Phase morphology development in reactively compatibilised polyethylene terephthalate/elastomer blends

Blends of poly(ethylene terephthalate) (PET) and a poly(ethylene-co-propylene) rubber (EPR) were reactively compatibilised using various compatibilisers., having either glycidyl methacrylate (GMA) or maleic anhydride (MA) functionalities. The examined compatibilisers include ethylene/glycidyl methacrylate copolymers (E-GMA8 and E-GMA12), glycidyl methacrylate-grafted EPR (EPR-graft-GMAx) and maleic anhydride-grafted EPR (EPR-graft-MA). To evaluate the compatibilisation efficiency of the different compatibilising agents used, a rheological and morphological comparative analysis was performed, It could be clearly established that the GMA-induced compatibilisation reaction is much more effective than the reaction between maleic anhydride and the PET end groups, at the applied processing conditions for the PET matrix. For the investigated GMA-containing compatibilisers, the E-GMA components provided the most effective and efficient compatibilisation of the basic PET/EPR blend system. The finest phase morphologies having submicron particle sizes were obtained with E-GMA8. The presence of only a small amount of E-GMA (10wt.-% within the dispersed phase composition) within the dispersed phase is sufficient to induce a pronounced reduction of the dispersed phase particle size, irrespective of the dispersed phase concentration. A coarse, non-spherical phase morphology is obtained when the dispersed phase contains a high E-GMA content (> 50 wt.-%). The occurrence of cross-linking reactions induced by the bifunctionality of the PET matrix and/or the presence of secondary hydroxyl groups is considered to be the most probable explanation for the observed morphology coarsening.