Modeling Of Bubble Nucleation And Growth During The Preparation Of Bi-modal Cell Structure Foams

Based on the experimental data in the reference, a modified classic nucleation model was constructed and used to analyze the effects of the solubility, surface tension, super saturation and temperature on the bubble nucleation. On the basis of the cell model, a bubble growth model was established and verified according to the experimental in-situ bubble growth data. The effects of various simulation variables on the bubble growth, such as the Henry’s law constant, diffusivity, relaxation time, zero-shear viscosity, surface tension, initial bubble radius and initial shell radius were investigated.Both the bubble nucleation model and bubble growth model were applied to simulate the bubble nucleation and growth during the preparation of bi-modal cell structure foams of polystyrene by using a two-step depressurization batch process and polypropylene by using a temperature-changing process. For the two-step depressurization batch process, the effects of the two-step depressurization rate and temperature, and the holding stage on the bubble nucleation and growth were studied. The results indicated that the holding stage between the two step depressurization steps played the key role on controlling the bi-modal cell structure. The effect of the depressurization rate and temperature in the second-step was more important than that of the first-step. For the temperature-changing process, the effect of the second-step temperature on bubble nucleation and growth was investigated. The results revealed that the bigger cell density and smaller cell size could be obtained at the higher second-step temperature in a certain range.