Durabilidade química e biológica de fibras vegetais tratadas com nanopartículas de prata para uso como reforço de matrizes cimentícias.

Abstract

Vegetal fibers have a low affinity to the high alkalinity of Portland cement matrices, in addition to presenting high dimensional instability in the presence of moisture. Besides, lignocellulosic fibers are subject to fungal biodeterioration, mainly during storage. Thus, treatments on the fibers and matrices are required to have a durable composite. Therefore, this work aims to propose a thermochemical treatment that generates fibers impregnated with silver nanoparticles (AgNP) to verify their influence on dimensional instability and fiber-matrix interaction, in addition to their chemical and biological durability. After treatment, the jute and sisal fibers were evaluated for their physical, thermal, morphological, and mechanical properties. The proposed AgNP impregnation method was satisfactory, with efficiency dependent on the AgNP concentration and fiber species. A change in the surface texture of the fibers was observed, becoming rougher, with better dimensional stability and reduced water absorption capacity of the modified fibers. It is believed that not only thermal cycles but also the low pH of the AgNP solution altered the microstructure of the fibers. The fibers treated in aqueous AgNP solution did not show significant changes in tensile strength or Young's modulus compared to natural fibers. Regarding fiber-matrix adhesion, evaluated by the pull-out jhtest, better performance was observed for hornificated fibers, due to the morphological modification of the surface; however, the adhesion strength of these fibers after treatment with AgNP did not show significant modification. When subjecting these fibers to alkaline attack, changes were observed in the thermograms with removal of hemicellulose, surface damage with defibrillation and, consequently, reduction in the mechanical performance of the tensile strength of these fibers, regardless of the treatment applied. On the other hand, when subjecting the fibers to fungal attack by direct contact, a superior performance of the fibers treated with AgNP was noted, evidenced by the little altered thermograms, absence of damage in the morphology, and maintenance of the tensile strength and Young's modulus. Thus, in general, the treatment of plant fibers with AgNP proved to be satisfactory for application in cementitious composites.