Formation mechanism of bi-modal cell structure polystyrene foams by synergistic effect of CO2-philic additive and co-blowing agent

A new method was developed for the formation of bi-modal cell structure polystyrene (PS) foams by synergistic effect of CO2-philic additive (PDMS) and co-blowing agent (alcohol). The results showed that PDMS and alcohol synergistically increased the solubility and diffusion coefficient of CO2 into PS and reduced the desorption rate from PS. The blowing agent formed a high-concentration area in the PDMS (6000 g/mol) phase to promote bubble nucleation and growth in advance. The moderate size and number of cells were pre-formed, slowing the CO2 desorption and increasing the duration of bubble growth, so that bi-modal cell structure PS foams with high cell density and volume expansion ratio were obtained. Moreover, the solution and diffusion behavior of CO2 and the cell morphology could be easily tuned by changing the composition of complex additives, which might be a promising strategy for preparing bi-modal cell structure in different foaming processes.