Characterization of methacrylonitrile‐grafted silk fibers

Abstract

AbstractThe structure and physical properties of silk fibroin fibers graft‐polymerized with methacrylonitrile (MAN) were analyzed in relation to the weight gain on the basis of the results of tensile properties as well as of thermal analysis and X‐ray diffractometry. The solubility of the specimen in NaOH solution and the moisture absorption decreased slightly with the duration of the MAN treatment. However, the polymerizing treatment with MAN did not affect significantly the tensile properties, i.e., strength and elongation at break of the original fibers. The position of the endothermic peak attributed to the thermal decomposition of the silk fibroin shifted to higher temperatures when the weight gain exceeded 25%, and a constant value at 328°C was obtained above a weight gain of 40%. Wide‐range X‐ray diffraction diagram of silk fibers with a weight gain of 10% showed diffraction maxima at the equator corresponding to the molecule oriented crystal structure of the silk fiber, in addition to the spots on a series of hyperbolic arcs arranged symmetrically at about the equator, which are associated with the crystalline form of the MAN polymer copolymerized in the specimen. Crystalline structure of the silk fiber remained unchanged essentially regardless of MAN treatment.