(140d) A Numerical Model to Simulate the Foaming Process and Address the Challenges of a Rapidly Changing Industry

As environmental regulations and demand for high efficiency insulations increase, the thermoplastic foams industry is looking for improved polymer properties and processing conditions which lead to small cell size (100-1000nm) and high porosity (>95%) foams using CO₂ as the blowing agent. A modeling tool that can help in the design of experiments for selecting the right polymer and processing conditions can reduce the product development time and speed up the process of commercialization.

In this presentation, we focus on the on-going work to develop a numerical model for simulating simultaneous nucleation and bubble growth in thermoplastic foams. Being based on the “Influence Volume Approach” the model differentiates between nucleation time and depressurization time as is the case in real foaming processes. Classical nucleation theory is used to predict the rate of nucleation of bubbles. By solving the mass, momentum and species conservation equations for each bubble, the model are capable of predicting average bubble size, bubble size distribution and bulk porosity.

Comparison of the model predictions to experimental data and the current model limitations are discussed. The effect of depressurization rate, blowing agent diffusivity, polymer viscosity and surface tension are also delineated. Enhancements to the model in the form of improved equation-of-state and its effect on the model predictions will also be presented.