A key FPL publication is Short Cellulose Nanofibrils as Reinforcement in Polyvinyl Alcohol Fiber by Ronald Sabo and Craig M. Clemons.
What is a nanofibril? Remembering that FPL is at the forefront of nanotechnology research, recall that nano means one billionth; for example, one nanometer is one billionth of a meter, or about the length that a fingernail grows in one second. A fibril is a fine fiber or filament.
Cellulose nanofibril-based reinforcements constitute a new class of naturally sourced fiber-based reinforcements. Trees are one type of organism that forms nanofibrils and microfibrils from cellulose molecules to act as the main reinforcing elements within the organism. The high reinforcing potential of native crystalline cellulose within these fibrils led research cooperators from FPL and the University of Wisconsin-Madison to extract cellulose nanomaterials for use in composites.
Those researchers found some challenges to efficiently using cellulose nanomaterials as reinforcing fillers, and the use of water-soluble polymers is one way to avoid many of the challenges if they are carefully selected and appropriately used. One such polymer is polyvinyl alcohol (PVA), which is water-soluble, biodegradable, and biocompatible, and has been broadly investigated for applications including tissue scaffolding, filtration materials, membranes, and drug release. PVA is also used as a reinforcing fiber. Short cellulose nanofibrils (SCNFs) were mechanically isolated from bleached hardwood kraft pulp after being pretreated with enzymes and investigated as reinforcement for PVA fibers. These SCNFs are similar in appearance to cellulose nanocrystals (CNCs) but do not require concentrated sulfuric acid for their preparation.
Further optimization of enzymatic pretreatment will reduce energy requirements, cost, and environmental footprint. Adding small amounts of the SCNFs aided in alignment of the polymer during fiber preparation and improved the performance of the fiber. This work opens the door to strengthening and improving engineered composite materials.