Study On Aging Resistance Of Different Coated Green-protected Bamboo

Moso bamboo has good wood properties and good toughness,and is the main bamboo species for bamboo utilization.Green-protected bamboo can maintain the appearance of green for a long time,enhance the use value of bamboo,expand the application range of bamboo,and has broad application prospects.At present,the reason for the preservation of bamboo is not clear,and its aging resistance needs further study.In this study,moso bamboo in Yibin,Sichuan Province was used as raw material,and the chlorophyll of moso bamboo at different ages was studied in combination with the analysis of the transformation of moso bamboo chlorophyll after green-protecting treatment.At the same time,five kinds of aging experiments（ultraviolet accelerated aging,artificial accelerated aging,outdoor natural aging,temperature aging,acid-base aging）were carried out on three groups of green-protected bamboo coated with wood wax oil,water-based paint and varnish.The aging performance of green-protected bamboo was evaluated from color change and film characteristics.The specific research conclusions are as follows:（1）Chlorophyll mainly gathered in the surface of moso bamboo.The chlorophyll content of 1a-3a moso bamboo increased gradually,and the chlorophyll content of 3a-5a moso bamboo decreased significantly.The chlorophyll thickness of 3a bamboo was the largest,the content was the highest（1.54 mg/g）,and the surface color was the best（a^*=-8.23）.Comparing the transformation of bamboo chlorophyll and chlorophyll sodium copper salt,it was proved that the Mg²⁺in the chlorophyll porphyrin ring was replaced by Cu²⁺in the green-protecting agent after the bamboo chlorophyll green-protecting treatment,which was transformed into a more stable chlorophyll sodium copper salt to achieve the green-protected effect of bamboo.The sodium copper chlorophyllin product obtained after the treatment of bamboo chlorophyll has good light resistance.UV-A（350 nm）,UV-B（300 nm）and visible light（420-2500 nm）all cause partial degradation of sodium copper chlorophyllin,and the degradation rate slows down with time.Among them,UV-A has the greatest impact on sodium copper chlorophyllin（Δ350 nm=-0.26）.（2）Green-protected bamboo is not suitable for long-term use in the environment of ultraviolet light intensity,complex hydrothermal conditions,high humidity or even soaking in water.Vacuum heating can be used in the process of hot pressing deformation in the later stage.It is not suitable to use strong acid and alkali agents（p H≤3 or≥11）,and the processing temperature should not exceed 100℃.The analysis of various aging data showed that the aging of green-protected bamboo was significant in ultraviolet accelerated aging test,outdoor natural aging test,artificial accelerated aging test and high temperature aging test（120°C and above）,the total color difference was large,the hardness of the paint film changed significantly,and the surface structure was seriously damaged.In the acid-base aging experiment,the aging was more significant,the total color difference was larger,the hardness of the paint film changed little,and the surface structure became rough or even damaged.In the low temperature aging test,the aging degree was very low,the surface color did not change significantly,the hardness of the paint film changed slightly.（3）Paint film has a protective effect on green-protected bamboo in all kinds of environments except extremely high temperature,among which varnish and wood wax oil are better than water-based paint.By comparing the aging data of four groups of green-protected bamboo without coating control group,wood wax oil coating group,water paint coating group and varnish coating group,it was found that in the high temperature aging experiment,the paint film was coked and denatured,and the aging resistance of the control group without coating was better.Low-temperature aging has little effect on the overall bamboo.In the other four aging tests,the total color difference of the coated group was smaller than that of the uncoated control group,and the surface structure was more complete.Combined with the color protection effect,paint film pencil hardness and surface structure data,varnish and wood wax oil were better than water-based paint.