A study of the dynamics of foam growth: Simplified analysis and experimental results for bulk density in structural foam molding

Abstract

D e p a r t m e n t o f Chemical Engineering University of D e l a w a r e N e w a r k , D e l a w a r eA cell model describing the diffusion-induced growth of closely spaced single bubbles developed in an earlier publication is now used as the microscopic building block of an analysis of low-pressure structural foam molding. Heat transfer, solidification, and bulk flow of the foam in the mold cavity are included in this macroscopic analysis. An experimental method is described whereby the bulk density of an expanding thermoplastic polymeric foam is measured as a function of time when the expanding foam is prepared by the short shot injection molding process. Instantaneous and final bulk foam density data obtained for various values of the controlling process parameters are compared with the predictions of the model. These predictions are found to be in qualitative agreement with the experimental measurements reported here. However, quantitative differences exist between the two. These differences are explained mainly by the omission of melt elasticity and bubble coalescence in the model.

Experimental and numerical studies on the effects of pressure release rate on number density of bubbles and bubble growth in a polymeric foaming process

“…Yoo and Han developed a structural foam molding process with a visual observation apparatus and compared the experimental data and the numerical calculations of bubble radius Yoo and Han, 1981). Amon and Denson (1986) developed a structural foam molding apparatus to observe the bubble growth phenomenon. They compared the transient foam bulk density with a numerical simulation result.…”

Modeling pore growth in semi-solid alloy foams

“…In light of this limitation, some researchers have initiated some effort to determine the effect of close spacing on bubble growth rate. In developing a model that is specific to the polymer foaming process, Amon and Denson [20,21] used a cell approach to account for the close spacing of the bubbles. More recently, Arefmanesh and Advani [22] used the cell approach, applying an upper-convected Maxwell model to describe the polymer rheology.…”

Modeling Foam Growth in Thermoplastics

“…However, they assumed an isothermal expansion and an initial bubble size of 1 lm. These simplifications are significant, and the work of Amon and Denson [8,9] and Advani and co-workers [10,11] addressed these assumptions with improved transport models, but still relied on assumed initial bubble sizes that were relatively large. Finally, in the late 1980s Flumerfelt [12±15] and students began development of a model that incorporated simultaneous nucleation and bubble growth.…”