Performance And Enhancement Mechanism Of Cell Wall Modification Of Fast-Growing Poplar Wood

The utilization of fast-growing poplar wood is restricted by dimensional instability,poor mechanical strength and susceptibility to biodegradation.In this research,aiming at the drawbacks of fast-growing poplar wood,various chemicals(rosin,furfuryl alcohol,polyethylene glycol diacrylate(PEGDA),methyl methacrylate(MMA),and nanomaterials)were used to modify poplar wood through impregnation,grafting copolymerization,and in-situ synthesis.The structure,chemical components and distribution,and properties of modified wood was evaluated and characterized via scanning electron microscope(SEM),confocal Raman spectrometer,X-ray photoelectron spectroscopy(XPS)and dynamic mechanical analysis,which finally interpreted the distribution and formation of modifier as well as the interfacial interaction between wood components and modifier,revealed the influencing mechanism of different modifications.The main results of this research are summarized as fo lows:(1)Hydrophilic chemicals easily penetrated into wood cell wall,swelled it,and reacted with the hydroxyl of cellulose.Cellulose was mainly located in S2 layer of wood cell wall while lignin was mainly in cell corner and middle lamella.The accessible hydroxyl content of poplar wood was 8.3×10-3 mol/g.Poplar wood exhibited high microfibril angle,low crystallinity,and hierarchical structure with plenty of nano/micro-scale voids.The penetrability of tangential section was higher than that of radial section.(2)Wood performance could be improved by rosin impregnation via filling effect in cell lumina,cell corner,and part of cell wall.In contrast to control,the elasticity modulus(MOE),parallel-to-grain compressive strength(CS),and hardness were respectively increased by 18.9%,31.6%,and 30.9%when the weight percent gain(WPG)was 31.9%.The maximum anti-swelling efficiency(ASE)was 36%.Rosin impregnation can reduce the humidity absorption and hydrophility od wood,but no significant effect on the bending strength(MOR).(3)Furfruylation could enhance the wood cell wall.Due to the low molecular weight and excellent swelling efficiency,furfuryl alcohol mainly occupied wood cell wall,cell corner,and parenchymal cell after polymerization.The relationship between WPG and MOE as well as MOR was not significant,whereas the impacts of WPG on ASE,water resistance and hardness were significant.Delignification could improve the acid and alkali resistance and thermal properties of furfurlated wood.(4)The synergistic modification of furfuryl alcohol and nanoparticles improved the comprehensive performance of wood.The ASE,water resistance,thermal stability,abrasive resistance,and mechanical properties of wood were improved by furfurylation and nano-SiO2.The ASE,water resistance,leachability and corrosion resistance of nanoparticles were enhanced by the combination of furfuryl alcohol and nano-Fe3O4.Moreover,wood was endowed with magnetic property by the incorporation of nano-Fe3O4.(5)Wood performance was remarkably improved via grafting copolymerization.Confocal Raman imaging and XPS results indicated modifiers can enter into cell wall and form a layer from interior of cell wall to cell lumen.The ASE of PEGDA or PMMA-grafting wood was higher than 50%.Additionally,the water uptake of PMMA-grafting wood was lower than 30%after 144 h water immersion.