Abstract
Thermal behavior and structural characteristics of styrene-grafted silk fiber, prepared by grafting the silk fiber with styrene, were investigated by means of differential scanning calorimetry (DSC), X-ray diffraction analysis and scanning electron micrograph observation. Styrene-grafted silk (above 20% degree of grafting) showed two endothermic peaks at around 320°C and 430°C on the DSC curve. The peak at 320°C was attributed to the molecular decomposition of silk fibroin, while the peak at 430°C to the thermal decomposition of the styrene-polymer grafted to silk. The enthalpic change observed at about 430°C on the DSC curve of styrene-grafted silk increased with increasing degree of grafting. These results suggest that the degree of grafting could be estimated from the enthalpic change arising from the thermal decomposition of styrenegrafted silk fiber.
X-ray diffraction patterns indicated that no structural changes occurred. Debye-Scherrer ring attributed to the presence of a styrene-polymer appeared on the X-diffraction pattern of styrene-grafted silk (above 20% degree of grafting) in addition to the diffractions from the silk II crystalline structure of silk fibroin. Scanning electron micrographs showed granular forms (0.7μm in diameter) which appeared chemically bonded to the surface of stryrene-grafted silk, when the degree of grafting exceeded 80%.
