摘要
为揭示竹材饱和蒸汽热处理的微观机理,并为竹材材性调控及热处理工艺参数的优化提供理论依据,采用傅里叶变换红外光谱法(FT-IR)和X射线衍射法(XRD)研究饱和蒸汽热处理毛竹竹束过程中,竹束初始含水率和热处理时间对其化学成分和相对结晶度的影响规律。结果表明:绝干竹束与初始含水率为20%的竹束相比,其相对结晶度迅速由0.62降低到0.50;进一步提高竹束初始含水率,热处理产物相对结晶度变化不大,维持在0.48左右。同时,热处理使竹束结晶区晶层距离变大,粒径增加。这主要是由于饱和蒸汽热处理会使竹束中产生宏观残余应力,导致晶格畸变,进而使晶格各向异性收缩。此外,随着热处理时间的延长,竹束中木质素含量逐渐提高,而半纤维素含量逐渐降低,处理50 min后半纤维素含量降低幅度分别为71.8%,68.6%,84.4%,52.2%和87.1%。纤维素含量呈现先降低后提高再降低的趋势,热处理30~40 min后,竹束中的纤维素含量达到最大值。分析认为,这主要是由于半纤维素热降解会产生大量乙酸,催化纤维素在非结晶区的降解,但随着热处理时间的延长,竹束中半纤维素降解越来越剧烈,导致纤维素相对含量增加。
Replacing wood with bamboo has become an effective way to alleviate the pressure of raw material resource shortage in the wood processing industry.In recent years,bamboo-based composites have been widely recognized by the society and developed quickly.Using saturated steam instead of air or oil as heat transfer medium could efficiently carry out the heat treatment process of bamboo-based materials without burning the bamboo,which would also effectively improve their corresponding physical and mechanical properties,benefiting the application of the heat-treated bamboo-based products.However,limited research has been completed on this treatment method,especially on the variation of the chemical composition and crystallinity properties of bamboo bundles during the saturated steam treatment.In this work,the effects of the initial moisture content and heat treatment time on chemical composition and relative crystallinity of bamboo bundles were examined by the Fourier transform infrared(FT-IR)spectroscopy and X-ray diffraction(XRD).The results showed that the effect of the initial moisture content of bamboo on the relative crystallinity of cellulose mainly performed during the period from absolute dry to 20%moisture content.The relative crystallinity of bamboo bundles decreased rapidly from 0.62 to 0.50 initially,and then the relative crystallinity remained unchanged at around 0.48 when further increasing the corresponding initial moisture content.Furthermore,the saturated steam heat treatment enlarged the crystal layer distance and the particle size of the contained cellulose in crystallization zone.This was mainly due to the macro residual stress in the cellulose of bamboo bundles caused by saturated steam heat treatment,resulting in lattice distortion and then making the lattice anisotropic shrinkage.In addition,with the prolongation of heat treatment time,the content of lignin gradually increased with the decrease of hemicellulose.After 50 min of treatment,the content of hemicellulose decreased by 71.8%,68.6%,84.4%
作者
娄志超
袁成龙
李延军
沈道海
杨淋添
刘杰
张爱文
LOU Zhichao;YUAN Chenglong;LI Yanjun;SHEN Daohai;YANG Lintian;LIU Jie;ZHANG Aiwen(College of Materials Science and Engineering,Nanjing Forestry University,Nanjing 210037,China;Hangzhou Dasuo Technology Co.Ltd.,Hangzhou 311251,China;Fujian Huayu Group Bamboo Industry Co.Ltd.,Jian ou 353199,Fujian,China)
出处
《林业工程学报》
CSCD
北大核心
2020年第2期29-35,共7页
Journal of Forestry Engineering
基金
“十三五”国家重点研发计划(2017YFD0600801)
江苏省农业科技自主创新项目(CX(18)3033)
江苏省高等学校自然科学研究重大项目(17KJA220004)
江苏省科技计划项目(BE2018391)
福建省科技计划项目(2019N3014)
关键词
竹束
重组竹
饱和蒸汽热处理
结晶度
化学成分
bamboo bundles
bamboo scrimber
saturated steam heat treatment
crystallinity
chemical composition
