Static and dynamic mechanical properties, morphology, and thermal behavior of polycarbonate (PC)/plasticized cellulose acetobutyrate (CAB) blends were investigated to determine whether the plasticizer of the CAB modifies the miscibility of the blend and the mechanical properties of this essentially incompatible blend. In spite of the lack of transparency of the blends, both dynamic mechanical and thermal analysis results show the presence, at all blend compositions studied, of a single glass transition temperature which varies with the composition of the blend. Considering the ternary nature of the blends, we propose that plasticizer migration and the difficulty of discerning the presence of one or two peaks in a narrow temperature range may account for the observed behavior. Scanning electron microscopy confirms the immiscibility of the blends. The blends show large positive deviations of the tensile moduli from linearity and very low ductility. The reported tensile strength data are discussed in terms of several different equations for composites. This mechanical behavior is explained as a consequence of the migration of the plasticizer and of its subsequent antiplasticizing effect on the properties of the blend. 相似文献
Crystallization behavior and morphology of polypropylene (PP)/polycarbonate (PC) blends have been studied by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). In the study of non-isothermal crystallization of the blends, the phenomenon of multiple crystallization peaks of PP/PC blends was related to the blend morphology in which PP was the dispersed phase as small droplets in the PC matrix. The phenomenon of a single crystallization peak of the PP/PC blends was related to the blend morphology in which PP was a continuous phase; in that case the crystallization peak temperatures of the blends were higher than that of the PP. The isothermal crystallization kinetics of the PP and PP/PC (80/20) blend were described by the Avrami equation. The results showed that the Avrami exponent of the PP/PC (80/20) blend was higher than that of the PP, and the crystallization rate of the PP/PC (80/20) blend was faster than that of the PP. The crystallization rate of the PP and PP/PC (80/20) blend were calculated according to the Hoffmann theory. Both the PP and PP/PC (80/20) blend had maximum crystallization rates. The temperature at the maximum crystallization rate for the PP/PC (80/20) blend was higher than that of the PP. 相似文献
The mechanical properties and morphology of polycarbonate/ethylene-1-octylene copolymer (PC/POE) binary blends and PC/POE/ionomer ternary blends were investigated. The tensile strength and elongation at break of the PC/POE blends decreased with increasing the POE content. The impact strength of the PC/POE blends showed less dependence on thickness than that of PC. And the low-temperature impact strength of PC was modified effectively by addition of POE. The morphology of the PC/POE blends was observed by scanning electron microscope. The PC/POE weight ratio had a great effect on the morphology of the PC/POE blends. For the PC/POE (80/20)/ionomer ternary blends, low content (0.25 and 0.5 phr) of ionomer could increase the tensile properties of PC/POE (80/20) blend and had little effect on the impact strength. And 0.5 phr ionomer made the dispersed domain distribute more uniformly and finely than the blend without it. But with high content of ionomer, the degradation of PC made the mechanical properties of the blends deteriorate. Blending PC and ionomer proved the degradation of PC, and the molecular weight decreased with increasing the ionomer content. 相似文献
The thermal analysis characteristics of ternary blends polystyrene(PS)/polycarbonate(PC)/tetramethylpolycarbonate (MPC) show that the PS forms mostly a pure PS phase, whereas the PC and MPC go into a second phase very close to a binary blend of the same PC/MPC weight composition. However, an additional broad glass transition is observed for most blends within the same temperature range (129–133°). On the other hand, the viscoelastic properties of the ternary blends containing 75% PC/MPC weight fraction exhibit an additional low frequency (large relaxation times) relaxation domain. This relaxation domain might be attributed either to a PS/MPC interphase or to PS “trapped” at the PS-PC/MPC interphase. 相似文献
Diallyl orthophthalate (DAOP) has been used as a reactive plasticizer for polycarbonate (PC) due to the low reactivity and high conversion at the gel point of DAOP and its high solubility in PC. Miscible blends of PC with various ratios of DAOP have been investigated using gel permeation chromatography, differential scanning calorimetry, rheometry, dynamic mechanical thermal analysis and optical microscopy (with and without polarised light), and the experimental results have shown that DAOP can act as an effective plasticizer in PC processing by lowering the melt viscosity, the melting and the crystallisation temperatures, and by reducing the glass transition temperature of the blend. However, the molecular mobility provided to the PC chains by DAOP causes crystallisation of the PC as shown by optical microscopy and DSC and this places limits on the potential reduction in the processing temperature of the blend. 相似文献
Poly(lactic acid) (PLA) and polycarbonate (PC) blends were prepared by melt processing with a twin-screw extruder. Ethylene-maleic anhydride-glycidyl methacrylate terpolymer (EMG) as compatibilizer and talc as nucleation agent were added in PLA/PC blends. The effect of EMG and talc on the mechanical properties including tensile, flexural, Izod notched impact properties and heat deflection temperature (HDT) of PLA/PC blends were investigated. The morphologies were observed by scanning electron microscopy (SEM). The crystalline behavior of PLA/PC blends was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The nanoscale mechanical properties of PLA/PC blends were investigated by atomic force microscope (AFM). The results showed that the addition of EMG and talc simultaneously with annealing treatment is the most effective process. 相似文献
Carbon nanotube (CNT)-filled polycarbonate (PC)/poly(butylene terephthalate) (PBT) and polycarbonate (PC)/poly(ethylene terephthalate) (PET) blends containing 1 wt% CNTs over a wide range of blend compositions were prepared by melt mixing in a torque rheometer to investigate the structure-electrical conductivity relationship. Field emission scanning electron microscopy was used to observe the blend morphology and the distribution of CNTs. The latter was compared with the thermodynamic predictions through the calculation of wetting coefficients. It was found that CNTs are selectively localized in the polyester phase and conductive blends can be obtained over the whole composition range (20 wt%, 50 wt% and 80 wt% PBT) for CNT-filled PC/PBT blends, while conductive CNT-filled PC/PET blends can only be obtained when PET is the continuous phase (50 wt%, 80 wt% PET). The dramatic difference in the electrical conductivity between the two types of CNT-filled PC/polyester blends at a low polyester content (20 wt%) was explained by the size difference of the dispersed phases on the basis of the transmission electron microscope micrographs. 相似文献
The influence of multiwalled carbon nanotubes (MWCNTs) on phase morphology, lamellar structure, thermal stability, melting behaviour and isothermal crystallisation kinetics of polycarbonate/polypropylene (PC/PP) blend nanocomposites has been investigated. Both neat blends and PC/PP (60/40)/MWCNT nanocomposites were prepared by melt mixing method. Morphological analyses were performed by high-resolution X-ray micro-computed tomography and scanning electron microscopy. The co-continuous morphology of the blend was retained irrespective of MWCNT loading. In addition, a substantial refinement in the co-continuous structure was observed. Wide angle and small angle X-ray scattering studies were used to analyse the structural properties of the blend nanocomposites. The addition of MWCNT increases the long period of polypropylene. The influence of addition of MWCNT on the crystallisation temperature and equilibrium melting temperature (Tm°) of polypropylene was followed. The MWCNTs promote crystallisation rate of polypropylene in the blend nanocomposites. 相似文献
Summary: This communication describes the compatibilization efficiency of organically modified montmorillonite (OMMT) in immiscible polycarbonate (PC)/poly(methyl methacrylate) (PMMA) blends for the first time. The size of the dispersed PC particles was reduced significantly upon the addition of OMMT (6 wt.‐%) to the blend. The compatibilization effect of the OMMT was also assessed by differential scanning calorimetry, mechanical properties and thermal stability analysis of the modified blend.
Differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) measurements show that, in the case of polycarbonate (PC) with tetramethylpolycarbonate (MPC), the homopolymers are miscible up to 70% PC weight fraction; at higher PC content, an additional PC phase appears. The partial miscibility of PC and MPC has been confirmed by ultrasonic attenuation measurements and scanning electron microscopy. The viscoelastic behaviour of these blends has been correlated with the blend composition and compatibility. The free volume contraction, found to explain the variations of glass transition temperature and viscosity with concentration, suggests strong intermolecular interaction in the compatible range. 相似文献
The miscibility of bisphenol-A polycarbonate (PC) with poly(methyl methacrylate) (PMMA) has been reexamined using differential scanning calorimetry (DSC) and optical indications for phase separation on heating, i.e., lower critical solution temperature (LCST) behavior. Various methods have been used to prepare the blends including methylene chloride (CH2Cl2) and tetrahydrofuran (THF) solution casting, melt mixing, and precipitation of PC and PMMA simultaneously from THF solution by using the nonsolvents methanol and heptane. It is shown that the resulting phase behavior for PC/PMMA blends is strongly affected by the blend preparation method. However, these blends are miscible over the whole blend composition range (unambiguous single composition-dependent Tg's and LCST behavior) when prepared by precipitation from solution using heptane as the nonsolvent. To the contrary, solution-cast and melt-mixed PC/PMMA blends were all phase separated, which may be attributed to the “solvent” effect and LCST behavior, respectively, not discovered in previous reports. Methanol precipitation does not lead to fully mixed blends, which demonstrates the importance of the choice of nonsolvent when using the precipitation method. 相似文献
The effect of annealing on the miscibility and thermal properties of poly trimethylene terephthalate (PTT)/bisphenol-A polycarbonate (PC) blends was examined using pressure-volume-temperature (PVT) measurements. The PTT/PC blends were thermally annealed at 260 °C for different times to induce various extents of transesterification reactions between the two polymers. The non-annealed blends are immiscible and exhibit the thermal properties of the blend components. Upon annealing, the original semi-crystalline morphology transforms to an increasingly amorphous nature. PVT and WAXS analysis confirmed that the PTT/PC blends completely lost their crystallinity when annealed at 260 °C for a period of 120 min or longer, indicating the formation of random co-polyesters due to chemical transreactions between the PTT and PC. The further increase in the specific volume with annealing time also indicates that after reaching a completely amorphous co-polymer the transesterification continuous until a fully random copolymer is formed. 相似文献