Effect Of Saturated Steam Heat Treatment Of Bamboo Bundle On Properties Of Bamboo Reconstituted Material

High temperature heat treatment technology has been widely used in bamboo wood modification treatment,thermal modification treatment can adjust the surface color of bamboo wood,improve its dimensional stability and biological durability and other properties,making the product has a wider application value.In this paper,the bamboo bundle of phyllostso moso is studied,in the pressure tank using saturated steam as heating medium,the bamboo bundle with different moisture content of high temperature heat treatment process test(heat treatment temperature of 150 ℃,160 ℃,170 ℃,180 ℃ and 190 ℃;The heat treatment time of dry bamboo bundle is 90 min,120 min and 150 min.The heat treatment time of wet bamboo bundle was 30 min,60 min and 90 min),and the changes of chemical composition content,crystallinity and ir spectra of bamboo bundle raw materials before and after heat treatment were analyzed.Then after processing bamboo bundle impregnated phenolic resin adhesive,drying,equilibrium moisture content and quantitative pavement made recombinant bamboo plate,hot pressing,analysis of the reorganization of bamboo material plate,the change rule of physical and chemical,mouldproof performance and analyze the correlation between performance,for high performance outdoor bamboo reorganization material manufacturing technology provides theory basis and the main research conclusions are as follows:(1)With the increase of the heat treatment temperature of saturated steam,the content of cellulose and hemicellulosic in both dry and wet bamboo bundles decreased,while the relative content of lignin increased with the increase of heat treatment temperature.At 190℃,the cellulose content of bamboo bundle material decreased 43.75% and 42.35% compared with the untreated sample.The effect of heat treatment time on the change of the main chemical components of bamboo bundle material is roughly the same as that of heat treatment temperature,but the effect of heat treatment time is not very significant.(2)Infrared absorption spectrogram showed that the chemical functional groups of dry bamboo bundle and wet bamboo bundle did not change in essence,but were different in content.Compared with untreated samples,the absorption peaks of-OH and carbonyl C=O in cellulose and carbonyl characteristic peaks in hemicellulose decreased significantly with the increase of heat treatment temperature.The characteristic peak strength of benzene ring skeleton structure of lignin decreased with the increase of heat treatment temperature.X-ray diffraction showed that the relative crystallinity of cellulose was higher than that of untreated samples.In general,the relative crystallinity of cellulose increased first and then decreased.SEM was used to observe the microstructure of untreated samples,and it was found that the cell wall was smooth and intact with obvious striae.The internal damage degree of the reconstituted bamboo bundle prepared by saturated steam heat treatment is greater than that of the sample without superheat treatment.Both dry and wet carbon processes,the microstructures of cells in cross section were severely pressed and distorted,and cracks appeared in cell walls.However,compared with the dry carbon process,the vascular bundle sheath of the reconstituted bamboo bundle prepared by the saturated steam heat treatment was denser,and the parenchyma cells were squeezed thinner and deformed more seriously.(3)The mechanical properties of the reconstituted bamboo bundle prepared by different saturated steam heat treatment processes showed that the static flexural strength and elastic modulus of the reconstituted bamboo bundle increased with the increase of time under the heat treatment condition of 180℃.After heat treatment at 190℃,the static flexural strength and elastic modulus decrease gradually with the extension of time,but the elastic modulus has little change with the increase of time.The effects of temperature and time of saturated steam heat treatment on elastic modulus and flexural strength of bamboo reconstituted material prepared by dry carbon process were more significant than those prepared by wet carbon process.After heat treatment,the shear strength and the expansion rate of water absorption thickness of the reconstituted bamboo decreased,and with the increase of temperature,the decrease was greater.When the heat treatment temperature was 190℃ and the time was 150 min,the shear strength and water absorption thickness expansion rate reached the lowest,decreasing by 60.56% and 50.58%.For the wet carbon process,the shear strength of the bamboo reconstituted material after heat treatment decreased more than that of the dry carbon process,but the expansion rate of the water absorption thickness did not decrease significantly.(4)The mildew proof test results showed that the untreated bamboo had the worst mildew proof ability,and mildew appeared on the 2th day,and all the bamboo surface was stained with mold on the 8th day.Compared with untreated bamboo,the mildew resistance of saturated steam treated bamboo was improved to a certain extent both in dry carbon and wet carbon heat treatment.The influence of heat treatment temperature on the mildew resistance of bamboo was greater than that of heat treatment time.When the heat treatment temperature exceeded 160℃,the observed infection time on the sample surface would continue to prolong,and the average control efficiency would continue to improve,up to 95.11%.After 30 days,most of the sample surface area of the reconstituted bamboo prepared by saturated steam heat treatment of wet bamboo bundle will be stained by mold,and the average control effect is less than 60%.The mildew prevention effect is similar,but the effect is not ideal.