The decomposition of unconfined rigid polyurethane foam has been modeled by a211u001ekinetic bond-breaking scheme describing degradation of a primary polymer and 211u001eformation of a thermally stable secondary polymer. The bond-breaking scheme is 211u001eresolved using percolation theory to describe evolving polymer fragments. The 211u001epolymer fragments vaporize according to individual vapor pressures. Kinetic 211u001eparameters for the model were obtained from Thermal Gravimetric Analysis (TGA). 211u001eThe chemical structure of the foam was determined horn the preparation techniques 211u001eand ingredients used to synthesize the foam. Scale-up effects were investigated 211u001eby simulating the response of an incident heat flux of 25 W/cm2 on a partially 211u001econfined 8.8-cm diameter by 15-cm long right circular cylinder of foam which 211u001econtained an encapsulated component. Predictions of center, midradial, and 211u001ecomponent temperatures, as well as regression of the foam surface, were in 211u001eagreement with measurements using thermocouples and X-ray imaging.
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