Essential work of fracture testing of PC-rich PET/PC blends with and without transesterification catalysts

Abstract

0.7 mm sheets of blends of polycarbonate (PC) with polyethylene terephthalate (PET) rich in PC in the presence and absence of three different transesterification catalysts have been obtained using reactive extrusion-calendering processing method in order to evaluate the fracture toughness of these materials applying the essential work of fracture (EWF) approach which has not been previously reported in the literature. The morphology has been characterized by scanning electron microscopy (SEM). In addition, the tensile properties of these materials were determined. There is a decrease on the essential term (w _e) values of PC/PET blends without transesterification catalysts while blends with transesterification catalysts present an increment in comparison with neat PC which may related to the product of the transesterification that plays like an emulsifier/compatibilizing agent to reduce the interfacial tension between the components of the blend and reduce the interfacial tension between the two immiscible or incompatible component phases to get a better fracture behavior. This is confirmed by the tensile test results obtained which demonstrate higher values for E and σ _y in the case of blends with transesterification catalysts compared with neat PC. For non-essential term of fracture (βw _p), blends without catalysts exhibit an increase compared with neat PC by increasing the amount of PET which may due to the lowering of the yielding stress. In contrary, the presence of transesterification catalysts and especially Zn-based shows decrease as a consequence of the restriction that occurred on the movement of PC segments during the transesterification reactions or as a decohesion of the dispersed phase during the test.