ABLATIVE CHARACTERISTICS OF POLYETHYLENE AND OTHER THERMOPLASTICS
AIR FORCE MATERIALS LAB WRIGHT-PATTERSON AFB OH
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The ablative characteristics of polyethylene and four substituted hydrocarbons were examined in arc heated air. The order of increasing penetration rates was polytetrafluoroethylene, a tetrafluoroethylene- hexafluoropropylene copolymer, polychlorotrifluoroethylene, polyethylene, and polyoxymethylene. Penetration rate was related to melting, softening, and viscous flow molecular structure sample thickness secondary reactions and surface temperature. A polyaminoborane analogy to polyethylene and a tetramethylammonium hydrotriborate derivative of boron hydride underwent penetration at rapid rates. Boron nitride was an efficient conducting heat sink. There was intense, wide-band radiative emission for all three boron-containing, noncharring materials. The major evaluation variables included effluent penetration time, exposure time, heat flux, sample thickness, sample features and surface temperature.