PREPARATION AND THERMAL CHARACTERIZATION OF GRAFT COPOLYMER OBTAINED BY RADIATION GRAFTING OF INDIVIDUAL AND BINARY MONOMER SYSTEMS

Graft copolymers were obtained by radiation-induced grafting of vinyl acetate (VAc) and N-vinylpyrrolidone (NVP) individually and in binary mixture on to polypropylene (PP) films. The effect of some grafting co nditions on the grafting yield was determined. The addition of Cu2Cl2 as inhibitor to the reaction medium inhibited the homopolymerization o f the comonomer. The grafting process was remarkably enhanced by using dioxan as a diluent compared with other solvents used. The addition o f some inorganic salts has a great influence on the individual graftin g of both monomers. The gel percent in the graft copolymer was determi ned; it increased as the grafting yield increased. The swelling behavi our and electrical conductivity for the grafted films slightly increas ed by grafting. The changes in thermal parameters such as glass transi tion (T-g), melting (T-m) and recrystallization (T-rc) temperatures an d heats of melting (Delta H-m) and recrystallization (Delta H-rc) of t he graft copolymers were also followed by differential scanning calori metry (DSC). These thermal parameters of PP were varied by grafting wi th VAc and NVP and depend on the graft yield, which reflects the chang e in its crystalline domains and formation of crosslinks in the graft chains. The heat of recrystallization of the graft copolymer by coolin g from the molten state decreases by grafting, which is a good indicat ion of crosslink formation, since crosslinking decreases the crystalli zability of the polymer matrix.