Combining Modification Of Wood With Glucose And Crosslinkers

Chemical modification can improve the dimensional stability and durability of wood via cell wall bulking,hydroxyl group deactivation and/or lumens filling.The commercialised methods in the present possess incomparable advantages but also shortcomings such as high cost,release of harmful volatile or wasted liquid,these issues greatly limited their application in both public and interior domains.An environmentally friendly chemical---glucose(GLC)could be used as a reinforced agent for wood modification.However,GLC is a polyol with relatively low reactivity.Therefore,GLC alone is hardly used to modify wood because of low fixation ratio.In this study,two crosslinkers,citric acid(CA)and 1,3-dimethylo1-4,5-dihydroxy ethyleneurea(DMDHEU),were used to modify wood together with GLC aiming at improving the fixation ratio of GLC.The effects of treatments on the physical and mechanical properties of wood were explored.In the presence of catalyst,the GLC treated wood exhibited a limited increase in weight percent gain(WPG)of 8%,which can be explained by the reaction between part of aldehyde end of GLC and hydroxy groups of wood,forming acetal bonds under catalysis of MgC12.As a result,glucose treated wood don't cause an obvious improvement in dimensional stability improvement where the anti-swelling efficiency(ASE)increased up to 11-18%.The impact and bending strength were reduced by 67%and 5-27%respectively.The bending modulus of elasticity(MOE)and compression strength were increased by 15%and 20-52%.CA bears three carboxyl groups,combining modification with CA and GLC can substantially improve the fixation degree of GLC in wood by increasing WPG up to 58%.FTIR spectrum suggested the possibility of esterification between wood/GLC and CA,both can bulk cell walls and catalytically react with hydroxyl groups,thereby dimensionally stabilizing wood.However,the excessively unreacted hydroxyl negatively affects the dimensional staibility of wood.Due to the acidic hydrolysis and crosslinking of the polysaccharides by CA,the treatment reduced the impact strength by 72-78%,the decrease of bending strength was inhibited with increasing the GLC concentration.Both MOE and compression strength of wood were increased by 6-14%and 30-75%respectively due to crosslinking and deposition of chemicals in cell walls.In addition,the maximum mass loss of CA and GLC combining treated wood during soft rot incubation was up to 35%,in spite of a gradual increase in mass loss with increasing GLC.Therefore,the treated wood exhibited an excellent soft decay resistance compared to the controls.DMDHEU molecule bears two reactive hydroxymethyl groups,treatments with GLC and DMDHEU can efficiently improve the fixation of GLC in wood.DMDHEU may act as a linker between GLC and wood via etherification reaction.Combining treatment with DMDHEU and GLC can bulk and crosslink the cell walls,thereby dimensionally stabilizing wood,where wood attains an increase in ASE and a decrease in moisture absorption.Nevertheless,the excessive unreacted hydroxyl groups may negatively affect the dimensional stability with the increase of GLC.The impact strength were considerably decreased by 72-79%due to crosslinking and acid catalyzed hydrolysis.The bending strength of the treated wood exhibited comparably to the untreated ones.Both MOE and compression strength showed positive correlation between the concentration of GLC increased by 17-34%and 56-106%respectively.The treated wood with DMDHEU and GLC can inhibit the soft decay at varying levels depending on the concentration of GLC used.The glucose concentration of treated wood ranging from 0 to 10 showed a mass loss<4%,demonstrating better soft decay resistance than the 7%mass loss when GLC exceeded to 15%.In conclusion,GLC can be used as a reinforcement agent to treated wood in the presence of crosslinkers,accompanying the increase of fixation of GLC and substantial improvement in certain wood properties.The use of GLC faciliates to improve the environmental friendliness of both the modifying agents and the modified wood products.The crosslinker systems used in the study are workable;however,DMDHEU is more effective in crosslinking GLC in wood.