Nanomechanical properties of cellulose nanofibrils (CNF)

Cellulose is an abundant green polymer, which can be obtained in a variety of nanoscale structures broadly grouped as nano/microfibrils (CNF/MFC), bacterial celluloses (BC) or nano/microcrystals (CNC/CMC). There is increasing interest of nanocelluloses by the research and industrial communities due to increasing available materials (facilities than can produce ton per day), impressive strength properties, low density, renewability and biodegradability. However, one problem is the lack of knowledge on the nanomechanical properties of cellulose nanofibrils, which creates barriers for the scientists and producers to optimize and predict behavior of the final product. In this research, the behavior of thin filmed (t≤100 μm) cellulose nanofibrils', located on aluminum pin stubs, under nano compression loads were investigated using an Asylum Research MFP-3D Atomic Force Microscope equipped with a nanoindenter. Unloading curves were analyzed using Oliver-Pharr. As a result of 58 successful nanoindents, the average modulus value was estimated as 16.6 GPa with the reduced modulus value of 18.2 GPa. The CNF Modulus values varied between 12.4 GPa - 22.8 GPa with 16.9% coefficient of variation (COV) while the reduced modulus ranged from 13.7 GPa to 24.9 GPa with a 16.2 % COV. This research provides practical knowledge for producers of nanocellulose, researchers and applications developers who focus on nanocellulose reinforced composite materials.