Thermal Assault and Polyurethane FoamEvaluating Protective Mechanisms

Rigid polyurethane foam utilizes a variety of mechanisms to mitigate the thermal assault of a “regulatory burn”. Polymer specific heat and foam k-factor are of limited usefulness in predicting payload protection. Properly formulated rigid polyurethane foam provides additional safeguards by employing ablative mechanisms which are effective even when the foam has been crushed or fractured as a result of trauma. The dissociative transitions from polymer to gas and char, and the gas transport of heat from inside the package out into the environment are also thermal mitigators. Additionally, the in-situ production of an intumescent, insulative, carbonaceous char, confers thermal protection even when a package’s outer steel skin has been breached. In this test program, 19 liter, “Five gallon” steel pails are exposed on one end to the flame of an “Oil Burner” as described in the US Federal Aviation Administration (FAA) “Aircraft Materials Fire Test Handbook”. When burning #2 diesel at a nominal rate of 8.39 kg (18.5 pounds)/hr, the burner generates a high emissivity flame that impinges on the pail face with the thermal intensity of a full scale pool-fire environment. Results of these tests, TGA and MDSC an