Proceedings of the Polymer Processing Society 28th Annual Meeting ~ PPS-28 ~ December 11-15, 2012, Pattaya (Thailand) COMBINING FUNCTIONALITIES IN MULTICOMPONENT SYNTHETIC FIBERS R. Hufenus 1 *, G. Fortunato 1 , L. Gottardo 1 , F.A. Reifler 1 1 Empa, Swiss Federal Laboratories for Materials Science and Technology, St. Gallen, Switzerland – rudolf.hufenus@empa.ch, giuseppino.fortunato@empa.ch, laura.gottardo@empa.ch, felix.reifler@empa.ch Abstract - Empa's laboratory for Advanced Fibers develops synthetic fibers with distinct functionalities in new combinations. Our custom-made pilot melt-spinning plant enables the prototype production of mono-, bi- and tri- component fibers with various cross-sections and material combinations. Ongoing projects include photocatalytic, drug- release, biodegradable, artificial turf, reinforcing, and rheological core fibers produced on our plant. Keywords: Synthetic fiber, bicomponent, melt-spinning, reinforcement, biomaterial. Introduction Melt spinning is the most commonly used method for manufacturing commercial synthetic fibers. The current trends in polymer melt spinning are manifold. Recent research activities include enhancement of mechanical properties [1, 2], implementation of electric or magnetic functions [3], introduction of biologically active species like drugs or silver composites [4, 5], as well as variation of fiber morphology by bicomponent spinning [6, 7]. Bicomponent fibers are among the most interesting developments in the field of synthetic fibers [8, 9]. Bicomponent or multicomponent fibers are synthetic fibers made from two or more polymers of different chemical and/or physical structure, extruded from a common spinneret to form a single filament [10]. The polymer flows are kept separate up to the spin pack and brought together in or before the spinneret capillary. When the filament leaves the spinneret, it consists of non-mixed components that are fused at the interface. Depending on the characteristics of the different polymers, the multicomponent fiber can provide functional properties such as thermal bonding, self-crimping, unique cross sections, and achieve functionality of special polymers or additives at reduced cost [11]. The three main geometries of multicomponent fibers are side-by-side, core-sheath, and multiple core configurations (Fig. 1). Figure 1 - Typical cross-sections of multicomponent fibers: a) concentric core-sheath, b) eccentric core- sheath, c) 50/50 side-by-side, d) unequal side-by-side, e) segmented pie, f) islands-in-the-sea. Side-by-side and eccentric core-sheath bicomponent fibers are most commonly used to produce self- crimping yarns applied in voluminous products. By combining two polymers that undergo different shrinkage, the yarn curls up after thermal or other relaxing treatment and develops spiral crimp. Core- sheath types are predominately used as binding fibers for nonwovens, with a standard polymer as core and a low softening-point as sheath. When such fibers are laid in a nonwoven structure and heated to a temperature above the softening point of the sheath polymer, the fibers adhere wherever they cross and touch [12]. Multiple core configurations, like islands-in-the-sea and segmented pie, are mainly applied to produce microfibers with diameters smaller than those obtained via conventional melt spinning [13]. Islands-in-the-sea fibers comprise fibrils dispersed in a dissolvable matrix polymer that will be removed in a follow-up process [12]. In the segmented pie technique, a bicomponent fiber is spun from two incompatible polymers that adhere poorly and split into microfibers when subjected to mechanical stress [11]. Fabrics made from microfibers are very flexible, and the high density of fibers makes them inherently wind- and water-proof, while water vapor from perspiration can evaporate easily. Experimental Empa's custom-made pilot melt-spinning plant enables the prototype production of mono-, bi- and tri- component fibers with various cross-sections and material combinations with a throughput of up to several kg/h. A schematic drawing of the melt spinning plant is shown in Fig. 2. The polymers are melted using two single screw extruders with diameters of 13 mm (1) and 18 mm (2), respectively. The maximum extrusion temperature is 400°C. Spin pumps enable a constant mass flow of 0.5-40 cm³/min. In order to produce tri-component fibers, an additional piston extruder (3) is installed, with a throughput of 1.5-15 cm³/min. A special spin pack (4) comprises an oil cooling and heating system (oil temperature 10-360°C) to keep the three polymer melt flows at different temperatures down to the spinneret plate. O-03-069