Fabrication Of Super Strong Cellulose Based Materials From Wood And Their Mechanical Properties

In recent years,strong cellulose-based material?SCBM?from wood have attracted extensive attention from academia and industry due to their excellent mechanical properties,environmental friendliness,wide range of raw materials,and potential low cost,which is expected to promote the application of cellulose-based materials in high-tech fields.However,there are still many problems with SCBM at this stage.Most of the research mainly focus on the preparation of SCBM.Few articles have started from wood raw materials to study the relationship between the basic characteristics of wood cellulose and the mechanical properties of SCBM.The main factors that influence the mechanical properties of SCBM and the intrinsic correlation between these major factors are not clear.In addition,the mechanism for the excellent mechanical properties of SCBM is still unclear.As a result,it restricts the controllable preparation and industrial production of SCBM.In this case,we use the fiber orientation structure in natural wood and reaslize the sufficient transfer of the excellent mechanical properties of nanocellulose to SCBM by combine the high-efficiency delignification pulping technology and the top-down pressure drying.Then,by studying the relationship between the chemical composition of wood and the structural parameters of fibers such as the degree of polymerization?DP?of cellulose,the fiber morphology and the crystallinity of cellulsoe and the mechanical properties of the SCBM,and summarize the main factors affecting the mechanical properties of SCBM.On the basis of the above study,the mechanism of the excellent mechanical properties of SCBM is clarified.Finally,a model for predicting the tensile strength of SCBM was established.It mainly includes the following five aspects:?1?The chemical composition,microstructure and mechanical properties of wood raw materials were analyzed.It was concluded that the microfibril angle of wood layer S₂ and the density of wood were the main factors affecting the mechanical properties of wood.The analysis of the fracture surface of wood is used to analyze the significant difference between the mechanical properties of wood and the mechanical properties of the reinforcing component cellulose.It provides ideas and material selection for the fabrication of SCBM using the natural orientation structure of wood fiber.?2?The excellent mechanical properties of nanocellulose are fully transferred to SCBM by combining chemical pulping and pressure drying process.The tensile strength of SCBM is up to 916±30.4 MPa,which is higher than that of high-carbon steel.At the same time,the anisotropic and isotropic SCBM is fabricated by stacking 2D high-strength cellulose materials through layers,using 2%carboxymethyl cellulose solution as an adhesive,and finally pressing and drying at 50°C.?3?The effects of different structural parameters such as the DP of cellulose,fiber morphology and crystallinity of wood fibers on the mechanical properties of SCBM were studied.The main factors afecting the mechanical properties of SCBM were screened out.The natural wood was treated with alkaline sulfite-anthraquinone-methanol?ASAM?,sulphate method?KC?,caustic soda cooking?CSC?and sodium chlorite cooking?SCC?cooking firstly and then the change of chemical composition of wood and the DP of cellulose,fiber morphology and crystallinity on the mechanical properties of SCBM were studied.The results show that the main factors affecting the mechanical properties of SCBM for the wood materials with small differences in fiber morphology are the DP of cellulose and the lignin content;The main factors in the mechanical properties of SCBM include fiber morphology in addition to the DP of celluliose and lignin content.?4?The mechanism of high tensile strength of SCBM was preliminarily clarified.From the perspective of the structure of SCBM,wood fiber morphology,chemical pretreatment and combined with the main factors affecting the mechanical properties of SCBM to elucidate the high-strength mechanism of SCBM.Firstly,from the structural perspective of SCBM,the excellent mechanical properties of SCBM are mainly derived from the nanofibers.The wood chips are chemically treated to remove most of the lignin to reduce the rigidity of the chips,while a large amount of hydroxyl groups exposes on the surface of the fibers.Then the directly mechanical press not only removes the defects affecting the mechanical properties of the wood fiber,but also enhances the hydrogen bond interaction between the fibers,thereby achieving the sufficient transfer of the excellent mechanical properties of the cellulose.From the perspective of wood fiber structure,wood fibers with longer length and larger width have larger overlapping areas between adjacent fiber cell walls,and hydrogen bond interactions are stronger after mechanical pressing.In addition,the ASAM pulping can rapidly remove most of the lignin and hemicellulose in the wood while maintaining a high degree of polymerization of the fibers,resulting in the excellent mechanical properties of SCBM.Based on the above factors,the mechanism of excellent mechanical properties of SCBM was clarified.It can provide reference and theoretical guidance for the fabrication of SCBM.?5?Established a tensile strength mechanical model of SCBM.Finally,the lignin content and cellulose polymerization degree were used as independent variables.The tensile strength of high-strength cellulose materials was used as the strain.A model to predict the tensile strength of SCBM were established.The research results in this paper can provide ideas and theoretical guidance for the research of SCBM.