SynopsisThe compatibility of polymer blends of poly(c-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) containing various acrylonitrile (AN) contents was studied to evaluate the influences of copolymer composition and PCL concentration upon blend compatibility. Blend compatibility was characterized by the occurrence of a single glass transition intermediate between the transitions of the respective pure components. The glass transitions were determined by differential scanning calorimetry (DSC) and dynamic mechanical measurement (Rheovibron). It was found that SAN and PCL form compatible blends when the AN content of SAN ranges from 8% to 28% by weight. These blends are compatible in all proportions except for SAN 28 (AN wt % = 28) and PCL blends containing 70 or 85 wt % PCL. Blends of PCL and SAN were found to be incompatible when the AN content in SAN is greater than 30 wt % or less than 6 wt %. Lower critical solution temperature (LCST) behavior, which can be attributed to phase separation, was found to occur when these blends were heated to elevated temperatures. The cloud point, or phase separation, was found to vary with AN content in SAN and the concentration of SAN in the blend.

SynopsisPolymer blends of poly(ecapro1actone) (PCL) and poly(styrene-co-acrylonitrile) (SAN), containing 24 wt 9% acrylonitrile (AN), were prepared, and their transition behavior was examined by thermal analysis and dynamic mechanical testing. The blends were judged to be compatible on the basis of the presence of a single, compositionally dependent glass transition. The results of thermal treatment upon blend glass transition behavior and the dependence of thermal history upon the crystallization of semicrystalline PCL were also studied. The crystallization of PCL from SAN/PCL blends was found to be retarded by the presence of SAN, and crystalline PCL was found to exist only in blends containing a high PCL concentration. Blends which do not contain crystalline PCL were transparent, and their glass transition behavior can be correlated by the Gordon-Taylor equation. Phase separation, which was characterized by lower critical solution temperature (LCST) behavior, was found to occur when blends were heated to elevated temperatures. SUMMARYPolymer blends of PCL and SAN, which contains 24 wt 96 AN, show a single glass transition by both DSC and dynamic mechanical measurements over the entire blend composition range. This is evidence that the amorphous phase in these blends is a single phase containing a mixture of both polymers. The glass transition of blends was found to be dependent on the thermal treatment of the samples, i.e., on the extent of crystallization of PCL from the compatible blend. Crystallization of PCL in a blend extracts material from the amorphous regions and hence changes the composition in the amorphous phase. For samples free of PCL crystals, the glass transition temperatures were able to be correlated as a function of composition by the Gordon-Taylor equation.Crystallization of PCL is retarded and the T, of PCL is depressed by the addition of SAN in the blend. The onset temperature of a PCL crystallization exotherm on a DSC thermogram, T,, for the reheating scan after quenching from the molten state, increases with increasing SAN concentration in the blends. These results provide further evidence to confirm compatiblity for this blend.A liquid-liquid-type phase separation at high temperature because of the existence of a LCST was also observed for this compatible system. The cloud point curve was found to be skewed toward high PCL concentrations due to differences in the molecular weight of blend components. A preliminary phase

A crystalline polymer, Nylon 6, was selectively blended with various amorphous polymers containing phenolic moieties. It was found that moisture absorption by the amide group in Nylon 6 could effectively be reduced by blending with p-Cl-novolac at ratios as low as 2 phr (part per hundred resin). Blends of Nylon 6 with vinylphenol homopolymer and its copolymer with styrene also showed reduced moisture uptakes, but the effect was less dramatic than that of the p-Cl-novolac blend at all blend ratios. Novolac content in excess of 5 phr shows little additional advantage in moisture reduction. Thermal transitions of blends of Nylon 6 with poly(vinyl phenol), its copolymer, and p-Cl-novolac were also investigated. At a blend ratio of 5 phr, p-Cl-novolac caused a larger increase in glass transition temperature than the other two blends. The melting temperatures of the blends were little influenced by low levels of the amorphous polymer incorporation, but broader melting endotherms in the differential scanning calorimetry scans were observed.

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