【作者】 孙丰波；

【导师】 江泽慧；

【作者基本信息】 中国林业科学研究院 ， 木材科学与技术， 2010， 博士

【摘要】 利用γ射线辐照处理竹材,研究竹材的理化性质,具有重要的理论意义和应用价值。本文以毛竹(Phyllostachys pubescens Mazel ex H de Lehaie)为研究对象,将竹材进行γ射线辐照处理,辐照剂量设置为:10KGy、20KGy、30KGy、50KGy、100KGy、300KGy、500KGy、1000KGy。通过对不同辐照剂量处理的竹材微观构造、物理力学和化学性质等的变化规律,初步揭示了竹材γ射线辐照效应、机理。并在此基础上,开展γ射线辐照技术在竹材防霉中的应用研究。研究结果为γ射线辐照技术在竹材功能性改良领域中的应用奠定了重要的理论基础。该方法有望成为竹材功能性改良的新手段,并对包括木材在内的其它天然生物质材料功能性改良具有良好的借鉴意义。论文主要结论如下:(1)分别利用场发射环境扫描电镜、X射线衍射仪对竹材横切面和微纤丝角进行表征,发现γ射线对竹材的维管系统、基本组织等没有明显损伤,对微纤丝角的影响也不明显,辐照过程中竹材细胞壁未发现有皱缩、断裂等现象。竹材的微观构造和微纤丝角均不是影响辐照过程中竹材物理、力学性能变化的主要因子。(2)利用核磁共振波谱仪、X射线衍射仪以及传统的竹材化学成分含量测试手段,对竹材细胞壁主要化学组分的结构和性质进行检测。结果表明,在辐照初期,竹材内半纤维素发生降解,并且其部分降解产物与纤维素、木质素等发生聚合反应,致使半纤维素含量降低,纤维素、木质素含量有所升高,竹材的相对结晶度升高。当辐照剂量升高至100KGy左右时,竹材主要化学组分的降解反应加剧,纤维素、半纤维素和木质素的含量均呈现降低趋势,竹材相对结晶度也有所降低,并且降低的幅度随着辐照剂量的增加而增大。(3)γ射线辐照竹材以后,使竹材细胞壁的主要化学组分发生反应,产生氢键、羰基、羧基和酚类物质等,降低了竹材的吸湿性能。而木质素的降解则导致竹材表面颜色变暗,但同时也提高了竹材表面颜色的光稳定性。竹材吸湿性能和表面颜色特性的变化幅度随辐照剂量的增加而不断增大。(4)γ射线辐照初期,纤维素、木质素等发生聚合反应,使竹材的弦向抗弯强度、顺纹抗拉强度有所升高。半纤维素的降解则导致竹材顺纹抗压强度降低。直至辐照剂量达到100KGy时,纤维素、半纤维素和木质素的降解反应加剧,竹材的弦向抗弯强度、顺纹抗拉强度呈现降低趋势。但因竹材发生了炭化,使得竹材的顺纹抗压强度升高。整个辐照过程中,竹材的弹性模量呈现波动升高趋势,可见γ射线辐照使竹材刚性、脆性变强。(5)利用动态力学热分析仪,测试竹材的动态粘弹性。测定的温度范围为40℃~300℃,频率为3Hz。在起始温度点,即温度为40℃时,辐照后竹材的存储模量大于普通竹材,说明辐照使得竹材的刚性增强。但在升温过程中,辐照后竹材的存储模量降低幅度更加显著,说明竹材细胞壁主要组分的分子链被切断,升温过程中链段反应加剧,因而竹材存储模量降低幅度加剧。另外,辐照使竹材玻璃化转变温度点也发生改变,当辐照剂量低于100KGy时,竹材在105℃、220℃附近的玻璃化转变温度,因纤维素、木质素的聚合,呈现波动上升的趋势。而当辐照剂量达到300KGy、500KGy和1000KGy时,竹材的两个玻璃化温度转变点则因细胞壁三种主要组分的剧烈降解,而均呈现下降趋势。(6)在研究竹材γ射线辐照效应的基础上,开展了γ射线辐照技术在提高竹材防霉性能中的应用研究。结果表明,竹材经γ射线辐照以后,竹材防霉性能提高,而且随着辐照剂量增加,防霉效果更佳。但由于γ射线对竹材有一定的劣化作用,因此在利用γ射线辐照对竹材进行防霉处理时,应根据材料的用途,设计合理的辐照工艺。更多还原

【Abstract】 It has very significant theory and application meaning to research on physical and chemical properties of bamboo irradiated by gamma ray. The Moso bamboo (Phyllostachys pubescens Mazel ex H de Lehaie) was used as experimental materials in this dissertation. it was treated with gamma rays at differerent irradiation dose, such as 10KGy、20KGy, 30KGy, 50KGy, 100KGy, 300KGy, 500KGy, 1000KGy. Through studying Moso bamboo’s microstructure and its physical, chemical and mechanical proterties during the process of irradiation, this study initially reveals the irradiation effects mechanism on bamboo treated with gamma rays. Based on which, the applications of gamma ray irradiation on the mildew proof of bamboo have also been researched. And the result could establish an important theoretical foundation for the functional improvement on bamboo with gamma rays. This method was expected to be a new way for bamboo functional improvement, and had some reference meaning for the functional improvement of wood and other biologic materials.Main results were concluded as following:(1) The cross section and microfibril angle of bamboo were characterized by field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). it can been found that the vascular tissue system and fundamental tissue system were not be injured by gamma rays, the influence on microfibril angle were not obvious, and the cell wall of bamboo were not found shrink and fracture during the process of irradiation. So both microstructure and microfibril angle were not the dominant factors on variation in physical-mechanical properties of bamboo during the process of irradiation.(2) The structure and quality of main chemical composition in cell walls of bamboo were tested by nuclear magnetic resonance spectrometer (NMR), X-ray diffraction (XRD) and traditional means in testing chemical composition content of bamboo. The result indicated that at the beginning of irradiation process, hemicellulose degraded and partial degrading substances polymerized with cellulose, lignin and so on. Which result in hemicelluloses content decreasing, the cellulose and lignin contents increasing, and the bamboo crystallinity also increased. As the irradiation dose was raised to about 100KGy, the main composition in bamboo degraded more quickly, so that the main chemical composition contents and crystallinity in bamboo reduced, and the more irradiation dose, the more reduction.(3)The gamma rays radiation reduced adsorption of bamboo materials through making chemical composition in cell wall interaction, which produced the hydrogen, carbonyl, carboxyl, phenolic etc. The appearance color of the bamboo became darker for lignin degradation, but improved the light stability of color on bamboo surface, and the change rates of them increased with radiation dose growed.(4) At the beginning of irradiation process,the gamma rays radiation enhanced both tangential compressive strength and tensile strength parallel to grain of bamboo, owing to oligomerization of lignin and cellulose. And the degradation of hemicellulose reduced compressive strength parallel to grain of bamboo. As the irradiation dose rose to about 100KGy, both tangential compressive strength and tensile strength parallel to grain of bamboo reduced with degradation reaction comintensifying of main compositions in bamboo. Yet, carbonization of bamboo material enhanced compressive strength parallel to grain of bamboo. In the whole process, modulus of elasticity of bamboo material fluctuated rising tendency. So, the gamma rays radiation intensified stiffness and brashness of bamboo.(5) The dynamic viscoelastic properties of bamboo were tested by dynamic mechanics analyzer (DMA), and the measurements were done in the temperature range of 40℃to 300℃at frequencies of 3Hz. In the initial temperature, temperature of 40℃, the irradiated bamboo had more storage modulus than ordinary bamboo, but with the increase of irradiation dose , the decrease of storage modulus with increasing temperature became more dramatically, because the chain of main components in the cell walls have been cut off, and chain made drasticer reaction during heating process. In addition, irradiation made bamboo glass transition temperature changes. As the irradiation doses was less than 100KGy, the glass transition temperature at 105℃and 220℃fluctuated rising tendency for the oligomerization of lignin and cellulose. And when the radiation dose reached 300KGy, 500KGy and 1000KGy, both glass transition temperatures decreased for the degradation of three main compositions.(6) on the base of study about gamma ray irradiation, the technology of improving the application of bamboo mould-proof performance was researched. The results showed that the mildew proof of bamboo was enhanced after irradiation. Furthermore, the effect was better and better with the irradiation doses increased. At the same time, gamma ray has a side-effect, so the reasonable irradiation technology should be counted on the usefulness of bamboo material.更多还原