At 75/25 concentration ratio, bisphenol a polycarbonate (PC)/styreneacry-lonitrile copolymer (SAN) blend has poor impact resistance compared to PC/ABS. A rubber phase methacrylate-butadiene-styrene (MBS) of core/shell type was dispersed in PC/SAN blend. The morphology of the unmodified and modified blend was investigated. The influence of the acrylonitrile ratio in the SAN on the microstructure was studied. It clearly shows that core/shell resides at the interface between PC and SAN. It seems that core/shell particles enhance the adhesion between the different phases. Their presence influences the interface mobility; i.e., the coalescence of the dispersed phase observed in pure PC/SAN is considerably reduced when the MBS particles are added. The impact resistance of the samples was correlated with the morphology. 相似文献
The crystallization behavior of PBT as well as PC is changed in the controlled-processed blend due to intermolecular interactions between the different macromolecules in molten state. If the kinetics of the crystallization process prevents a crystallization-induced separation, the partial miscibility of the amorphous phases, measured by the glass transition temperatures, will lead to a decrease of the crystallinity of PBT. The crystallinity, normalized to the concentration of PBT in the blend, is independent from the concentration of PC at low coolling rates. At high cooling rates, PBT is crystallizing stepwise in the blend PBT/PC 40/60 wt.-%. The crystallization temperature in the anisothermic crystallization process is increased at low contents of PC due to a changed nucleation mechanism. The half-time of crystallization is increasing in blends with an increasing PC-content in isothermic crystallization experiments. The normally amorphous PC crystallizes considerably fast in presence of PBT in PC-rich blends. The crystallization or change in the state of order of PC was measured in situ by X-ray diffraction. Calorimetric experiments confirm this result and allow a quantitative estimation of the PC-crystallinity, which amounts to some 20% in the blend PBT/PC 5/95 wt.-%. 相似文献
Reactive modification of polycarbonate (PC) with a small amount of ultra-high molecular weight polydimethylsiloxane (PDMS) provides an effective route to a novel blend polymer with superior flow and excellent impact toughness. Low temperature impact toughness for such a blend was found to be comparable to polycarbonate copolymers made by interfacial copolymerization of bisphenol A and specialty silicones with phosgene. Interestingly, the blend also showed strong shear thinning behavior and a viscosity that is almost an order of magnitude lower than the starting PC resin. Analysis of the blend composition and blend morphology revealed the presence of both PC-PDMS copolymer and un-grafted siloxane as a dispersed phase in the polycarbonate matrix. The PC-PDMS copolymer provides a compatibilization effect for the stable sub-micron blend morphology in an otherwise immiscible PC-PDMS blend system. Improvement of low temperature ductility (e.g., at −40 °C) by PDMS was thus made possible. The lubricating effect from siloxane and the possibility of fibrillation flow at high shear stress are suspected to be the main reasons for high flow characteristics of these blends. 相似文献
The intrinsically impact brittle nature of the PC/PET blends can be effectively toughened by incorporating butylacrylate core-shell rubber. The rubber-modified PC/PET blend possess both excellent low temperature impact properties and reduced notch sensitivity. The ductile-brittle transition temperature of the blend decreases with the increase of rubber content. The presence of rubber in the PC/PET blend does not relieve the strain rate induced yield stress increase. Two separate modes, localized shear yielding and mass hear yielding, work simultaneously in the rubber toughening mechanism. The plane-strain localized shear yielding dominates the toughening mechanism at lower temperature and results in brittle failure. At higher temperature, the planestress mass shear yielding dominates the toughening mechanism and results in ductile failure. The critical plastic zone volume can be used to interpret the observed phenomenon. 相似文献
The objective of the study is preparation of shape memory blend of polycarbonate (PC) and thermoplastic polyurethane (TPU). Polycarbonate is blended with three types of TPUs and subsequently mechanical, thermal, morphological, and shape memory properties of the PC/TPU blends are studied. When TPU content in the blend is higher than 40% (by weight), the glass transition temperature related to PC is not shown in the differential scanning calorimetry thermogram, indicating loss of PC properties. The 60/40 optimized blend of PC/TPUs exhibits maximum increment of about 1100% in elongation and 43% decrement in tensile strength. The shape recovery of the optimized blend obtained by addition of 40% (by weight) of TPUs in PC polymer is found to be 65% and shape fixity is 97%. These results suggest that the blend of PC/TPU may be utilized for various applications where shape memory property is required including strategic applications. 相似文献
Summary: Polycarbonate (PC)/high density polyethylene (HDPE) in situ microfibrillar blends were fabricated by a slit die extrusion, hot stretching, and quenching process. Despite PC and HDPE having a high viscosity ratio, which is usually disadvantageous to fibrillation, the morphological observation indicated that the blends had well‐defined PC microfibrils. The size and amount of the PC fibrils were nonuniform through the thickness of the extrudate, and were also affected by the PC concentration and hot stretch ratio. There were coarse and dense fibrils in the core zone, while these fibrils became finer and reduced in number toward the surface. The melt flow rate (MFR) of the PC/HDPE microfibrillar blend decreased with the increase of PC concentration, but increased with the larger hot stretching rate (or hot stretching ratio, HSR). Besides, it was found that the fibrillar blend had better flowability than the common blend with spherical particles at the same PC concentration. Temperature was also an important factor influencing the MFR due to the temperature dependence of PC and HDPE viscosity, and the PC phase morphology. The PC microfibrils could not be preserved beyond 230 °C and transformed into spherical particles. The rheological behaviors at various shear rates were studied by capillary rheometer. The orientation of PC fibrils and HDPE molecules with higher shear rate led to a decrease in the viscosity of microfibrillar blend. The data obtained in this study can help construct the technical foundation for recycling and utilization of PC and HDPE waste by manufacture of microfibrillar blends in future work.
SEM micrograph of the PC/HDPE microfibrillar blend. 相似文献
A novel polymer blend comprising polyethylene (PE) and poly(vinyl acetate) (PVAc) with a biocompatible surface was developed for fabricating medical devices. This blend was obtained by a new synthetic method using supercritical carbon dioxide fluid. Further, the acetyl group on the surface of this blend was converted to the hydroxyl group following the phosphorylcholine (PC) group. Surface analysis of the blend with attenuated total reflection Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and dynamic contact angle measurement revealed that the PC groups were located on the surface. Biocompatibility was evaluated by the adsorption of the bovine serum albumin and bovine plasma fibrinogen on the sheet surface. The hydrophilicity of the blend depended on the surface chemical structure introduced by surface reactions. Plasma protein adsorption decreased with the surface hydrophilicity. The PC groups were highly effective in reducing protein adsorption. We conclude that our process is a promising procedure for synthesizing new polymer materials including biomaterials. 相似文献