Polyurethane/polyurea

In addition to the primary appHcation of PTMEG ia polyurethanes, polyureas, and polyesters, a considerable number of reports of other block and graft polymers highlighting PTME units have appeared. Methods have been developed that allow the conversion of a cationicaHy polymerizing system to an anionic one or vice versa (6,182). 

MCHD from ring reduction of I DA (60,78) has been cited as an epoxy curative (79) and is available from Air Products and Chemicals as a developmental cycloaHphatic diamine. Ring reduction of stericaHy hindered arylenediamines such as diethyltoluenediamine [68479-98-1J -ptovides slower-reacting alkylated 1,3-cyclohexanediamines for polyurethane, polyurea, and epoxy use (80). 

Almost all IDA derived chain extenders are made through ortho-alkylation. Diethyltoluenediamine (DE I DA) (C H gN2) (53), with a market of about 33,000 t, is the most common. Many uses for /-B I DA have been cited (1,12). Both DE I DA and /-B I DA are especially useful in RIM appHcations (49,53—55). Di(methylthio)-TDA, made by dithioalkylation of TDA, is used in cast urethanes and with other TDI prepolymers (56). Styrenic alkylation products of TDA are said to be useful, eg, as in the formation of novel polyurethane—polyurea polymers (57,58). Progress in understanding aromatic diamine stmcture—activity relationships for polyurethane chain extenders should allow progress in developing new materials (59). Chlorinated IDA is used in polyurethane—polyurea polymers of low hysteresis (48) and in reinforced polyurethane tires (60). The chloro-TDA is made by hydrolysis of chloro-TDI, derived from TDA (61). 

In a yet further variation of the process developed by Shell, diethanolamine (HOCH2CH2NHCH2CH2OH) is used instead of hydrazine and this leads to what is referred to as a polyurethane/polyurea supension. 

The nature of a hydrophilic prepolymer permits the addition of large amounts of water. The isocyanate reacts with the water to abstract COt. The amine that also results from the reaction then reacts with an isocyanate group to produce a urea linkage. The reaction continues until the water or the isocyanates are consumed. If provisions are made to trap the CO2 in the mass, a foam is produced. If such provisions are not made, the CO, will bubble away, leaving behind a low gel-strength hydrogel. Careful examination of the resultant molecule might cause one to rename it a polyurethane/polyurea. 

A sample polymerization reaction, showing the synthesis of a polyurethane, is shown equation 3. Using similar synthetic strategies, various polyurethanes, polyureas (eq. 4), and polyamides (eq. 5) have been synthesized.14-17 Note that the step polymers in these reactions have a metal-metal bond in every repeat unit. Copolymers are straightforwardly synthesized by adding appropriate difunctional organic molecules into the reaction mixture (e.g., eq. 6). 

When the prepolymer chain is extended with a diol, the polymer formed has only urethane linkages. The polymer formed with the diamine chain extender is strictly a polyurethane polyurea. The first urethane component is from the initial chain extension when the prepolymer is prepared. A diamine curative will form urea linkages (Figure 2.3) between chains. 

Low modulus elastomers are materials that have found wide use in the automobile industry for fascia, bumper covers, and trim parts. Other applications include integral window seals and a wide variety of applications where it is replacing molded rubber. Most of these materials are not pure polyurethane, but polyurethane/polyurea hybrids with improved processing and properties when compared with the earlier allurethane systems. 

Properties of fibers can be altered by carrying out interfacial polymerizations on their surfaces. Thus the shrink resistance of wool can be improved by immersing the fiber first in a solution containing one component of a condensation polymer and then immersing it in another solution containing theother component. Polyamides, polyurethanes, polyureas, and other polymers and copolymers may be grafted on wool in this manner. 

Today a vast range of BP classes are available, including polyesters, polyamides, polyurethanes, polyureas, polyethers, polyanhydrides, poly(orthoester)s, polypeptides,... 

Scheme 1.10. Formation of urethane prepolymer and subsequent reaction with a diol or diamine extender to give a polyurethane or a polyurethane-polyurea. Adapted from Hepburn (1982).

This prepolymer (Scheme 1.10) is then reacted with a chain-extender diol or diamine to give the final polyurethane or polyurethane-polyurea block copolymer, respectively. The diversity in properties that the final urethane block copolymers exhibit is governed by the nature of the three building blocks the diol-terminated polyester, the di-isocyanate-terminated polyurethane and the chain extender (Hepburn, 1982). As shown in Figure 1.17, these form flexible blocks (from the polyester) that undergo phase segregation as structures of size 1000-2000 nm. 

Preparation Methods for Condensation Polymers Polyamides Polyesters Polyimides Polyurethanes Polyureas Polycarbonates Polyanhydrides... 

The term "condensation polymers" was introduced by W. H. Carothers in his early work on the preparation of polyesters and polyamides to distinguish this class of polymers from vinyl polymers made by addition reactions. Condensation polymers were defined as polymeric molecules that may be converted by hydrolysis, or its equivalent, into monomers that differ from the structural units by one molecule of H2O, HCl, NHj, etc. This broad definition includes many polymers made by ring-opening or addition reactions, for example, lactone and lactam polymers, polyurethanes, polyureas, polyimides, and polyhydrazides, as well as polymers made by true condensation reactions. 

Polyamides Polyurethanes Polyureas Amino-plastics Polyacrylonitrile and copolymers Polyvinyl-carbazole Polyvinylpyrrolidone... 

Heinrich, R. Erensch, H. Albrecht, K. Pressure-resistant microcapsules with a polyamide outer shell and an inner composition structured by polyurethane-polyurea and their use. DE 3020781, 1981. 

The photochemistry above has been demonstrated with a variety of polymers, including polyurethanes, polyureas, vinyl polymers, and polyamides (e.g., see structure I). 

Van An twerp WP. 1999. Polyurethane/polyurea compositions containing silicon for biosensor membranes. United States Patent 5,882,494. 

Condensation polymers can be regarded as a sequence of monomer units containing fxmctional groups immobilized into the polymer structure. Their decomposition pathways will often be dominated by the polarity and by the reactivity of the fxmctional groups within their structure, and their thermal decomposition reactions will be ionic and selective, rather than radical and imselective. Such are the thermal degradation processes occurring in polyesters, polyamides, polycarbonates, polyurethanes, polyureas, and in several other cases. ... 

The thermostability of these dianhydroalditol monomers may be higher than that of other aliphatic diols, which raises the Tg of the corresponding polymers. The most representative dianhydroalditol-based polymers that have been synthesized are polyesters, polycarbonates, polyethers, poly(ester carbonate)s, poly(ester anhydride)s, polyurethanes, polyureas, and poly(ester amide)s. 

Table 6.1. gives examples of some nonlinear chromophores. These nonlinear opties ehromophores are intended for incorporation into polyimides, polyurethanes, polyureas, and polyamides. Among them are some promising chromophores that were reported by Jen and coworkers. ... 

In analogy to isocyanate crosslinking, which mimics polyurethane/polyurea chemistry, epoxy glue chemistry has also been adopted for crosslinking, whereas amine-modified silica reacts with multifunctional epoxies [61]. Epoxide-crosslinked aerogels based on the... 

Microcapsules with desired release rates according to the application involved can be prepared by incorporating a selected fluid (solvent), while keeping the other capsule parameters constant. These fluids include dearomatized and isoparaffinic hydrocarbons, aromatic hydrocarbons, acetate derivatives, and blends of these [51], In the preparation of polyurethane-polyurea microcapsules containing hep-tenophos (liquid pesticide, b.p. 64 °C), it has been reported that the porosity of microcapsules can be controlled by the addition of 2-ethoxy ethyl acetate or ethyl acetate in the organic phase containing isocyanate prepolymer and pesticide [52]. 

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