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 G MA, were used as interface modifiers, These were incorporated into PP blend s (with either 70 or 90 wt% PET), replacing 1/5 of PP in the system. The us e of these modifiers changed the blends' tensile mechanical behavior from f ragile to ductile. Blend tensile strength was improved by 10% and elongatio n at break showed 10 to 20-fold increases while stiffness remained constant . Scanning electron micrographs showed the PP average domain size in inject ion molded specimens to decrease to the micron/sub-micron size upon additio n of the GMA modified resins, while the unmodified blends exhibited heterog eneous morphology comprising large lamellae 10-20 mu m wide. The low-GMA gr aft 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 limite d effects on the blends' mechanical behavior in the range of GMA graft dens ity provided by the two modified resins investigated.