FUSION BONDING OF MALEIC-ANHYDRIDE GRAFTED POLYPROPYLENE TO POLYAMIDE6 VIA IN-SITU BLOCK-COPOLYMER FORMATION AT THE INTERFACE

Bond formation between maleic anhydride-g-polypropylene (PPg) and poly amide 6 (PA) by in situ block copolymer formation has been investigate d. The effects of bonding temperature and time on the critical strain energy release rate, G(C), of the bonds were studied. The G(C) values were measured using a wedge test in an asymmetric double cantilever be am geometry. Electron spectroscopy for chemical analysis (ESCA) and sc anning electron microscopy (SEM) observations of the fracture surfaces were used to provide detailed information on the locus of failure and the failure mechanisms. An increase of G(C) with bonding temperature was observed with two well defined transitions corresponding to the me lting temperature of PPg and PA. Below the PPg melting temperature, th ere is no significant adhesion due to the absence of intimate contact between the adherends. Above this temperature, G(C) increases graduall y with temperature. This is explained by the increased mobility of mal eic anhydride grafted PP chains which can migrate towards the interfac e and react with the amine end-groups of the PA. Optimal bonding, howe ver, requires melting of both polymers and results in the highest G(C) values which approach the cohesive G(C) of PPg. Analysis of these fra cture surfaces via ESCA and SEM have shown that failure was cohesive i n the PPg and accompanied by significant plastic deformation. This is interpreted as saturation of the interface by block copolymer due to t he mutual migration of the PA and grafted PP polymer chains that becom es possible when the PA melts. It is suggested that as crystallization proceeds each half of the block copolymer is incorporated into crysta lline domains on their respective sides of the interface, producing th e highest G(C) values observed.