Development of mechanically robust and flame-retardant epoxy/bamboo composites utilising cable-like phytic acid–Cu2 + layer-by-layer structures on bamboo fibres

Bamboo/polymer composites are eco-friendly, lightweight, and strong. However, their intrinsic flammability restricts their application. Traditional flame-retardant methods often fail to balance flame resistance and mechanical performance. This study introduces a novel approach for constructing layer-by-layer flame-retardant structures on bamboo fibres, inspired by cable protection designs. Partially delignified bamboo was processed to develop a porous structure, which was esterified to improve its copper ion-binding capacity. Coordination bonds served as crosslinking agents to incorporate ammonium phytate, forming a durable and continuous composite layer that adhered to parenchyma cells. The continuous layer-by-layer protective structures effectively inhibited heat transfer and flammable gas penetration while enhance the toughness of the parenchyma cells and reduced load during external impacts on the bamboo material. The treated bamboo/epoxy composite increased the limiting oxygen index (LOI)from 23.4 % to 31.1 %, and decreased the total heat release (THR)and total smoke production (TSP) by 49.2 % and 74.0 %, respectively. It also maintained an excellent flexural strength of 360.1 MPa along with outstanding superhydrophobicity (initial contant angle was 158.5°) and antibacterial properties (large-scale inhibition of Staphylococcus aureus ). These features render the bamboo/epoxy composites suitable for outdoor construction, marine vessels, and bridges, advancing high-value bamboo utilisation.