The gas that was dissolved in the polymer melt in the initial step of the Microcellular injection molding process will diffuse out of the melt in the foaming stage, nucleating and growing bubbles in the process.
The gas diffusion model used in an analysis is given by the following equation:
where:
-
is the diffusion coefficient -
is the temperature - and
and 
are data-fitted coefficients
If the value of is zero, then the diffusion coefficient will be constant at .