A model is developed to describe thermally‐initiated polymerization of styrene between 100 and 170 °C. The model accounts for generation and consumption of styrene adduct. Chain transfer to adduct is the only transfer reaction used. Autoacceleration is modeled using the break‐point method of Hui and Hamielec. Using formal ranking and parameter selection techniques that account for parameter sensitivity, correlation and uncertainty, 4 of the 40 model parameters are selected for estimation to improve fit between model predictions and data. After estimation, the model predicts conversion data with a standard error of 5%, and provides excellent fit to a MWD curve obtained at 100 °C. Simulation results confirm that high‐temperature degradation reactions are not important in the temperature range of interest.

Styrene polymerization literature is reviewed and a model with dicumyl peroxide and benzoyl peroxide initiators is developed. Nine parameters are selected for estimation using statistical methods that account for the influence of parameters on model predictions, correlated effects of parameters and uncertainties of initial literature values. Updated parameters result in improved fits to conversion and molecular weight data from three research groups, reducing the least-squares objective function by 73%. Use of industrial data from 19 batch reactor runs increases the number of estimable parameters to 16. Good predictions are obtained for validation runs with temperature ramps using both initiators.