Effect of Length and Tenor of the Introduction of Sansevieria cylindrica Fibers on the Mechanical Performance of Natural Fiber Composites

Abstract

The substitution of synthetic fillers, such as carbon black, with biobased ones in natural rubber (NR) is a trend of interest in view of increased sustainability and exploitation of agroforest waste in the materials sector. In this work, NR was filled with short fibers extracted from Sansevieria cylindrica (SC) leaves of various length (10, 20, 30, or 40 mm) and in different amounts (3, 6, or 10 g per 100 g NR). The 12 different composite combinations obtained are compared among them and with the unfilled NR, as regards properties, such as density, tensile performance, and tear strength. Density was gradually increased by filling the matrix by higher amounts of SC fibers. The introduction of up to 30 g SC fibers enabled strengthening and stiffening the pure matrix, while some decline was indicated by increasing SC fibers content to 40 g. In absolute terms, though, the best tensile performance was offered by the combination including 20 g of 6-mm-long SC fibers, namely resulting in 10.44 MPa tensile strength, 627.6% elongation at break, and 2.36 MPa Young’s modulus. The superiority of this combination is confirmed when dealing with tear strength, which was always improved by the introduction of SC yet reached 34.99 N/mm for the composite with 20 g of 6-mm-long fibers. Morphological fracture observation using scanning electron microscope indicated the likeliness of pullout by interference caused when an excessive amount of SC fibers is introduced, showing rather clean fiber surface when separating from the matrix. In general terms, SC/NR composites showed improvement over the pure matrix, yet some interfacial issues need to be addressed by better compatibilization of the natural fibers.