Rapidly recyclable, monomer recovery and flame-retardant bio-based polyimine networks

With the development of a circular economy and sustainable environment, efficient and sustainable recycling of useful chemicals from thermosets is of great significance. However, most commercial thermosetting materials are difficult to reprocess, degrade, and recycle due to their permanent cross-linked network, and the preparation process consumes much fossil energy and causes serious environmental pollution problems. Furthermore, the high flammability makes them unsafe during service life and limits their applications. Herein, we used renewable lignin derivative vanillin as bio-based materials to synthesize a trialdehyde monomer (TMP) with phosphorus element and developed the bio-based polyimine dynamic networks with excellent comprehensive properties including outstanding reprocess ability, degradation recyclability, and fire resistance performance based on polyetherimide and 4-aminophenyl disulfide. The prepared bio-based polyimine materials with the dual dynamic networks (BPDNs) exhibited outstanding mechanical property with tensile strength of 61.6 MPa, super-rapid degradation rate and high monomer recovery rates of 70.5 %. The prepared BPDNs samples showed great flame retardancy with V0 rating and V1 rating in UL-94 vertical burning test and high LOI value of 29 %. Moreover, BPDNs could be reprocessed within 10 min at elevated temperatures (150 °C). This work provides a very effective method to prepare bio-based advanced thermosetting materials with multiple functions.