Phase structure and viscoelastic properties of compatibilized blends of PET and HDPE recyclates

Immiscible blends of recycled polyethylene terephthalate) (R-PET), containing some amount of polymeric impurities, and high-density polyethylene (R-PE), containing admixture of other polyolefins, in weight compositions of 75 : 25 and 25 : 75 were compatibilized with selected compatibilizers: maleated styrene- ethylene/butylene-styrene block copolymer (SEBS-g-MA) and ethylene-glycidyl methacrylate copolymer (EGMA). The efficiency of compatibilization was investigated as a function of the compatibilizer content. The rheological properties, phase structure, thermal, and viscoelastic behavior for compatibilized and binary blends were studied. The results are discussed in terms of phase morphology and interfacial adhesion among components. It was shown that the addition of the compatibilizer to R-PET-rich blends and R-PE-rich blends increases the melt viscosity of these systems above the level characteristic for the respective binary blends. The dispersion of the minor phase improved with increasing compatibilizer content, and the largest effects were observed for blends compatibilized with EGMA. Calorimetric studies indicated that the presence of a compatibilizer had a slight affect on the crystallization behavior of the blends. The dynamic mechanical analysis provided evidence that the occurrence of interactions of the compatibilizer with blend components occurs through temperature shift and intensity change of a P-relaxation process of the PET component. An analysis of the loss spectra behavior suggests that the optimal concentration of the compatibilizers in the considered blends is close to 5 wt %. (C) 2001 John Wiley & Sons Inc.