Abstract

The purpose of this work is to diagnose the processing feasibility of randomly aligned silk fibroin fiber-reinforced biodegradable polymer matrix biocomposites by extrusion and injection molding and also to further improve the properties by electron beam irradiation technique. And unidirectional silk fibroin/PBS biocomposites were fabricated by means of compression molding with heat and pressure and irradiated with various electron beam absorption doses. The effect of radiation on the their mechanical and thermal properties were extensively studied.
Randomly aligned waste silk fibroin/waste wool/PBS biocomposites with various silk fibroin fiber contents (0, 10, 20, 30, and 40 wt%) were successfully processed using extrusion and injection molding technique. The coefficient of thermal expansion of silk fibroin/PBS biocomposites was decreased with increasing the silk fibroin fiber content. The storage modulus, tensile modulus and flexural modulus of silk fibroin/PBS biocomposites were increased with increasing the silk fibroin fiber content, whereas the tensile strength and impact strength were decreased. It was noted that silk fibroin fiber content of 30 wt% was optimal in the present biocomposite system.
Randomly aligned EB-waste silk fibroin/EB-waste wool/PBS biocomposites with various electron beam absorption doses (0, 1, 5, 10, 30 and 50 kGy) on silk fibroin fibers were successfully fabricated. The tensile strength, flexural strength showed the increasing tendency up to 10 kGy and then decreased. The thermo-dimensional stability of biocomposites were increased with increasing the electron beam absorption doses.
Unidirectional silk fibroin/EB-PBS biocomposites irradiated with various E-beam absorption doses (0, 30, 50 and 70 kGy) were successfully fabricated. Here, the PBS matrix was directly irradiated with the electron beam. The thermal stability and thermo-dimensional stability of silk fibroin/PBS biocomposites were increased with increasing the electron beam absorption dose. In particular, the CTE value, storage modulus, tensile strength and flexural strength were lowest at 50 kGy. Heat deflection temperature (HDT) of silk fibroin/PBS biocomposites showed the increasing tendency with increasing the electron beam absorption dose, reflecting the increased stiffness of the biocomposites with increasing electron beam absorption dose. The maximum peak of tan δ showed the decreasing according to increasing the electron beam absorption does. The electron beam absorption dose of 50 kGy was optimal for improving the thermal and mechanical properties of silk fibroin/EB-PBS biocomposites processed using towpregs and prepregs by a hot-melt method.