Recent, attention has been given to shift from glass fibers and carbon fibers to natural fibers for FRP composites for the goal of protecting the environment. This paper concerned with the application of silk fabric for composite materials. Polypropylene (PP) was used for the matrix material and the silk fabric composites were molded using a compression molding method. Especially, the effect of sericin on mechanical behaviors of composite materials was discussed. Good adhesion between silk and PP was obtained by removing the sericin existing around the fibroin. The tensile modulus of composite decreased with decreasing the sericin because of the flexibility of silk fibers without sericin. In particular, the higher Izod impact value was obtained for the composites containing the silk fibers without sericin.

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Flammability of polymer is a phenomenon of oxidation reaction at near surface of products. Distribution of filler and flame-retardant at surface of products is thought to influence the flammability. So model samples that have various distributions of flame-retardant and filler, were made by using high-speed sandwich injection moldings. In this study, two types of flame-retardant, bromine type and phosphorous type, were used. The model sample which had high flame-retardant content in surface layer and high filler content in core layer, had good flammability and mechanical properties. Especially, phosphorous flame-retardant showed superior effect in that small amount of flame-retardant achieved same flammability as flame-retardant PP without filler. Control of distribution of flame-retardant and filler by using high-speed sandwich injection molding is cost-effective method with low flame-retardant addition.

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