Degradation resistance of alkali-treated eucalyptus fiber reinforced high density polyethylene composites as function of simulated sea water exposure

Abstract

To enhance the resistance of eucalyptus (EU) reinforced high density polyethylene (HDPE) composites to exposure in simulated seawater, the EU fibers were modified by alkali treatment with NaOH to prepare wood-plastic composites (WPCs). The materials were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), moisture absorption, mechanical properties, and color change tests. After exposure to the sea water, all composites experienced deterioration of water repellency and mechanical properties, and color change. The NaOH concentration greatly influenced the properties of the EU/HDPE composites both before and after exposure. The alkali-treated EU fibers presented low polarities, which resulted in better interfacial bonding, improved mechanical properties, lower moisture absorption, and lower color change relative to the untreated samples after immersion in simulated sea water. The results showed that the HDPE composite prepared with 3% NaOH treated EU fiber had better degradation resistance compared with the untreated composite. The tensile strength, flexural strength, flexural modulus, and impact strength increased 29.9%, 19.8%, 35.4%, and 39.3%, respectively, in comparison with the untreated composite after 21 d exposure. The improved degradation resistance of the alkali-treated EU/HDPE composites could ensure the expected service life of their products and widen their practical applications.