Joint effects of long-chain branching and specific nucleation on morphology and thermal properties of polypropylene blends

Abstract

The influence of long-chain branching and specific -nucleation on polymorphic composition, melting and crystallization, and morphology of polypropylene blends were investigated by wide-angle X-ray scattering, differential scanning calorimetry, and scanning electron microscopy. Linear polypropylene and long-chain branched polypropylene were used for the preparation of blends in various proportions. N,N-dicyclohexylnaphthalene-2,6-dicarboxamide was introduced (0 or 0.03 wt%) as a -specific nucleating agent into prepared blends. It was found that LCB-PP strongly induces -phase formation in the blends and suppresses the nucleation activity of a -specific nucleating agent. Blends containing a predominant amount of -and -phases showed higher thermodynamic stability within melting, as compared to the samples rich in -phase. During crystallization, LCB-PP in the blends increases nucleation density by self-seeding effect, manifesting itself in the shift of crystallization temperature. -phase in the blends is distinctly separated in spherulites, while -and -phases coexist on the lamellae level.