Quantitative small‐angle light‐scattering studies of the melting and crystallization of LLDPE/LDPE blends

Abstract

Abstract Small‐angle light‐scattering (SALS) patterns were obtained during melting and crystallization of blends of linear low‐density polyethylene (LLDPE) with conventional low‐density polyethylene (LDPE). Quantitative measurements of these SALS patterns using a two‐dimensional optical multichannel analyzer apparatus (OMA2) indicate that the LLDPE which is miscible with the LDPE component in the molten state crystallizes first, forming volume‐filling spherulites. The LDPE then crystallizes within the preformed spherulites. These findings are supported by optical microscopy studies showing that the blend samples were volume filled with one kind of the spherulites having a radius comparable to that of the pure LLDPE. The SALS intensity curve changes with composition of the blends in a manner that may be interpreted by considering the orientation of crystals within spherulites. It has been observed that the spherulites in the blend have more diffuse boundaries as the LDPE content increases. The lattice spacing and long spacings in blends were obtained by wide‐angle and small‐angle x‐ray scattering, respectively. The SALS technique along with differential scanning calorimetry (DSC) is shown to be useful for determining the crystallization behavior of a crystallizable polymer blend system.