Polyether-elastomer block copolymers

Table 6. Trade Names of Multiblock Thermoplastic Elastomers Based on Polyurethane/Elastomer, Polyether/Elastomer, and Polyamide/Elastomer Block Copolymers...

In contrast, organophilic PV membranes are used for removal of (volatile) organic compounds from aqueous solutions. They are typically made of rubbery polymers (elastomers). Cross-linked silicone rubber (PDMS) is the state-of-the-art for the selective barrier [1, 43, 44]. Nevertheless, glassy polymers (e.g., substituted polyacetylene or poly(l-(trimethylsilyl)-l-propyne, PTMSP) were also observed to be preferentially permeable for organics from water. Polyether-polyamide block-copolymers, combining permeable hydrophilic and stabilizing hydrophobic domains within one material, are also successfully used as a selective barrier. 

T nterest in polyether-ester block copolymers that are both thermoplastic - and elastomeric continues at a sustained pace (1-9). Most of the recent communications have dealt with the tetramethylene terephthalate/ poly(tetramethylene ether) terephthalate copolymers which are continuing to find increased use in commercial applications requiring thermoplastic elastomers with superior properties. 

Thomas and co-workers [1986] studied effects of gamma-irradiation on a thermoplastic elastomer, TPE, a polyether-ester block copolymer from 1,4-butanediol, polybutylene glycol and terephthalic acid (Hytrel D40), TPE, and its blends with PVC, in air, at doses of 1, 10, 100 and 500 kGy. Visual inspection of the samples showed no color change up to 500 kGy, but the samples irradiated at 500 kGy showed surface cracks. 

TPE-E Thermoplastic polyether ester elastomer Block copolymer... 

Hytrel Thermoplastic polyether-ester block copolymer elastomers, 1,4-butanediol-polybutylene glycol-terephthalic acid copolymer, TPE E. I. du Pont de Nemours... 

The fiber used in this study was Twaron 2200 a poly(p-phenylene terephthalamide) (PPTA) aramid fiber, supplied by Akzo Nobel Research (Arnhem). The fibers have modulus Ef= 136 GPa, tensile strength, thermoplastic elastomer, polyether amide block copolymer supplied by Atofma known commercially as Pebax . These thermoplastic elastomers (TPE) consist of linear chains of hard polyamide (PA) blocks covalently linked to soft polyether (PE) blocks via ester groups. The grade of Pebax used was Pebax 7033, with a modulus Eva. = 128 MPa, yield stress ay = 32 MPa, Yield strain ey = 25 %, ultimate failiue stress a m = 67 MPa and an ultimate strain e m = 400 %. 

All these elastomers, especially poly(ethylene- (9-butylene) and poly(ethylene- (9-propylene), are nonpolar. The corresponding block copolymers can thus be compounded with hydrocarbon-based extending oils, but do not have much oil resistance. Conversely, block copolymers with polar polyester or polyether elastomer segments have Htde affinity for such hydrocarbon oils and so have better oil resistance. 

Block copolymers may also be made by condensation polymerization. Elastomer fibers are produced in a three-step operation. A primary block of a polyether or polyester of a molecular weight of 1000-3000 is prepared, capped with an aromatic diisocyanate, and then expanded with a diamine or dihydroxy compound to a multiblock copolymer of a molecular weight of 20,000. The oxidative coupling of 2,6-disubstituted phenols to PPO is also a condensation polymerization. G. D. Cooper and coworkers report the manufacture of a block copolymer of 2,6-dimethyl-phenol with 2,6-diphenylphenol. In the first step, a homopolymer of diphenylphenol is preformed by copper-amine catalyst oxidation. In the second step, oxidation of dimethylphenol in the presence of the first polymer yields the block copolymer. 

Block copolymers were developed rapidly in the 1960s when living anionic polymerization was first utilized to synthesize triblock thermoplastic elastomers or elastoplastics. At the same time, step or condensation polymerization to produce thermoplastic polyurethanes, urea-urethane spandex fibers, and later more specialized materials, such as the semicrystalline polyester-polyether copolymers were developed [10]. Imide block or segmented copolymers utilizing... 

Polyetheramide. These thermoplastic elastomers are typically block copolymers of polyether rubber with nylon crystalline domains. 

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. 

Commercial copoly(ether-ester) elastomers (e.g., Hytrel , DuPont Lomod , GEC) are segmented block copolymers containing a polyether soft segment such as poly(tetramethylene oxide) and a hard segment that is chemically identical to polybutylene terephthalate. When the soft segment is > 50%, these block copolymers exhibit... 

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