HIGH GLASS TRANSITIONS OF HIGH-PERFORMANCE THERMOPLASTICS

Demand of high-performance engineering thermoplastics in industrial co untries drives the development of this class of materials in over 30 y ears. They display high heat distortion temperature, high modulus and strength, dimensional stability, chemical resistance, inherent flame r etardancy and share the commonality of high glass transition. The obse rved variations of T-g with composition are compared with the postulat ed using Van Krevelen's structural group contribution theory. The pred icted T-g does not differentiate the variations affected by moisture a nd crystallinity. The 'wet' T-g's are determined by modulated temperat ure-DSC (MT-DSC), while the 'dry' or the constained T-g due to orienta tion and/or annealing is detectable by standard DSC. The glass transit ions of the constrained domains in highly crystalline polymers can be followed by DMA, DEA and thermal expansibility. (C) 1998 Elsevier Scie nce B.V.