Project Description:
This capstone project investigates the use of plasma surface treatment to improve adhesion between EPDM insulation and HTPB liner used in solid rocket motors. Due to EPDM’s inherently low surface energy and difficulty bonding, the current industry method relies on manual mechanical abrasion, which introduces contamination and inconsistency. This project proposes replacing this method with controlled plasma functionalization to modify the EPDM surface chemistry without damaging the material, thereby benefiting many industry stakeholders, including the project sponsor, Northrop Grumman. The process began with a literature review and parameter selection, followed by iterative testing of exposure time at constant RF power and gas flow rate, using water contact angle measurements and surface roughness (RMS) analysis to determine plasma conditions that improved wettability without degrading the surface. Once the parameters were finalized at 80 W, 10 sccm, and 3 minutes, EPDM samples were prepared under four surface conditions, bonded to HTPB, cured, and mechanically tested using flatwise tensile (ASTM C 297) and lap shear (ASTM D 3164) methods. Results showed that plasma-treated samples had the highest ultimate tensile and shear strengths and exhibited more cohesive failure modes than mechanically abraded samples, indicating stronger interfacial bonding. Overall, the project validates the proof of concept that plasma treatment is a more consistent, cleaner, and more effective alternative to mechanical abrasion for improving insulation-liner adhesion for solid rocket motor applications.
