Characterization of the morphological changes in linear low-density polyethylene during the melting process using synchrotron radiation

Abstract

Time-resolved SAXS diffraction data-as obtained by synchrotron radiation-of isothermallycrystallized linear low-density polyethylenes with propene and 1-octene as the comonomer have been usedto clarify the complex morphology of these samples. The data have been obtained under DSC conditionswhere, for most of the samples, up to four melting endotherms can be detected. On the basis of long spacingand invariant analysis, combined with fractionation experiments, it can be shown that the morphology involvesphase segregation and results from sample heterogeneity both with respect to molecular weight and comonomerdistribution, type, and content; these parameters affect crystal thickness, crystal perfection, crystallinity, andmelting behavior. The melting domain of all samples starts as low as A38 "C and extends up to final meltingat i130 "C. The classical two-phase model cannot be used to quantify all the observed data.