A Novel Multi-monomer Grafting PP Preparation, Characterization And Application In PP/PVC Blends

In recent years, multi-monomer melt grafting has become a widely used method to functionalize PP, which is due to minimizing the matrix degradation, improving the grafting yields and preserving the mechanical proprieties. As a compatibilizer, the functionalized PP may be an effective for PP blends with many other engineering plastics.In this article, a novel graft polymer was prepared by one step, using free-radical melt grafting way in a single-screw extruder. The effects on the grafting reaction were investigated, that is, styrene (St), graft monomer (MMA), the molar ratio of MMA to St, the content of DCP, the reactive temperature and time, and so on. The grafting degree and the melt flow rate were confirmed by means of FTIR and MFR test, respectively. The results showed that the addition of a second monomer, styrene, in the grafting process can enhance MMA grafting onto PP further and suppress the degradation of the PP matrix. Therefore, the matrix PP can be not only given the high polarity, but also kept its good mechanical properties. Otherwise, a reasonable mechanism was arisen from this article latter.Because of higher polarity, we added the multi-monomer grafting polymer, PP-g-(St-co-MMA), to PP/PVC blend. The influences of PP-g-(St-co-MMA) on mechanic properties, rheological behavior and morphology of PP/PVC blend were investigated by means of tensile test machine, capillary rheometer and SEM. The results showed that up to 15% increase in the tensile strength of PP/PVC blends was obtained, and had a maximum value; but the impact strength was unchanged as that of pure PP/PVC. The blends belong to pseudo-plastic fluids.In order to study the compatibilization further and compare with PP/PVC blends, we directly blended gPP with PVC. It has been found that the mechanical properties of the gPP/PVC blends are better than that of the PP/PVC blends. The compatibility and morphology of PP/PVC and gPP/PVC blends were studied by means of DSC and SEM. The result of DSC showed that Tg of PVC did not change with the blends compositions of PP/PVC, and Tg of PVC decreased with the increase in weight fraction of gPP in gPP/PVC blends; results from SEM showed that gPP/PVC blends exhibits reduced size of the disperse phase, enhanced interfaced adhesion as compare with the blends of PP/PVC. All these showed the compatibility between PP and PVC was improved, and the gPP/PVC blends is a partially miscible system, it implied thatthe multi-monomer grafting PP was an effective compatibilizer of PP/PVC blend. But the pseudo-plastic fluids had no change; in addition, the phase transition has a considerable effect on the mechanical properties of the blends.