【作者】 章伟伟；

【导师】 肖惠宁；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2014， 博士

【摘要】 纸张作为绿色环保材料被应用在越来越多的领域，传统的疏水改性-施胶已经不能满足纸张的防潮抗水性能。目前对纸张的防潮处理一般采取纸-塑或纸-金属的复合材料，阻隔水蒸气的效果明显，但纸张的绿色环保性能难以保证；而超疏水纸张的研究尚处于研发阶段，国内外报道较少。本论文主要通过纸张的内部添加、表面涂布和纤维改性的方法，对纸张的抗水蒸气和抗水性能及其机理进行了较为系统的研究。将蜂蜡乳化后进行湿部添加或表面涂布，并结合热处理和抛光等后续处理，考察了它们对纸张水蒸气阻隔效率和抗水性能的影响。通过对水蒸气透过材料的热力学和动力学分析可知，具有孔隙结构的纸张对水蒸气几乎不存在阻隔性能；纸张表面的均匀致密薄膜在满足低溶解系数和低扩散系数的条件下，才能有效抑制水蒸气的扩散。通过对液体接触角的模型分析可知，疏水性物质的表面粗糙度能强化其疏水性能。壳聚糖-蜂蜡双层涂布纸张的结果表明，其水蒸气阻隔性能随着壳聚糖浓度的升高而增强，但是起水蒸气阻隔作用的蜂蜡涂布量却随之降低。通过微观结构分析可知，蜂蜡涂布量的降低得益于预涂布壳聚糖的成膜性。同时，在壳聚糖-蜂蜡双涂层界面上存在一定的界面效应，使得复合膜的水蒸气阻隔效果优于单纯的蜂蜡物质。通过对蜂蜡-壳聚糖乳液涂布纸张的涂层微观形态观察可知，在较高温度下干燥乳液涂层时，蜂蜡颗粒的融化和再融合过程，弥补了乳液涂布时的微小细缝的缺陷；再加上乳液在高温下蜂蜡发生团聚和凝聚作用而产生的相分离作用，使得高温干燥下的乳液涂布对水蒸气阻隔性显著提高。物质的表面自由能和微观形态都能显著地影响超疏水性能，其中微观结构的影响相对更为重要。由蜂蜡和棕榈蜡组成的混合蜡乳液涂布在纸张表面，在合适的温度下，蜡质颗粒中的蜂蜡成分处于“液态”而棕榈蜡成分处于“固态”，两相发生分离，在球状混合蜡颗粒表面产生大量褶皱或碗状结构。该结构的尺寸与蜡质微球相比，属于亚微米级结构，因而构成了微米-亚微米的二级结构，大大地降低了蜡质表面与水的接触面积，产生了超疏水的涂布纸张。与TMCS和DMDCS相比，MTCS具有三个Si-Cl键，反应活性大大提高，疏水改性效果最明显。首先，MTCS与纤维表面的羟基缩合，形成厚度在10nm以下的聚甲基硅氧烷的单分子涂层；其次，溶剂中的MTCS在合适的水浓度下在涂层表面形成直径为20-50nm的细丝结构。这些在微米级纤维表面形成的纳米结构，形成了纳米-微米的二级结构，从而保证了超疏水界面的产生。纸张的强度由纤维之间的氢键提供，但在MTCS的改性过程中，纸张中的氢键数量大大减少，因而强度下降。为控制MTCS处理仅发生在在纸张界面上，纸张可以通过“半溶解-析出”的处理，得到致密的纤维素薄片。改性后的纤维素薄片既具有超疏水效应，又能保持较高机械强度。更多还原

【Abstract】 Cellulosic paper is applicated in more and more areas as one kind of green andenvironmently friendly materials. However, troditional hydrophobiczation-sizing-cannot meetthe demands of moistrue and water resistance. Nowadays composite materials of paper-plastic/metal are usually ustilized to retard water vapor, which enhace the water vapor barrierevidently. The inherent advatanges of paper is no longer preserved in the meantime. Thesuperhydrophobization of paper rises recently years and there are few of studies in domesticand international reports. In this paper, a systematic study about the superhydrophobization ofpaper for enhaced moistrue and water resistance and its mechanisam, was carried out throughwet-end, surface coating and cellulose modification.The effects of beeswax aditive methods (wet-end aditive, surface coating, dip coating) andpost treatments (heat treatment, polishing) on water and moisture resistance were investigated.The results showed that water with pore structure had almost no barrier properties to watervapor. According to the thermodynamics and kinetics of water vapor through materials, thesurface coating film could be effective shield against the moisture in the condition of lowsolubility diffusion coefficient of the material. The roughness of hydrophobic material couldimprove its hydrophobicity according to the contact model analysis.The results of chitosan-beeswax bilayer coated paper showed that the WVTR was reducedas the chitosan concentration increased. However, the beeswax coating weight decreased dueto the good film forming of chitosan based on the microstructure observation. Besides, theinterface effect between beeswax and chitosan layers made the water vapor barrier of compositefilm better than pure beeswax. In the experiment of beeswax-chitosan emulsion coating, themicrostructure showed that the beeswax particles melted and re-agglomerated during heattreatment, and the creaming process of beeswax-chitosan emulsion magnified at highertemperature, both of which resulted in an improved moisture barrier property of the coatedpaper.The effort of surface morphology played a larger part than surface free energy did on thesuperhydrophobicity. Wax mixture, composed of beeswax and carnauba wax, was emulsified and coated at paper surface. At proper temperature, the beeswax part in the wax particles wasin "liquid state", while the carnauba wax part in "solid state", resulting mass of bowl-shape orfold structure at the surface of wax particles during phase seperation process. The hierarchicalsubmicro-/-micro-structure greatly reduced the contact area between wax miture and water,thus producing superhydrophobic surface.Compared with TMCS and DMDCS, MTCS had three Si-Cl bonds and showed the mostactive chemical reaction and thus best hydrophobization property. First, the MTCS condensedwith the hydroxyl group at the fire surface, resulting in the formation of self-assemblymonolayer (SAM) of polymethylsilane with a thickness of less than10nm; then, the MTCSpolymerised within its molecular to form filaments in a diameter of20-50nm at the SAMsurface. The formation of hierachical nano-/micro-structure composed of hydrophobic fibre andfilaments enssrured the production of superhydrophobic surface. In the process of silanizationof fibre, the hydrogen bonds, which provided the mechanical strength of paper, decreaseddramatically due to the condensation reaction and the strengh of papre was reduced. In order tocontrol the reaction sites just at the paper surface, the paper was treated with partially-dissolution and precipitation to obtain the dense cellulosic cellulosic flake. The modifiedcellulosic flake had a superhydrophobic surface and the mechancial strength was also preserved.更多还原