【作者】 肖红；

【导师】 于伟东； 施楣梧；

【作者基本信息】 东华大学 ， 纺织材料与纺织品设计， 2005， 博士

【摘要】 对四川攀枝花地区生产的木棉纤维结构和性能作了研究,首次获得了自然状态下木棉纤维横截面和头端的清晰实物照片。结果表明木棉纤维具有壁薄、大中空、梢端封闭、根端在自然状态下紧闭的独特形态结构;0.03g/cm³的体积质量,10.8%的回潮率;较棉纤维低的结晶度和取向,较棉纤维疏松的胞壁结构;较棉纤维弱的碱液抵抗能力。 通过四氧化锇前染和铅铀片染,成功地制取了木棉纤维超薄切片,通过透射电镜观察获得了木棉纤维胞壁清晰可见的层状结构和明显的原纤结构,首次建立了木棉纤维的微细结构模型:木棉胞壁可分为致密的表皮层S、胞壁Ⅰ层W₁、胞壁Ⅱ层W₂、胞壁Ⅲ层W₃和内皮层IS共五个基本的层次,在W₁和W₂层间、W₂和W₃层间分别存在过渡层L₁和L₂。各层聚集密度由大到小依次为S,W₁,W₃,W₂和IS层,其中,表皮层最为致密,为纤维的保护层,厚度约40～70nm;过渡层（L₁和L₂）原纤排列最为疏松,导致层间原纤的结合力较层内原纤的结合力弱;内皮层较为疏松,厚度在40nm以下。 W₁,W₂,W₃层具有精细的原纤结构,W₁层原纤排列与棉纤维初生层相似,W₃层内的原纤排列与棉纤维的次生层原纤排列类似;其原纤几何尺寸通常在基原纤和原纤的尺度内变化,同时也分布着不同尺寸的更大的原纤。其中,160～240nm厚的W₁层中原纤呈网络状排列,宽度约10nm。W₂和W₃层厚度相当,约500nm,其内的原纤均平行致密、与纤维轴呈一定夹角排列;最小可见原纤宽度约3.2～5.0nm,其宽度尺度和棉纤维的基原纤相当;但两层内原纤长度和与纤维轴的夹角存在差异,根据勾股定律,W₂层内的原纤长度大于132nm,和纤维轴的夹角约16.3°,而W₃层内的原纤长度则大于153nm,和纤维轴的夹角约为36.6°。 实验发现NaOH对木棉纤维的可及性存在显著个体差异、对同一纤维胞壁各层的溶胀也存在显著差异,这与棉纤维的可及性显著不同。其中W₂层和IS层是最易被溶胀的。内皮层结构疏松,原纤容易被分离出来,游离在中腔内。 在理论分析和实验验证基础上,建立了基于力分析的纤维浸润性能判定测试方法及其理论分析。通过分析纤维水平进入液体过程中,纤维和液体初始接触的力值变化和纤维完全进入液体时液面闭合时的力值变化,可以判定液体对纤维的浸润性能。所构建的更多还原

【Abstract】 The structures and performances of the kapok fiber from the Pangzhihua area in Sichuan province have been investigated. The cross section and ends are photographed in natural status. The kapok fiber shows a unique morphology with hollow lumen, thin cell walls, and two closed ends in nature. The fiber is very light in weight with the density of 0.03g/cm³. Its crystallinity and oritation degree are lower than those of the cotton fiber, the structure of the cell wall is looser than that of cotton fiber, the moisture regain is about 10.8% which is higher than that of cotton fiber, and the resistance to alkali is weaker than that of cotton fiber.By staining of osmium tetroxide and uranyl acetate and lead salts, a clear cell structure of the ultrathin sections of the stained kapok fibers were observed using transmission electron microscopy （TEM）. The ultrastructure of kapok fiber was presented in first time. The wall of kapok fibre can be divided into five layers, including skin layer, S;primary wall, W₁;secondary wall, W₂;tertiary wall, W₃;and inner skin, IS. There are transition layers between adjacent layers, namely, L₁ between W₁ and W₂, and L₂ between W₂ and W₃. An interlaced fibril-like network is the characteristics of the primary wall, W₁, with about 160²40nm in thickness;the fibrils in the secondary wall, W₂, incline to the cell axis at a constant angle of 16.3°;and the fibrils in the tertiary wall, W₃, are closely packed and aligned in at a certain angle of 36.6° to the fiber axis. The W₂ and W₃ walls have the same thickness about 500nm. The highest packing density lies in the skin layer which is the protective layer of the fiber with about 40⁷0nm in thickness. The structures of W₁ and W₃ are more compact than that of W₂. The inner skin with thickness below 40nm is relatively loose. The loosest packing density is within the transition layers. The interaction between fibrils in the transitional layers （L₁ and L₂） is weaker than that in the individual layers. The scale of the visible minimum structure units is not the same for different walls. The minimum fibril size of kapok fiber is 3.2nm⁵.0nm thick and near to the dimension of the protofibril of cotton fiber. Some larger fibrils with different sizes are also in the different walls. The ultrastructure of kapok fibre show that there is an obvious fibril structure and the geometric scale belongs to the range from protofibrils to fibrils.Kapok fiber swollen by alkali shows an evident difference among the different layers in the same cross section, and W2 and inner skin are most easily swollen and are most weak resistant to alkali. The fibrils are easily departed from the inner wall and dispersed into the lumen. It is obviously different from cotton fiber swollen by alkali.In order to measuring the wettability of the short and fine single fiber with poor wettability, a new wettability evaluation method for the single fiber measure has been developed, the systemically theoretical analysis was carried out, and the quantitative parameters were put forward. A fiber in horizontal is forced into and withdrawn from the liquid at a certain speed, and the force changes are detected simultaneously. The experimental results show that the force impulse can be found at fiber contacting with liquid and immersed into liquid, and its value depends on the wettability of the fiber. According to the force impulses of different fibers, the immerging behavior of the fibers can be obtained and categorized into four sorts. Meanwhile, the wettability of the fiber can be evaluated with the wettability factor, w, derived from the fiber immerging curve, where w is the ratio of the force increment on fiber initially contacting with the liquid to the force increment on liquid surface closing with fiber immerging into the liquid, and with the contact angle, 9, calculated from the wettability factor {0 = ix/（w+l）) supposed that the fiber is a circular cross-section. The force measurement indicates that the method can be used for various fibers with short length, or lower density than that of the liquid, or poor wettability.The influencing factors in quantitative calculations are discussed. The force impulses during the initial contacting process and the liquid surface closing process increase with the increase of the fineness of the fiber, but the fineness does not affect the wettability of the fiber. The shape of the cross section of the fiber is an important factor to the wettability calculation. By this new method, the contact angle between the kapok fiber and the distilled water is about 157° that is similar to the value measured from the sessile drop method.The capillary performance of the fibrous assemblies with positive wettability has been studied by using the dynamic capillary method, and the factors affecting the performances of the fibrous assemblies with negative wettability were deduced. The bulk density, the fineness of the single fiber, the surface characteristics of the fiber, and the liquid surface tension are the important factors to the wettability of the fibrous assemblies. The fiber profile is also a reason influencing the wicking property but less than the fineness and the bulk density do. The modified Lukas-Washburn equation is only suitable to the initial capillary process. The shapefactor of the fibrous assemblies can be obtained when the contact angle is known.Through the compression tests of the kapok fibrous assemblies, this present thesis emphasizes on the importance of the initial bulk density. At the same pressure and compressing time, the fibrous assembly in random alignment will approach to a constant bulk density despite of the different initial bulk density. If the initial bulk density of the fibrous assemblies is lower than the constant value, the compression rate decreases and the compression recovery rate increases with the increases of the initial bulk density of the fibrous assemblies.The reasonable bulk density of the kapok fibrous assemblies as buoyancy materials ranges from 0.038g/cm3 to 0.05g/cm3. In fact, if kapok fibers are immerged in the water for the long time, the moisture regain of the fibers will increase. The experimental results show that the weight of the kapok fibrous assemblies increases to 45%⁵5% after 24hr immerging in water. The theoretical model for the buoyancy evaluation of the fibrous assemblies has been established. It can be used to guide the design of fibrous assemblies as buoyancy materials.The investigation on the three composite buoyancy materials indicates that the multiple layers buoyancy material made of the kapok layers piled up with the three-dimension-crimp polyester layers forms a good and stable supporting structure, which can improve the compression recovery rate comparing to the pure kapok fibour assemblies. The buoyancy material made of kapok fibers and low melting point fiber forms a steadier structure than the pure kapok assemblies and has good resistance to the compression. It is a better composite buoyancy material with a higher buoyancy factor and low buoyancy loss. However, the mixed fibrous assembly of the kapok fibers and the three-dimension-crimp polyester fibers by carding process cannot form a good buoyancy material.In short, all the experimental results show that the typical morphology of the kapok fiber is unique with large lumen, thin cell walls, two closed ends and elaborate fibril structure. Its fibrous assembly is a good buoyancy material with good resistance to water and lower bulk density. The composite made of the kapok fibers bonded with the low melting point fibers has a stable structure and better buoyancy behavior.更多还原