【作者】 胡月；

【导师】 李大纲；

【作者基本信息】 南京林业大学 ， 材料学， 2012， 硕士

【摘要】 本文以杨木和棉花为原材料通过化学机械相结合的方法制备了高长径比纳米纤维素，且通过混合搅拌法、冷冻干燥浇铸法、薄膜浸渍法三种方法制备了纳米纤维素/聚乙烯醇复合膜，其中，浸渍法制得的薄膜性能最佳。本文旨在利用纳米纤维素提高聚乙烯醇的综合性能，扩大其在医药、生物包装以及园艺等方面的生物基复合膜的应用。本文使用的检测手段有电子扫描电镜、傅里叶红外、透光率测试、力学性能测试、热力学性能测试以及降解性能测试。测试结果如下：1、从电子扫描电镜照片可知，本论文中从杨木和棉花中提取的纳米纤维素的直径主要分布在50～150nm之间，长径比在1000～4000之间。观察浸渍法制得的复合膜的拉伸断裂面可知，纳米纤维素膜和聚乙烯醇是相互渗透，紧密结合为一体的，且断裂面为韧窝状，说明纳米纤维素膜对聚乙烯醇有很好的增强作用。2、傅里叶红外分析表明了杨木和棉花在在经过亚氯酸钠处理之后，代表木质素的波峰变弱了；经过氢氧化钾处理之后，代表半纤维素的波峰变得不明显；经过盐酸处理之后，代表纤维素的波峰增强。综上所述，经过化学处理之后，本论文去除了杨木和棉花的木质素和半纤维素等杂质，成功提取了纤维素。复合膜的红外光谱图表明纳米纤维素膜和聚乙烯醇的结合是物理性质的，而不是化学性质的。3、透光率测试表明随着纳米纤维素膜的厚度的增加，不论是可见光透过率还是紫外光透过率均有所下降。其中，棉花的透过率稍高于杨木的透过率，这是因为杨木纳米纤维素含有200nm以上纤维素比棉花纳米纤维素多些。复合膜的透光率随着纳米纤维素质量分数的增加也有缓慢的降低趋势。4、拉力试验结果表明，杨木和棉花的纳米纤维素复合膜的力学性能相当。纳米纤维素膜的力学性能极好，拉伸强度高达101.79MPa，弹性模量高达5741MPa。当纳米纤维素膜的厚度为0.03mm时，力学性能达到最佳，可提高聚乙烯醇的弹性模量200%。5、热力学性能分析可知纳米纤维素的热膨胀系数极低，热力学性能极佳，将它们加入到聚乙烯醇中可以制备理想的低热膨胀系数的复合膜，且复合材料的热稳定性也会随着纳米纤维素含量的增加而略有提高。6、生物降解试验表明，纳米纤维素膜/聚乙烯醇复合膜可生物降解，且随着纳米纤维素含量的增加，降解性能越高。本论文制备的复合膜是环境友好增强型材料。综上所述，本论文成功制备了具有低热膨胀系数、透明性、力学性能较好、可生物降解的纤维增强聚乙烯醇复合物。而且，因为这些纳米纤维素都取自天然的植物杨木和棉花，来源不仅丰富而且可环保可降解。这些优势必将促进纳米复合材料的发展，扩大聚乙烯醇的应用领域。更多还原

【Abstract】 This work was to prepare the high aspect ratios (length/diameter) nano cellulose extractedfrom poplar and cotton with mechanochemistry treatment. There are three methods to preparenano cellulose/PVA composite: Mixture of mixing method; Freeze drying casting method and theFilm immersion method, among them, the last method is the best. Successful preparation of suchbio-based composites could open up ways to new applications in e.g. medicine, bio-packaging orhorticulture. The nano cellulose and composite films were characterized with scanning electronmicroscope (SEM), fourier transform infrared spectrometry (FTIR), ultraviolet-visible spectra(UV-vis), tensile testing machine, thermo mechanical analysis(TMA) and constant temperatureand humidity incubator. Test results are as follows:1、SEM showed the diameter of the cellulose was mainly range between30~100nm and highaspect ratio was mainly range between1000～4000. Observe the composite film tensile fractureswith film immersion method, the nano cellulose film and PVA were mutual blend, touchedclosely, and the fracture present dimple that suggested nano cellulose film had very good enhanceeffect on PVA.2、FTIR indicated after poplar and cotton through the sodium chlorate treatment, the peaksrepresented of lignin become weak and also the peak of hemicellulose after potassium hydroxidetreatment. After the hydrochloric acid treatment, representatives the peak represented of celluloseincreased. To sum up, after mechanochemistry treatment, this work successfully extractedcellulose from poplar and cotton. FTIR indicated the interaction between nano cellulose andmatrix is physical rather than chemical in origin.3、UV-vis showed that with the thickness of nano cellulose film increased, no matter thevisible light or uv light transmittance, they were all decreased. Among them, the cotton was betterthan the poplar, this is because poplar contained more nano cellulose fiber that bigger than200nm. The light transmittance of composite film also decreased with the content of celluloseincreased.4、The mechanical properties of PVA were improved significantly and the two plantnanofibers had the similarly reinforcing effects in the matrix. The mechanical properties of nanocellulose film were wonderful, tensile strength was reached up to101.79MPa, and elasticmodulus was reached up to5741MPa. When the thickness of nano cellulose film was0.03mm,the mechanical properties reached the best, improved the elastic modulus of poly (vinyl alcohol)200%.5、TMA suggested that the thermal expansion coefficient of nano cellulose was extremelylow. When added them to the PVA, there can be made of ideal composite film with low thermalexpansion coefficient, and thermal stability of composite material was increased with the content of nano cellulose slightly increased.6、Biological degradation test showed that nano cellulose/PVA composite film wasbiodegradable. With the content of nano cellulose increased, the degradation property becomebetter. This composite film was environment friendly enhanced material.In conclusion, cellulose nanofibers as a future resource have tremendous potential since theyare one of the most abundant organic resources on the earth. The potential applications ofcellulose nanofbers are as thickeners in food products, as strengthening agents for packagingmaterials, as barrier coatings, and in lightweight and strong polymer nanocomposites.更多还原