Enhanced compatibility of SAN and PC in their blends exposed to extremely high shear field

Originally incompatible blends of SAN 30% and PC 70% were extruded with extremely high shear rate up to 10⁷ s⁻¹ as a typical example of the blends. The materials were examined with a scanning electron microscope (SEM), a pulsed NMR, etc. The molecular weight of the blends was also measured with gel permeation chromatography. The blends are of binary systems microscopically in the first run of extruding, in which the minor constituent is present as small spherical particles in the major constituent. The apparent volume fraction of the spherical minor constituent estimated from the microscopic photographs decreases with the shear rate. The fraction is decreased also with the repeated runs. SEM observation reveals that dimple fracture of microsize takes place on SAN sphere dispersed in PC matrix. And at the bottom of the dimple, a small particle, which would be composed of PC, is present. From these, SAN in the blend is thought to be partly ductile even at the temperature of liquid nitrogen. At the fifth run, the blend appears uniform or structureless. Dynamic loss tangent gives two peaks corresponding to that of SAN and that possibly attributed to PC. The latter shifts to lower temperatures with the number of extruding run. These show that some of SAN is mixed with PC in a compatible form. The pulsed NMR analysis supports the conclusion. Furthermore, the analysis suggests that some of SAN is mixed in PC. This result shows the compatibility of SAN with PC is enhanced in extremely high shear rate processing.