Elastomeric heat-shielding materials containing microspheres modified with a heteroorganic modifier*

The changes in the thermophysical and fire- and heat-shielding properties of compounds based on ethylene propylene rubber when hollow aluminosilicate microspheres (MSPs) are introduced were studied. The MSPs were treated with a heteroorganic modifier – phosphorus–boron–nitrogen-containing oligomer (PEDA), which is a combustion inhibitor. The physicomechanical characteristics of the vulcanisates and the magnitude of the Payne effect were determined. The vulcanisates contained 30 parts filler BS 120 and a sulphur vulcanising group, and also 1 part MSPs. The optimum MSP/PEDA ratio was 1:3. The ultra-high-frequency treatment of the mixture of MSPs and PEDA was especially effective. Using a Versa 3D electron microscope, the increase in the diameter of MSPs as a result of modification and the change in the atomic composition of the surface of MSPs were recorded. The modification of MSPs leads to a reduction in the Payne effect, to an increase in the interaction between rubber and filler, to a reduction in density, and to an increase in the cohesive strength. By comparison with a specimen without MSPs, the rate of linear combustion according to GOST 28157-89 decreases by 10%. The modification of MSPs leads to a decrease in this parameter by 5% by comparison with a specimen containing unmodified MSPs. The time of heating to 100°C of the unheated surface of a specimen heated on the other side to 2000°C increases by 50–60% and 11–19% respectively. The resistance to separation under conditions of erosion entrainment increases by 4–7%. The use of PEDA makes it possible to improve the adhesion of coating to substrate. A scheme of the interaction of MSPs and PEDA is put forward.