Effect of Surface Biopolymeric Treatment on Sisal Fiber Properties and Fiber-Cement Bond

Abstract

Sisal fiber, available in various semi-arid regions around the world, is the most studied natural fiber for the reinforcement of polymeric and cement-based composites. However, to improve the fiber–matrix interaction and to reduce the hydrophilicity of the fiber, it is necessary to establish surface treatments that employ sustainable materials, unlike conventional surface treatments. In this work, sisal fibers were coated separately with cellulose acetate, hydrophobic starch, and cassava starch biopolymers in order to verify the possibility of reducing the water absorption capacity of the fiber by the use of a biodegradable resin. A combination of Fourier transform infrared spectroscopy, scanning electron microscopy, and water absorption and tensile tests was used to investigate the effects of the surface treatments on the sisal fiber properties. Pullout tests of sisal fibers with embedded lengths of 20 mm and 40 mm were performed to determine the influence of the treatments on the bond stress with cement mortar. Composites with 4 vol % short fiber were produced and tested for flexion. The study results indicated that all treatments reduced the mechanical properties of the fiber; however, the layer of the cellulose acetate biopolymer film formed on the fiber surface was effective in reducing the fiber hydrophilicity. Experimental tests on the composites revealed that the cellulose acetate treatment reduced the bond stress and, to a lesser degree, the flexural toughness of the composite, despite the increase in flexural strength.