A scattering study of nucleation phenomena in polymer crystallisation

The mechanism of primary nucleation in polymer crystallisation has been inv estigated experimentally and theoretically. Two types of experiments have b een performed on polypropylene, polyethylene, and poly(ethylene terpthalate ). Crystallisations with long induction times, studied by small and wide an gle X-ray scattering (SAXS and WAXS), reveal the onset of large scale order ing prior to crystal growth. Rapid crystallisations studied by melt extrusi on indicate the development of well resolved oriented SAXS patterns associa ted with large scale order before the development of crystalline peaks in t he WAXS region. The results suggest pre-nucleation density fluctuations pla y an integral role in polymer crystallisation. A theoretical model has been developed which qualitatively describes the experimental results.