Development And Performance Of A Novel Wood Preservative System Of Isothiazolone Microemulsion

Metal-based water borne preservatives has been widely applied across the world for decades,but it was restricted regarding to its toxic threat to human health and environment.To address this concern,we used low-toxic 4,5-dichloro-2-octyl-2H-isothiazol-3-one(DCOIT)as an active ingredient,combined with low-toxic solvents,nonionic surfactants as well as deionized water to develop a novel system of isothiazolone microemulsion.The particle size and the stability of isothiazolone microemulsions over a range of concentrations were analyzed.Wood samples treated with various concentrations of isothiazolone microemulsions were assessed in water absorption rates,dimensional stability,leaching,mold and decay resistance.Further,the biodegradation of DCOIT by brown-rot fungus Gloeophyllum trabeum was investigated and the possible mechanism was proposed.Lastly,other modifying reagents were added to the isothiazolone microemulsion to achieve a multifunctional preservative system.The primary conclusions are shown below:(1)The optimal recipe for the isothiazolone microemulsion system was:2.8g DCOIT,8g organic solvents(linolenate and propylene glycol phenyl ether),12g surfactants,Ig stabilizaing additive,and deionized water.This isothiazolone microemulsion system has shown the excellent performace in storage stability,centrifugal stability,thermal stability.(2)Isothiazolone microemulsion has demonstrated the high level of permeability to southern pine(Pinus spp.).Wood samples treated with the isothiazolone microemulsion have shown an improved dimensional stability as oppsed to untreated wood samples.Moreover,after 14d-leahcing test,retention rates of DCOIT in treated samples were around 80%,suggesting the high leaching resistance.(3)No mold growth was observed on the samples soaked with isothiazolone microemulsions(0.05%DCOIT)for 10 minutes,indicating a high activity in inhibiting mold fungi.Moreover,in the decay tests with G trabeum and C.versicolor,DCOIT-treated wood samples showed the reduced mass losses as opposed to untreated samples.Therefore,DCOIT-treated wood samples are highly resistant to biological attack.(4)DCOIT was rapidly depleted in the early stages of incubation by G.trabeum.The CMF treatment was shown to oxidatively decompose DCOIT by producing reactive oxygen species,and the molecular structure of an identified DCOIT degradation intermediate is proposed.This evidence suggests that the CMF chemistry employed by brown-rot fungi contributes to the rapid depletion of DCOIT during G.trabeum exposure,although this does not rule out other possible mechanisms for the biodegradation of DCOIT.(5)The presence of antioxidants(DTPA)has enhanced the resistance of DCOIT treated wood against G.Irabeum.Wax emulsion has shown the ability to improve the dimensional stability of wood samples treated with the DCOIT microemulsion,suggesting that a water-repellent preservative was achieved by combining wax emulsion and the isothiazolone microemulsion.The treatment of DCOIT/IPBC/dyes have shown the feasibility in improving both the aesthetic performance of wood samples and the resistance against mold fungi.