Abstract: Six cell models of polystyrene (PS) chains including sotactic, syndiotactic and atactic single chains consisting of 40 repeating units were established. The equilibrium adsorption behaviors of O2/N2 in PS melt were analyzed by Monte Carlo method, and then diffusion behaviors of pure gases and their mixture in different PS melts were studied under a coupling effect of temperature and pressure with an introduction of Compass force. The results indicated that O2/N2 mixture improved the overall adsorption in different structural PS melts, but the adsorption capacity of pure gases was suppressed. The mixed gas also improved the gas diffusion capability in a certain extent. Moreover, the backbone activity and the size of gas molecular influenced the diffusion coefficient. The diffusion behaviors of O2/N2 presented a conversion from non-Einstein diffusion to the Einstein one and also exhibited a skip and cavity diffusion manner in PS melt.

Key words: injection molding, oxygen, nitrogen, adsorption, polystyrene, molecular dynamics