An X-ray study of the influence of processing and thermal treatment on polycaproamide

Wide-angle X-ray scattering has been used to study the crystalline structure and some structural properties of untreated and thermally treated samples of polycaproamide obtained by hydrolytic and anionic polymerisation of caprolactam. For untreated samples of polycaproamide two crystalline forms exist: a stable alpha-monoclinic form and an unstable gamma*-pseudohexagonal modification. There are initial differences in the crystalline parameters of polycaproamide, i.e. content of alpha- and gamma*-form, degree of crystallinity and size of lamellae. A more ordered structure has been observed for samples obtained by anionic polymerisation. Both temperature and duration of annealing have a considerable influence on the polymorph transition of the unstable gamma*-pseudohexagonal crystalline form into the stable alpha-crystalline form, on the degree of crystallinity and on the lamellar thickness. It was found that the largest change in these parameters occurred at an annealing temperature at the lower end of the melting point range of polycaproamide. (c) 2006 Society of Chemical Industry.