Adhesion between rocket solid propellant and EPDM rubber treated by RF plasma: An alternative for flexible thermal protections

Abstract

The actual technology of solid propellant rocket of the Brazilian Space Program uses NBR (acrylonitrile-butadiene) rubber as thermal protection of the rocket chamber. However, the NBR has high density, is very expensive, and liberates toxic byproducts during the propellant burning. One interesting alternative to the NBR is the EPDM (ethylene-propylene-diene monomer) rubber, which possesses excellent mechanical and thermal properties, low density; low process cost and is environment friendly. Nevertheless, it has non-polar surface and consequently low adhesion properties. In order to improve the adhesion of the propellant to the rubber surface, the later must be activated. Cold plasma is a technology that offers a more economical, rapid, and environmental friendly rubber surface treatment, once the treatment is done using non-toxic gases. This technique also allows us to treat the rubber surface without affect the rubber bulk properties. In this work we present the results on the plasma surface treatment of EPDM performed in RF glow discharge using gas mixtures of O2/Ar, N2/H2/Ar and N2/Ar. The treated and non-treated rubber surfaces were analyzed by contact angle measurements. The adhesion strength test indicates that plasma treated EPDM rubber is a strong candidate to be used as thermal protection of rocket chambers. Copyright IAF/IAA. All rights reserved.