Preparation of boroxine-based self-healing polyurethane with repeatable adhesive property under mild conditions

Based on the hydrolysis and dehydration of boroxine and boric acid, a boroxine was prepared from 3-Aminobenzeneboronic acid (3-ABBA). Then a novel boroxine-based self-healing polyurethane (BPU) which has a repeatable adhesive property under mild conditions was synthesized by using boroxine and polyurethane prepolymer. The chemical structure and thermal property were confirmed by Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). When the mole ratio of isophorone diisocyanate (IPDI) and polypropylene glycol 2000 (PPG 2000) was 3:0, the mechanical strength and elongation at break of BPU film reached 1.63 MPa and 1577.79%. Meantime, BPU could be healed under the action of a water molecule and the self-healing rate was up to 92.02%. BPU film took on excellent self-healing property under mild conditions. In addition, BPU film could easily dissolve in N, N-dimethylacetamide (DMAC) to become an adhesive. The bonding strength of BPU adhesive to leather substrate reached 1.73 MPa, which was nearly the same as the standard value of adhesive used for shoes and bags. Interestingly, after the bonded leather was separated into two parts, they can adhere together again by spraying water on the bonding part. Through healing the bonding strength of BPU adhesive was still 1.65 MPa. Therefore, BPU is characterized by excellent repeatable adhesive property which has great potential application.