The dissolution of gas into the polymer melt will impact on the viscosity model used for Microcellular injection molding.
The viscosity model for microcellular injection molding is given by the following equation: 
where:
 is the viscosity of the polymer-gas system
      is the viscosity of the polymer-gas system  r is the viscosity of the resin (without gas)
     r is the viscosity of the resin (without gas)  is the volume fraction of the nucleated gas bubble
      is the volume fraction of the nucleated gas bubble  is the initial gas concentration
 is the initial gas concentration  ,
,  and
 and  are data-fitted coefficients
 are data-fitted coefficients