X-Ray Long Periods in Bulk Crystalline Polymers

Abstract

Small-angle X-ray diffraction, supplemented by electron microscopy, has been used to probe the morphology of bulk crystallized polyoxymethylene (POM), isotactic polypropylene (PP), isotactic polystyrene (PS), and 1,4-trans-β-polyisoprene (PIP). Samples crystallized isothermally from the melt as well as annealed samples were investigated. The temperature range covered extended from 0[ddot]C to near the melting point. It was found that POM gave rise to three discrete small-angle scattering maxima and that PP gave two, whereas PS and PIP had only one. Attempts at correlating the long spacings corresponding to these maxima with readily identifiable morphological features were not entirely successful. Using the long spacing data in equations based on the Lauritzen and Hoffman theory of polymer crystallization, interfacial free energies were calculated. The values obtained are lower than those reported by other authors using radial spherulitic growth rate data on the same polymers. Various interpretations of the multiple long spacings are examined in the light of the newly acquired information. © 1967, Taylor & Francis Group, LLC. All rights reserved.