Thermoset phenolic matrices reinforced with unmodified and surface-grafted furfuryl alcohol sugar cane bagasse and curaua fibers: Properties of fibers and composites

Composites based on phenolic matrices and unmodified and chemically modified sugar cane bagasse and curaua fibers were prepared. The fibers were oxidized by chlorine dioxide, mainly phenolic syringyl and guaiacyl units of the lignin polymer, followed by grafting furfuryl alcohol (FA), which is a chemical obtained from a renewable source. The fibers were widely characterized by chemical composition analysis, crystallinity, UV-vis diffuse reflectance spectroscopy, SEM, DSC, TG, tensile strength, and C-13 CP-MAS NMR. The composites were analyzed by SEM, impact strength, and DMA. The SEM images and DMA results showed that the oxidation of sugar cane bagasse fibers followed by reaction with FA favored the fiber/matrix interaction at the interface. The same chemical modification was less effective for curaua fibers, probably due to its lower lignin content, since the reaction considered touches mainly the lignin moiety. The tensile strength results obtained showed that the fibers were partially degraded by the chemical treatment, decreasing then the impact strength of the composites reinforced with them. In the continuity of the present project, efforts has been addressed to the optimization of fiber surface modification, looking for reagents preferably obtained from renewable resources and for chemical modifications that intensify the fiber/matrix interaction without loss of mechanical properties.