纳米纤维素基泡沫材料孔结构调控技术的研究

发布时间：2018-04-21 16:00

本文选题：可生物降解泡沫材料 + 纳米原纤化纤维素　；参考：《陕西科技大学》2017年硕士论文

【摘要】：随着环境污染问题的日益严重和石油资源的枯竭,研究开发可生物降解、资源丰富、可回收利用的新型泡沫缓冲材料替代传统泡沫塑料已成为社会上亟需解决的重大问题。目前,纳米纤维素基泡沫材料被认为是极具开发前景的可生物降解泡沫材料之一,研究其制备工艺与微观泡孔结构及性能的关系,开发泡孔结构调控技术,对获取不同结构和应用性能的纳米纤维素基缓冲材料具有重要的意义。因此,本文重点研究了纳米纤维素基泡沫材料泡孔结构的调控技术,主要内容如下:首先,对纳米原纤化纤维素(NFC)的物化特性进行表征。在此基础上,通过改变NFC浓度和冷冻温度对NFC泡沫材料的泡孔结构进行调控。NFC浓度增大使其泡孔分布变均匀,孔径尺寸减小,但局部会出现大孔或致密结构;低温冷冻使泡孔分布变得更加均匀,孔径尺寸减小。其次,采用醇类有机溶剂对NFC泡沫材料的结构进行调控。研究发现:添加乙醇、异丙醇和正丁醇后泡沫材料的泡孔结构近似于蜂窝多孔材料,泡孔排列有规则,分布均匀且呈层状结构,但孔径尺寸较大;添加甲醇后孔径尺寸变均匀,但泡孔分布杂乱无章;添加叔丁醇后泡孔分布均匀,孔径尺寸较小,但形状无规则。此外,添加有机溶剂后泡沫材料的密度减小,孔隙率增加,收缩率减小,但导热系数和热稳定性基本没有变化。综合分析确定乙醇的调控效果最佳。然后,研究了乙醇浓度、冷冻温度和NFC浓度对NFC泡沫材料结构与性能的影响。乙醇浓度增大使泡沫材料的泡孔分布和孔径尺寸变均匀,形状趋于圆形;冷冻温度降低和NFC浓度增加使泡孔呈现层状结构排列,层与层之间出现柱状纤维结构,泡孔分布变均匀,形状趋于矩形;但冷冻温度较低,NFC浓度较高时,层状结构和柱状结构消失,孔径尺寸减小。最佳制备工艺为:乙醇浓度为5wt%,NFC浓度为3wt%,冷冻温度为-55℃。此条件下,泡沫材料的平均孔面积为3231.44μm2,平均孔壁厚度为2.46μm,泡孔密度为4.89×106个/cm3;密度为35.90kg/m3,孔隙率为97.66%,导热系数为0.0384W/(m·K)。最后,探讨了支链淀粉含量、冷冻温度和固含量对NFC基复合泡沫材料结构与性能的影响。随着支链淀粉含量的增加,泡沫材料的泡孔分布变均匀,孔径尺寸增大,出现孔壁结构,但含量超过70%时,泡孔尺寸变小且分布不均匀。固含量增加使泡孔形状变得不规则,分布不均匀,孔径尺寸减小。冷冻温度的降低使泡孔分布变均匀,泡孔大小变小,出现闭孔结构,但孔壁较薄,强度提高较少。支链淀粉与NFC混合均匀后可形成类似“钢筋混凝土”结构,使支链淀粉/NFC复合泡沫材料的强度提高。最佳制备工艺为:支链淀粉含量为30%,固含量为3wt%,冷冻温度为-55℃。此条件下,泡沫材料的平均孔面积为195.99μm2,平均孔壁厚度为1.04μm,泡孔密度为4.68×108个/cm3;杨氏模量为713.14KPa,屈服强度为92.28KPa,能量吸收值为13.24kJ/m3。综上,通过调节NFC浓度和冷冻温度,以及醇类有机相介入和支链淀粉增强等技术手段,可实现纳米纤维素基泡沫材料泡孔结构的有效调控。原料资源丰富、工艺过程清洁,为制备高性能、可生物降解的纳米纤维素基复合泡沫材料提供了可能。
[Abstract]:With the increasingly serious environmental pollution problems and the depletion of oil resources, the research and development of biodegradable and rich resources, the new foam cushioning materials can be recycled to replace the traditional foam plastics have become a major problem to be solved in society. At present, nanoscale foam foam material is considered to be a very promising biodegradable material. One of the foam materials is to study the relationship between the preparation technology and the microstructure and properties of the microbubbles. The development of the regulation technology of the pore structure is of great significance for obtaining the nanofibric buffer materials with different structures and application properties. Therefore, the main research on the regulation technology of the pore structure of nanofibrous foam materials is mainly studied. The contents are as follows: first, the physicochemical properties of nano fibrinolytic cellulose (NFC) are characterized. On this basis, the bubble pore structure of NFC foam is regulated by changing the concentration of NFC and the freezing temperature. The pore size of the foam is more uniform and the size of the pore size decreases, but there will be large pore or compact structure in the local area; cryopreservation makes the bubble. The pore size distribution becomes more uniform and the size of the pore size decreases. Secondly, the structure of NFC foam is regulated by alcohols organic solvents. It is found that the bubble pore structure of the foam materials with ethanol, isopropanol and n-butanol is similar to the honeycomb porous material, and the bubble holes are arranged regularly, distributed uniformly and layered, but the size of the pore size is larger. After the addition of methanol, the size of the pore is disorderly, and the pore size distribution is uniform and the size is smaller after adding TERT butanol, but the shape of the pore is irregular. In addition, the density of the foam material decreases, the porosity increases and the shrinkage decreases, but the thermal conductivity and thermal stability are basically unchanged. The effect of alcohol is the best. Then, the effects of ethanol concentration, freezing temperature and NFC concentration on the structure and properties of NFC foam materials are studied. The increase of ethanol concentration makes the bubble pore distribution and aperture size become uniform, the shape tends to round, and the freezing temperature decreases and the concentration of NFC increases the layer structure arrangement, between the layer and the layer. There is a columnar fiber structure, the distribution of the bubble holes becomes uniform and the shape tends to be rectangular, but the freezing temperature is low. When the concentration of NFC is high, the layer structure and columnar structure disappear and the size of the pore size decreases. The optimum preparation process is as follows: the concentration of ethanol is 5wt%, the concentration of NFC is 3wt%, and the freezing temperature is -55. The average thickness of the pore wall is 2.46 mu m, the density of the bubble hole is 4.89 x 106 /cm3, the density is 35.90kg/m3, the porosity is 97.66%, the thermal conductivity is 0.0384W/ (M. K). Finally, the effect of the amylopectin content, the freezing temperature and the solid content on the structure and properties of the NFC based composite foam material is discussed. If the content is over 70%, the size of the bubble hole becomes smaller and the distribution is uneven. The increase of the solid content makes the shape of the hole become irregular, the distribution is uneven, the size of the pore size decreases. The reduction of the freezing temperature makes the distribution of the hole even, the size of the bubble hole becomes smaller and the structure of the hole is smaller, but the wall of the hole is thinner and the strength is stronger. Less improvement. The mix of amylopectin and NFC can form a similar "reinforced concrete" structure to improve the strength of the amylopectin /NFC composite foam material. The optimum preparation process is: the amylopectin content is 30%, the solid content is 3wt%, the freezing temperature is -55 C. Under this condition, the average pore area of the foam material is 195.99 Mu m2, and the average pore wall is the pore wall. The thickness is 1.04 mu m, the density of the bubble hole is 4.68 x 108 /cm3, the young's modulus is 713.14KPa, the yield strength is 92.28KPa, the energy absorption value is 13.24kJ/m3., and the effective modulation of the pore structure of the nanoscale foam material can be realized by adjusting the NFC concentration and freezing temperature, as well as the alcohols organic phase intervention and the amylopectin enhancement and so on. Raw materials are rich in resources and clean in process. It is possible to prepare high-performance, biodegradable nano cellulose based composite foam materials.

【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ328

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