Sisal cellulose whiskers reinforced polyvinyl acetate nanocomposites

Sisal nanowhiskers were used as novel reinforcement to obtain nanocomposites with polyvinyl acetate (PVAc) as matrix phase. They are seen as attractive materials due to the widespread availability and low cost of the sisal source material. Statistical analysis of the sisal whisker length and diameter resulted in average values of 250 nm and 4 nm, respectively, resulting in an average aspect ratio in the upper range of reported cellulose nanowhisker values. The high aspect ratio ensures percolation, with resulting mechanical improvements and thermal stability, at lower fiber loads. Water uptake and thermal behaviour of the sisal whisker-PAVc composites were studied. Whisker addition was found to stabilize the nanocomposites with no benefit seen when increasing the whisker content beyond the percolation threshold: For all whisker contents studied above percolation, the water uptake stays constant, and the Tg does not vary with whisker content at a given relative humidity. The water diffusion rate however increases due to water accumulation at the whisker-PVAc interface. Below whisker percolation, stabilization is only noticed at low relative humidity, whereas high humidity results in disruption of whisker-PVAc interactions. This work shows the potential of cellulose nanowhiskers to stabilize polar polymers even at high humidity conditions with minimal reinforcement addition.