Silica-Filled EPDM Rubbers as Ablative Insulating Materials

These materials are intended to replace other materials that will soon be unavailable.

Silica-filled polymers made from ethylene propylene diene monomer (EPDM) have been found to be useful as ablative thermal-insulation materials. These polymers have been investigated as candidates to replace some previously developed polymeric ablative rocket-engine insulating materials that will soon become commercially unavailable. Although these materials have been developed specifically for use in and on solid-fuel rocket motors, they may also be useful in terrestrial applications in which there are requirements for protection against high temperatures for short times.

Several formulations of silica-filled EPDM polymers have been investigated. These formulations incorporate improvements where possible. Examples of improvements include the use of a tackifier or the choice of one or more accelerator(s) to obtain a longer scorching time as well as desired curing properties. For each formulation, the ingredients are mixed according to ordinary rubber-processing techniques in a two-pass mixing procedure implemented in an internal mixer. All the ingredients except the accelerator(s) and sulfur (if used) are added during the first pass; the accelerators and sulfur (if used) are added during the second pass. In ablative tests, some formulations unexpectedly performed better than others did.

This work was done by David G. Guillot of Thiokol Corp. for Marshall Space Flight Center. For further information, please contact the company at This email address is being protected from spambots. You need JavaScript enabled to view it..

Title to this invention has been waived under the provisions of the National Aeronautics and Space Act {42 U.S.C. 2457(f)} to Thiokol Corporation. Inquiries concerning licenses for its commercial development should be addressed to

Thiokol Propulsion

Intellectual Property Department

PO Box 707

M/S A11

Brigham City, UT 84302-0707

Refer to MFS-31406, volume and number of this NASA Tech Briefs issue, and the page number.

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