Crystalline insulating polymer

PET is a semi-crystalline thermoplastic polymer used in the manufacture of fibres, packaging films, bottles, electrical insulators, etc. As shown in Scheme 2.1, PET can be produced by two different routes by condensation between terephthalic acid (TPA) and ethylene glycol (EG) or through the reaction of dimethyl terephthalate (DMT) with ethylene glycol. Both alternatives lead to the monomer bis(hydroxyethyl) terephthalate (BHET), which is further polymerized into PET. 

Potential applications of liquid crystalline templated polymer gels range from separation media (membranes, chromatography columns, or electrophoresis gels) to low dielectric constant insulators for microelectronic devices, to nano-structured optoelectronic devices, to catalysts supports, drug carriers, or materials for controlled release. 

Why should the enzymes be stable in polymer melt whereas they quickly deactivate in water or dry form We postulate a proposed mechanism, shown in Figure 9, for excellent thermal stability of molded strips. We speculate the enzyme is surrounded very tightly by coils of PHEMA at room and elevated temperatures. Temporary melting of the crystalline insulator regions of the... 

Lu G, Tang H, Qu Y, Li L, Yang X (2007) Enhanced electrical conductivity of highly crystalline polythiophene/insulating-polymer composite. Macromolecules 40 6579-6584... 

A 50 50 mol/mol copolymer of hexafluoroisobutylene (CH2 = C(CF3)2) and vinylidene fluoride was made available by Allied Chemical in the mid-1970s as CM-1 Fluoropolymer. The polymer has the same crystalline melting point as PTFE (327°C) but a mueh lower density (1.88g/cm ). It has excellent chemical resistance, electrical insulation properties and non-stiek characteristics and, unlike PTFE, may be injeetion moulded (at 380°C). It is less tough than PTFE. 

Materials of these types have T s of some 290-300°C and some grades are claimed to be stable to about 400°C. Whilst resistant to hydrocarbons, halogenated hydrocarbons, ethers and acids the polymers are soluble in such materials as dimethylformamide, N-methylpyrrolidone and pyridine. Bases can cause stress cracking. These non-crystalline polymers are tough at temperatures as low as -46°C whilst at 260°C they have the strength shown by PTFE at room temperature. The polymers also exhibit excellent electrical insulation properties. 

Although it is a polar polymer, its electrical insulating properties at room temperature are good even at high frequencies owing to the fact that since room temperature is well below the transition temperature dipole orientation is severely restricted. Some data on the crystallinity of poly(ethylene terephthalate) are presented in Table 25.5. 

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