Comparison of the effect and efficiency of two impact modification approaches in polypropylene

Polypropylene (PP) hybrid composites were prepared with talc, a reinforcing filler, and an additional impact modifier. Impact resistance was improved by the use of a traditional elastomer and by the new approach of adding a synthetic polymer fiber, poly(vinyl alcohol) (PVA), in this case. The results showed that the use of PVA is more efficient than that of the elastomer. The latter decreases stiffness considerably, from the 3.5 GPa value of the PP/talc composite to around 1.5 GPa, it does not carry practically any load, and even its impact modification efficiency is somewhat smaller than that of the PVA fibers. On the other hand, PVA increases stiffness to some extent, up to 5 GPa, tensile strength considerably, especially in the presence of a coupling agent, and the large impact resistance of 20 kJ/m2 can be achieved with it at moderate fiber contents. The positive property profile achieved is the result of the local deformation mechanisms occurring in the PP/talc/PVA composites. Properties can be further adjusted to purpose by the application of a functionalized PP coupling agent.