INFLUENCE OF LONG THERMAL EXPOSURE ON FIRE SAFETY OF POLYMERIC MATERIALS

All the polymeric materials used for manufacturing external contour of complex technical systems are undergoing influence of an environment. The greatest influence on polymeric materials is associated with factors of temperature and the increased humidity. Influence of these factors on materials leads to degradation of their main certificates of service. One of the major characteristics for polymeric materials is its fire safety. In the given work the influence of the long thermal exposure simulating 15–20 years of operation without taking into account influence of humidity, on characteristics of fire safety was studied. Research was executed for four kinds of fibreglasses on following kinds of polymeric matrixes: polyester resin, cold-setting epoxy resin, hot-setting epoxy resin containing fire-retardant additives, phenolic fire resistance resin. Tests of initial samples of materials and after thermal aging at raised temperature +120 °C within 2000 hours was carried out. Following characteristics of fire danger according to requirements of aviation norms were defined: flammability, optical smoke density, heat release. Also the complex index of fire danger was calculated. It is shown, that after the chosen dose of thermal exposure the characteristics of fire safety as a rule improved:there were a reduction of duration of residual burning and
or lengths of a burn-out, optical density of a smoke, the maximal heat release rate. The greatest changes have been registered for glass-reinforced plastics on polyester binder and cold-setting epoxy resin. It is the most probable that the occurred changes are caused due to post cure effect of a polymeric matrix, elimination and additional cross-link processes, and also removal from the material combustible low-molecular products.