Basic research to control the morphology of polyacrylonitrile based carbon fiber is crucial for next generation composites as it determines their mechanical properties and final usage. Poor molecular design through the incorporation of several comonomers that are not distributed evenly attributes to these morphological defects which leads to mechanical limitations. Utilizing the controlled polymerization technique, reversible addition fragmentation chain transfer (RAFT) of novel acrylamide comonomers will afford well-defined precursors with precise control of their precursor molecular design. This new synthetic pathway will tailor ring-closing thermo-oxidative stabilization, exotherm, and final black fiber morphology. Varying the molecular design by comparing evenly (Semi-Batch RAFT) and randomly (Free Radical) distributed comonomers was performed and its effect on the thermal properties was determined. RAFT precursors produced more ring closed systems with lower exotherm peak temperatures than their respective Free Radical precursors. Additionally, differences in comonomer choice showed that n-ethyl acrylamide based copolymers released more water and produced greater stabilization during thermo-oxidative stabilization as compared to n-tertbutylacrylamide copolymers. Ultimately, this research provides new knowledge on the effect of controlling precursor molecular design on thermal properties and sub sequentially, their morphology.

Controlling the morphology of polyacrylonitrile based carbon fiber precursors by molecular design

255th National Meeting (2018)

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