Study On Properties Of Bamboo And Its Reconstituted Bamboo Under γ-ray Irradiation

Due to the large amount of starch and polysaccharide in bamboo,it is easy to rot and mildew,which greatly reduces the utilization rate of bamboo and the service life of bamboo products.It is an efficient and environmentally friendly method to modify bamboo by γ ray.In recent years,people have higher and higher requirements for outdoor materials.Although the emergence of reconstituted bamboo has improved the strength and utilization rate of bamboo,it cannot achieve the effect of long-term mildew prevention.Therefore,it is urgent to develop and manufacture a kind of reconstituted bamboo with high strength,high dimensional stability and high weather resistance to realize high quality development and high value utilization of bamboo.In this study,bamboo bamboo 3-4 years old was used as the research object.Orthogonal tests of four factors and three levels(different radiation dose,radiation dose rate,moisture content and thickness of bamboo)were carried out on bamboo strips.The bamboo bundle was irradiated by different optimum processes(different irradiation dose and moisture content).The physical and chemical properties of bamboo strip/bamboo bundle/reconstituted bamboo prepared by irradiated bamboo bundle under different irradiation processes were investigated to provide theoretical reference for realizing efficient utilization of bamboo.The main conclusions are as follows:(1)Irradiation can degrade the three elements and starch of bamboo strip/bundle.Irradiation dose had the most significant effect on hemicellulose and starch.With the increase of irradiation dose,the content of cellulose firstly increased and then decreased.The contents of hemicellulose and starch showed a decreasing trend.When the irradiation dose increased from 150 KGy to 250 KGy,the contents of hemicellulose and starch decreased significantly and were lower than those of untreated materials.The relative content of lignin increased with the irradiation dose due to the degradation of cellulose and hemicellulose.(2)There is no significant difference in the crystal plane spacing of bamboo strip/bamboo bundle after irradiation,and the characteristic peaks and group absorption peaks of bamboo strip/bamboo bundle after irradiation are consistent with those of untreated wood.The relative crystallinity of cellulose increased firstly and then decreased with the increase of irradiation dose.By observing the microstructure of parenchyma cells of bamboo,it was found that there were a large number of starch particles in the lumen of parenchyma cells of bamboo strips without irradiation,and the starch particles in parenchyma cells of bamboo strips after irradiation decreased greatly.(3)The flexural strength,flexural elastic modulus,tensile strength and compressive strength of bamboo strip/reconstituted bamboo bundle were greatly affected by the radiation dose.With the increase of radiation dose,the mechanical strength of bamboo strip/reconstituted bamboo bundle increased first and then decreased.The dry shrinkage rate of bamboo and the hygroscopic thickness expansion rate of the reconstituted bamboo decreased with the increase of theirradiation dose,and reached the lowest at the irradiation dose of 250 KGy.Under this process,the dimensional stability of bamboo and reconstituted bamboo was the best.With the development of irradiation process,the color of bamboo strip becomes red,dark and finally brown.The reconstituted bamboo prepared by irradiated bamboo bundle was lighter in color and more widely used than the reconstituted bamboo bundle prepared by saturated steam heat treatment at 180 ℃.(4)The mildew resistance of untreated materials is the worst.The mildew resistance of bamboo strips and the reconstituted bamboo beams were improved to different degrees.Irradiation can kill the eggs and microorganisms of the sample itself,degrade polysaccharides and starch,weaken the suitable living environment of microorganisms,and reduce the erosion of mold.When the irradiation dose was less than 100 KGy,the time of mycelia was initially observed on the sample was prolonged.With the increase of the irradiation dose,when the irradiation dose increased to 250 KGy,the control efficacy of bamboo strips and recombinant bamboo against Aspergillus Niger was improved.