Poly(ethylene terephthalate) (PET) resin is one of the most widely used engineering plastic with high performance, but the poor impact strength limits its applications for the notch sensitivity. In this research, toughened PET alloy was prepared by blending recycled PET with polycarbonate (PC) and MDI (methylenediphenyl diisocyanate). Intrinsic viscosity and melt viscosity measurements proved increase of the molecular weights of PET via chainextending reaction. FTIR and DMA results proved that some PET-PC copolymers were produced and the compatibility of PET phase and PC phase was improved. In addition, the reaction induced by MDI also affected the crystallization behaviors of PET, as observed from DSC results, and the crytallinity of PET decreased with the increase of MDI content. For all of these effects of MDI of increasing of molecular weight, improving of compatibility, and limiting the crystallization behaviors of PET/PC alloy, the notched-impact strength was greatly improved from 17.3 to 70.5 kJ/m 2 .

The processing of poly(ethylene terephthalate) (PET) involves thermal and hydrolytic degradation of the polymer chain, which reduces not only the intrinsic viscosity and molecular weight, but also the mechanical properties of recycled materials. A novel PET/bisphenol A polycarbonate/styrene-ethylene-butylene-styrene alloy based on recycled PET scraps is prepared by low temperature solid-state extrusion. Hydrolysis and thermal degradation of PET can be greatly reduced by low temperature solid-state extrusion because the extrusion temperature is between the glass-transition temperature and cold-crystallization temperature of PET. Modification of recycled PET by low temperature solid-state extrusion is an interesting method; it not only provides an easy method to recycle PET scraps by blend processing, but it can also form novel structures such as orientation, crystallization, and networks in the alloy.

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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 g ) 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 mm. 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.