Gas Detection System for Cure Process Management of Polyimide Composites

Polyimides offer superior thermal stability and mechanical performance as compared to other resin systems, making them appealing for applications with sustained high temperature environments. Processing these materials creates unique challenges beyond the higher temperatures required. It can be difficult to manufacture high quality polyimide parts due to the off gassing of solvent and cure by-product volatiles during processing. Typical polyimides are highly solvented to facilitate lamination and have condensation cure reactions, both of which can contribute to significant generation of gas in the part. Trapped expanding gas can cause lofting and excessive resin flow which must be managed to minimize porosity, distortion, wrinkling, and/or delamination.Key to process improvement in polyimides and other high temperature composites is a better real-time measurement and understanding of the flow rates and total flow of off-gassed solvents, reaction species, and monomers. High temperatures, pressures and a wide range of gas flows at or near condensation conditions, combined with potentially unknown species and limitations of existing manufacturing equipment, have contributed to complexity of these measurements in a full-scale environment. The goal of this project is to develop both real-time factory scalable measurement hardware for leak detection and species identification, as well as a corresponding base off-gas modeling approach that can be used to identify and optimize key process parameters to improve production rates and quality in production. The objective of this work is a prototype for near real-time species detection, identification, and quantification of volatiles produced that can be industrialized for production full scale use. Additionally, a framework for processing simulation capabilities of polyimides will be developed with a focus on solvent evolution and evacuation as a complimentary tool for cure cycle design and optimization. The scope also includes development and/or extension of modeling capabilities which include imidization extent, volatile generation, and gas transport for prediction of species evolution and transport during processing. The approach will be extendable to other material systems beyond those studied in this work. The industrialization plan will include an approach to extend the species detection and modeling toolsets to additional materials as well as road mapping the scale-up.This system will fit in line with existing vacuum lines during the bagging and cure of composite parts. Based on the off-gassed volatiles detected, the tools will provide real time information on evolution of gases and guidance on when sufficient off gassing has occurred to ensure part quality. The final product will fill a gap in the market for real time detection and management of volatiles in highly solvated composites.