Accurate determination of bubble size and expansion ratio for polymer
foaming with non-isothermal PBB model
A non-isothermal pressure-balanced bubble-growth (PBB) model has been
proposed based on mass, momentum and energy conservation, which
additionally considered the decrease in the internal energy of gas due
to the work done by gas expansion in bubble. The model could accurately
predict the bubble size and expansion ratio for the melt foaming of four
polymers for a wide range of cell densities from 1.5×1013 to 1.9×1015
cells/m3. Furthermore, the simulation results indicate that the bubble
shell resisted bubble growth and consumed significant energy, preventing
the growth of some small nucleations. During the melt foaming process,
the energy cost of the linear polymer had a long-term effect, which
reduced the bubble size, while that of the long-chain branched polymer
had a short-term effect, thereby increasing the expansion ratio.
Finally, we defined the gas efficiency of the foaming agent to evaluate
the economic feasibility of the foaming agent in a foaming process.