Hot-air aging failure mechanisms of carbonyl iron powder/methyl vinyl silicone rubber microwave-absorbing materials

A rubber microwave-absorbing material was prepared by compounding methyl vinyl silicone rubber (VMQ) and 45 vol% carbonyl iron powder (CIP). When used in a high-temperature environment at long periods, the material undergoes thermal aging and rapid degradation. This work mainly aimed to investigate the thermal behavior and aging failure mechanisms of such material during hot-air aging at 200°C. The mechanical and electromagnetic properties were measured with an electronic tensile testing machine and a network analyzer, respectively. Results indicate that CIP was oxidized by oxygen in the aging process and produced reactive oxygen species, which catalyzed the cross-linking of VMQ. The increased cross-linking density changed the mechanical properties and enhanced the thermal stability of the CIP/VMQ composite-absorbing material. Thermal aging gradually penetrated the surface and proceeded into the interior of the material. The microwave-absorbing properties deteriorated after hot-air aging.