High Temperature Paste Adhesives and Sealants

The manufacturing processes for fiber reinforced composites and our knowledge base for predicting their bulk mechanical response have matured considerably over the past few decades.  Rapid development has been driven by the high specific strength, stiffness, and toughness, as well as our ability to tailor their bulk properties for individual applications.  While composites have found wide use in aerospace structures, joining of composite materials to skins or primary structures poses certain challenges due to their notch sensitivity which limits the use of traditional fasteners.  Adhesives are typically used to bond composite materials, however these thermosetting polymers are typically designed to possess a high degree of toughness to resist shear loading which consequently results in low thermal stability making them unsuitable for high temperature applications.  In applications that require high Tg, such as components around the engine, the choice of polymers is narrow.  Ultimately, current aerospace resins that achieve a high Tg require long cure times, often require autoclave curing and are generally not well suited for depot repairs.  The limitations of current high temperature resins provides a significant opportunity for Trimer Technologies due to our thermosetting resin which has been shown to cure in as little at 30 sec at 250° F, achieve a Tg > 700° F without a post cure and attain mechanical properties equivalent to the highest performance polymers used in the aerospace industry.  Notably, the high Tg can be obtained with a far lower cure temperature than any state-of-the-art resin currently available.  This resin provides Trimer with the unique opportunity to develop a new class of high-performance adhesives for use in extreme temperatures.  Trimer will develop methods to increase the viscosity to attain a paste which can be used as a filler for surface imperfections such as ply drops.  The formulated resin systems will be evaluated to measure the mechanical and adhesive properties at temperatures up to 550° F and after aging for 1,000 and 2,000 hours at 500° F.  Testing will also be performed to optimize bond line thicknesses and processing conditions.  The program goal will be to exceed BR 57-2 paste adhesive performance while providing a rapid low temperature cure cycle compatible with both OEM fabrication and depot repair.  Trimer will work closely with Northrop Grumman Aeronautic Structures to validate material performance on representative structures, validate test results and evaluate the dielectric behavior of the resin for application to radar windows. This Phase II SBIR will yield new adhesives chemistries that cure in minutes, exceed the performance of current state of the art resins, reduce raw material cost and provide a material free of NMP that can cure without the porosity found in Polyimides.  Ultimately this SBIR will provide the adhesives/sealants required for the next generation of aerospace vehicles.