Selection Of Anti-Leaching Boron-based Preservative Formulas And Properties Of Wood Treated With Optimized Formulas

With the increase of the environmental awareness of people,some wood preservatives with potential risk to the environment and human health have been or will be gradually restricted or prohibited. Borates are efficient wood preservatives and safe for the mammals and environment.However,the use of their treated wood in outdoor is limited because of the migration of boron.In order to improve the leaching resistance of borates,more than twenty kinds of additives were used to in cooperation with borates.Two optimized formulations were selected and the properties of their treated wood were determined.Then,the component of the two optimized formulations was used as the intermediate medium to introduce organo-modified montmorillonite(OMMT) into wood to prepare the OMMT composite preservation wood and the properties of the composite wood were measured.The results of this study are summarized below.1) A variety of additives such as proteins,glyoxal / glycerol,alcohols,metal salts,as well as ethylene monomer were used in this study and all of them could improve the leaching resistance of the three kinds of borate(boric acid,borax,disodium octaborate tetrahydrate) in different extents through variety forms.But the results were not very evident.2) Sodium tetraphenylborate(TPBNa) has better water leaching resistance and good decay resistance. And the leaching resistance was improved after amelioration.But its prices were very expensive and not suitable for industrial production.But it were be used in some specific applications.3) Optimized formula 1:A method to treat wood with the mixed solution of water-soluble PF and borate is first put forward to increase the retention of boron;in the decay and termite resistant tests,the specimens treated with high concentration of borates and PF had no mass loss;the dimensional stability and water absorption and mechanical strength of treated wood have been improved a lot;FTIR analysis showed that the PF reacted with certain groups of the wood cell wall material(cellulose,hemiceilulose and lignin).SEM analysis showed that the PF had nice permeability to the wood and could reach all parts of the wood.PF could attach to the cell wall of wood firmly after curing at high temperature, which would fix borate in the timber commendably.4) Optimized formula 2:A new method to treated wood with quaternary ammonium salt(QAS) and inorganic borate(IB) in two steps is posted for the first time.This optimized formula displayed high leaching resistance of boron and the physical and mechanical material properties were improved. Retention of boron increased with the increasing of concentration of QAS and IB.And even wood treated with the lowest concentration of IB and QAS showed excellent resistance to fungi and termites. FTIR analysis showed that QAS and the reaction products of IB and QAS would be fixed on wood mainly through the cation exchange reaction with the hydroxyl,carboxyl etc.of the cellulose and lignin; SEM analysis showed that the reaction products of IB and QAS distributed in the wood cells with the form of very small particle.5) On the basis of the experiments of the two optimization formulas,QAS and PF were used as the intermediate medium to introduce organo-modified montmorillonite(OMMT) into wood to prepare OMMT composite preservation wood.The results showed that the immission of OMMT didn't impact the retention of boron.Through SEM,the irregular distribution of OMMT on the tracheids and around the pits was observed.But on the whole the amount of OMMT introduced into wood was relatively limited and failed to fill the interstice of wood such as cell wall and cell cavities very effectively.So its contribution to improve the physical and mechanical properties of wood is not very clear.