Robust, malleable, degradable, self-healable, weldable and recyclable polyimine thermosets from natural peach gum and chitosan

Abstract

The increase in nondegradable polymer waste and the depletion of nonrenewable fossil resources result in environmental concerns and unsustainable industrial development. It is significant to fabricate polymer thermosets with degradable, self-healable, weldable and recyclable performances from biomass. Herein, for the first time, natural peach gum (PG) as an attractive feedstock was employed to prepare degraded and recycled polyimine (PI) networks, due to the hydrolysable and renewable nature of PG. Firstly a peach gum polysaccharide with pendent –CHO groups (PGP-CHO) was synthesized through a graft reaction between 4-formylbenzoic acid and PGP; then it was cured with chitosan (CS) via a moderate and catalyst-free Schiff base reaction resulting in fully biobased PI networks (PGCS). The resultant PGCS-100 networks display good mechanical properties (tensile strength of ∼56.5 MPa and Young's modulus of ∼439 MPa) and high thermal stability (initial decomposition temperature around 227.1 °C). Meanwhile, the PGCS-100 network containing the most dynamic imine bonds exhibits superior self-healing, welding, shape memory and reprocessing performances. Moreover, PGCS-100 can be degraded completely under acidic conditions, allowing sustainable recycling. Furthermore, PGCS-100 can be applied in recycled adhesion, exhibiting excellent adhesion strength (10.5 MPa). Briefly, a new strategy to develop green environmentally friendly PI networks with high performance from biomass is provided, contributing to the reduction of polymer waste and sustainable industrial development.