Influence of Gamma Radiation Treatment on the Mechanical Properties of Sisal Fibers to Use into Composite Materials

Abstract

The use of treatments in natural fibers is largely used, because it can improve the interfacial adhesion of polymer composites. However, the choice of the most appropriate treatment should take into account environmental factors, due to the need of new materials to meet requirements related to the concept of sustainability. This article investigated the influence of the mercerization, acetylation and gamma radiation treatments on the mechanical properties of sisal fibers, to use in composite materials. Experimental conditions were defined with different concentrations of reagents and radiation doses in order to understand the impact of these reactions on the tensile properties of sisal fibers. Thermal gravimetric analysis (TGA) and Fourier Transform Infrared (FTIR) spectroscopy were used to investigate the fiber degradation process and the chemical modifications after the treatments. The use of mercerization (0.1 M and 1.0 M NaOH concentrations) combined with acetylation increased the hydrophobic character of the sisal fiber, which may improve its interaction with polymeric matrices. In addition, mercerized sisal fiber at 0.5 M NaOH concentration, exposed to 25 kGy gamma radiation dose, showed physical and chemical structural changes that positively influence the fiber-matrix adhesion in polymer composite materials. All treatments made can reduce the natural tensile properties of the sisal fibers, because they can remove fundamental components to the structure and the stiffening of these fibers. Considering changes in the mechanical behavior, the use of gamma radiation presented similar results of the traditional chemical treatments, being less aggressive to the fibers and not causing the same negative impact on the environment.