Experimental and theoretical studies of bubble nucleation, growth, and migration in the polymer literature have related primarily to the production of foams and to the devolatilization step in polymer processing. Polymer foams are produced through expansion of a supersaturated solution of a blowing agent added to a polymer melt. During devolatilization, volatile components such as unreacted monomers, solvents, and precipitators (e.g. water) are removed after polymerization by reducing the ambient pressure below the equilibrium partial pressure of the volatile gases at an elevated temperature. In both cases an isothermal situation may be assumed, since production of gases is primarily induced by a change in pressure.
To the knowledge of the author, the details of bubble generation in the complex and highly nonisothermal case of thermoplastic materials undergoing thermal degradation have not been investigated. In the absence of such studies, approaches suggested by the polymer foam and devolatilization literature are used to treat bubble behavior in this model.