Effects of a compatibilizing agent on the morphology, interface and mechanical behaviour of polypropylene/poly(ethylene terephthalate) blends

Three maleic anhydride-grafted-polypropylene (PP) derivatives [N, N-dihydro xyethyl monomaleic amide (C-2A), octodecyl monomaleate (C-3), and 2-(N, N-d ihydroxyethylamino)ethyl monomaleate (C-4)] were prepared by melt grafting and utilized to compatibilize polypropylene/poly(ethylene terephthalate) (P P/PET) blends. The resulting blends were characterized by means of scanning electron microscopy, thermal analysis and testing of mechanical properties . The results show the compatibilizing effects of the three PP grafts are v ery different and strongly dependent on the functional groups present. Comp atibilizer C-4 produced the finest dispersed phase morphology, whereas C-3 showed little compatibilizing effect. Substitution of 40 wt.% of C-2A with a tert-butyl phenolic resin further improved the compatibilizing effect and resulted in much finer domains of the dispersed phase. Modulated-temperatu re differential scanning calorimetry (M-TDSC) determination revealed that t he glass transition (T-g), crystalline temperature (T-c), melting temperatu re (T-m), and enthalpy of crystallization (Delta H-c) of the PET component all declined to some extent by comparison with neat PET. The increment of h eat capacity at the glass transition, Delta C-p, was found to be changed by the compatibilizers and displayed a trend in Very good agreement with that of the morphology, as well as with the mechanical properties. The decrease in the Delta C-p value may be used as a new parameter for quantitative est imation of the extent of compatibilization, as the decrease in Delta C-p is related to the increase of interface content. (C) 1999 Elsevier Science Lt d. All rights reserved.