Identification of volatiles during thermal degradation of epoxy resins for detection of incipient fire conditions in composites

This work reports the qualitative and quantitative identification of volatile products from thermal and thermooxidative decompositions of different epoxy resins to allow selection of the particular chemical species most likely to be detectable in situ by infrared and chemical sensors. Thermogravimetry coupled with Fourier transform infrared analysis (TGA-FTIR) has been carried out on three resins at heating rates ranging from 20 to 70 degrees C/min in increments of 10 degrees C/min to understand the effects of the severities of different heating environments. Pyrolysis-FTIR has been conducted to complement the TGA-FTIR study under static atmospheric conditions hence revealing the volatile production under oxidative conditions. While the evolution of water, CO2, phenolic, carbonyl, aliphatic, aromatic and N-containing species could be observed in all resin types, the intensities and times of evolution of different components varied. Higher heating rates resulted in the evolution of volatiles occurring earlier and at greater intensities, but with a lower total amount of each product being evolved. From detection of CO, CO2 and aliphatic hydrocarbons in early stages of resin decomposition, i.e., prior to ignition, it can be inferred that sensors detecting these gases could be deployed in composites to provide a warning of any potential fires.