Mechanical properties of degraded PMR-15 resin

Thermo-oxidative aging produces a non-uniform degradation state in PMR-15 r esin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized s urface layer from: the properties of interior material. Test specimens were aged at 316 degrees C in either air or nitrogen, for durations of up to 80 0 h. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and coefficient of thermal expansion (CTE) of nitrogen aged specimens were measured directly. Four-point-bend tests were performed to d etermine modulus of both the oxidized surface layer and the interior materi al. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core m aterials have substantially different properties.