Mutual Diffusivity of Volatile Materials in Molten Polystyrene

Abstract

A new method is developed for the determination of mutual diffusivity of low-molecular weight materials in concentrated polymer solution far above the glass transition temperature. The most important feature of the present method is that the diffusivity of the monomer can be determined by consideration of the simultaneous diffusion and polymerization of the monomer. This method can be easily applied to systems containing non-reactive diffusant as well.
The diffusivities of styrene monomer and ethylbenzene in molten polystyrene and their temperature dependency are determined over a temperature range from 423 to 523 K and a concentration range up to 3 wt% of diffusant. Treating the diffusivities as constant regardless of concentration over the experimental range of concentration, we correlate the diffusivities as

D = 6.97 × 10^–2 exp(–42400/RT)

for styrene and

D = 1.17 × 10² exp(–72600/RT)

for ethylbenzene, where the units of D, R and T are cm²·s^–1, J·mol^–1·K^–1 and K, respectively.