Study On The Effect Of Hydrothermal And Lye Treatment On The Performance Of Compacted Bamboo

As a biomass material,bamboo has very high environmental value and economic value.It not only has the natural and environmental characteristics of degradability,but also has many excellent properties such as fast growth rate,short cycle,strong sustainability and high strength.Therefore,bamboo has been regarded as a high-strength,lightweight and multi-functional structural material with great potential.In this study,bamboo was modified and optimized into multi-functional structural material with high strength,light weight and mildew resistance by combining pretreatment and compacting process.By means of scanning electron microscopy(SEM),Fourier infrared analysis(FTIR),X-ray diffraction(XRD),chemical composition determination and other characterization methods,the effects of hydrothermal pretreatment and lye pretreatment on the density,microstructure,chemical composition,dimensional stability,mechanical properties and mildew resistance of dense bamboo were investigated.The main research conclusions are as follows:(1)The effects of different pretreatment methods on bamboo structure were different.Hydrothermal pretreatment had the least destructive effect on cell wall structure of bamboo,and partially degraded lignin and hemicellulose of bamboo.Its mass loss rate and chemical composition content changed little,the peak value of infrared spectral characteristics related to hemicellulose and lignin weakened slightly,and the crystallinity value showed a slow rising trend.The mass loss rate and chemical composition content of wood lignin and hemicellulose were changed greatly.The infrared spectral characteristic peaks related to hemicellulose and lignin were slowed down or even partially disappeared.The alkaline sodium hydroxide pretreatment mainly destroyed the lignin and hemicellulose in the amorphous region of cellulose,so the crystallinity of wood showed a relatively rising trend.(2)Compared with natural bamboo,the properties of compacted bamboo prepared by pretreatment were significantly improved.Compared with the water-heat densified bamboo,the density of the alkali pretreatment densified bamboo is relatively small,but the hardness and mechanical properties are relatively large,and the dimensional stability is relatively good.The tensile strength and tensile modulus of the water-heat densified bamboo are 347.1(±3.8)MPa and 40.3(±2.1)GPa,which are 3times and 2.3 times of that of the natural bamboo,respectively.The tensile strength and modulus of lye compacted bamboo were 410(±10.5)MPa and 41.8(±1.0)GPa,3.5 times and 2.4 times of that of natural bamboo,respectively.Water heat and alkali densification bamboo compared the mechanical properties of natural bamboo improved significantly,this shows that the densification of the preparation of two kinds of pretreatment of bamboo lignin and hemicellulose degradation,not only the relative contents of cellulose increased,the number of intermolecular hydrogen bonds in cellulose effective promotion,van der Waals force increases,and the internal compression of low density polymer formed a stable network structure.Compared with the bamboo compacted by hydrothermal pretreatment,the condensation network structure phenomenon of the bamboo compacted by lye pretreatment is more obvious.(3)By exploring and analyzing the mildew resistant properties of natural bamboo,hydrothermal pretreatment and alkali liquor pretreatment,it was concluded that compared with natural bamboo,hydrothermal pretreatment and alkali liquor pretreatment had certain mildew resistant properties,and alkali liquor pretreatment and alkali liquor pretreatment had relatively optimal mildew resistant properties.The mildew control efficacy of water-heat compacted bamboo against three kinds of mold were 27%(±2.6%),99%(±1%)and 59%(±1%),respectively,and the comprehensive control efficacy was 61.67%(±0.88%).The mildew control efficacy of the lye compact bamboo against three kinds of mold were 89.5%(±0.5%),99%(±1%)and 100%,respectively,and the comprehensive control efficacy was 96.2%(±0.43%).This is because the extracts of starch and sugars in the lye densified bamboo are fully removed,and the degradation of lignin and hemicellulose is great,which reduces the nutrient source of mold and thus inhibits the growth of mold.In addition,lye compacting bamboo itself is weak alkaline,which also plays an inhibitory role in the growth of mildew which likes weak acidic environment,so that its mildew prevention effect is better.