Study On The Mildew Resistance Of Chemically Modified Radiata Pine And Moso Bamboo

Wood and bamboo was easy to mildew in using process.This phenomenon seriously limits the scope of wood and bamboo.It is the general ways to use mildew proof to inhibit molds..Chemical modification is an effective method to improve the dimensional stability,durability,anticorrosive,anti weathering performance and flame retardant performance of wood.But milew resistance of the modified materials was seldom reported.Some reagents were currently used in modifiding wood such as a N-methylol resin(1,3-dimethylol-4,5-dihydroxyethyleneurea,DMDHEU)citric acid,sucrose,glutaraldehyde,etc.This paper modified wood and bamoo with chemical regents,which was a N-methylol resin(1,3-dimethylol-4,5-dihydroxyethyleneurea,DMDHEU)citric acid,sucrose,glutaraldehyde,and tested the milew resistance of wood and bamboo of modifiding.Using the same concentration of DMDHEU to treat wood and bamboo,the weight gain of radiata pine and moso bamboo was significantly different,and the maximum weight gain of Pinus radiata was 2 times of the maximum weight gain of moso bamboo.The equilibrium moisture content of radiata pine and moso bamboo of modifing with DMDHEU was decreased.The hygroscopicity of radiata pine and moso bamboo was also decreased,the size stability of pinus radiata and moso bamboo was improved after modifing with DMDHEU.In the test of Aspergillus niger,the infection surface area of radiata pine and moso bamboo was 100%,and the milew resistance properties of Aspergillus niger were not improved.However,in the test of penicillium citrinum,the surface of the sample was not completely covered with mildew.The mass loss of the modified material was higher than the controls,and the moisture content was higher than control after mold test,which was in the range of 100%-200%.The weight gain of glutaraldehyde treated radiata pine and moso bamboo were 24.0% and 9.4%,respectively.The hygroscopicity of glutaraldehyde treated radiata pine and moso bamboo decreased,and the dimensional stability of glutaraldehyde treated radiata pine and moso bamboo was improved.After mold test,resistant efficacy of glutaraldehyde treated pinus radiata and moso bamboo was more than 90%,so treatment with glutaraldehyde were significantly improved milew resistance.The mass loss was increased with the increase of glutaraldehyde concentration.Under the light microscope,the mold can be observed obviously.in the controls,but the mold can not seen in the odified materials.The maximum weight gain of flame retardant treated radiata pine and moso bamboo was 19.33% and 4.61%,respectively.After the experiment of mildew,the resistant efficacy of FRW treated radiata pine was more than 75%,and the resistant efficacy of FRW treated moso bamboo was more than 33.75%.FRW treatment could improve the mildew resistance.The mass loss and moisture content of treated radiata pine and moso bamboo were higher than controls after mold ttest.Scanning electron microscope observation showed that hyphae and spores could be obviously observed in the controls,but FRW treatment was not observed.Mixing citric acid and sucrose were used to improve the fixation ratio of sucrose in wood.The reason was that citric acid could be used as crosslinking agent to react with wood and sucrose.Wood treated with10% citric acid and 20% sucrose,the weight gain of wood was increased by 32%,the bulking was increased by 3.5%,the hygroscopicity of wood decreased,and the dimensional stability of wood increased.The mass loss of the samples increased with the increase of the concentration of the treated solution.The moisture content of the penicillium citrinum was higher than that of Aspergillus niger.The resistant efficacy of wood treated with 10% citric acid and 20%sucrose in the test of Aspergillus niger was up to 75%,which could improve the milew resistance of wood against Aspergillus niger.Summing up,pinus radiata and moso bamboo modified with DMDHEU can not improve the milew resistance.Glutaraldehyde treatment could significantly improve the anti mildew properties of pinus radiata and moso bamboo,FRW treatment can improve the mold performance,but the effect is not good glutaraldehyde.The treatment of citric acid and sucrose had a certain resistant efficacy on Aspergillus niger.