Events Calendar

PhD Defense

Speaker: Yijia Ma , Mork Family Department of Chemical Engineering and Materials Science, University of Southern California

Talk Title: Chemical Recycling of Amine/Epoxy Composites at Atmospheric Pressure

Abstract: Because of the increasing demand for lightweight structures in aerospace, automotive, and wind energy industries, the global market size for carbon fiber polymer composites is anticipated to reach $ 35 billion by 2020. Carbon fibers from end-of-life composites retain properties nearly equivalent to virgin fibers, yet few are recovered and/or reused due to a lack of viable recycling technologies. This absence of recovery/recycling is especially true for thermoset composites that undergo irreversible cure reactions. At the present juncture, composite recyclability is essential to the sustainability of the growing composite industry. Without a robust and effective method to recycle composites and complete the material life-cycle, these materials will not be able to compete with steel and aluminum in mass market applications, for which recycling rates are already high.
The objective of my research is to develop an effective chemical recycling method for cleavage of polymer matrices using moderate conditions (atmospheric pressure and moderate temperature) and safe chemicals that can recover near-virgin quality fibers and potentially useful polymer components. These features are critical to practical, large-scale composite recycling, but have not been reported to date. My investigation focuses on amine-cured epoxies, which is the most widely used polymer matrix in high-performance composites.
Findings indicated that acid digestion was an effective dissolution process for highly crosslinked amine/epoxy composites. Near-virgin quality carbon fibers in the original fabric form were recovered after digestion. The reaction mechanism for acid digestion was identified, and target catalysts were evaluated to accelerate the reaction rate. Furthermore, a parametric study that investigated the relationship between composite properties and matrix dissolution rate was performed, and key parameters affecting the dissolution rate were identified. Data showed that the major rate-limiting factor for acid digestion was the diffusion rate, rather than the chemical reaction rate. Two strategies to enhance the diffusion rate -“ pre-treatment and mechanical shredding -“ were evaluated, and both were effective. Lastly, I recovered the decomposed matrix residues from chemical solutions after acid digestion and demonstrated routes for reusing the matrix residues in virgin resin formulations, effectively closing the recycling loop.

Location: Hedco Pertroleum and Chemical Engineering Building (HED) - 116

Audiences: Everyone Is Invited

Contact: Karen Woo/Mork Family