The effect of sodium hydroxide surface treatment on the tensile strength of cellulose nanofibre
The use of cellulose nanofibres in the reinforcement of polymers has applications in bio-based building materials. However, one problem observed when using cellulose nanofibres within composites is the difficulty of ensuring their adequate dispersion. The phenomenon of agglomeration is attributed to the high density of polarized hydroxyl groups at the surface of cellulose nanofibres. Initial observations of cellulose nanofibre agglomeration, in a cement matrix at volume fractions larger than 0.1%, are theorized to have contributed to the brittle failure mode of the casts. In order to expand the use of cellulose nanofibres in bio-based building materials, it is necessary to reduce their agglomeration and improve their dispersion within a polymer through surface modifications in effort to improve their reinforcing capability. As such, a mild alkali treatment with sodium hydroxide (NaOH), also known as mercerization, was chosen for use in this study due to its longstanding establishment as a common, low cost, and simple process. Alkali treatment was found to improve the values of tensile strength and modulus, compared to the untreated strips, by 20% and 24%, respectively. These results could be attributed to the rearrangement of fibrils along the direction of tensile deformation, as a result of the dissolution of lignin and hemicelluloses fractions. This paper reports the initial results of a larger, ongoing study into the feasibility of utilising cellulose nanofibres as reinforcements within cement composite building materials.