Transitions and relaxations in poly(1,4-phenylene ether)

✍ Scribed by Wrasidlo, Wolfgang

• Publisher: Wiley (John Wiley & Sons)
• Year: 1972
• Tongue: English
• Weight: 479 KB
• Volume: 10
• Category: Article
• ISSN: 0449-2978
• DOI: 10.1002/pol.1972.160100908

✦ Synopsis

Abstract

Transitions and relaxation phenomena in poly(1,4‐phenylene ether) were studied over temperature range from 100 to 800°K by applying a combination of calorimetric, dilatometric, dynamic mechanical, and dielectric techniques. Amorphous polymer, exhibiting no x‐ray crystallinity, is obtained only by quenching molten samples at extremely fast cooling rates (ca. 1000°C/sec) and by minimizing thermal gradients within specimens. A weakly active mechanical relaxation region with a loss maximum at 155°K of unknown origin was observed. The glass transition interval of completely amorphous polymer is characterized by a discontinuous jump in heat capacity of 2.76 cal/deg per chain segment occurring at 363°K (corrected for kinetic effects), and a fourfold increase in the coefficient of linear thermal expansion. Strongly active, dynamic mechanical relaxations occur in the T~g~ interval with a loss maximum at 371°K (f = 110 cps) and resulting in a drop in the dynamic storage modulus from 10^11^ to 10^9^ dyne/cm^2^. Cold crystallization takes place just above T~g~, to yield a polymer with an x‐ray crystallinity of 0.7 and a heat of crystallization of 270 cal/mole. The crystalline polymer shows a complex melt structure. Depending upon the thermal history, multiple endothermic peaks indicative of structural reorganizations occur just prior to fusion. Very high dielectric losses with a wide distribution of relaxation times were observed in the melt interval. The mechanical relaxation spectrum in this region is typical of viscous flow behavior.