Melting points and heats of fusion of some polyamides and polyesters

Abstract

Abstract Melting points of three polyamides, four polyesters, and their mixtures with diluents have been determined by application of dilatometry to observe the latent volume change during gradual melting extending over many days in each case. Heats of fusion were calculated from the depressions of the melting point by varying volume fractions of diluents. The results, given in °C. and in cal./g., respectively, are as follows: decamethylene sebacamide, 216°, 24.5; decamethylene azelamide, 214°, 27; the sebacamide of 1,10‐dipiperazyldecane, 129.5°, 34.5; decamethylene azelate, 69°, 31; nonamethylene azelate, 65°, 33; decamethylene terephthalate, 138°, 36; hexamethylene terephthalate 160.5°, 34. The results are compared with those previously reported for related polymers. A possible explanation is suggested for the fact that the heats of fusion of polyesters exceed those for the corresponding polyamides. High melting points appear to be associated with low entropies of fusion rather than with high heats of fusion.