MODELING OF FREE-RADICAL POLYMERIZATION UP TO HIGH CONVERSION .1. A METHOD FOR THE SELECTION OF MODELS BY SIMULTANEOUS PARAMETER-ESTIMATION

A systematic quantitative method for the selection of models for the h igh-conversion free radical polymerization exhibiting gel and glass ef fects has been developed. Four representative models were selected fro m the literature and were compared on the basis of the same experiment al data. All models describe the isothermal time-conversion data over the entire conversion range for a single type and loading of initiator well. Models that are not considering the effect of molecular weight of the polymers on the diffusion of macro radicals fail to describe th e time-conversion data if the concentration of the initiator varies at the same time. By simultaneous fitting of the conversion and polymeri zation degree data it was shown that the Marten-Hamielec model and its extended form (Panke-Stickler-Hamielec model) were not able to descri be the number average polymerization degree Pn at the final conversion , where the glass effect occurs. This occurred because both models neg lect the change of the radical efficiency f in this region, which has more effect on Pn than the change of the propagation rate coefficient (see part II of this series). (C) 1997 John Wiley & Sons, Inc.