Natural rubber-polymethyl methacrylate interpenetrating polymer networks as impact modifier for polypropylene

Abstract

Natural rubber - polymethyl methacrylate interpenetrating polymer networks (IPNs) were synthesized by emulsion polymerization process. The bipolar redox initiating system tert-butyl hydroperoxide/tetraethylene pentamine promoted a coreshell arrangement. A prevulcanized natural rubber latex was coated with a shell of polymethyl methacrylate (PMMA). IPNs polymerization was carried out by varying concentrations of the initiator, emulsifier, crosslinking agent, reaction time, and reaction temperature. Both IPNs and semi-IPNs were prepared and characterized by evaluating their morphology and mechanical properties. The particle morphology of IPNs was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The optimum condition was 1.5 phr of the initiator concentration, 0.25 % wt crosslinking agent, 1.5 % wt emulsifier concentration, and temperature at 60 ๐c for 2 hours. From this experiment, the IPNs showed higher tensile strength, modulus, flexural strength and finer phase distribution than the corresponding semi-IPNs, while the latter exhibited higher elongation at break. The IPNs products were used as an impact modifier in polypropylene (PP). The IPNs products (10, 15, 20, and 25 phr) and PP blends were prepared. The effects of IPNs products content on tensile strength and hardness decreased with increasing the IPNs product content, while the impact strength increased. The appropriate amounts of IPNs products were 10 and 15 phr.