Effects of saturated steam treatment on the cell-wall mechanics and moisture sorption properties of kenaf fibers

Abstract

To improve their hygroscopicity, kenaf fibers were thermally modified by saturated steam at 180 °C for 5, 10, 20, and 40 min. The chemical structure, cellulose crystallinity, cell-wall mechanics, and moisture sorption properties of kenaf fibers were analyzed to evaluate the modification effectiveness. Mass loss and Fourier transform infrared spectroscopy spectra (FTIR) changes indicated that the lignin content and cellulose crystallinity (CrI) increased with the reduction in hemicellulose after a steam treatment, especially for a long duration. The increased CrI and relative lignin content resulted in an increased elastic modulus (Er) and hardness (H) of fiber cell walls after the steam treatment. The reduction in hydrophilic groups and increased stiffness of the cell wall after the steam treatment caused an obvious reduction in the equilibrium moisture content (EMC) at the given relative humidity (RH). It also reduced the moisture increment/decrement and sorption hysteresis during the adsorption and desorption process.