The preparation of poly[N(n‐butoxymethyl) methacrylamide] grafted silk fibers by polymerization using a low pH system

Abstract

AbstractThe graft polymerizations of the N(n‐butoxymethyl) methacrylamide (BMA) monomer onto silk fibers were effected after reducing the pH of the grafting system to 2.5 by the addition of a formic acid solution. We compared the grafting efficiencies, surface characteristics, and thermal behaviors, as well as the whiteness levels and the extent of reduction of the rate of yellowing following UV irradiation, with the equivalent features of poly(BMA)‐grafted silk fibers, prepared under normal (pH 6) conditions. The grafting efficiency [as poly(BMA) weight gain] onto silk fiber that was attained was almost 100% through optimization of the pH environment in the polymerization system by the addition of formic acid. The stiffness of the silk fabrics observed, following the conventional grafting, was markedly higher than that of equivalent silks after the polymerization at pH 2.5. The rates of yellowness index increase, for these latter silk fabrics following UV irradiation were also reduced, specifically in the initial irradiation period (up to 60 h).The SEM of the grafted silk fabrics reveal the absence of granules on the surface of the grafted silk fiber, when the silk was grafted with poly(BMA), after reducing the pH of the grafting system to 2.5. These findings suggest that the BMA monomer was polymerized specifically within the silk fiber and not on the surface. It is suggested that the increase in the polymer weight gain, and the reduced adverse effect on the fabric handle, arise because of the modified polymer location. © 1993 John Wiley & Sons, Inc.