Isocyanates. polyurethanes from

We create polyurethanes from prepolymers by chain extension. In the case of hydroxyl-terminated prepolymers the chain extender is an isocyanate. If we use a diisocyanate, the resulting polymer is linear. If we substitute some or all of the diisocyanate with a tri- or... 

PMDA, 20 266. See also Polymeric methylenedianiline (PMDA) PMDA-ODA, gel casting of, 20 271-272 PMDA-ODA structures, 10 214 PMDI polymeric isocyanate, 25 456, 457, 462. See also Polymeric methylene diisocyanate resins (PMDI) rigid polyurethanes from, 25 471-472 PMF/PMUF resins, 15 779 PMF resins, hardening of, 15 781 PMMA ionomer, 4DA and, 14 479 PM optimization (PMO), 15 466 PM process, 21 50 Pneumatic classification, 22 288 health and safety factors related to,... 

Belin L, Wass U, Audunsson G, et al Amines Possible causative agents in the development of bronchial hyperreactivity in workers manufacturing polyurethanes from isocyanates. BrJ Ind Med 40 251-257, 1983... 

The synthesis of polyurethanes from tetramethylene urea, 1,2-propylene carbonate, and ethylene carbonate shows an interesting alternative route to polyurethanes 26 and 27 (Figure 11). The tetramethylene urea ring is not opened to form an isocyanate under the reaction conditions applied <2004MAC888>. 

E. and Salthammer, T. (2003) Time course of isocyanate emission from curing polyurethane adhesives. Atmospheric Environment,... 

Polyurethanes from 4,4-MDI and glycols Polyurethanes from VORANOL polyols and BCB isocyanate 3 209.0 8.19 2.7 0.9951... 

Similarly, an aqueous treatment for wool uses an isocyanate blocked with a bisulfite. In this case, the by-product bisulfite salt can be removed, and possibly recycled, by washing the fabric with water at the end. The dissociation temperature decreases in the following order alcohol > lactam > phenol > ketoxime > active methylene compound. e-Caprolactam is a typical lactam, ethyl acetoacetate a typical active methylene compound. This thermal reversibility has been used to prepare a polyurethane from 1,4-butanediol, 4,4 -diphenyldiiso-cyanate, and 4,4 -isopropylidenediphenol (bisphenol A) (2.30) that can be recycled just by remolding.76... 

The extruder can be used for a variety of polymerizations even if no preformed polymer is present.89 These include the continuous anionic polymerization of caprolactam to produce nylon 6,90 anionic polymerization of capro-lactone 91 anionic polymerization of styrene 92 cationic copolymerization of 1,3-dioxolane and methylal 93 free radical polymerization of methyl methacrylate 94 addition of ammonia to maleic anhydride to form poly(succin-imide) 95 and preparation of an acrylated polyurethane from polycaprolactone, 4,4 -methylenebis(phenyl isocyanate), and 2-hydroxyethyl acrylate.96 The technique of reaction injection molding to prepare molded parts is slightly different. Polyurethanes can be made this way by... 

STRUCTURE 4.1 Hydrogen bonding in a hydroxyurethane. (Reprinted from E. Delebecq, J-P. Pascault, B. Boutevin, and F. Ganachaud, On the Versatility of Urethane/Urea Bonds Reversibility, Blocked Isocyanate, and Non-Isocyanate Polyurethane, Chem. Rev. 113 (2013) 80-118. With permission.)... 

STRUCTURE 4.2 Example of polyfunctional cyclic carbonate-tricyclic carbonate on the base of propoxylated glycerin. (Reprinted from O. Figovsky and L. Shapovalov, Cyclocarbonate-Based Polymers Including Non-Isocyanate Polyurethane Adhesives and Coatings, in Encyclopedia of Surface and Colloid Science, ed. P. Somasundaran, vol. 3, 1633-1653. New York Taylor Francis, 2006. With permission.)... 

Polyurethanes are widely used in several important applications including foams, elastomers, coatings, and adhesives. They result from the reaction between an alcohol and an isocyanate, and from this reaction, hyperbranched polymers can also be prepared from AB2 monomers having both functional groups in the proper ratio. The high reactivity of isocyanates, even in self-condensation, can lead to the formation of dimer or carbamates by reaction with... 

Butanediol was also used as an intermediate in the production of polyurethanes. These novel plastics had been discovered by Otto Bayer, Reppe s counterpart at Leverkusen, in 1937.52 formed by the condensation of di-isocyanates (derived from... 

Stepwise polymerization includes most condensation processes, but also some reactions involving ring opening, and even addition reactions (typified by the formation of polyurethane from a di-isocyanate and a di-alcohol). The viscosity serves as a sensitive indication of the growth of the polymer. Therefore, in stepwise polymerization the viscosity of the system increases slowly and reaches high levels only toward the end of the reaction. In chain polymer-... 

The SMMs were synthesized using a two-step solution polymerization method (Carman 1956 Fang et al. 1994 Khayet et al. 2005a,b Suk et al. 2006 Qtaishat et al. 2009a,b). The solvent DMAc was distilled at about 25°C under a pressure of 133.3 Pa. Methylene bis(j)-phsay isocyanate) (diphenylmethane diisocyanate MDI) was also distilled at 150°C under 66.7 Pa (0.5 Torr). PPG, a,a)-aminopropyl PDMS, and 2-(perfluoroalkyl)ethanol (FAE) were degassed for 24 h under 66.7 Pa. The first polymerization step was conducted in a solution with a predetermined composition to form polyurethane from the reaction of MDI with PPG or to form polyurea from the reaction of MDI with PDMS as a prepolymer. In the second polymerization step, the prepolymer was end-capped by the addition of FAE, resulting in a solution of SMM. 

Polymeric polyisocyanate n. A generic term for a family of isocyanates derived from aniline-formaldehyde condensation products, used as reactants in the production of polyurethane foams. 

Chemically reactive polyurethanes include both one- and two-component systems. One-component systems are usually based on a polyether polyol treated with a polyisocyanate to give an isocyanate-terminated polymer. A one-component system cures when exposed to moisture at room temperature. One-component polyurethane hot-melt adhesives are also cured by moisture after application. Two-component systems result from the reaction of low molecular mass polyols and isocyanates or from isocyanate-terminated prepolymers with either polyols or polyamines. Two-component systems cure at room and/or elevated temperatures. 

Figure 7.2 Synthesis of diol cured polyurethane from monomeric diol and isocyanate terminated prepoiymer...

Figure 7.3 Synthesis of diamine cured polyurethane from isocyanate terminated prepoiymer and monomeric diamine...

It was also noted that water-based release agents may affect polyurethane surface properties because of chemical reaction between water and isocyanate groups. From this reaction carbon dioxide is formed in the surface layers of the part, which creates small voids beneath the surface. ... 

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