Preparation And Properties Of Hemicellulose-based And Wood Based Composite Materials

The global shift towards biodegradable composite has made biomass materials green alternatives to synthetic polymers owing to their biocompatibility,sustainability,and eco-friendliness.The separation of cellulose,hemicellulose,and lignin from lignocellulosic biomass is beneficial for their high-value utilization.In this work,we successfully fabricated hemicellulose-based nanocomposites and wood-based composites by making full use of the natural structure,characters,and the product of different separation degree of lignocellulosic biomass.The study revealed some details in the relationships between structure(multilayered structure)and properties of hemicellulose-based and wood based composites.The proposed synthetic strategy could make the lignocellulosic biomass useful for fabrication of fire-protective films,coatings,packaging,and nanofluidic membrane,etc.The quaternized hemicelluloses(QH)were successfully prepared to increase the value of hemicelluloses.The objective of this work was the intercalation of different ratios of cationic biopolymer chitosan(CS)and QH in montmorillonite(MMT),providing compact and robust nanocomposite films with nacre like structure and multifunctional characteristics.It was also found that the tensile strengths of films QH-MMT-CS(F_0.08)were 57.8 MPa,which suggested that the addition of CS was supposed to contribute to mechanical properties due to the strong electrostatic interactions and the enhanced hydrogen bonding.The thermal stability of nanocomposite films,the oxygen permeability,and water vapor permeability had been improved due to the small amount of CS.These observations create an important foundation in the experimental design of the high-performance lignocellulosic biomass based nanocomposite materials.Wood auto-hydrolysates(WH),extracted from Eucalyptus wood chips,is mainly composed of 61.3%hemicellulose and 10.5%lignin.A robust and environmentally friendly method similar to paper-making was adopted to fabricate the WH-MMT based nanocomposite films.A proper balance of the network of interactions between the constituent molecules was further advanced by addition of the reinforcing agent CMC and graphene oxide GO.The results showed that the mechanical properties of the film designated F_CMC0.05 exhibited an enhanced tensile strength of 91.5 MPa,and lower oxygen permeability.In addition,the nanocomposite film WH-MMT-r GO(F_{0.8%r GO})with only 0.8 wt%r GO exhibited promising features,such as a high strength of 124 MPa which was better than other hemicellulose-based films,and a hydrophobic surface(contact angle from 36.6°to 88.8°).The combustion behavior of WH-MMT-GO films suggested the film WH-MMT-r GO also had excellent fire resistance.In summary,converting wood auto-hydrolysates into value-added materials(films)can lower the production costs,covert waste material into a value added product,and also benefit the environment.This work promotes a potential application for these materials in packaging,coatings,and flame-retardant materials.We demonstrate a strong,flame-retardant,and thermally insulating wood composites featuring a compact structure that we synthesized by infiltrating delignified basswood with bentonite nanosheets,followed by hot-pressing to densify the material.Bentonite nanosheets can be infiltrated into the microchannel of the delignified wood to achieve a good compatibility and 3D flame resistant protective surface.The wood composites also exhibit a high tensile strength of 330 MPa,which is 8-times higher than the natural basswood starting material.In addition,the wood composites exhibit lower thermal conductivities and excellent flame resistance.The demonstrated wood composites show great promise as a high-performance structural material with excellent flame-retardant,thermally insulating,and mechanical robust properties that are needed for the construction of energy efficient buildings.A highly conductive cationic membrane is developed directly from natural wood via a two-step process,involving etherification and densification.Etherification bonds the cationic functional group((CH₃)₃N⁺Cl^-)to the cellulose backbone,converting negatively charged(?potential of-27.9 m V)wood into positively charged wood(+37.7 m V).Densification eliminates the large pores of the natural wood,leading to a highly laminated structure with the oriented cellulose nanofiber and a high mechanical tensile strength of?350 MPa under dry conditions.The nanoscale gaps between the cellulose nanofibers act as narrow nanochannels with diameters smaller than the Debye length,which facilitates rapid ion transport that is 25 times higher than the ion conductance of the natural wood at low KCl concentration of 1 m M.The demonstrated cationic wood membrane exhibits enhanced mechanical strength and excellent nanofluidic ion-transport properties(ionic conductivity:1.3 m S cm^-1),representing a promising direction for developing high-performance nanofluidic material from renewable,and abundant nature-based materials.