MELT BLENDS OF ALPHA-SAN WITH A PHENOXY

Melt blends of poly(alpha-methyl styrene-co-acrylonitrile) (alpha SAN) with a phenoxy were prepared using a Brabender Plasticorder. Morpholo gical, thermal, rheological, and mechanical properties of the blends w ere studied. DSC (differential scanning calorimetry) measurements show ed two T-g (glass transition temperature) of the blends. T-g of alpha SAN decreased by 5 to 7 degrees C, whereas that of phenoxy increased s lightly. Melt viscosity measured using an RDS (Rheometrics dynamic spe ctrometer) showed a small negative and relatively large positive devia tion in alpha SAN- and phenoxy-rich blends, respectively. Transverse v iews of SEM (scanning electron microscopy) micrographs of the fracture d surfaces again showed two phases, regardless of composition. Traces of full-out upon fracture were seen in alpha SAN-rich but not in pheno xy-rich blends, indicating stronger interfacial adhesion in phenoxy-ri ch blends. Longitudinal views of the SEM micrographs showed highly elo ngated structure of disperse phases (30 to 70% of phenoxy), especially when phenoxy forms dispersed phase, resulting in finer and well devel oped phenoxy fibrils. Tensile modulus and strengths showed a negative deviation in alpha SAN and positive deviation (strength) or additivity (modulus) in phenoxy-rich blends.