Frontal Polymerization-Enabled 3D Printing of Recyclable High-Performance Carbon Fiber Reinforced Polymers

Thermoset composites often face a challenging trade-off between recyclability and high performance. In this study, an innovative closed-loop manufacturing approach that integrates frontal ring-opening metathesis polymerization (FROMP) with 3D printing to produce fully recyclable carbon fiber-reinforced polymers (c-CFRPs) is presented. A self-propagating FROMP-enabled direct ink writing (DIW) printing technology is developed, enabling in situ curing within seconds. This breakthrough eliminates the need for post-processing and reduces energy consumption by two orders of magnitude compared to traditional autoclave methods. By copolymerizing dicyclopentadiene (DCPD) with a commercial spiroacetal monomer (≤3 wt.%), acid-degradable resins that retain the tensile strength of conventional thermosets are introduced while allowing for matrix depolymerization under mild conditions. The DCPD-based c-CFRPs demonstrate remarkable tensile strengths of up to 817 MPa and glass transition temperatures exceeding 160 °C. In a significant advancement, the recovered carbon fibers retain their pristine morphology and over 95% of their original mechanical properties, enabling repeated recycling without performance loss. Additionally, recovered oligomers can be repolymerized into new resins, further enhancing sustainability. This work presents a groundbreaking solution for high-performance composite manufacturing, addressing critical energy and waste challenges in the thermoset industry.