Melt-spun liquid core fibers: physical and morphological characteristics

Application of different polymers and fillers in multi-component fibers has recently emerged as an effective approach in textile industries. Recent investigations have extensively demonstrated that hollow fibers can be melt-spun and subsequently filled with liquids; however, introduction of a liquid into a fiber core and filling it up with that liquid, specifically at extended lengths, remains challenging. In this study, based on the results previously obtained for the simulation and extrusion of polymer melt and liquid co-flowing, continuous production of the liquid core bi-component filaments via melt spinning through specially designed spinneret is discussed. In fact, core/shell bi-component filaments 50 μm in diameter consisting of polypropylene sheath and complex ester core were produced undergoing 1500 m/min continuous melt spinning with drawing ratio of 5. Physical properties of the developed fibers were investigated which were in acceptable condition with those of the reference solid and hollow fibers. Successful presence of a liquid in an eccentric channel 15 μm in diameter was demonstrated by microscopic observation. Furthermore, the ester oil was retained inside the fiber due to its low contact angle against polypropylene, thereby resolving the need for sealing the fiber’s outlet. Also, TGA and FTIR analysis confirmed the presence of liquid inside the bi-component fibers. DSC tests showed a similar crystallinity for liquid core and hollow fibers, which was about 37 %, while solid fiber had 5 % more crystallinity. Due to the vast available liquids and polymers with various properties, developed liquid core fibers will provide a suitable platform for a large number of applications in future.