Publications

Hybrid polyurethane cyanate ester foam for fire environments

Erickson, Kenneth L.; Celina, Mathias C.; Nicolette, Vernon F.; Hogan, Roy E.; Aubert, James H.

Polymer foams are used as encapsulants to provide mechanical, electrical, and thermal isolation for engineered systems. In fire environments, the incident heat flux to a system or structure can cause foams to decompose. Commonly used foams, such as polyurethanes, often liquefy and flow during decomposition, and evolved gases can cause pressurization and ultimately failure of sealed containers. In systems safety and hazard analyses, numerical models are used to predict heat transfer to encapsulated objects or through structures. The thermo-mechanical response of systems involving coupled foam decomposition, liquefaction, and flow can be difficult to predict. Predicting pressurization of sealed systems is particularly challenging. To mitigate the issues caused by liquefaction and flow, hybrid polyurethane cyanate ester foams have been developed that have good adhesion and mechanical properties similar to currently used polyurethane and epoxy foams. The hybrid foam decomposes predictably during decomposition. It forms approximately 50 percent by weight char during decomposition in nitrogen. The foam does not liquefy. The charring nature of the hybrid foam has several advantages with respect to modeling heat transfer and pressurization. Those advantages are illustrated by results from recent radiant heat transfer experiments involving encapsulated objects, as well as results from numerical simulations of those experiments.