PHYSICAL-PROPERTIES OF SILK FIBERS GRAFTED WITH A BINARY MIXTURE OF STYRENE AND N-BUTYL METHACRYLATE

The mechanical and physical properties, as well as the crystalline str ucture of silk fibers grafted with a binary mixture of styrene (St) an d n-butyl methacrylate (BMA) were studied as a function of the weight gain. The size of the fiber's increased linearly with the extent of gr afting. 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 measure d in dry and wet states decreased beyond weight gain of 50% because of the hydrophobic properties of grafted silk fibers. The thermal behavi or was determined by differential scanning calorimetry (DSC), thermome chanical analysis (TMA), and thermogravimetric analysis (TGA) measurem ents. 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 ons et and the position of the dynamic loss modulus (E'') peak to lower te mperature when the weight gain increased. X-ray diffraction curves dem onstrated that the crystalline structure of silk fibers remained uncha nged regardless of the St/BMA grafting. (C) 1993 John Wiley & Sons, In c.