The effect of acrylonitrile content of SAN on the bending morphology of PCL/SAN blends was studied. The blends were prepared from solution with different compositions, and isothermally crystallized at a certain temperature. During crystallization at 45°C, the truncated lozenge-shaped morphology of the PCL crystals being modified to regular/inverted S- or C-shaped morphology for PCL/SAN blends with 9.5–25% AN in SAN. The bending curvature increases by lowering the crystallization temperature, and the growth rate of PCL decreases with SAN reflecting the miscible nature of the blends. For blends with 30% AN in SAN, mix morphologies with different crystal growth rates reflects the immiscible nature of the blends. Raman spectroscopy reveals at lower crystallization temperature, for miscible blends, a small amount of SAN is retained in the PCL crystal, with a regular increase in concentration from the midpoint to the edge of the crystal, whereas a homogeneous distribution of SAN is found in immiscible blends. Those distribution of SAN are completely absent at higher crystallization temperatures due to a higher crystallographic order of the PCL crystals. 相似文献
Starch modified polyurethane(St-PCL) was synthesized via chemical modification of corn starch with hexamethylene diisocyanate terminated polycaprolactone. The obtained St-PCL with different grafting rates was used as compatibilizer of starch/polycaprolactone(St/PCL) blend. The structure of St-PCL was confirmed by FTIR, and the grafting rate could reach as high as 64%. In addition, a lower St-PCL amount can effectively improve the compatibility of St/PCL blends. And the thermal, mechanical and hydrophobic properties of St/PCL blends could be tailored by the amount of St-PCL. 相似文献
Two series of segmented polyurethanes were prepared with systematic variation in soft and hard segment length. The soft segment was constituted by polycaprolactone (PCL) blocks of molecular masses 530 or 2000 and the hard segment (HS) by urethane blocks, in a concentration that varied from 12% to 44% in weight of the whole polyurethane. Morphological analyses indicated that the amount of crystallinity of copolymers was strongly dependent on the PCL molar mass and hard segment content. The copolymers with longer PCL soft segments (Mn=2000) were semicrystalline, but those with shorter PCL segment (Mn=530) were unable to crystallize. The primary factor affectingthe biodegradability of copolymers as evaluated by Sturm tests was the extent of the phase separation, and that the segmental blending of the less biodegradable polyurethane (HS) blocks with PCL in the amorphous phase had a critical unfavorable consequence, which may be attributed to the size of the accessible area by microorganisms. 相似文献
Summary: The effect of poly(ε‐caprolactone) (PCL) molecular weight on the orientation of crystalline PCL in miscible poly(ε‐caprolactone)/poly(vinyl chloride) (PCL/PVC) blends, melt crystallized under strain, has been studied by a combination of wide angle X‐ray diffraction (WAXD) and small angle X‐ray scattering (SAXS) studies. An unusual crystal orientation with the b‐axis parallel to the stretching direction was observed in miscible PCL/PVC blends with PCL of high molecular weight (>21 000). SAXS showed the presence of nanosize confined PCL in the PCL/PVC blends, which could be preserved at temperatures higher than the Tm of PCL but lower than the Tg of PVC. A mechanism based on the confinement of PCL crystal growth was proposed, which can explain the formation of b‐axis orientation in PCL/PVC blends crystallized under strain.
SAXS pattern of stretched PCL/PVC blend after annealing at 90 °C for 5 min. 相似文献