Mechanochemical Recycling of Highly Cross-Linked Thermosets: Economic-Friendly and Pollution-Free

Highly cross-linked thermosets possess superior mechanical properties and have found broad applications in engineering. However, due to the dense cross-links, it is extremely challenging to recycle highly cross-linked thermosets, causing serious environmental and sustainable concerns. Herein, a mechanochemical recycling strategy is proposed for highly cross-linked thermosets via the synergy of mechanics and chemistry, which is economic-friendly and pollution-free. To demonstrate the strategy, diverse metal-complex catalysts are employed to recycle highly cross-linked epoxy incorporated with switchable covalent bonds at certain pressure, temperature, and time. The effect of each catalyst on the efficiency of recycling is evaluated, which follows a descending order: Zr⁴⁺ > Mn³⁺ > Co³⁺ > Fe³⁺ > Co²⁺ > Zn²⁺ > OTi⁴⁺ > Ni²⁺. The results show that the mechanical properties, such as Young's modulus, ultimate strength, peak strain, impact strength, flexural modulus and strength, as well as thermal stability of the recycled samples are almost identical to those of as-synthesized ones. The effectiveness of the method is further confirmed via micromorphology.