Characteristics of hydroxybenzoic acid‐ethylene terephthalate copolymers and their blends with polystyrene, polycarbonate, and polyethylene terephthalate

Abstract

Abstract We present a basic study of the thermal, dielectric, Theological, and mechanical properties of hydroxybenzoic acid‐ethylene terephthalate copolymers (PHB‐PET). It is argued that they have two‐phase structures, one rich in ethylene terephthalate (PET) and one rich in hydroxybenzoic acid (PHB). Polystyrene (PS) is immiscible in 60% PHB‐PET (60‐PHB‐PET) blends. Polycarbonate (PC) is partially miscible with the high PET phase of 60‐PHB‐PET. PET seems completely miscible with this high PET phase. Shear viscosity measurements on blends indicate that 60‐PHB‐PET gives rise to large reductions of viscosity. Extrudates and melt‐spun fibers have been prepared. The phase morphologies of low PHB‐PET blends as determined by scanning electron microscopy indicate ellipsoids or long fibrils of the, 60‐PHB‐PET in PS or PC matrices. High extrusion rates and melt spinning produce fibrillar structures. The mechanical properties of films, extrudates, and melt‐spun fibers were studied. Blends with 10% 60‐PHB‐PET exhibited significant increases in Young's modulus and tensile strength.