Reinforcement of Cellulose Nanofibers On the Stiffness and Strength of Composite Sheets Under Dry and Wet Conditions

Abstract

The objective of this study was to evaluate how a wide range (0–100%) of cellulose nanofiber (CNF) addition affects the mechanical properties of composite sheets made of bleached pulp fibers and CNFs. It was found that adding CNFs could reduce the porosity of the sheets, thus increasing the dry Young’s modulus within the CNF addition range of 0–100%, whereas the dry specific Young’s modulus of all the sheets was constant. The dry tensile strength of the sheets increased as the CNF addition increased to 70% because of the increased hydrogen bond density between the pulp fibers. However, there was no further improvement in the dry tensile strength when the CNF addition was more than 70%. Although the wet Young’s modulus decreased when the CNF addition was more than 20% owing to the increase in the thickness of the sheets, the wet tensile strength of the sheets increased almost linearly as more CNFs were added up to 70%, and the maximum wet strength retention reached nearly 10% at 40% CNF addition.