Preparation and Reaction Kinetics of Polypropylene-graft-Cardanol by Reactive Extrusion and Its Compatibilization on Polypropylene/Polystyrene

Polypropylene-graft-cardanol (CAPP) was prepared by reactive extrusion with polypropylene (PP) and natural renewable cardanol, which improved the inherent defects of PP such as its chemical inertness and hydrophobicity. Moreover, the cardanol grafted onto PP resolved the degradation of PP during reactive extrusion and use. The effects of reactive extrusion on the change of the molecular structure of PP, the change in the free-radical concentration during processing, and the compatibilization of CAPP on the PP/polystyrene (PS) composite materials were examined in this study. The constants of the grafting reaction rate at the beginning of reactive extrusion were also deduced. The results show that cardanol was grafted onto PP, and the p- conjugate system in cardanol was observed to stabilize free radicals. The grafting reaction rate (R-g) at the initial stage of the grafting reaction process was calculated through the equation R-g=k(g)[M][Cardanol], where k(g) is the constant of the apparent grafting reaction rate and [M] is the concentration of free radicals in the reaction system. k(g) first increased with the growth of temperature and then began to decrease when the temperature exceeded the critical temperature of 200 degrees C. The mechanical properties showed almost no change after the samples were aged for 72 h. This was due to CAPP, which changed PP/PS to a ductile material from a brittle one. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39911.