Pull out specimen of single fiber bundle (diameter of about 50-70μm), which is bundled with filaments with diameter of about 12μm, was fabricated using different surface-treated silk fibers and biodegradable PBS(Polybutylene succinate) plastic, and interfacial strength between silk fiber and PBS matrix was evaluated using pull out specimens. Three types of surface treatment were the untreatment, the about 45% removal of the content of sericin covered on the silk fiber(fibrous) and the "ensui processing" of silk fiber. Unidirectional silk fiber/PBS composites and injection molded silk short fiber/PBS composites were fabricated, and their mechanical properties were investigated and characterized with regard to the surface treatment and content of fiber using these specimens. As a result, it is found that the mechanical properties of composites have a close relation with the change of the interfacial strength and the content of fiber.
