Silk grafting with methacrylamide: A near-infrared spectroscopy study

The grafting of methacrylamide (MAA) onto silk has taken importance not only as weighting process but also as finishing operation to improve the properties of the silk fibers. It was confirmed that the MAA monomer concentration, the initiator amount, and the liquor ratio are the major parameters affecting the yield of the reaction. Varying these parameters, a large number of samples, i.e., silk yarns with different grafting yields and exhaust grafting baths with different residual MAA concentrations, were obtained. Near infrared (NIR) spectroscopy was used for the quantitative determination of MAA in silk yarns and MAA in exhaust baths after grafting. A correlation between silk yarns grafting yield and NIR spectra of MAA grafted yarns was obtained. This correlation shows a coefficient of determination (R²) of 0.96 and a standard error of calibration (SEC) of 8.37 w/w for a mean value (M) of 31.82% w/w. A second correlation between MAA in exhaust grafting baths and NIR spectra was obtained. This correlation shows a R² of 0.95 and a SEC of 2.93 g/L for a M of 17.16 g/L. Previous correlations were improved using silk samples cleaned by extraction of sizing agents and detergents which could interfere with MAA grafting and modify absorption spectra of bath solutions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011