Convert bamboo into high-performance, long-time durability, and fire-retardant with hyperbranched polyethylene glycol and boron

Abstract

Despite renewable bamboo globally available and has been applied in industry, the bamboo modification still absents for achieving long-term anti-mildew, stability and desirable toughness, owing to its inherent hierarchical porous structures, that cannot fully insert and retain ideal drugs/polymers. Hence, a hyperbranched polymer (HPB) with polyether as backbone and phenylboronic acid as binding groups via epoxy ring-opening reactions with amino was designed, and subsequently in situ synthesized in the multi-scaled cellular structures in bamboo. It was demonstrated that the hyperbranched polyether chains filled and swollen the hierarchical bamboo cell walls, which could efficiently replace the inner hydroscopic water in bamboo and greatly improved the bamboo stability, resulted in the wet swelling and dry shrinkage rates reduced by 20.3 % and 14.8 %, respectively. Both the side groups of phenylboronic acid and epoxy on HPB outer layers could generate covalent bonding with bamboo cell walls, which twisted the easy-losing facts of boron and gained a 60.6 % retention rate, surpassed most reported modified bamboo literatures and conferred bamboo with good fire resistance and long-time anti-mildew performance. Importantly, with the cavitation effect of HPB to help stress transmission, the modified bamboo had not expensed bamboo strength, instead of reaching satisfied bending strength and toughness at 154.1 MPa of flexure strength and 10.8 % of bending strain, respectively. That expand the industrial application of bamboo.