奈米纖維素水性聚氨酯複合材料之研究

Abstract

隨著全球對環保以及環境友善意識的提高，水性聚氨酯（waterborne polyurethanes, WPUs）在現今受到越來越多的重視。相較於傳統溶劑型聚氨酯，水性聚氨酯在低揮發性有機物含量與不易燃的特性佔有優勢，然而，水性聚氨酯在機械性質、熱性質與耐水性方面表現不如溶劑型聚氨酯。因此，為提升水性聚氨酯的性質，並同時考量材料間的相容性，本研究選用纖維素奈米微晶（cellulose nanocrystals, CNCs）與纖維素奈米纖維（cellulose nanofibers, CNFs）作為加固材，加入合成所得之陰離子水性聚氨酯與陽離子水性聚氨酯中，其中奈米纖維素的親水性促使纖維材料可以藉由超音波分散至水性聚氨酯的水相之中，以形成性質優越的環保複合材料。本研究進行數項物理性、機械性和化學性的分析與鑑定，得以了解奈米纖維素對於複合後之水性聚氨酯複合材料的各項性質加固效果。由於CNCs與CNFs具有相異的型態與帶電性質，並陰離子水性聚氨酯與陽離子水性聚氨酯亦有不同之表面帶電特性，因此本研究也著重探討多種的纖維－基質交互作用。大致而言，添加奈米纖維素有助於提升水性聚氨酯基質材料之機械性質，且提高其熱穩定性與耐水性。本研究顯示出以CNCs或CNFs複合水性聚氨酯所形成的複合材料在未來工業領域中具有可發展之潛力。

With the increased global awareness about environmental issues and the trends of eco-friendliness, waterborne polyurethanes (WPUs) have received more and more attention nowadays. Compared with the conventional solvent-borne PUs, WPUs predominant at aspects of zero or low Volatile Organic Compound (VOC) content and noninflammability. However, WPUs are inferior to solvent-borne PUs in areas such as mechanical properties, thermal properties, and water resistance. Accordingly, to enhance the properties of WPUs, and also by considering the compatibility between the materials, cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) were added into the synthesized anionic WPUs and cationic WPUs to form outstanding green composites. The hydrophilic nature of nanocellulose allowed effortless filler dispersion in the water phase of WPUs by blending through sonication. A number of investigations were conducted including physical, mechanical, and chemical evaluations to reveal the nanocellulose reinforcing effects on the properties of the filled WPU composites. Due to the divergent morphologies and electric properties between CNCs and CNFs, as well as the different surface charges for anionic and cationic WPUs, the varied filler-matrix interactions were hence presented and discussed in this study. Generally, the nanocellulose addition resulted in WPU composites having enhanced mechanical properties, better thermal stability, and higher resistance to water absorption. Overall, the results of this study implied the great potentials for these CNC- or CNF-filled WPU composites to be applied in future industrial fields.