Prediction of open porosity of polystyrene foams based on simulation of bubble wall rupture during bubble growth

Abstract

The bubble wall rupture (BWR) behaviour and the resultant cell connections of polystyrene (PS) foams were thoroughly investigated. The experimental results indicated that the open porosity ψ of the PS foams was highly dependent on the nucleation density ρn but had multiple varying paths at different expansion ratios Er. The non-uniformity of the bubble wall during bubble growth was considered herein as the key to explaining the multiple paths; the non-uniformity was quantified in terms of a heterogeneity factor γ. The bubble wall shape evolution model was employed to theoretically calculate the bubble wall shape after the bubble growth. The open porosity ψ and bubble wall non-uniformity γ had good regularity because the macroscopic changes in ψ were governed by the microscopic BWR. The functional image of ψ with respect to Er and ρn, considered as two independent variables, was obtained, and the image accuracy was further verified experimentally.