Silk grafting with methacrylamide: a Near Infrared Spectroscopy study

ABSTRACT: 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. VC