A solid state 13C high resolution NMR study of raw and chemically treated sisal fibers

The use of natural fibers as reinforcement in composites is a new field of research, which has been growing in the last decades and has been given a great interest by the automotive industry. However, the lack of good interfacial adhesion is a restriction for the use of natural fiber reinforced composites for high performance applications. This problem can be overcome by treating the fibers with suitable chemicals. Mercerization, acetylation, and resorcinol/hexamethylenetetramine (R/H) treatments have been applied to sisal fibers in order to improve their adhesion in composites materials. The effect of chemical modifications on the structure and morphology of the fibers has been studied by 13C VACP-MAS NMR in solid state, and SEM. The results have shown that the best treatment conditions for sisal fibers were mercerization (5% NaOH, 3 h, 50 °C) and acetylation prior to the treatment with 20/10 g/L R/H solution for 15 min.