AbstractThe bubble growth in polymeric fluids under nonisothermal conditions has been molded using the viscoelastic constitutive equation of Leonov incorporating the diffusion of gas from the melt to the bubbles. The gas diffusion seems to be the primary mechanism of bubble growth. The theoretical predictions for Han and Yoo's isothermal experiment compare well with the experimental data. The bubble size distribution in a foam molded specimen of NORYLRegistered trademark of the General Electric Company.resin has also been determined by measuring the bubble size from micrographs. Theoretical predictions for this specimen are in reasonable agreement with the data. A parametric study indicates that the blowing agent concentration has the strongest influence on the final bubble size, followed by melt and the mold temperature.