Environmental Protection Agency. 4 August 2015.
  50. ^ "Home : ISOPA". www.isopa.org.
  51. ^ Avar, G. (October 2008). "Polyurethanes (PU)". Kunststoffe International (10/2008): 123–7.
  52. ^ "Market Study: Polyurethanes and Isocyanates". Ceresana. July 2013.
  53. ^ Jakhmola, Swati; Das, Sonalee; Dutta, Kingshuk (2023-10-31). "Emerging research trends in the field of polyurethane and its nanocomposites: Chemistry, Synthesis, Characterization, Application in coatings and Future perspectives". Journal of Coatings Technology and Research. 21 (1): 137–172. doi:10.1007/s11998-023-00841-z. ISSN 1935-3804. S2CID 264908475.
  54. ^ "Discoloration of polyurethane foam" (PDF). Foamex Information sheet. Archived from the original (PDF) on 2010-09-24. Retrieved 2010-09-26.
  55. ^ Valentine, C.; Craig, T.A.; Hager, S.L. (1993). "Inhibition of the Discoloration of Polyurethane Foam Caused by Ultraviolet Light". Journal of Cellular Plastics. 29 (6): 569–88. doi:10.1177/0021955X9302900605. S2CID 208363195.
  56. ^ Blair, G. Ron; Dawe, Bob; McEvoy, Jim; Pask, Roy; de Priamus, Marcela Rusan; Wright, Carol (2007). The Effect of Visible Light on the Variability of Flexible Foam Compression Sets (PDF). Orlando, FL: Center for the Polyurethane Industry. Retrieved 2008-01-26.
  57. ^ Newman, Christopher R.; Forciniti, Daniel (2001). "Modeling the Ultraviolet Photodegradation of Rigid Polyurethane Foams". Industrial & Engineering Chemistry Research. 40 (15): 3346–52. doi:10.1021/ie0009738.
  58. ^ "Hydrolysis, The Crumbling of Shoe Soles explained | Safety Shoes and Gloves". www.safetyjogger.com.
  59. ^ Toward, Gary T. (June 2002). "Biodegradation of polyurethane: a review". International Biodeterioration & Biodegradation. 49 (4): 245–252. Bibcode:2002IBiBi..49..245H. doi:10.1016/S0964-8305(02)00051-3.
  60. ^ Russell, J. R.; Huang, J.; Anand, P.; Kucera, K.; Sandoval, A. G.; Dantzler, K. W.; Hickman, D.; Jee, J.; Kimovec, F. M.; Koppstein, D.; Marks, D. H.; Mittermiller, P. A.; Nunez, S. J.; Santiago, M.; Townes, M. A.; Vishnevetsky, M.; Williams, N. E.; Vargas, M. P. N.; Boulanger, L.-A.; Bascom-Slack, C.; Strobel, S. A. (2011). "Biodegradation of Polyester Polyurethane by Endophytic Fungi". Applied and Environmental Microbiology. 77 (17): 6076–84. Bibcode:2011ApEnM..77.6076R. doi:10.1128/AEM.00521-11. PMC 3165411. PMID 21764951.
  61. ^ "Could Plastic-Eating Mushrooms Solve mankind's Plastic Problem?". Sciencemint. 2021-04-14. Archived from the original on 2021-07-09. Retrieved 2021-07-02.
  62. ^ Cappitelli, F.; Sorlini, C. (2007). "Microorganisms Attack Synthetic Polymers in Items Representing Our Cultural Heritage". Applied and Environmental Microbiology. 74 (3): 564–9. Bibcode:2008ApEnM..74..564C. doi:10.1128/AEM.01768-07. PMC 2227722. PMID 18065627.
  63. ^ Tokiwa, Yutaka; Calabia, Buenaventurada P.; Ugwu, Charles U.; Aiba, Seiichi (2009). "Biodegradability of Plastics". International Journal of Molecular Sciences. 10 (9): 3722–42. doi:10.3390/ijms10093722. PMC 2769161. PMID 19865515.
[edit]
  • Center for the Polyurethanes Industry: information for EH&S issues related to polyurethanes developments
  • Polyurethane synthesis, Polymer Science Learning Center, University of Southern Mississippi
  • Polyurethane Foam Association: Industry information, educational materials and resources related to flexible polyurethane foam
  • PU Europe: European PU insulation industry association (formerly BING): European voice for the national trade associations representing the polyurethane insulation industry
  • ISOPA: European Diisocyanate & Polyol Producers Association: ISOPA represents the manufacturers in Europe of aromatic diisocyanates and polyols