Influence of rosin emulsion impregnation on the properties and mold resistance of bamboo

The inherent hydrophilicity of bamboo severely limits its dimensional stability, durability, and resistance to mold in humid environments. In this study, a waterborne rosin emulsion was employed to improve the performance of bamboo. Bamboo strips were impregnated with rosin emulsions with different solid contents using a vacuum-pressure process at ambient temperature. The effects of rosin impregnation on microstructure, pore structure, physical and mechanical properties, thermal stability, and mold resistance were systematically investigated. Results demonstrated that rosin effectively penetrated cell lumina, pits, and micropores, reducing porosity and blocking moisture transport pathways. Consequently, the treated bamboo exhibited significantly reduced water absorption, enhanced surface hydrophobicity, and improved dimensional stability with an anti-swelling efficiency of 31.54% at a relatively low weight percent gain of 4.29%. Moderate improvements in bending strength and stiffness were also observed. Thermogravimetric analysis indicated that rosin impregnation increased the thermal stability of bamboo by shifting the main degradation temperatures to higher values. Furthermore, rosin-treated bamboo demonstrated markedly improved mold resistance, particularly against Trichoderma viride and Penicillium citrinum. These results demonstrated that rosin emulsion impregnation provides a green, efficient, and scalable strategy for enhancing the performance of bamboo for applications in humid environments.