As a naturally renewable material,wood boasts advantages in terms of environmental protection,processing,application characteristics and environmental qualities.Therefore,wood has been widely used in various human production and lifestyle fields.This study aimed to address the issue of the inability to combine the strength and toughness of lignocellulosic materials,by developing a technology for designing and preparing high-strength and toughness lignocellulosic materials through analyzing the molecular structure of wood cell wall.The materials’ properties were analyzed by using a universal mechanical testing machine,scanning electron microscope(SEM),X-ray diffractometer(XRD)and thermogravimetric analyzer(TGA).The main conclusions are as follows:(1)Natural poplar wood was pre-treated with 2 wt% acid sodium chlorite for 72 hours at a p H of 3.5,which was found to remove hemicellulose and a small amount of pectin.Subsequently,the pre-treatment was completed by treating the wood with 3 wt% sodium hydroxide at 80°C for 7 hours.The sodium chlorite/sodium hydroxide pre-treatment system resulted in a cellulose content of 79.4%,with the hemicellulose and lignin content decreasing by 6.2% and 32%,respectively.The surface hardness decreased by 61.3%,and the linear tensile strength decreased from 89.6 ± 6.3 MPa to 453.6 ± 8.2 KPa.The pre-treatment effectively exposed the cellulose skeleton,enabling subsequent modifications to be made.Furthermore,the pre-treatment’s effects on wood’s surface hardness and tensile strength were evident.(2)Carboxyl lignocellulosic materials were prepared through directional oxidation that involved cutting off the hydroxyl group of cellulose molecules using sodium periodate,sodium chlorite,and other oxidants.The materials were further improved using balanced water content treatment and hot-pressed process.The experimental results indicated that carboxyl lignocellulosic materials exhibited good mechanical properties when the content of carboxyl group reached 0.55 mmol/g.When compared to a content of carboxyl group of 0.26 mmol/g,a content increase of 0.29 mmol/g was found,resulting in a maximum tensile strength of 328.8MPa,the best Young’s modulus of 8.1 GPa,and the best toughness of 8.3 MJ/m~3.These qualities significantly improved on natural poplar wood’s characteristics,boosting the tensile strength(89.8 MPa),Young’s modulus(5.3 GPa)and toughness(0.6 MJ/m~3).The optimum indentation creep ratio of carboxyl lignocellulose was 11.38%,and the deformation resistance improved by 2.53% compared to the material.(3)The carboxyl group on the carboxyl lignocellulosic material was activated by EDC and NHS,following which the sample was aminated.Amidation modification allowed for strong hydrogen bonding between cellulose molecules,resulting in the best tensile strength,best Young’s modulus,and best toughness of 439.0 MPa,11.7 GPa,and 0.9 MJ/m~3,respectively.When compared to material,the tensile strength,Young’s modulus,and toughness increased by3.8 times,1.2 times,and 50%.The optimum crystallization width was 5.74 nm at 1:16 and the highest relative crystallinity was 86.9%.Finally,the amideated lignocellulosic material had an optimum indentation creep ratio of 13.36%,with deformation resistance increasing by 4.51%compared to the material and by 1.98% compared to the carboxyl lignocellulosic material. |