Reactive compatibilization of polypropylene polyethylene terephthalate blends

The reactive compatibilization of polypropylene/polyethylene terephthalate (PP/PET) blends by addition of glycidyl methacrylate grafted PP (PP-g-GMA) was studied. Two PP-g-GMA copolymers, containing either 0.2 or 1.2 wt% of GMA, were used as interface modifiers, These were incorporated into PP blends (with either 70 or 90 wt% PET), replacing 1/5 of PP in the system. The use of these modifiers changed the blends' tensile mechanical behavior from fragile to ductile. Blend tensile strength was improved by 10% and elongation at break showed 10 to 20-fold increases while stiffness remained constant. Scanning electron micrographs showed the PP average domain size in injection molded specimens to decrease to the micron/sub-micron size upon addition of the GMA modified resins, while the unmodified blends exhibited heterogeneous morphology comprising large lamellae 10-20 mu m wide. The low-GMA graft content PP seemed slightly more efficient than the high GMA content PP in emulsifiying PP/PET blends. The GMA grafting level on PP had very limited effects on the blends' mechanical behavior in the range of GMA graft density provided by the two modified resins investigated.