Adhesive, brittle resin insulation

Microcrystalline quartz is obtained by pulverizing quartz sands and is a hard solid (7 Mohs). It increases the thermal shock resistance in brittle resins - some filled thermosetting resins are cracked by relatively few thermal cycles between, say, ambient temperature and 100°C - when added at high concentrations (typically 100-200 parts per hundred by weight). It can be surface treated with an aminosilane to enhance adhesion, when used in epoxy compositions to improve flexural modulus, electrical insulation or thermal properties, and in the case of unsaturated polyesters, it can be treated with a methacrylic silane. 

The forward bulkhead of the motor case is exposed to stagnant but hot gases, and thus must be lined with an insulative material. The modulus of this insulator is sufficiently low so as to transmit the chamber pressure into the external structural member. Insulators that are brittle tend to crack during the initial pressurization, with possible catastrophic burn-through of the motor case wall. Insulators are composed of an elastomer-modified charring resin (like a copolymer of butadiene-acrylonitrile and phenolic) with various reinforcements and/or low conductivity fillers. The bulkhead insulator is generally premolded in segments and then adhesively (plastic) bonded in place. 

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