Time resolved USAXS study of the shish-kebab structure in PE : Annealing and melt crystallization

Real time changes in the shish–kebab structure of high molecular weight polyethylene samples, produced by elongational flow injection moulding, were investigated by ultra small angle X–ray scattering (USAXS) using synchrotron radiation. The variation of the two typical long periods has been followed in situ, during heating and cooling from the molten state, as a function of temperature and time. Values of the length of the coherently diffracting domains perpendicular to the lamellar stacking planes, as derived from the USAXS maxima, are also presented. Results are discussed in the light of a shish–kebab model in which two different lamellar populations are respectively associated with an epitaxial growth from the columnar shish fibrils and with a secondary lamellar crystallization.