Evaluation of High Temperature Structural Adhesives for Extended Service

Abstract

Polyphenylquinoxaline (PPQ) and Polyimide (LARC- TPI) adhesive systems were evaluated for titanium metal bond characteristics in various environments. Each polymer was chemically analyzed prior to fabrication into glass reinforced films and bonded into titanium test coupons. Effects of 45°F continuous exposure upon selected adhesives demonstrated that LARC-TPI bonds were stable to at least 10,000 hours. PPQ in the same high temperature environment exhibited significant loss of bond strength between 5,000 and 10,000 hours exposure. Failures were attributed to disbond between PPQ primer and the oxide layer of the titanium surface. Exposure of both adhesive systems to various aircraft fluids showed very little effect upon bond strength except for minor degradation in the presence of Skydrol. Large area bond titanium metal-to-metal and metal sandwich panels were fabricated using processes developed on the program.