Green Preparation And Properties Of Wood(Bamboo) Powder/Bacterial Cellulose Composites

Natural wood is an abundant biomass resource with environmentally friendly,renewable and biodegradable properties,which makes wood and its derivatives potential candidates to replace petroleum-based plastics.The wood-based structural materials reported usually require a partial delignification of lignin and hemicellulose to increase the percentage of cellulose,which can improve the mechanical properties of the composites.However,the extensive use of acid or alkaline solutions in the delignification process has not made the preparation of these composites truly environmentally friendly.Based on this,this thesis explores the additive strategy of adding bacterial cellulose(BC)as a green binder and component regulator to wood powder/bamboo powder,and wood(bamboo)powder/bacterial cellulose composites were prepared using a greener process,and its morphology,mechanical properties,flame retardant properties,thermal insulation and stability were investigated.The main contents are as follows:(1)Wood powder/bacterial cellulose composites(WBC)were prepared by aqueous phase dispersion of wood powder and bacterial cellulose.The mechanical properties,microscopic morphology,stability to water,thermal stability and thermal insulation of WBC was investigated.The results showed that the tensile strength of WBC increased gradually with the increase of cellulose,the tensile strength of WBC-70 could reach 81±8.05 MPa,and the tensile strength of wet WBC-70 could still reach 26.87±2.30 MPa.It can retain its original shape after static water immersion of 50 days.Theresults of the thermal analysis and cone calorimeter tests showed that the maximum decomposition temperature of WBC was up to362～366℃,much higher than that of wood powder(337.33℃).WBC-40 had similar ignition time,lower heat release rate and peak heat release rate(207.56 k W/m~2),lower total heat release(12.95 MJ/m~2)and total smoke release compared to that of wood-plastic composites with flame retardants.WBC exhibited good thermal insulation due to the dense,multilayer structure of WBC.Ultraviolet-Visible-Near infrared results showed that WBC-50had high reflectance(～76%)and emissivity(～96%),which makes it a potential as a passive radiative cooling material.(2)The bamboo powder was treated with water glass solution to in-situ reconstitute the hemicellulose and lignin in bamboo powder,and further compounded with BC to prepare bamboo powder/bacterial cellulose composites(Bm BC).The bamboo powders treated with the water-glass were analyzed by Fourier infrared spectroscopy,scanning electron microscopy and laser particle size measurement and compared with that of 9 wt%Na OH aqueous solution treatment.It was found that the water-glass solution could effectively partially remove hemicellulose;while the 9 wt%Na OH aqueous solution could further remove some lignin.The effect on the refinement of bamboo powder particle size was similar for the same treatment time at low/high temperature.The mechanical properties of Bm BC showed that the particle size of bamboo powder also had a significant effect on its mechanical properties,and the smaller the particle size of bamboo powder,the higher its tensile strength.The use of bamboo powder treated with water glass solution can increase the tensile strength of Bm BC and the tensile strength of Bm BC-70 could reach 39.26±9.03 MPa.The maximum decomposition temperature of Bm BC was also increased from 300℃ to 310～312℃ for bamboo powder(water glass 10℃).