The Effect of In situ Melt Pre-shear Induced Oriented Precursors on the Crystallization of Poly(1-butene)/Polypropylene Blends

Melt pre-shear induced crystallization of polymer blends holds great significance in industrial processing and product application. In this work, two typical PB/PP blends (50/50, 90/10), possessing commercial value and academic hotspot, were employed to investigate the effect of melt pre-shear on the crystallization of isotactic poly(1-butene) (PB) and polypropylene (PP) by applying shearing slightly above the melting temperature of PP with subsequent non-isothermal crystallization to simulate actual processing conditions. It was discovered that in PB/PP (90/10) blend, in situ melt pre-shear generated oriented PP precursors induced the formation of PP-FIC (Flow-induced crystallization) which acted as row crystal nucleus significantly promoting PB crystallization into spherulite with higher melting temperatures (T_m), crystallinity (X_c), and thicker lamellar thickness (d_c). While in PB/PP (50/50) blend, the melt pre-shear generated PP-shish precursors induced the formation of PP shish-kebab that exerted a confining effect on the crystal growth of PB, resulting in truncated spherulite formation with higher T_m and thicker d_c but lower X_c. This research provides insight into the mechanism underlying oriented crystal structure formation, crystal properties, and phase morphology of PB/PP blends under melt pre-shear fields, which have significant theoretical and practical implications for their industrial processing and preparation of high-performance products.