高得率浆纤维结合性能的评价体系构建以及其对纸浆物理强度的影响机理研究

In recent years, high-yield pulp (HYP) has been found an increasing application in many paper grades due to its unique properties, such as high bulk and stiffness. However, the physical strength properties of HYP are usually lower than those of chemical pulps, which can highly hinder its further value-added applications. Firstly, some modern instruments and techniques, such as Confocal Laser Scanning Microscopy (CLSM), X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM), will be used in this project, to measure the fiber structure (ultra-molecular structure and microfibril structure), chemical composition and fiber characteristics (flexibility, charge properties and surface properties) of different HYP fiber fractions. The "real" bonding areas between HYP inter-fibers are determined, and the evaluation system for the bonding characteristics of HYP fibers will be constructed. Then, the interactions between the fiber properties of different HYP fiber fractions, especially for the microfibrils absorbed on the surface of long-fiber fractions, and their bonding characteristics (bonded area and bonding strength) and/or the tensile strength of HYP fibers will be investigated. Subsequently, the correlative parameters will be analyzed based on the rationale of response surface methodology (RSM) and the semi-theoretical models will be established. Further, the influencing mechanisms of bonding characteristics of HYP fibers will be clarified, with the supports of the images' analyses of surface topography and bonded areas of HYP inter-fibers. Finally, the interpretation regarding the effect mechanisms of the bonding characteristics of HYP fibers to their physical strength properties will be obtained. In a word, the high-yield pulping theories can be enriched and developed through the researching conclusions in this project, and the basic technical foundations can be provided to produce HYP fibers with relatively high physical strength properties and to enlarge the value-added applications of HYP fibers in more paper grades and other fiber engineering fields.

高得率浆由于具有较高的松厚度、挺度等独特性能在许多纸种中逐渐得到广泛应用，但与化学浆相比，高得率浆的物理强度较差，大大限制了其高值化应用。本项目拟运用共聚焦激光扫描显微镜、X射线光电子能谱、原子力显微镜等先进仪器和手段，探明高得率浆纤维的结构（超分子结构和原纤结构）、化学组成与纤维性能，测算纤维间实际结合面积，构建纤维结合性能的评价体系；揭示不同长度级分高得率浆的纤维性能（特别是吸附于长纤维表面的细小组分）与其结合性能（结合面积、结合强度）以及抗张强度的构效关系；通过响应曲面设计实验并建立半理论模型，结合纤维表面形貌和纤维间结合区域的图像分析，明确高得率浆纤维结合性能的作用机制，阐明高得率浆纤维的结合性能对其纸浆物理强度的影响机理。本项目的研究成果将丰富和发展高得率制浆工艺理论，为生产较高物理强度的高得率浆、扩大高得率浆纤维在更多纸种及其他纤维材料领域中的高值化应用提供理论基础和技术依据。

高得率浆由于具有较高松厚度、挺度等独特性能在许多纸种中得到广泛应用，但仍存在物理强度较差的问题。本课题利用多种现代分析手段评价了高得率浆纤维的结构特征、化学组成和纤维表面性能，探讨了几个关键因素对纤维结合性能的影响机制；利用CLSM“光学切片”技术检测高得率浆纤维间的实际结合面积，构建其结合性能评价体系；运用聚电解质吸附理论剖析了纤维细胞壁不同部位电荷对其结合性能的贡献；采用“液桥”模型测定纤维接触角用于计算表面自由能（表征表面润湿性），明确了纤维表面润湿性对其形变性和结合性能的关系；建立数学模型分析高得率浆纤维形变性能，探讨了纤维形变性与其结合性能的构效关系；利用吸附模型分析细小组分提高高得率浆纤维结合性能的作用行为。研究表明：高得率浆抗张指数随纤维长度增加而下降，结合指数随其比表面积增加而增大，Z向抗张强度随其表面电荷密度增加而增大；利用CLSM“光学切片”技术检测高得率浆纤维间实际结合面积，长纤维间的实际结合面积大于短纤维，而短纤维间的相对结合面积（RBA）大于长纤维；与单独增加纤维表面电荷相比，增加纤维总电荷对纤维保水值、柔顺性以及成纸紧度、抗张强度等指标的提升更显著；当纤维总电荷从155 mmol/kg增加到682 mmol/kg时，结合强度指数(B)提高370%，成纸抗张指数提高430%；增加纤维总电荷对结合强度的提升显著，而提高纤维内部电荷主要改变纤维相对结合面积；随着纤维表面润湿性增强，RBA增加，纤维形变性明显提升（柔软度从4.44×108N-1•m-2提高到1.18×109N-1•m-2），B从4.6 N•m•g-1提高至10.9 N•m•g-1。随着木素含量减少，单根纤维的断裂应力和弹性模量呈现减小趋势，纤维形变性增强，其相对结合面积和剪切结合强度增大；利用功能化细小纤维不仅可以提高高得率浆纤维结合强度，还可以保持较高松厚度。上述科研成果丰富和发展了植物纤维性能评价手段，对于深刻理解高得率浆纤维结合性能、改善其物理强度以及后期扩大其在高附加值纸种和其他纤维材料领域的广泛应用提供了良好的基础理论依据。