Sustainable Composites
Printed circuit boards (PCBs) are ubiquitous in electronics and make up a substantial fraction of environmentally hazardous electronic waste when devices reach end-of-life. Their recycling is challenging due to their use of irreversibly cured thermoset epoxies in manufacturing. Here, to tackle this challenge, we present a PCB formulation using transesterifcation vitrimers (vPCBs) and an end-to-end fabrication process compatible with standard manufacturing ecosystems. Our cradle-to-cradle life-cycle assessment shows substantial environmental impact reduction of the vPCBs over conventional PCBs in 11 categories. We successfully manufactured functional prototypes of Internet of Things devices transmitting 2.4 GHz radio signals on vPCBs with electrical and mechanical properties meeting industry standards. Fractures and holes in vPCBs are repairable while retaining comparable performance over multiple repair cycles. We further demonstrate a non-destructive recycling process based on polymer swelling with small-molecule solvents. Unlike traditional solvolysis recycling, this swelling process does not degrade the materials. Through dynamic mechanical analysis, we fnd negligible catalyst loss, minimal changes in storage modulus and equivalent polymer backbone composition across multiple recycling cycles. This recycling process achieves 98% polymer recovery, 100% fbre recovery and 91% solvent recovery to create new vPCBs without performance degradation. Overall, this work paves the way for sustainability transitions in the electronics industry.
Healable Vitrimer Composites
Despite extensive research, fatigue remains a significant issue causing failure in carbon-fiber reinforced polymeric (CFRP) composites. Existing methods, including nano-scale additives and self-healing polymers, only slow crack growth or offer single-use repair, failing to effectively address fatigue. Our study introduces a vitrimeric system capable of repeatedly reversing fatigue damage by heating the material above its topology freezing transition temperature. This facilitates intermittent healing of fatigue-induced damage in the vitrimer matrix. Using this system, we demonstrate that fatigue failure in vitrimers and carbon-fiber reinforced vitrimers (vCFRP) can be indefinitely postponed. This approach suggests a future for materials that can periodically reverse natural aging and fatigue processes, ensuring reliable long-term performance.
Recycled Continous Carbon Fiber Composites
This research presents a novel, sustainable approach to recycle continuous carbon fibers from end-of-life thermoset composite parts using Joule heating, efficiently reclaiming carbon fibers from composite scrap for fresh composite production. Applying electric current to the conductive carbon fibers generates heat that degrades the surrounding matrix, easing fiber separation post heating. The tensile properties and surface chemistry of these reclaimed fibers, in comparison with as-received fibers and fibers recycled through traditional oven pyrolysis, were comparable in terms of elastic modulus, but showed a 10-15% decrease in tensile strength. Fabrication of composites using the recycled fibers demonstrated comparable mechanical properties to conventionally recycled counterparts. This study validates DC heating as a scalable, out-of-oven carbon fiber recycling method.
Rapid Synthesis of Energy Storage Materials
Entropy stabilized oxides (ESOs) represent a new class of metal oxides with unique properties, limited by energy-intensive fabrication processes. We introduce an energy-efficient method for ESO synthesis using carbonaceous materials, including carbon fibers and graphene, which respond rapidly to radio frequency (RF) fields within the 1–200 MHz range. This RF-initiated combustion synthesis enables efficient ESO fabrication (Mg0·2Co0·2Ni0·2Cu0·2Zn0.2)O with heating rates of 203 °C/s at 20 W power, reducing formation time to under a minute. The resulting ESO-carbon fiber and ESO-graphene composites were extensively analyzed, with ESO-coated carbon fibers exhibiting minimal change in mechanical properties. This study highlights the potential for rapid, efficient ESO-carbon composite synthesis using non-contact RF heating.