Transition and relaxation processes in ω-amino acid polyamides

Abstract

Differential thermal analysis has been used to study the thermal transitions that occur on heating efficiently quenched samples of ω-amino acid polyamides. With ‘even’ amino acid polyamides (nylons-4, -6, -8, etc.) an endothermic type of transition was observed in the region of 30–40°C; this was followed immediately by an exothermic transition. No such transitions were observed with the ‘odd’ polyamides (nylons-5, -7, -11, etc.). From X-ray diffraction spectra and structural considerations, these transitions have been shown to be associated with the formation of hydrogen-bonded structures, that are possible with ‘even’ polyamides, but not with the ‘odd’ members. From a combination of differential thermal analysis, density and X-ray diffraction data, a new picture of the low temperature crystallization behaviour of this type of polyamide has emerged.