The overall program objective was to develop a flexible compound which not only functioned in a manned aerospace environment as an effective electrical insulation, but whose flammability characteristics in 16.5 psia, 60% oxygen40% nitrogen were evidenced by rapid self-extinguishment and minimal thermal (pyrolysis) degradation. The following polymeric matrices were examined in depth: fluoroelastomers, modified fluoroelastomers, silicone RTV's, and modified silicone and fluorosilicone RTV's. Almost none of these systems burned in air, but all burned in 6.2 psia oxygen. Inorganic, organic, and inorganicorganic additives were evaluated in conjunction with these polymers in order to achieve the required survival in the 16.5 psia 6040 environment. Depending upon formulations, it was possible to achieve non flammable products when tested in the 14 in. x 14 in. x 1 in. configuration, even up to and including 16.5 psia oxygen. However, in order to assure this level of flame resistance, it was found necessary to heavily load the matrix with the additives. mns mechanical propertiesoptimization This resulted in a significant reduction in mechanical properties and large increases in viscosities. Optimization of formulations to obtain a suitable balance between these properties and flammability resistance led to the final selection of Formulation 387 as the primary system. (Author)
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