Characterization of Eumelanin as an Additive in High-Temperature Phthalonitrile-Based Resin Blends

Bio-manufactured eumelanin is investigated as a sustainable high-char carbon additive for use with moldable high temperature resins. Blends of Bisphenol A poly-ether-ether-ketone (PEEK)-based phthalonitrile (PN) with 0-30 wt% melanin are prepared and characterized for their compositional, thermal, and mechanical properties. Although the char yield increases from 10 to 30 wt% melanin loading, the presence of melanin decreases the thermal stability compared to PN resin alone. Despite this, the melanin-PN resins still maintain a very high char yield (>64%) up to 1000 & DEG;C under nitrogen. Rheology, thermal analysis, and mechanical measurements suggest off-gassing of the melanin and increased crosslinking between the melanin and PN, leading to a lower flexural strength resin with higher additive loadings. Spectroscopic studies suggest possible interaction between melanin and PN during co-curing, which ultimately can affect the processing and final properties of melanin-additive composite materials.