Scanning electron microscopy study of chemically modified coir fibers

Chemical-surface modification of coir fibers was done by dewaxing, using an alkali treatment (5% and 10% NaOH), vinyl grafting with methyl methacrylate (MMA) and cyanoethylation. The chemically modified fibers were characterized by Fourier transform infrared (FTIR) spectroscopy. In addition, the surface features of untreated, dewaxed, alkali-treated, grafted, and cyanoethylated coir fibers were studied using scanning electron microscopy (SEM). Progressive changes in surface morphology were observed. SEM observations showed the removal of tyloses from the surface of coir as a result of alkali treatment (5%), resulting in a rough fiber surface with regularly spaced pits. At a lower percentage of grafting (PMMA), the surfaces became more or less uniform, while the surfaces of the coir fibers with a higher percentage of grafting were increasingly covered with grafted materials, resulting in canal-like cavities between the overgrowths of the grafted materials on the unit cells. Cyanoethylated coir-fiber surfaces showed an insufficient deposit of cyanoethyl groups. SEM analysis of the samples was corroborated by measurements of a mechanical property (maximum stress at break). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1169–1177, 2001