Functionalization of ethylene-propylene-diene monomer rubber with maleic anhydride in the melt state through high-shear stress-induced initiation

The functionalization reactions of ethylene-propylene-diene monomer rubber (EPDM) with maleic anhydride (MAH) in melt state through high-shear-stress-induced initiation by an increase in the screw rotation speed of the twin-screw extruder and through compounded initiation by the addition of some initiator and an increase in the screw rotation speed were investigated. The results show that, with increasing screw rotation speed and reaction temperature, the percentage grafting and melt flow rate of the functionalized products (EPDM-g-MAH) were noticeably increased, and the viscosity-average molecular weight decreased, which implied that the grafting reaction consisted of the chain scission and grafting reaction of the produced macroradicals with MAH. In the presence of a certain peroxide initiator, the crosslinking reaction during melt extrusion was suppressed by an increase in the screw rotation speed. The percentage grafting of EPDM-g-MAH amounted to 1.1%, its melt flow rate was between 0.3 and 4.0 g/10 min, and its gel content was less than 1.0%, depending on the screw rotation speed and reaction temperature. Impact testing and scanning electron microscopy showed that the functionalized product prepared through the high shear stress-induced initiation had a higher blocking activity with the amide terminated of PA66 than that prepared through the peroxide initiation or through the compound initiation, and the impact strength of the PA66/EPDM blends, improved by the high-shear-stress-induced product was noticeably higher than those of the peroxide-initiated product or the compound-initiated one.