Elastomeric Polyamides

A semicOTitinuous manufacturing process in which two liquid compmients are metered in the calculated ratio by high pressure piston pumps, mixed by impingement mixing and injected into a mold cavity or cavities, where the reactants are polymerized or cured. The process has been used to polymerize polyamides, elastomeric polyurethanes, and polyurethane foams. 

Uses Detergent with high foaming and soil-suspending props, for scouring cotton/ elastomeric and polyamide/elastomeric blends... 

Elastomeric adhesives Elastomeric copolymei Elastomeric fibers Elastomeric polyamide... 

Other elastomeric-type fibers iaclude the biconstituents, which usually combine a polyamide or polyester with a segmented polyurethane-based fiber. These two constituents ate melt-extmded simultaneously through the same spinneret hole and may be arranged either side by side or ia an eccentric sheath—cote configuration. As these fibers ate drawn, a differential shrinkage of the two components develops to produce a hehcal fiber configuration with elastic properties. An appHed tensile force pulls out the helix and is resisted by the elastomeric component. Kanebo Ltd. has iatroduced a nylon—spandex sheath—cote biconstituent fiber for hosiery with the trade name Sidetia (6). 

Cycloahphatic diamines react with dicarboxyUc acids or their chlorides, dianhydrides, diisocyanates and di- (or poly-)epoxides as comonomers to form high molecular weight polyamides, polyimides, polyureas, and epoxies. Polymer property dependence on diamine stmcture is greater in the linear amorphous thermoplastic polyamides and elastomeric polyureas than in the highly crosslinked thermo set epoxies (2—4). 

Use of 1,3 cycloaHphatic diamines in polyamides may be similarly limited by internal amide dehydration of the conformationaHy labile cis isomers to form a tetrahydropyrimidine (38) rather than high molecular weight polyamide. 1,3-Cyclohexanediamine is, however, a component of Spandex polyureas Du Pont uses the hydrogenation product of y -phenylenediamine [108-45-2] (24) captively to produce Lycra (see Fibers, elastomeric). 

Applications of the elastomeric polyamides include keyboard pads, sports footwear, loudspeaker gaskets and, in the case of filled grades, watch straps. 

The mechanical and thermal behaviors depend partly on the degree of crystallinity. For example, highly disordered (dominantly amorphous) polymers make good elastomeric materials, while highly crystalline polymers, such as polyamides, have the rigidity needed for fibers. Crystallinity of polymers correlates with their melting points. 

Jha A., Bhowmick A.K., Eujitsuka R., and Inoue T. Interfacial interaction and peel adhesion between polyamide and acrylate rubber in thermoplastic elastomeric blends, J. Adhes. Sci. Technol., 13(6), 649, 1999. 

Both low molecular weight materials [145] and polymers [146,147] can show liquid crystallinity. In the case of polymers, it frequently occurs in very stiff chains such as the Kevlars and other aromatic polyamides. It can also occur with flexible chains, however, and it is these flexible chains in the elastomeric state that are the focus of the present discussion. One reason such liquid-crystalline elastomers are of particular interest is the fact that (i) they can be extensively deformed (as described for elastomers throughout this chapter), (ii) the deformation produces alignment of the chains, and (iii) alignment of the chains is central to the formation of liquid-crystalline phases. Because of fascinating properties related to their novel structures, liquid-crystalline elastomers have been the subject of numerous studies, as described in several detailed reviews [148-150]. The purpose here will be to mention some typical elastomers exhibiting liquid crystallinity, to describe some of their properties, and to provide interpretations of some of these properties in molecular terms. 

These materials exhibit the same type of morphology as the copolyether esters, the polyamide providing the hard segment, and the polyester the soft elastomeric phase. The service temperature is lower than that of the copolyether esters, but apart from this difference they exhibit similar properties. 

Elastomeric polyurethane fibers [96, pp. 609-615], are contained in stretch articles and in knitted fashion materials. Light shades can be dyed tone-on-tone on polyamide-polyurethane mixtures with disperse dyes at 95-98°C and pH 6-7. However, the wetfastness of these dyeings on polyurethanes is lower than on polyamide. Because of the temperature sensitivity of polyurethane fibers, mixtures of elastomeric and polyester fibers must be dyed with small-molecular, rapidly diffusing disperse dyes in 30 min at 120 °C according to the HT process [148], Modified PES fibers that are dyeable at 100°C without a carrier are often used in mixtures with elastomeric fibers. In all dyeing processes for elastomeric fibers, dyeing equipment that permits low-strain guidance of the material and the lowest possible thermal stress are important. 

The thermal stability of elastomeric polyacetaldehyde could be improved by end-capping the hydroxyl end groups with acetic anhydride in order to prevent chain unzipping. Further stabilization was obtained by adding polyamide as a thermal stabilizer and an aromatic amine antioxidant. 

The elastomeric polyamides are relatively expensive (for Pebax about 10.00/kg for low-quality grades and about 17.00 for high-quality grades for Grilamid ELY the prices are almost double), but because in finished articles the density is lower, the wall thickness much lower, and the molding cycles shortened, the final cost may be lower than that of corresponding goods in rubber. 

Thermoplastic elastomers are most commonly formulated from elastomeric polyurethane or block copolymers of polystyrene-elastomer, polyamide-elastomer, or polyether-elastomer bases. Thermoplastic elastomers are provided as a raw material in pelletized form for subsequent compounding. The internal domain structure that is required for thermoplastic-elastomeric performance has been established by specific considerations of blending and structural-chemical interactions. In compounding operations, specific temperature ranges are required to assure that phase separation does not occur in the TPE base polymer. 

The preparation of polyamides having metallocenes incorporated into the backbone can be achieved by the use of bifunctional ferrocene derivatives, such as diacid chlorides or diamines. In the following, a few examples of such reactions are presented. In the early 1960s Knobloch and Rauscher reported the preparation of polyamides and polyesters by the reaction of 1,1 ferrocenyldicarbonyl chloride 14 with several diamines and diols by interfacial polycondensation.80 The synthesis of elastomeric polyamides 54a, Mn = 10,000-18,000) in high yields was reported by Rausch and co-workers from 1,1 -bis((3-aminoethyl)ferrocene 53 and diacid chlorides (Scheme 12.11). The reaction with bis-isocyanates allows the formation of ferrocene-containing polyureas 54b. 

Scheme 12.11 Synthesis of elastomeric polyamides from 1,1 -bis((5-aminoethyl)ferrocene 53 and diacid chlorides, (i) (i CO R CO—Cl (ii) OCN—R —NCO.

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