Mechanical and morphological characterization of coconut fibers treated superficially for use as reinforcement in polymers

ABSTRACT

Due to the environmental issue, the demand for materials that use more natural and renewable resources increased, such as natural fibers reinforced polymers. Surface treatments are performed for better adhesion of the fiber to the polymer matrix, the most common is mercerization through NaOH solution. Coconut fiber was analyzed under four conditions: varying between treated and untreated, oven dried and naturally dried. Then they were analyzed by tensile test, scanning electron microscopy (SEM) and x-ray tomography to study the mechanical and morphological characteristics and observe the adhesion to the polymer. After the chemical treatment, lignin and hemicellulose were removed from the fiber surface. In the treated and dried fibers, micro-cracks appeared that could compromise the mechanical properties. By processing the images of the fiber cross-sections, an effective area between 39.6% and 43.3% was obtained. For fibers below 300 µm, the tensile strength converges to 20 to 60 MPa and the modulus of elasticity between 1 and 3 GPa. The treatments increased the tensile strength and modulus of elasticity of the fibers, contributing to the use of coconut fiber as reinforcement in polymers.

Keywords
Coconut fiber; Scanning electron microscopy; X-ray tomography; Tensile test; Natural fiber reinforced polymer