Effect of alkali treatment on the mechanical properties of date palm fibers and their adhesion to epoxy resin

The fibers of date palms, which are widely available in the south of Iran, are a variety of natural fibers that can be used as a reinforcement in polymer composites. This work investigates the effect of alkali treatment on the mechanical properties of date palm fibers and their adhesion to thermoset polymer. The sodium hydroxide (NaOH) solution at three different concentrations (1 wt%, 3 wt%, and 5 wt%) was used to treat the fibers. The single fiber tensile test and fiber pull-out tests were performed to measure the mechanical properties and fiber/matrix interfacial share strength, respectively. Comparing the SEM images of the untreated and treated fibers showed that the 3% NaOH treatment could effectively remove non-cellulosic materials, i.e. lignin and wax, with minimum damage to the fiber surface. The experimental results showed a clear improvement of the mechanical properties and fiber/matrix adhesion after treatment. It was found that the 3% NaOH solution is the optimal concentration to achieve the maximum improvement in the fiber and bonding properties.