Publications

Modeling pressurization caused by thermal decomposition of highly charring foam in sealed containers

Erickson, K.L.; Dodd, Amanda B.; Hogan, Roy E.

Polymer foam encapsulants provide mechanical, electrical, and thermal isolation in engineered systems. In fire environments, foams, such as polyurethanes, can liquefy and flow during thermal decomposition, and evolved gases and vapors can cause pressurization and failure of sealed containers. Liquefaction and flow of decomposing foam can cause serious modeling issues in systems safety and hazard analyses. To mitigate the issues resulting from liquefaction and flow, a hybrid polyurethane-cyanate-ester-epoxy foam was developed that has mechanical properties similar to currently used polyurethane foams. The hybrid foam behaves predictably, does not liquefy, and forms 40-50 percent by weight uniform char during decomposition in nitrogen. The char forms predictably and is a relatively uniform "participating medium." A previous paper discussed the experimental and modeling approach developed to predict radiation and conduction heat transfer through decomposing hybrid foam in vented containers. This paper discusses application of a similar approach to the more difficult problem of predicting heat transfer, foam decomposition, and pressure growth in sealed containers. Model predictions are compared with results from radiant heat transfer experiments involving foam encapsulated objects in sealed containers. All model parameters were evaluated from independent laboratory-scale experiments such as TGA and DSC. The time dependent-pressure in the container and the timedependent temperature near the surface of a foam-encapsulated object agreed well with experimental data. © (2010) by BCC Research All rights reserved.