Amorphous copolyester/polyoxymethylene blends: Thermal, mechanical and morphological properties

Amorphous copolyester/polyoxymethylene (POM) blends were produced by melt blending covering the whole composition range. As copolyester poly(ethylene glycolco-cyclohexane-1, 4-dimethanol terephathalate) (PETG) was selected. Injection and compression molded specimens of the blends were subjected to various rheological, thermal, thermomechanical and mechanical investigations. Many properties of these incompatible PETG/POM blends followed the additivity rule as a function of composition, such as melt flow index, density, tensile and flexural stiffness. However, the elongation at break, energy absorbed until tensile failure, flexural strength, notched Izod impact strength and static fracture toughness, K-c showed lower values than either of the neat blend components. This was traced to the poor interfacial adhesion between PETG and POM. A co-continuous morphology was ascertained by the combination of selective extraction and scanning electron microscopy (SEM) for the blends PETG/POM 60/40 and =50/50 wt%/wt%. The tensile fracture surface of the 50/50 blend exhibited a fibrillar morphology owing to the injection molding-induced distortion of the initial co-continuous phase structure.