KINETIC-BEHAVIOR OF CHEMICAL-REACTIONS IN HOMOGENEOUS AND HETEROGENEOUS POLYMER MELTS

This paper compares the kinetic behaviour of a given chemical reaction in homogeneous and heterogeneous polymer melts using a batch mixer as reactor. The underlying chemistry was the addition esterification of epoxy groups attached to a polymer backbone and a carboxylic acid. Spe cifically, the homogeneous polymer melt was composed of 1-naphthylacet ic acid (NAA) and a random copolymer of ethylene, ethyl acrylate and g lycidyl methacrylate (CoGMA). The organic acid was soluble in the CoGM A melt under the reaction conditions. The heterogeneous polymer melt w as the aforementioned homogeneous polymer melt to which was added an i nert polymer, polystyrene (PS). The PS and the CoGMA were immiscible w hile NAA was miscible with both polymers. Experimental results showed that the overall reaction rate in the homogeneous polymer melt was con trolled by its intrinsic kinetics only while that in the heterogeneous polymer melt was dictated not only by the intrinsic kinetics, which i s the same as that in the homogeneous polymer melt, but also by the pa rtition coefficient of NAA between the CoGMA and the PS phases. These results can be justified by the fact that the rate of diffusion of NAA is much greater than the rate of reaction for both homogeneous and he terogeneous polymer melt systems, as mechanical mixing was necessary o nly at the initial stage of the reaction. (C) 1997 Elsevier Science Lt d.