The Study On Properties Of Poplar Wood Treated With Furfuryl Alcohol And Ammonium Dihydrogen Phosphate

With the implementation of natural forest commercial logging policy in China and the increasing limitations on international wood import-export trades,making full use of the abundant fast-growing forest plantation resources for wood supply will be an inevitable way to alleviate the wood supply-demand contradiction in China and to ensure the national wood security.However,in spite of its stock abundance,fast-growing plantation wood normally possesses some undesirable intrinsic properties,such as dimensional instability,inferior mechanical strength and flammability,limiting its usage as an engineering material.Furfuryl alcohol?FA?is a biomass-derived chemicals derived from renewable resources;wood furfurylation is an environment-friendly wood modification technology with great potential for commercial application.In this dissertation,we report a green and facile approach for upgrading the low-quality poplar wood via a combined treatment with biomass-derived furfuryl alcohol?FA?and ammonium dihydrogen phosphate?ADP?acting as a flame retardant additive.Wood/PFA/ADP composites were prepared by impregnation of the FA precursor solutions into the wood matrix,followed by in situ polymerization upon heating to form hydrophobic FA resin/ADP network within the wood scaffold.This process resulted in an improved poplar wood with integrative properties such as high wood density,dimensional stability and flame retardancy.The modification mechanism of wood furfurylation was also explored.The main results are as follows:?1?Different amounts of FA?5,10,20,30,50 and 70wt%?were used to prepare furfurylated wood?wood/PFA?and to explore its impact on its physical properties.The results showed that the weight percent gain?WPG?and wood density of the furfurylated wood increased with increasing FA concentration,while the equilibrium moisture content?EMC?and water uptake?WU?decreased with increasing FA concentration.Anti-swelling efficacy?ASE?and bulking effect?BE?increased at first and then decreased with the increasing FA concentration;the ASE reached a maximum value when the FA concentration was set as 30%.Confocal laser scanning microscopy?CLSM?images showed that the FA resin was mainly distributed in the cell wall at low FA concentration,and then distributed in the cell cavity when the FA concentration was high.?2?Wood/PFA/ADP composites were prepared via a combined treatment with furfuryl alcohol?FA?and ammonium dihydrogen phosphate?ADP?.The wood density,parallel-to-grain compression strength?CS?and modulus of elasticity?MOE?are remarkably improved by 56.8%,43.2% and 33.3% after the combined treatment,and the modulus of rupture?MOR?shows a minor reduction.While the addition of ADP shows little effect on the physical properties of the modified wood.In-depth SEM-EDX and CLSM analysis reveal the wide distribution of the FA resin/ADP complexes in cell cavities and cell walls.Leaching tests showed that the hydrophobic FA resin/ADP complexes allows good fixation of phosphorus in wood.FA functions as a fixing agent capable of forming a hydrophobic FA resin network to anchor ADP in wood,thus reducing its leaching into water.?3?The thermal stability and combustion of wood/PFA/ADP were remarkably improved.Thermogravimetric?TG?analysis revealed that wood/PFA/ADP exhibited higher final residues?40%?than the wood/PFA?21%?and control?10%?.The addition of a small amount of ADP has strong effect on the thermal behavior.The cone calorimeter analysis showed that the HRR peaks,total heat release?THR?,smoke produce rate?SPR?,and total smoke release?TSR?of wood/PFA/ADP are significantly decreased,suggesting that the addition of a small amount of ADP greatly enhances the flame retardancy of the modified wood,meanwhile effectively suppressing smoke production during its combustion.ADP is known to thermally decompose into HPO3,which can react with the wood components causing their dehydration to form thermally stable char,meanwhile reducing the release of flammable combustion products from wood.?4?FTIR and ¹³C NMR analyses were used to investigate possible chemical reactions occurring between FA and the wood cell wall polymers.Characteristic peaks associated with FA resin appeared on both the FTIR and NMR spectra of wood/PFA/ADP,indicated that FA resin was successfully introduced into wood.Meanwhile,the intensity of peaks attributed to hemicelluloses decreased,suggesting the occurrence of acid hydrolysis of hemicelluloses during wood furfurylation.FTIR and NMR results provide no evidence for chemical reactions between FA and the wood cell wall polymers.