Study on thermodynamic parameters of volatile components in polydimethylsiloxane and polystyrene

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In polymer production, devolatilization is an important unit operation that separates low molecular weight components from the polymer system. The presence of volatile matter not only reduces the quality of the product, but may also cause harm to users and the environment. The Henry’s coefficient is the most fundamental parameter in the vapor–liquid equilibrium relationship. The Henry’s coefficient of n-pentane, n-hexane, and n-octane for polydimethyl siloxane (PDMS) and polystyrene (PS) were measured using the pressure difference method. The influence of different operating conditions on Henry’s coefficient has been studied. The results indicate that as the experimental temperature increases, the Henry’s coefficient of volatile matter gradually increases. The viscosity of polymers has little effect on the Henry’s coefficient. Under the same volatile matter conditions, when the viscosity increases from 50 cst to 5000 cst, the maximum growth rate of the Henry’s coefficient is only 5%. As the number of carbon atoms increases, the Henry’s coefficient decreases. This work provides theoretical guidance for polymer devolatilization processes in industry.