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Low-molecular-weight 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) was used to modify bamboo strips catalyzed by maleic anhydride. In this study, response surface methodology (RSM) was applied to optimize the treatment conditions for DMDHEU modification of bamboo. Three selected parameters, DMDHEU concentration, curing temperature, and curing time, were further optimized using response surface methodology via the box behnken design (BBD). The equilibrium moisture content (EMC), water absorption (WA), anti-swelling efficiency (ASE), mechanical properties, and mold resistances to (Aspergillus niger V. Tiegh, Penicillium citrinum Thom, Trichoderma viride Pers. ex Fr., and Botryodiplodia theobromae Pat.) were evaluated as the dependent variables. The results show that the dimensional stability and mold resistance of bamboo were enhanced remarkably, and the modulus of rupture (MOR) of bamboo was decreased after DMDHEU modification, while the modulus of elasticity (MOE) changed slightly, and the parallel-to-grain compressive strength (CS) was increased. Furthermore, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) were used to investigate the effect of modification on the bamboo microstructure and functional groups. In the context of SEM, TGA, and FTIR analyses, the thermal stability of bamboo modified with a medium or high concentration of DMDHEU was improved, the starch granules in the parenchyma cells of modified bamboo dissolved, and few resins were distributed in the lumens of treated bamboo. [ABSTRACT FROM AUTHOR]

As a high-strength biomass composite material, the development of bamboo scrimber (BS) was limited by its flammable characteristics. In this study, different immersion orders of ammonium polyphosphate (10 wt%, APP solution) for bamboo bundles were selected in order to evaluate its influence on the interphase behavior, mechanical and combustion properties of BS. The flattened bamboo bundles, phenol-formaldehyde (PF) and APP solution were utilized to fabricate the BSs. The interphase behavior of the treated bamboo bundles was characterized by the contact angle measurement, Fourier transform infrared spectroscopy (FTIR) analysis, fluorescence microscope and SEM-EDS measurement. Thermogravimetric analysis, limiting oxygen index (LOI), mechanical properties before and after combustion test were assessed for various BSs. The results showed that significantly increased equilibrium contact angle of PF droplet on the surface of bamboo after immersed in APP solution while the decrement was for APP solution droplet on the surface of bamboo after immersed in PF. Varied intensities of chemical bonds and distribution forms of APP and PF were observed for the treated BSs depending on the immersion orders. These variations have a great effect on the mechanical and combustion properties. No significant decrement of compressive strength and bending strength was observed for APP-treated BSs with different immersion orders compared with the control sample. Higher compressive strength, bending strength, and modulus of elasticity (MOE) were found for the APP-PF-BS with increments of 31.60%, 21.70%, and 29.01%, respectively. Significantly increased thermal stability was observed for bamboo bundles after immersed in APP and PF especially for the temperature over 300 °C. After the combustion test (duration of 40 min), a higher LOI of 35.4, retention rates of mechanical properties of 39.96–78.97%, and lower mass loss of 15.93% were obtained for the PF-APP-BS. Finally, the immersion order of low concentration of APP solution has a great effect on the interphase behavior, mechanical and combustion properties of BSs, which plays a significant role in the optimized fabrication of fire-resistant BSs. • Varied interphase behavior was observed for APP-treated bamboo and BSs. • No obvious decrease of compressive and bending strengths was for APP-treated BSs. • Significantly increased thermal stability was observed for APP-treated bamboo. • Better fire-resistant behavior was obtained for PF-APP-BS with higher LOI and lower mass loss. • Higher retention rates of mechanical properties of 39.96–78.97% were observed for PF-APP-BS. [ABSTRACT FROM AUTHOR]