An Experimental Study on Swelling of Cellulose Nano-fiber Films in Epoxy Resins and Water

The current breed of natural-fiber based polymer composites, because of their biobased and possibly biodegradable nature, offer an alternative as a ‘green’ material available for automotive and other engineering applications. However such composites suffer from the drawback of low strength and fatigue properties compared to the carbonor glass-fiber based polymer composites. Cellulose nanofibers (CNFs) are a new type of nanofibers made purely from cellulose molecules and have very high mechanical properties compared to other natural fibers, even approaching that of inorganic reinforcing fibers. However, there remain several hurdles in the use of CNF films for the production of polymer composites through the liquid composite molding technologies. One such problem is the swelling of these films during the manufacturing of such composites. In this study, we have microscopically studied the swelling of CNF films when they come in contact with three different liquids: water, epoxy, and bio-based epoxy. It was observed that the swelling rate was very high in the beginning but decreased subsequently. The swelling process was seen to be complete within two minutes for all the three liquids. The highest and lowest swelling of CNF films were observed for water and bioepoxy, respectively.