Poly thermoplastic, reversible

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. 

In the major thermoplastics, there was more rapid price erosion than had been anticipated, accompanied by phenomenal growth in volume but serious degradation of profits. Statistical studies have indicated that individual plastics frequently have a price elasticity factor of 2 to 3 i.e.f a 1% price decline resulted in a 2 to 3% volume increase. The effect upon profits, however, was often just the reverse as the expanding volume was not sufficient to compensate for the drastically reduced profit margin. In some areas, such as low density polyethylene and general purpose poly-... 

Thermoplastic resins can be introduced into wood either in solution or as liquid monomers, which are then polymerized in situ (2, 3). Cross-linking agents can be included with the monomer to produce a thermosetting resin upon polymerization, initiated by heat, catalyst, or 7 irradiation (4), Even if there is no cross-linking, the prospects for reversibility are not very good for such systems (3). Surface residuals of poly(methyl methacrylate), polystyrene, and polyester mixtures could only be removed with some diflSculty with solvents (5). The present discussion will be limited to thermoplastic resins that can be introduced into wood in solution. 

Urry. D. W. Jaggard, J. Prasad, K. U. etal. Poly(Val1-Pro2-Ala3-Val4-Gly5) A Reversible, Inverse Thermoplastic Plenum Press New York, 1991 p 265. 

Abstract Poly(trimethylene terephthalate) (PTT) fibers, as a new type of polyester, are characterized by much better resilience and stress/recovery properties than poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT). PPT chains are much more angularly structured than PET and PBT chains and such chains can be stretched by up to 15% with a reversible recovery (Ward et al. 1976). These properties make PTT highly suitable for uses in fiber, carpet, textile, film, and engineering thermoplastics applications. 1,3-Propanediol (PDO), as one of the polyester raw materials for PTT, has also attracted interest. 

A novel class of materials, which employ metal-ligand binding as a reversible, dynamic interaction, was reported in 2005 by Rowan, Beck, and Ineman. Thermoplastic elastomeric films were formed from a telecheUc poly-THF, end-capped with a terdentate ligand such as 2,6-bis(F-methylbenzimidazolyl)-4-oxypyridine (12), which enabled chain-extension by coordination to a range of metal(ll) centers (Figure 21). 

An early, and widely used, commercial example of side-chain functionalities inducing interactions between polymer chains are ionomers, hydrocarbon macromolecules bearing, for example, carboxylic acid groups [e.g., poly(ethylene-co-methacrylic acid)], which are partially or fuUy neutralized with metal or quaternary ammonium ions. These ionomers are thermoplastic ionic polymers boasting unique physical properties such as enhanced impact strength, toughness, and thermal reversibility. They were developed and commercialized by DuPont, and have recently attracted attention due to their self-healing properties. ... 

S. Fakirov, C. Fakirov, E. W. Fischer, M. Stamm and A. A. Apostolov, Reversible morphological changes in poly (ether ester) thermoplastic elastomers during deformation as revealed by SAXS, Colloid. Polym. Set., 271 811-823,1993. 

Poly(propylene terephthalate) (PPT), the first and most studied polyester of 1,3-propanediol, is available in the market [2]. The polymer is suitable for industrial fiber production. PPT fibers are characterized by much better resilience and stress/recovery properties than PET and PBT. These properties are due to the crystal structure of PPT. PPT chains are much more angular structured than PET and PBT chains due to the odd number of methylene groups of the diol segment. Therefore these chains can be stretched up to 15% with a reversible recovery [3]. PPT is anticipated to gain a significant share in the thermoplastic polyesters market in the next years. However, like the other terephthalate polyesters, PPT is not susceptible to degradation in the environment. 

Thermoplastics soften when heated (and eventually liquefy) and harden when cooled — processes that are totally reversible and may be repeated. On a molecular level, as the temperature is raised, secondary bonding forces are diminished (by increased molecular motion) so that the relative movement of adjacent chains is facilitated when a stress is applied. Irreversible degradation results when a molten thermoplastic polymer is raised to too high a temperature. In addition, thermoplastics are relatively soft. Most linear polymers and those having some branched structures with flexible chains are thermoplastic. These materials are normally fabricated by the simultaneous application of heat and pressure (see Section 15.22). Examples of common thermoplastic polymers include polyethylene, polystyrene, poly(ethylene terephthalate), and poly(vinyl chloride). 

The hydrosilylation reaction has also been employed in the reverse way. A poly(dimethyl-siloxane) backbone exhibiting a number of silane (Si-H) functions is reacted with a polystyrene or a poly(methyl methacrylate) fitted at its chain end with allyloxy groups. The latter species can be obtained readily by reacting a living anionic polymer first with oxirane and then with allyl bromide. The hydrosilylation reaction yields poly(dimethylsiloxane- ra/t-styrene) or poly(dimethylsiloxane-graft-mQthyl methacrylate), which have been characterized as such. They exhibit typical behavior of thermoplastic elastomers over a rather broad range of compositions. ... 

Muramatsu S and Lando J B (1998) Reversible crystal deformation of poly(tetra-methylene terephthalate) segments in semicrystalline segmented poly(ether-ester) thermoplastic elastomers, Macromolecules 31 1866-1870. 

Balth Calleja F J, Boneva D, Krumova M and Fakirov S (1998) Microhardness under strain. 4. Reversible microhardness in polyblock thermoplastic elastomers with poly(butylene terephthalate) as hard segments, Macromol Chem P/it/s 199 2217-2220. 

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