Fabrication of fiber-reinforced single-polymer composites through compression molding of bicomponent fibers prepared by high-speed melt spinning process

Fiber-reinforced single-polymer composites were fabricated through the compression molding of sheath-core bicomponent fibers consisting of low and high molecular weight poly(ethylene terephthalate), LMPET and HMPET, as the sheath and core components, respectively. The LMPET/HMPET bicomponent fibers were prepared through the high-speed melt spinning process. When the take-up velocity exceeded a certain level, orientation-induced crystallizaion started to occur in the HMPET while the LMPET remained in an amorphous state. After the starting of the crystallization of the HMPET in the melt spinning process, orientation relaxation of the LMPET proceeded. Accordingly, the sheath-core fibers consisting of the highly oriented and crystallized core component (HMPET) and the amorphous and low oriented sheath component (LMPET) were obtained. Compression molding of such sheath-core fibers was conducted at a temperature above the glass transition temperature and below the melting temperature of PET where the rubbery softening of the amorphous phase was utilized for the fusion of the sheath component to form matrix phase while maintaining the well-developed fiber structure of the core component intact. The fabricated fiber-reinforced single-polymer composites showed fairly high mechanical properties. Good recyclability of the composites is expected because the composites are consisting of only pure PET.