Model Describing the Steady-State Pyrolysis of Bubble-Forming Polymers in Response to an Incident Heat Flux

摘要

A theoretical model is developed to describe the in-depth effect of bubbles on the steady-state transport of volatile gases (monomer) from the surface of a polymer subjected to an incident heat flux. In this model the effect of the bubbles on the surrounding (liquid) polymer is felt through the bubble number distribution function, n, which appears in the equations for conservation of mass, momentum, species and energy in the melt. The equation for the evolution of n includes the effects of bubble growth, convection and nucleation; its derivation requires preliminary study of the growth and motion of an individual bubble in a liquid with a temperature gradient. With these equations, formulas for the mass flux of volatiles from the polymer surface and the bubble void fraction are developed, for the special case of constant polymer mass fraction.