Study of the Influence of Polymer Microspheres on the Efficiency of Elastomeric Fire and Heat-Protective Coatings

Abstract

The influence of polymeric thermally expanding microspheres on the behavior of fire- and heat-protective elastomeric materials based on ethylene propylene diene rubber when exposed to flame has been studied. Estimation of protective characteristics of elastomeric compositions is carried out by the rate of heat flux isotherm advancement in the material matrix under the influence of plasmatron gas jet on the coating surface. It is shown that the heating rate of elastomeric compositions containing microspheres decreases by two or more times compared to the basic composition. The increase in the efficiency of the compositions is associated with the appearance of a porous pre-pyrolysis layer in the matrix before the beginning of the destruction of the elastomeric component. The temperature of occurrence of the pre-pyrolysis layer, which is related to the temperature of the beginning of thermal expansion of microspheres, is determined. The influence of the microspheres' expansion degree on the efficiency of protective coatings is shown. The temperature providing the maximum expansion of coatings due to the influence of microsphere characteristics is determined. The conditions of the pre-pyrolysis layer formation are determined by the parameters of thermally expanding microspheres included in the elastomeric material. It is shown that it is possible to regulate the parameters of the pre-pyrolysis layer of compositions by varying the characteristics of polymer microspheres, which is associated with the temperature of the onset of expansion and the maximum degree of expansion of each type of microspheres used. Based on the obtained data, the choice of microspheres is justified. The volume change of compositions containing polymeric thermally expanding microspheres ranged from 150 to 450 percent compared to the base material. The regularity of change of the heating time of compositions due to the influence of the type and characteristics of polymer microspheres on the parameters of the pre-pyrolysis layer was established.