Fiber Structure, Tensile Behavior and Antibacterial Activity of Polylactide/Poly(butylene terephthalate) Bicomponent Fibers Produced by High-Speed Melt-Spinning

Various types of bicomponent fibers composed of polylactide (PLA) and poly(butylene terephthalate) (PBT) with different molecular weights, arranging the polymers separately in the skin or core, were produced by high-speed melt-spinning. The bicomponent spinning, arranging the PLA with high molecular weight (melt flow rate =1.9 g/10 min, L-lactide content = 98.7%) in the skin and the PBT with low molecular weight (IV = 0.835-0.865 dL/g) in the core, resulted in orientation-induced crystallization in the PLA component at the spinning speed of 2 km/min. This crystallization effect was ascribed to a chain-extending treatment applied to the original PLA (MFR = 4.0 g/10 min) to increase its molecular weight. By the treatment the PLA could crystallize when spun even at 1 km/min in its single-component spinning. On the other hand, the bicomponent spinning system interfered with the orientation-induced crystallization of PBT in the core. As a result, the critical spinning speed needed to generate the orientation-induced crystallization in the core PBT was elevated to 4 km/min. The inferior tensile behavior of the bicomponent fibers, as compared to the single-component PLA or PBT fibers, suggested poor compatibility between PLA and PBT. Transesterification reactions rarely occurred at the interface of the two polymers. The bicomponent fibers prepared from high molecular weight PLA and low molecular weight PBT, however, showed sufficient antibacterial activity and physical properties to be suitable for designing medical clothing materials.