Interfacial Banded Transcrystallization of Polyoxymethylene/Poly(butylene succinate) Blends Induced by the Polyamide 6 Fiber

Interfacial crystallization of polyoxymethylene/poly(butylene succinate)blends induced by the polyamide 6(PA6)fiber was investigated.Due to strong heterogeneous nucleating ability,dense nuclei were generated on the surface of the PA6 fiber,which compelled the growth of twisted lamellae perpendicular to the PA6 fiber.As a result,unique interfacial banded transcrystallization was formed,which is rarely found before.Crystallization temperature was dominant in determining the nucleation activity of the PA6 fiber,further affecting the architecture of banded transcrystallization.With the increase of crystallization temperature,the nucleation density decreased to give more growth space for the twisted lamellae around the fiber.The wave-like banded stripes were transformed into fan-like stripes.Accordingly,band spacing and eccentricity respectively showed positive and negative correlation with crystallization temperature.These meaningful results shed light on regulating the architecture of banded crystals in polymer composites.

SPATIAL HIERARCHY AND INTERFACIAL STRUCTURE IN INJECTION-MOLDED BARS OF POLYPROPYLENE-BASED BLENDS AND COMPOSITES

The hierarchical structure and interfacial morphology of injection-molded bars of polypropylene （PP） based blends and composites have been investigated in detail from the skin to the core. For preparation of injection-molded bars with high-level orientation and good interfacial adhesion, a dynamic packing injection molding technology was applied to exert oscillatory shear on the melts during solidification stage. Depending on incorporated component, interfacial adhesion and processing conditions, various oriented structure and morphology could be obtained. First, we will elucidate the epitaxial behavior between PP and high-density polyethylene occurring in practical molded processing. Then, the shear-induced transcrystalline structure will be the main focus for PP/fiber composites. At last, various oriented clay structures have been ascertained unambiguously in PP/organoclay nanocomposites along the thickness of molded bars.

EFFECTS OF MATRIX MOLECULAR WEIGHT ON STRUCTURE AND REINFORCEMENT OF HIGH DENSITY POLYETHYLENE/MICA COMPOSITES

Three types of high-density polyethylene （HDPE） with different molecular weights （high, medium and low） were adopted to evaluate the influence of matrix molecular weight on the structure-property relation of injection-molded HDPE/mica composites through a combination of SEM, 2d-WAXS, DSC, DMA and tensile testing. Various structural factors including orientation, filler dispersion, interfacial interaction between HDPE and mica, etc., which can impact the macroscopic mechanics, were compared in detail among the three HDPE/mica composites. The transcrystallization of HDPE on the mica surface was observed and it exhibited strong matrix molecular weight dependence. Obvious transcrystalline structure was found in the composite with low molecular weight HDPE, whereas it was hard to be detected in the composites with increased HDPE molecular weight. The best reinforcement effect in the composite with low molecular weight HDPE can be understood as mainly due to substantially improved interfacial adhesion between matrix and mica filler, which arises from the transcrystallization mechanism.