Experimental and Numerical Analyses of n-Pentane Solubility and Diffusivity in Polystyrene/Poly(methyl methacrylate) Blends

The solubility and diffusivity of n-pentane in blends of a low-molecular weight polystyrene (PS) and a high-molecular weight poly(methyl methacrylate) (PMMA) were investigated through experimental and numerical analysis. The Sanchez-Lacombe (SL) equation of state was used to evaluate the swelling behavior of n-pentane-impregnated blends. The Areerat model was also used to predict the diffusion coefficient of n-pentane. A good agreement between the experimental and numerical analyses was observed. The results revealed that the increase in pressure increased the n-pentane solubility and diffusivity coefficient in all systems. The increase in temperature also increased the n-pentane diffusivity coefficient; however, the solubility of n-pentane in blends was suppressed with temperature. This occurred when the n-pentane solubility and diffusivity were noticeably higher in blends with higher PS contents. This was most likely due to the lower molecular weight of PS than PMMA which could facilitate the diffusion and dissolution of n-pentane molecules. Moreover, the higher affinity of nonpolar n-pentane and styrene units could also cause higher dissolution of n-pentane in systems with higher PS contents. The foaming behavior of the blends also showed that a bimodal cellular structure appeared in foamed blend with a similar large cell population but in different populations and sizes of the smaller cells. This was while the growth of the smaller cells seemed to be easier in blends with a higher PS content because of the dissolution of a higher amount of dissolved n-pentane, although saturation temperature also played a determinative role on the foaming behavior of the blends.