Physical properties of silk fibers grafted with a binary mixture of styrene and <i>n</i>‐butyl methacrylate

Abstract

Abstract The mechanical and physical properties, as well as the crystalline structure of silk fibers grafted with a binary mixture of styrene (St) and n ‐butyl methacrylate (BMA) were studied as a function of the weight gain. The size of the fibers increased linearly with the extent of grafting. The strength, the elongation at break, and the tensile modulus decreased with increasing weight gain, but the breaking load remained almost unchanged. The difference among the tensile properties measured in dry and wet states decreased beyond weight gain of 50% because of the hydrophobic properties of grafted silk fibers. The thermal behavior was determined by differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and thermogravimetric analysis (TGA) measurements. Silk fibers attained a higher thermal stability as the amount of loaded polymer increased. The thermally induced molecular movement of St/BMA‐grafted silk fibers was enhanced as judged by shifting the onset and the position of the dynamic loss modulus ( E ″) peak to lower temperature when the weight gain increased. X‐ray diffraction curves demonstrated that the crystalline structure of silk fibers remained unchanged regardless of the St/BMA grafting. © 1993 John Wiley &amp; Sons, Inc.