GRAFT COPOLYMERIZATION OF POLYPROPYLENE COPOLYMER WITH MALEIC ANHYDRIDE: EFFECT OF GRAFTING ON THERMAL, MECHANICAL PROPERTIES, AND PAINTABILITY

Graft copolymerization of polypropylene copolymer (PCP) with maleic anhydride (MA) was studied in melt in Brabender Plasticorder, Twin Screw Extruder by using peroxide initiators, such as benzoyl peroxide (BPO), lauryl peroxide (LPO), luperox-101 (LPU), and dicumyl peroxide (DCP). The variation of MA and initiator concentrations on percent grafting (G), melt flow index (MFI), torque, and gel formation was investigated. Graft copolymers (PgMA and PgMAT) were characterized by FT-IR, DSC, and TGA. Melt flow index increased and torque values decreased with an increase in initiator concentration. The increase in MFI values are in the order: DCP>LUP>BP0>LPO. Maximum chain scission was observed by using DCP and LUP as indicated by their MFI values. The incorporation of MA in PgMA and PgMAT was confirmed by the presence of carbonyl groups at 1712 cm−1 and a shift in crystallization peak temperature from 113 to 123°C due to nucleating effect of the poly(maleic anhydride). The thermal stability was increased by the presence of PgMA. Addition of PgMAT as an additive to PCP, PCP/PP, and amines improves mechanical properties and paintability. Primary amines are more reactive towards PgMAT compared to tertiary amines.