Enhancing heat-resistance of epoxy with conductive and crosslink networks by designing imide-based chain extender

Electromagnetic coatings on aircraft need high heat tolerance because high-speed friction bring high temperature. However, high molecular interaction and strong bonding, related to high heat-resistance, lower down the molecular motion ability, causing non-uniform dispersion of conductive fillers, especially for the epoxy type coatings, which has crosslink network. Here, we developed a novel curing system merging diethylenetriamine and dicarboxylic phthalimide to enhance temperature resistance and filler dispersion in epoxy resin. This system allows imide, strong bonding to enhance heat-resistance, to extend the chain of the epoxy resin, maintaining the molecular motion ability and optimizing the dispersion of fillers. Our study reveals that the epoxy composite’s decomposition temperature rises to 383.8℃, suitable for speeds exceeding Mach 3. Additionally, the percolation threshold for carbon black fillers drops to 8.1 vol.%, much lower than the traditional volume-exclusive systems (ca. 70 vol.%). This finding confirms the maintained molecular motion ability of epoxy segments in crosslink netwrok. The electrical performance with volume resistivity dropping to 0.2 Ω·m when filler content is at the percolation threshold, meeting anti-static product requirements. This work proves that designing chain extenders can achieve high heat tolerance with minimal influence in crosslink and conductive networks.