Binding Off The Supercritical Co < Sub > 2 < / Sub > Foamed Ps Foam Pore Structure Control And Mechanical Properties Research

In this study, in order to investigate the practicality of microcellular foaming products, supercritical CO2was used as blowing agent and a quick-heating method was applied to study the process of constrained foaming of polymers in mold. PS was chosen for matrix. The effects of saturation pressure, foaming temperature and foaming time on the microcellular structure of free foaming or constrained foaming were analyzed by SEM. The effects of relative density and foaming process conditions on the tensile properties and impact performance of foamed PS were researched by Universal material testing machine.The results showed that when the mold was used as barrier constraints, the saturation time and the amount of supercritical CO2dissolved in PS changed little. However, compared with the free foaming process, cell structure with more uniform distribution of cell size and smaller cell diameter was obtained in the constrained foaming process. The minimum value could be reduced to321nm. Besides, the phenomenon of cell collapse was reduced significantly in the constrained foaming process. In addition, the cell diameter increased with increasing foaming temperature or foaming time, and first decreased with increasing saturation pressure and then increased with a further increase in saturation pressure. The cell density first increased and then decreased with increasing foaming temperature or saturation pressure. But the effect of saturation pressure on the apparent density was not obvious.Compared with the original samples, the elongation at break of PS increased20%and the tensile strength reduced30%after supercritical CO2saturation. The tensile strength, Young’s modulus and the relative modulus of foamed PS increased with the increasing relative density, the relative modulus and the relative density satisfy the relationship of Ef/Es=0.953[ρf/ρs)1.1478and the relative density is the only structure variable of Young’s modulus. Furthermore, a lower foaming time or foaming temperature and a higher saturation pressure were more favorable for obtaining better tensile strength of foamed PS. The impact strength of foamed PS related with cell diameter closely, the impact strength increased with decreasing diameter. The research of this paper provides experimental basis for the practical application of microcellular materials.