Relationship between tensile properties and film formation kinetics of epoxy resin reinforced with nanofibrillated cellulose

The effect of the addition of nanofibrillated cellulose (NFC) on the tensile properties of epoxy resin was investigated. NFC was added to the epoxy resin at different weight percentages (0.05, 0.1, 0.2, 0.25, 0.5 and 1%). The tensile properties, including, strength, elongation, toughness and Young modulus, were investigated. Adaptive speckle imaging interferometry (ASII) was used to study the relationship between the film formation kinetics and the tensile properties of the epoxy composites. In addition, scanning electron microscopy (SEM) was used to investigate the morphology of the formed composite to better understand the proposed relationship.The addition of NFC to the epoxy resin significantly improves the tensile properties of the epoxy composite. The largest increase was found at the addition level of 0.1%. At this level, the maximum stress increased by 120%, the strain to failure increased by 73%, the toughness increased by 300% and the Young modulus increased by 64% in comparison to the pure epoxy resin.During drying, the shortest interdiffusion stage occurs at the optimum level of NFC (0.1%). The extent of interdiffusion is related to the tensile strength build up in the epoxy coating film and the amount of fibers present. SEM revealed the excellent adhesion of fibers in the optimum filler content. However, the additional NFC led the resultant NFC-epoxy matrix to exhibit fiber agglomeration, which affects the matrix strength and decreases the tensile properties.

► The optimum NFC amount that causes best epoxy composite tensile properties was at 0.1 wt.%.
► The tensile properties increase was larger than other nano-scale materials reported in the literature.
► Further addition of NCF beyond 0.1% causes decrease in the epoxy tensile properties.
► Interdiffusion extent is related to the tensile strength build up in the epoxy film.
► Optimum NFC amount enhance the particles deformation leading to a faster uniform film.