【作者】 马艾丽；

【导师】 常杰；

【作者基本信息】 华南理工大学 ， 能源环境材料及技术， 2014， 博士

【摘要】 随着化石资源的日益短缺，在出现能源短缺问题的同时，以化石资源为基础的化学品的短缺问题也随之而来，利用植物生物质基材料补充石油基高分子材料变得日益重要。由于木质素中含碳量较高（一般在55%～66%之间），因此可作为碳纤维原料进行利用；而且木质素中含有各种羟基和醚键等基团，可以与高分子产生较强的分子间作用力，因而可以用于和树脂共混制备复合材料。本文首先以木质素为原料制备纳米碳纤维，对木质素基纳米碳纤维的制备工艺、结构性能进行系统研究；然后用木质素增强PVC制备木质素/PVC复合材料，考察不同比例掺杂对共混物的力学性能、热学性能的影响。最后对复合材料的热氧老化降解性能进行了研究。探索制备高值化的木质素/PVC复合材料的最佳工艺条件及配比，为木质素的高值化利用提供数据基础和理论指导。以玉米秸秆木质素为原料，以DMF为溶剂，以PAN为共混组分，采用静电纺丝技术制备木质素基纳米纤维，经研究发现，纯木质素溶液很难静电纺丝，木质素溶液浓度在40%以下时只能形成球状颗粒，直到木质素浓度达到50%时，可纺性增加，能够形成带珠粒的丝状纤维；木质素与可纺性高的PAN混纺，在木质素与PAN比例为1：4时能形成直径分布均匀、取向程度好、无串珠的连续纤维；静电纺丝最佳工艺参数为纺丝电压15-20kV、推速0.02mm/min、接收距离17cm、辊筒转速2000r/min，此工艺条件下得到的纤维取向程度好，直径分布均匀。以玉米秸秆木质素和PAN为原料，通过静电纺丝工艺在纺丝电压15kV，推速0.04mm/min，接收距离为12cm条件下制备木质素基纳米碳纤维。对制得纳米纤维先驱丝在200-300℃进行预氧化，在600-1000℃进行碳化处理制备木质素基纳米碳纤维，并对纳米碳纤维进行表征后发现，900℃碳化温度下得到的木质素基纳米碳纤维直径比较均匀，光洁度高，形貌较好，结构致密度最高，结构缺陷最少，热稳定性好。所有木质素基纳米碳纤维石墨化程度较低，呈乱层石墨结构。以普通PVC板材配方为基础，以竹碱木质素为原料，设计出木质素/PVC复合材料的配方并对不同木质素添加量的复合材料进行表征，研究发现，复合材料当中木质素和PVC分子之间没有化学键结合，两者之间以分子间作用力和偶极作用连接在一起；木质素添加入复合材料体系中，对复合材料的力学性能产生很大的影响。弹性模量在添加量为30phr时达到最大值，拉伸强度在木质素添加量20phr时最接近没有添加木质素的PVC板材的值，而最大断裂延伸率却是在木质素添加量为25phr时最高。复合材料体系还是呈现两相分布，木质素大部分是溶解在PVC基体当中。以木质素为原料，优化配方制备出的高强度木质素/PVC复合材料中，并对不同比例的木质素共混改性效果进行评价和表征，研究发现，添加木质素后，PVC的耐热温度普遍提高了50-70℃，提高了PVC的耐热性，木质素添加量为30phr时，其综合力学性能最佳，共混效果最好；通过配方优化，木质素提高了PVC的耐热性和机械性能，对于木质素在PVC当中的使用起到了推动作用。不同木质素/碳酸钙比例的PVC复合材料在热氧化炉中进行人工加速老化处理，热氧老化处理温度为100℃。实验考察了木质素添加量（木质素/碳酸钙比例）和热氧老化时间对复合材料老化降解性能的影响。研究发现，木质素能够抑制降解。木质素部分溶解在PVC当中，充当纳米碳酸钙和PVC之间的相容剂。适量的木质素/碳酸钙添加比例具有良好的协同效应，其增强效果可以长时间保持，两者比例为10/10时为最佳，其共混改性效果最理想。此配方中填料分散均匀，所得复合材料的初期热稳定性最高，耐热老化性能良好，综合力学性能指标优良。更多还原

【Abstract】 With the growing shortage of fossil resources, the energy shortages occur, as well as theshortage of chemicals based on fossil resources has cropped up simultaneously. So the use ofbiomass-based materials as the supplement of petroleum-based polymer materials isbecoming increasingly important. Due to the higher carbon content of lignin (from55%to66%), it can be carried out as the raw material of carbon fiber. Meanwhile, lignin containsvarious hydroxyl group and ether bond, it can produce strong intermolecular forces wit h thepolymer, and thus can be used for preparation of composite materials with resin blends. In thispaper, lignin was used as a raw material for preparing carbon nanofibers firstly. Thepreparation technology, structures and properties of lignin-based carbon nanofibers aresystematically studied. Then the lignin was used as filler to enhance PVC. Different content oflignin reinforced PVC composite material were prepared to investigate blends mechanicalproperties, thermal properties and at last the study on thermal aging degradation performanceof lignin/PVC composite materials was carried out. The optimum technics and formula ofhigh-value lignin/PVC composite materials were explored. The study provides a solidfoundation of data and theoretical guidance for the high-value use of lignin in industry.Lignin/polyacrylonitrile (PAN) nanofibers were prepared by electrospinning oflignin/PAN solutions in different blend concentrations. Fibers morphology was observedunder a scanning electron microscope (SEM) and effects of processing parameters includingelectrospinning voltage, flow rate, tip-to-collector distance, and rotational speed on themorphology of electrospun lignin/PAN fibers were studied. The beadless, uniform lignin/PANnanofibers with a diameter of200-300nm were obtained when the weight ratio of PAN tolignin is80%. It was also found that the electrospinning, and had important influences on theaverage fiber diameter and diameter distribution, whereas could significantly affect the degreeof fiber alignment. The prime technics parameters were as follows: voltage is15-20kV, flowrate is0.02mm/min, tip-to-collector distance is17cm and rotational speed is2000r/min.Then the precursor fibers were pre-oxidation at200-300℃and then carbonized at atemperature from600℃to1000℃respectively to prepare biomass based carbon nanofibers.The influences of carbonization temperature on prepared carbon nanofibers were investigatedby XRD, RAMAN, TGA, DSC and SEM. The results indicated that the carbon fiberscarbonized at900℃had highest thermal stability, good morphology and most compactstructure. Therefore,900℃is the optimal carbonization temperature for preparinglignin-based carbon nanofibers in this technique. Lignin/PVC composite materials were prepared and the effect of lignin incorporationwas investigated by means of mechanical properties, FTIR and scanning electron microscopy(SEM). The results showed when lignin was no more than25portions (mass), theperformance of lignin/PVC composite materials was ideal.Lignin/PVC composite plates with various ratios of lignin were prepared by blendingand molding process. The intermolecular bonding between lignin and PVC was determinedvia FTIR analysis and was correlated to mechanical properties. Lignin has been found todisperse in PVC resulting in the shift in IR frequency. The morphology of composites wascharacterized by SEM indicating good compatibility of lignin and PVC. The dispersion oflignin in PVC was uniform. Mechanical and thermal properties were comprehensively studied,showing that composites with lignin exhibit improvement in thermal stability and mechanicalstrength compared to PVC without lignin.Different lignin/calcium ratio of the PVC composite undergo artificial accelerated agingtreatment in thermal oxidation furnace, and thermal aging treatment temperature is100℃.Experimental study on the effects of the added amount of lignin (lignin/calciumcarbonate ratio) and thermal aging time aging to composite materials’ degradationperformances were carried out. It was found lignin can suppress the degradation of PVC.Lignin was partially dissolved in PVC which acted as a compatibilizer between calciumcarbonate and PVC. The right amount of lignin/CaCO3ratio has good synergy effects that itsmodification effect can be maintained longer. The best ratio of lignin/CaCO3was10/10,whose modification effect was ideal. The composite with this formulation has uniform fillerdispersion, good thermal stability at the beginning, good heat aging resistant properties andexcellent comprehensive mechanical properties.更多还原