EFFECT OF BLOCK MOLECULAR-WEIGHT ON THE MECHANICAL AND DYNAMIC-MECHANICAL PROPERTIES OF SEGMENTED POLYAMIDE

Segmented polyamides also known as polyether-ester-amides, are compose d of polyether and polyamide structural units. Dynamic mechanical meas urements of these polymers have been carried out over a wide range of temperatures. The polymers with hard block molecular weight of 7400 an d 4100 exhibit three peaks, designated as alpha, beta and gamma in the tan delta-temperature curve. At a constant soft segment molecular wei ght of 1000, the alpha transition shifts to lower temperature and merg es with beta transition, with decreasing hard block molecular weight. The damping also increases. However, at a constant hard block molecula r weight of 1100, though the alpha and beta transitions merge together , the damping decreases on increasing the soft segment molecular weigh t. The mechanical properties and percent crystallinity decrease with d ecrease in hard block molecular weight or increase in soft segment mol ecular weight. The polymers with hard block molecular weight of 7400 a nd 4100 exhibit a higher set values and yielding characteristics. The results on dynamic mechanical studies are explained with the help of t he segmented structure of the block copolymers. (C) 1998 Elsevier Scie nce Ltd. All rights reserved.