Thermoplastic elastomers , glass

The strategies used to produce block polymers can be well demonstrated with the example of a three-block polymer, (styrene)m(butadiene) (styrene)m, which is commercially available as a thermoplastic elastomer. This three-block polymer can best be produced in a two-stage process with bifunctional initiators. Sodium naphthalide or dilithium compounds can be used as initiators (see Section 18.1). Styrene is added on to the dianion produced, B , and SmBnS is formed. The initiators mentioned above, however, are only effective in tetrahydrofuran and other ethers. But butadiene blocks of only limited c/5-1,4 content are produced in these solvents, and this has an undesirable effect on the thermoplastic elastomer (glass transition temperature is too high). Consequently, well-dissolving aromatic dilithium compounds are preferably used in the presence of small amounts of aromatic... 

Casting resin Thermoplastic elastomer Cast resin, flexible Mineral- and/or glass-filled Epoxy molding and encapsulating compound Polystyrene... 

Ethylene-norbomene copolymers of interest as thermoplastics were discussed in Section 11.6.2. It is however to be noted that copolymers with a norbomene content of about 30 wt% have a glass transition temperature of about 0°C and that copolymers with norbomene contents up to this amount are being evaluated as thermoplastic elastomers... 

Table I serves to illustrate how the nature and size of the substituent attached to the P-N backbone can influence the properties of the poly(organophosphazenes). The glass transition temperatures range from -84 °C for (NP CH-CH ) to around 100 °C for the poly(anilinophosphazenes). Polymers range from elastomers to flexible film forming thermoplastics or glasses at room temperature.

Thermoplastic elastomers (TPE), 9 565-566, 24 695-720 applications for, 24 709-717 based on block copolymers, 24 697t based on graft copolymers, ionomers, and structures with core-shell morphologies, 24 699 based on hard polymer/elastomer combinations, 24 699t based on silicone rubber blends, 24 700 commercial production of, 24 705-708 economic aspects of, 24 708-709 elastomer phase in, 24 703 glass-transition and crystal melting temperatures of, 24 702t hard phase in, 24 703-704 health and safety factors related to, 24 717-718... 

T [Tick] free Tm TMPCl TPE o Glass transition temperature Concentration of free and uncomplexed TiCl4 Melting temperature 2-Chloro-2,4,4-trimethylpentane Thermoplastic elastomer Tensile strength... 

A comparatively new group of materials— thermoplastic elastomers or thermoplastic rubbers —combines the ease of processing of thermoplastics with qualities of traditional vulcanized rubbers, especially elasticity. Because of convenience in processing there is much interest too in blends of plastics with elastomers, which may be modified by the inclusion of filler or glass fibre. As an example, a rubber-like material that can be processed as a thermoplastic can be made by blending and melt-mixing an ethylene-propylene rubber with polypropylene. The use of such blends may be helpful when there are needs to reclaim and re-process material, and in order to obtain products with qualities intermediate between those of the main components of the blends. 

Before BASF investigated this product, Quirk and Hsieh [1], Yuki and coworkers [2,3] and Fischer [4] carried out investigations with this monomer. The first two used the anionic polymerization mechanism and Fischer tried to copolymerize this monomer using free radical polymerization. In the latter case the yields were very low. The use of S/DPE blocks in thermoplastic elastomers [5] has also been briefly described. Some of the work carried out at BASF has been published in a recent review article [6], Owing to the enhanced thermal properties of this copolymer in comparison with atactic polystyrene - the glass transition temperature increases up to 180 °C, depending... 

Copoly(ester ester)s belong to the family of thermoplastic elastomers (TPEs) and consist in general of thermo-reversible hard and elastic soft domains [11]. The copoly(ester ester) used here consists of 60% poly(butylene terephthalate), 35% poly(butylene adipate) and 5% 4,4 -methylenebis(phenyl isocyanate), and shows domain sizes of about 20 nm [12]. The material possesses a rubber plateau between the glass transition temperature of the mixed amorphous PBA/PBT phase (the PBT phase is semi-crystalline) at about -30°C and the melting point of the PBT at about 220°C. Due to the vulnerability of the amorphous PBA/PBT soft domains towards water attack [13] the PBT/PBA copoly(ester ester) is used here to study the existence of ESC of a chemical rather than a physical nature. For the sake of clarity it should be emphasized that no additives have been used in the copoly(ester ester) described here. 

Table 5.5. Composition, pretreatment, crystallinity, glass transition temperature Tg and experimental and calculated microhardness values, Hg p, and Hgai and their difference AH = Hgai — Hg p for thermoplastic elastomers of PEE-or PEEC-type. 

Modification of polymers by incorporating block sequences having low glass transition tenperatures is a means of changing the mechanical properties and is especially useful for the formation of thermoplastic elastomers if the basic pol3nner is semi-crystalline. These rubber-like blocks are usually formed by ionic or transition metal catalyzed reactions. Radical pol3nmeri-zation on the other hand is experimentally simpler and applicable to a wide variety of monomers. 

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