Wetting behaviour, moisture up-take and electrokinetic properties of lignocellulosic fibres

The wetting and moisture up-take behaviour, as well as the electrokinetic properties of various lignocellulosic fibres were characterised. Knowledge of surface and water uptake properties of this kind of materials will help to tailor their potential use in different end user applications. The surface tension of the fibres was determined from wetting measurements using the capillary rise technique. The wetting data were used to determine the surface tension of the fibres. Our results show that the surface tension of the lignocellulosic fibres is a linear function of their cellulose content. Zeta-potential measurements were exploited to characterise the surface chemistry of the fibres. Measuring the zeta-potential as function of time enables the rapid assessment of the water up-take, i.e. the swelling behaviour of the fibres. The results obtained by the zeta potential measurements correlate, with the exception of flax, in a linear manner with the results obtained from conventional moisture uptake measurements. Even though all lignocellulosic fibres are very hydrophilic due to the presence of polar oxygen containing groups they have different grades of hydrophilicity, which is also reflected in the different water uptake capabilities measured. The wetting, moisture uptake and electrokinetic properties of the lignocellulosic fibres are determined by the availability of the surface functional groups present, which is usually consequence of the processes used to separate, and extract the fibres from the plant (retting), as well as any further processing used to improve the fibre quality.