Reactive compatibilization of blends of PET and PP modified by GMA grafting

The melt radical grafting of glycidyl methacrylate (GMA) onto isotactic polypropylene (PP) was carried out in Brabender internal mixer and the influence of reaction procedure, radical initiator concentration and addition of co-monomer (styrene) on the grafting efficiency was examined. The viscosity, the thermal behaviour and melt rheology of PP-g-GMA samples was then analysed as a function of grafted GMA content. Blends of poly(ethylene terephthalate) (PET) with PP and PP-g-GMA (5.2 wt% GMA), prepared in internal mixer, were characterised by SEM, DSC and melt viscosimetry. The morphological analysis of PET/PP-g-GMA blends (80/20, 50/50 w/w) pointed out a marked improvement of phase dispersion (with particle size of about 0.6 μm for 80/20 blend) and interfacial adhesion, as compared to non-compatibilized PET/PP blend. The results of mixing torque and thermal analysis supported the occurrence of in-situ compatibilization reaction between epoxy groups of GMA modified PP and carboxyl end-groups of PET in the melt.