The effect of plasma surface modification from a rotary plasma reactor on the styrene grafting onto a polypropylene surface

In this investigation, the influence of an initiator, benzoyl peroxides (BPO), plasma pretreatment and grafting time of the styrene (St) grafting onto the surface of polypropylene (PP) were studied. At first, the PP pretreated by rotary glow discharge argon (Ar) plasma (PPP) and then styrene was grafted onto the PPP by using a thermal-induced grafting method with or without adding an initiator (BPO). It was found that plasma pretreatment was useful for grafting a vinyl monomer onto the surface of PPP. The ATR-FTIR spectra showed that adding an initiator and plasma pretreatment possessed a synergistic effect on the styrene grafting co-polymerization. ATR-FTIR spectra also showed that the grafting degree of styrene was increased with increasing grafting time. However, long-term plasma treatment was disadvantageous for grafting styrene onto the PPP, resulting from surface cross-linking. From SEM, a number of star-polygon structures can be found on the styrene-grafted PPP surface. This is because the amorphous region of the PP spherulite structure was etched by Ar plasma ion and re-appeared after grafting PS. The spherulite of PP could be revealed by grafting styrene onto the surface of PPP and its size could be estimated by SEM. In this investigation, the spherulite size of PP ranges between 20 and 30 μm.