Readily recyclable, high-performance thermosetting materials based on a lignin-derived spiro diacetal trigger

Conventional thermosets, widely used in composites, coatings, electronic packing materials, etc., are typically made of non-sustainable fossil resources and cannot be recycled under mild conditions. Degradable thermosets are promising alternatives, while combining ready degradability and high performance is a challenge. In this paper, for the first time, a spiro diacetal structure was utilized to synthesize readily recyclable thermosetting materials with high performance. A renewable bioresource, lignin derived vanillin, was used to produce a rigid spiro diacetal trigger and further built into three thermosets. Among them, spiro diacetal epoxy resin was systematically investigated and was proved to be readily degradable under mild acidic conditions while maintaining stability under neutral or basic conditions and showing outstanding thermal stability. Meanwhile, its glass transition temperature, tensile strength, modulus, elongation at break are comparable to or even better than those of conventional bisphenol A epoxy resin. Moreover, facilely recyclable carbon fiber reinforced composites and convenient-removal coatings were achieved from this epoxy resin accompanied by excellent performances.