| The pioneering work on polyurethane polymers was | | | | RRIM, reinforced RIM, which provided improvements in |
| conducted by Otto Bayer and his coworkers in 1937 | | | | flexural modulus (stiffness) and thermal stability. This |
| at the laboratories of I.G. Farben in Leverkusen, | | | | technology allowed production of the first plastic-body |
| Germany. They recognized that using the polyaddition | | | | automobile in the United Sates, the Pontiac Fiero, in |
| principle to produce polyurethanes from liquid | | | | 1983. Further improvements in flexural modulus were |
| diisocyanates and liquid polyether or polyester diols | | | | obtained by incorporating preplaced glass mats into the |
| seemed to point to special opportunities, especially | | | | RIM mold cavity, also known as SRIM, or structural |
| when compared to already existing plastics that were | | | | RIM. Starting in the early 1980s, water-blown |
| made by polymerizing olefins, or by polycondensation. | | | | microcellular flexible foam was used to mold gaskets |
| The new monomer combination also circumvented | | | | for panel and radial seal air filters in the automotive |
| existing patents obtained by Wallace Carothers on | | | | industry. Since then, increasing energy prices and the |
| polyesters.Initially, work focused on the production of | | | | desire to eliminate PVC plastisol from automotive |
| fibres and flexible foams. With development | | | | applications have greatly increased market share. |
| constrained by World War II (when PU's were applied | | | | Costlier raw materials are offset by a significant |
| on a limited scale as aircraft coating), it was not until | | | | decrease in part weight and in some cases, the |
| 1952 that polyisocyanates became commercially | | | | elimination of metal end caps and filter housings. |
| available. Commercial production of flexible | | | | Highly filled polyurethane elastomers, and more recently |
| polyurethane foam began in 1954, based on toluene | | | | unfilled polyurethane foams are now used in |
| diisocyanate (TDI) and polyester polyols. The invention | | | | high-temperature oil filter applications. Polyurethane |
| of these foams (initially called imitation swiss cheese | | | | foam (including foam rubber) is often made by adding |
| by the inventors) was thanks to water accidentally | | | | small amounts of volatile materials, so-called blowing |
| introduced in the reaction mix. | | | | agents, to the reaction mixture. These simple volatile |
| These materials were also used to produce rigid | | | | chemicals yield important performance characteristics, |
| foams, gum rubber, and elastomers. Linear fibres were | | | | primarily thermal insulation. In the early 1990s, because |
| produced from hexamethylene diisocyanate (HDI) and | | | | of their impact on ozone depletion, the Montreal |
| 1,4-butanediol (BDO). The first commercially available | | | | Protocol led to the greatly reduced use of many |
| polyether polyol, poly(tetramethylene ether) glycol), was | | | | chlorine-containing blowing agents, such as |
| introduced by DuPont in 1956 by polymerizing | | | | trichlorofluoromethane (CFC-11). Other haloalkanes, |
| tetrahydrofuran. Less expensive polyalkylene glycols | | | | such as the hydrochlorofluorocarbon |
| were introduced by BASF and Dow Chemical the | | | | 1,1-dichloro-1-fluoroethane (HCFC-141b), were used as |
| following year, 1957. These polyether polyols offered | | | | interim replacements until their phase out under the |
| technical and commercial advantages such as low | | | | IPPC directive on greenhouse gases in 1994 and by |
| cost, ease of handling, and better hydrolytic stability; | | | | the Volatile Organic Compounds (VOC) directive of |
| and quickly supplanted polyester polyols in the | | | | the EU in 1997 (See: Haloalkanes). By the late 1990s, |
| manufacture of polyurethane goods. Another early | | | | the use of blowing agents such as carbon dioxide, |
| pioneer in PU's was the Mobay corporation. In 1960 | | | | pentane, 1,1,1,2-tetrafluoroethane (HFC-134a) and |
| more than 45,000 tons of flexible polyurethane foams | | | | 1,1,1,3,3-pentafluoropropane (HFC-245fa) became more |
| were produced. As the decade progressed, the | | | | widespread in North America and the EU, although |
| availability of chlorofluoroalkane blowing agents, | | | | chlorinated blowing agents remained in use in many |
| inexpensive polyether polyols, and methylene diphenyl | | | | developing countries. |
| diisocyanate (MDI) heralded the development and use | | | | Building on existing polyurethane spray coating |
| of polyurethane rigid foams as high performance | | | | technology and polyetheramine chemistry, extensive |
| insulation materials.Rigid foams based on polymeric MDI | | | | development of two-component polyurea spray |
| (PMDI) offered better thermal stability and combustion | | | | elastomers took place in the 1990s. Their fast reactivity |
| characteristics than those based on TDI. In 1967, | | | | and relative insensitivity to moisture make them useful |
| urethane modified polyisocyanurate rigid foams were | | | | coatings for large surface area projects, such as |
| introduced, offering even better thermal stability and | | | | secondary containment, manhole and tunnel coatings, |
| flammability resistance to low density insulation | | | | and tank liners. Excellent adhesion to concrete and |
| products. | | | | steel is obtained with the proper primer and surface |
| Also during the 1960s, automotive interior safety | | | | treatment. During the same period, new |
| components such as instrument and door panels were | | | | two-component polyurethane and hybrid |
| produced by back-filling thermoplastic skins with | | | | polyurethane-polyurea elastomer technology was used |
| semi-rigid foam. In 1969, Bayer AG exhibited an all | | | | to enter the marketplace of spray-in-place load bed |
| plastic car in Dusseldorf, Germany. Parts of this car | | | | liners. This technique for coating pickup truck beds and |
| were manufactured using a new process called RIM, | | | | other cargo bays creates a durable, abrasion resistant |
| Reaction Injection Molding. RIM technology uses | | | | composite with the metal substrate, and eliminates |
| high-pressure impingement of liquid components | | | | corrosion and brittleness associated with drop-in |
| followed by the rapid flow of the reaction mixture into | | | | thermoplastic bed liners. The use of polyols derived |
| a mold cavity. Large parts, such as automotive fascia | | | | from vegetable oils to make polyurethane products |
| and body panels, can be molded in this manner. | | | | began garnishing attention beginning around 2004, |
| Polyurethane RIM evolved into a number of different | | | | partly due to the rising costs of petrochemical |
| products and processes. Using diamine chain | | | | feedstocks and partially due to an enhanced public |
| extenders and trimerization technology gave | | | | desire for environmentally friendly green products. One |
| poly(urethane urea), poly(urethane isocyanurate), and | | | | of the most vocal supporters of these polyurethanes |
| polyurea RIM. The addition of fillers, such as milled | | | | made using natural oil polyols is the Ford Motor |
| glass, mica, and processed mineral fibres gave arise to | | | | Company. |