Abstract: The main objective of this investigation is to valorize a Moroccan crop residue (Sabra fibers, Agave Americana L.) and to compare with Alfa fibers (Stipa tenacissima L.) as reinforcement in an elastomeric matrix in term of the relaxation properties, mechanical and rheological properties. The preparation and properties of these two natural fibers embedded in Styrene-Butadiene Rubber (SBR) are presented with and without the addition of Styrene-Ethylene-Butadiene-Styrene grafted with Maleic Anhydride (SEBS-g-MA) as a coupling agent. Five different series (SBR, SBR/Alfa, SBR/Alfa/SEBS, SBR/Sabra and SBR/Sabra/SEBS) were compounded by extrusion and compression molding. As a result, the addition of the coupling agent in the elastomeric matrix improves the relaxation properties, mechanical and rheological properties. Moreover, Sabra fibers show the good results compared to Alfa fibers. Finally, the Zener model was used to determine the rheological time response of the composites. A good agreement between the experimental data and the model was observed (R2 = 0.99).

Key words: Sabra fibers, Alfa fibers, SBR, biocomposite, relaxation, mechanical and rheological properties, Zener model