Repairable, reprocessable and recyclable rigid silicone material enabled by dual dynamic covalent bonds crosslinking side-chain

Abstract

Although many dynamic crosslinked silicone materials with repairability, reprocessability and recyclability have already been developed, these materials are still challenged by their weak mechanical properties and low glass-transition temperature (Tg). Herein, a dual dynamic covalent bonds crosslinking side-chain concept is proposed to fabricate repairable, recyclable and reprocessable silicone material with high mechanical strength and Tg. Specifically, the dynamic imine bond and aminal bond are synergistically integrated into the polysiloxane crosslinked network, where diethylenetriamine functionalized polysiloxanes are crosslinked by 1,4-phthalaldehyde. The resultant silicone materials exhibit maximum tensile strength and Tg of ∼ 25 MPa and ∼ 170 °C, respectively, which are much higher than the reported dynamic crosslinked silicones. More importantly, the dynamic behavior of this rigid silicone can still be effectively activated by raising the temperature. Based on this, after the damaged materials are repaired by thermally pressing them with silicone powders, they can recover more than 95 % of virgin tensile strength. The pulverized silicone powders can also be reprocessed into new samples after thermally pressing at 150 °C for 45 min, and ∼ 85 % of the tensile strength is repeatedly restored. In addition, the carbon fiber/silicone composite with a tensile strength of 110 MPa can also be recycled for carbon fiber and silicone material. When the recycled carbon fiber and silicone material are thermally remolded into new composite, they repeatedly recover ∼ 95 % of mechanical properties. Obviously, this dynamic crosslinked silicone material will meet the potential applications requiring high mechanical properties under high temperature conditions.