Solid‐state blending of poly(ethylene terephthalate) with polystyrene: Extent of compatibilization and its dependence on blend composition

Polystyrene (PS) and poly(ethylene terephthalate) (PET) were blended together in the solid state via cryogenic mechanical attrition (CMA) and in the melt through conventional twin‐screw extrusion. Consecutive modulated differential scanning calorimetry (MDSC) and thermogravitometric analysis (TGA) investigations allowed for the quantitative estimation of the extent of blend compatibility through the accurate determination of sample composition. The extent of blend compatibility, i.e., the amount of PET calculated to have been removed from the bulk and into interphase entanglements with PS, was found to be higher for milled blends than for extruded blends. This compatibility enhancement was the most pronounced for PET‐rich blends. The other benefits of CMA are more precise compositional homogeneity through intimate mixing and the ability for more amorphous PET chains to be entangled with the amorphous PS phase at the interphase. POLYM. ENG. SCI., 2008.