Thiokol Corporation

James W Sinclair

Larry W Poulter

Russell A Crook

Kyung J Min

Kenneth J Schulte

David Lefgren

A surface preparation process has been developed for aluminum and aluminum alloy substrates that greatly improves the resulting bond. The process improves bond strength, fracture toughness, durability and failure mode of adhesive bonds. The process also decreases the sensitivity of aluminum substrates to processing variables such as humidity, temperature and hence the processing timelines. The process involves treating an aluminum surface with a solution of an alkali metal metasilicate, and subsequently treating the surface with a solution of an organofunctional silane. Employing this two step process, bonding to the aluminum substrate is improved.

Method of surface preparation of aluminum substrates

A system and composition is disclosed for binding rocket motor propellants directly to the insulation layer within the rocket motor. Conventionally, it is necessary to place a liner layer between the insulation and the propellant. The present invention is particularly adaptable for use with hydroxy-terminated polybutadiene-type (HTPB) propellants. The method of the invention involves coating the insulation layer with a reactive material, such as a solution of isophorone diisocyanate (IPDI). The reactive material is then allowed to penetrate the insulation layer. Once sufficient penetration is achieved, the HTPB-based propellant is applied over the insulation layer to form a rocket motor propellant grain. The IPDI reacts with both the insulation layer and the propellant and forms a strong bond between the two. In the case of the propellant, additional urethane linkages are generally formed, which results in an area near the bond which may be harder than the propellant grain as a whole. In certain instances it is desirable to add further materials to the reactive material, such as di- and tri-functional aziridines.

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Logan, UT, United States of America

James W Sinclair