| Bamboo is an important renewable biomass material with characteristics of fast growth,high strength,strong toughness and high hardness.However,bamboo is extremely susceptible to attack by decay fungi and mold fungi in outdoor applications.Organic preservative treatment can effectively prevent biological degradation,such as decay,insects and mold.Triazole formulations have anti-decay and anti-mold effect.To investigate the mold resistance,leaching resistance and metal corrosion resistance,Moso bamboo?Phyllostachys edulis?treated by triazole formulations was selected for long-term protection including leaching and metal corrosion in this study.Cellular automaton?CA?was used to investigate the morphology of metal corrosion in treated bamboo.The poly?urea-formaldehyde??UF?/tung oil microcapsule self-healing coatings was synthesized and used for achieving the purpose of long-term protection.The main results of this study are listed below:?1?Mold resistance of bamboo treated with triazole formulationsThe mold resistance of bamboo treated with triazole formulations was excellent.When the concentrations of propiconazole?PPZ?-tebuconazole?TEB?/iodopropynyl butylcarbamate?IPBC?were greater than 0.06/0.05wt%at retention of 0.124/0.104 kg·m-3,the control efficacy on both mold and stain fungi were 100%.When the concentrations of Methylchloroisothiazolinone-methylisothiazolinone?MCI-MI?in PPZ-TEB/MCI-MI were 0.17wt%at retention of 0.341 kg·m-3 and 0.26wt%at retention of 0.517kg·m-3,the control efficacy on stain fungi were 100%.?2?Leaching resistance and metal corrosion resistance of bamboo treated with triazole formulationsThe leaching resistance of PPZ,TEB and IPBC in bamboo treated with triazole formulations was good,and the leaching rates of PPZ/TEB/IPBC at retention of 0.072/0.072/0.284 kg·m-3were 2.02%,1.2%and 0.65%,respectively.The leaching rates of MCI/MI at retention of 0.543/0.181 kg·m-3 were higher than PPZ/TEB/IPBC,at 14.78%and 48.87%,respectively.Compared with stainless steel,aluminum alloy and copper metal,bamboo treated with triazole formulations has severe metal corrosion to ferrous metal.And the corrosion rates of Q235 steel and 65Mn steel in contact with bamboo treated with PPZ-TEB,PPZ-TEB/IPBC and PPZ-TEB/MCI-MI were 69.39?132.70?m?a-1,81.58?171.10?m?a-1 and111.39?324.22?m?a-1;56.03?95.49?m?a-1,64.86?114.73?m?a-1 and 95.08?250.57?m?a-1,respectively.?3?Study on metal corrosion morphology of treated bambooThe initial model and growth model of corrosion pits were obtained from the local corrosion characteristics of Q235 steel in contact with bamboo treated with triazole formulations.Based on the initial model and growth model,the CA model was established.The results show that the CA model could well simulate the metal corrosion evolution process of treated bamboo.?4?Microcapsule self-healing coatings for long-term protection of treated bambooThe encapsulation process parameters of UF/tung oil microcapsules were as follows:p H value of3?3.5,emulsifier dosage of 10ml and stirring speed of 400rpm.The average particle size,particle size distribution and encapsulation rate of the microcapsules were 97?m,22?185?m,and 71wt%,respectively.The average core content was about 77wt%,and the thermal degradation temperature was about 220?.The UF/Tung oil microcapsule self-healing coatings had the ability to automatically repair damaged areas,and the impact resistance and adhesion strength had not been significantly reduced.UF/Tung oil microcapsule self-healing coatings can effectively improve the leaching resistance and reduce the metal corrosion resistance.After applying the self-healing polyurethane and acrylate coatings,the leaching rates of MCI and MI of 0.3wt%MCI-MI under the comprehensive aging conditions were reduced by 0.63%and 3.04%,9.80%and 6.05%,compared with the control coatings,respectively;the average weight loss rates of Q235 steel and 65Mn steel in contact with bamboo treated with PPZ-TEB/MCI-MI?720h?were reduced by 58.2%and 66.3%,44.9%and 67.1%,compared with the control coatings,respectively. |
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