Grafting of maleric anhydride onto polyethylene and polypropylene : grafting efficiency and rheology study

Abstract

Maleic anhydride (MAH) grafted high-density polyethylene (HDPE) and polypropylene (PP) are important compatibilizers in polymer blends, as adhesion promoters and bonding agents for polymers. In this research, modifications of HDPE and PP, through melt grafting MAH in the presence of dicumyl peroxide (DCP) in a co-rotating twin screw extruder were carried out to prepare the samples as compatibilizers. The grafting efficiency of the maleated samples was measured by back-titration and FT-IR spectroscopy methods. The extent of chain branching/crosslinking side reactions were evaluated with melt flow index determination and the melt viscosities of the grafted samples were measured using a capillary rheometer. It was found that the maximum grafting degree of HDPE at 2.44 % was obtained by the application of 4 phr of MAH and 0.125 phr of DCP, and the maximum grafting degree of PP at 2.67 % was obtained by the application of 5 phr of MAH and 0.3 phr of DCP. These results were attributed to the limited solubility of DCP and MAH in the polyolefin melt and suggested that the reactant concentration played a major role in the properties of the grafted samples.