Recycling of poly(ethylene terephthalate)/polycarbonate blends

Weathering and recycling of poly(ethylene terephthalate) (PET) causes degradation of the polymer backbone and results in the loss of physical properties. To enhance the properties, PET waste was blended with polycarbonate (PC) which shows a higher glass transition temperature as compared with PET. Three PET/PC blends were studied: 80/20, 70/30 and 50/50 wt.% PET/PC, respectively. Different grades of recovered materials (pellets, plates, and injection-moulded specimens) were tested by differential scanning calorimetry (DSC) and rheological measurements. The results indicate that the blends have better properties than neat PET. Moreover, a comparison of mechanical properties of injection-moulded specimens prepared from pellets and from flakes demonstrates that twin-screw extrusion is an essential operation in the recycling process as it permits a small amount of transesterification reaction between both polymer phases during blend preparation. This is a key factor to improve the polymer compatibility. Thus, it becomes possible to process new articles from 100% PET/PC waste blends with suitable thermo-mechanical properties.