KINETIC PARAMETER-ESTIMATION IN PEROXIDE INITIATED DEGRADATION OF POLYPROPYLENE

The chain scission rate constant and the initiator decomposition effic iency are very important kinetic parameters in the chemically initiate d degradation of polypropylene. These two kinetic parameters have been estimated using both deterministic and stochastic modelling procedure s. To relate the chain scission rate constant to measurable properties of this system in a deterministic model, the stationary state hypothe sis for the peroxide radical concentration has been relaxed and a new model relating both the overall chain scission rate constant and the p eroxide decomposition efficiency to three average molecular weights ha s been formulated. Using Monte Carlo simulation results, the sensitivi ty of the kinetic parameter posterior probability surface to the react ion time has been investigated. The results indicate that there is an optimum time for collection of experimental data in the reaction syste m so that the estimated values of the kinetic parameters are more reli able. Based on simulated data at a reaction time of 30 seconds, the po int estimates and the joint confidence region have been obtained for t he chain scission rate constant (k(1)) and the peroxide decomposition efficiency (f) using a Bayesian approach to statistical inference.