Structure and Properties of Multilayered PET/PC Composites

With the aid of layer multiplying coextrusion techniques, polymer composites comprising up to thousand of uniform and alternating layers polyethylene terephthalate (PET) and polycarbonate (PC) were produced. Morphology and micromechanical deformation processes in these composites were investigated by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM). In particular, the effect of thickness of individual layers on the large strain deformation micromechanisms was analyzed. On decreasing the thickness of individual polymer layers, a transition in deformation mechanism from two-component behaviour (i.e. the localization of shear bands in individual layer) to one-component-like behaviour (with the shear bands passing unhindered through different layers) was observed at the layer thickness of ca. 1 μm. On further decreasing the layer thickness below 100 nm, the composites exhibited homogeneous plastic deformation (i.e. no localization of deformation). In contrast to pure PET, even after long annealing, the composites showed tough behaviour during tensile loading.