Properties and morphology of recycled poly(ethylene terephthalate)/bisphenol a polycarbonate/poly(styrene-b-(ethylene-co-butylene)-b-styrene) blends by low-temperature solid-state extrusion

Among the various methods available for recycling plastics waste, blending technology is a straightforward and relatively simple method for recycling. In this paper, a new blending technology, low-temperature solid-state extrusion, was discussed. Several recycled poly(terephthalate ethylene)/bisphenol a polycarbonate/poly(styrene-b-(ethylene-co-butylene)-b-styrene) blends (R-PET/PC/ SEBS blends) have been prepared by this technology. The results show that thermal and hydrolytic degradation of R-PET is improved when extruding temperature was between the glass transition temperature (T.) and cold crystallization temperature (T-cc). Elongation at break and notched impact strength were increased evidently, from 15.9% to 103.6, and from 8.6 kJ/m(2) to 20.4 kJ/m(2), respectively. The appropriate rotating speed of screws was between 100 and 150 rpm. At the same time, the appropriate rotating speed of the screws brings a suitable shear viscosity ratio of R-PET and PC, which is of advantage to blending of R-PET and PC together with SEBS. Dispersion of minor phase, PC and SEBS, became finer and smaller, to about 1 mu m. Chain extender, Methylenediphenyl diisocyanate (MDI) can react with the end-carboxyl group and end-hydroxyl group of R-PET. FT-IR spectra testified that the reactions have been happened in the extruding process. A chain extending reaction not only increased the molecular weight of PET and PC, but also can synthesize PET-g-PC copolymer to act as a reactive compatilizer. An SEM micrograph shows that a micro-fiber structure of PET was formed in the blend sample. Copyright (c) 2007 John Wiley & Sons, Ltd.