High modulus man-made cellulose fibers by common air-gap spinning technology

The demand for fiber reinforced plastics is contineously growing, especially for lightweight applications. The most used technical fiber for mass application is indeed glass fiber. Taken into account the values for the specific strength and modulus, it clearly can be seen that cellulose man-made fibers are an real alternative for replacing glass fibers in certain applications. Technical man-made cellulose fibers produced via the viscose process, often called rayon, are produced in amounts of some 100,000 tons mainly used for rubber good reinforcement. For these so-called Super 3 tire cord yarns, typical (single filament) tensile strengths are around 850 MPa with moduli in the range of 20 GPa. With a density of 1.5 g/cm3, lightweight construction potential in composite manufacture is offered by this kind of bio-based fibers. Using various alternative methods, it has been demonstrated that cellulose technical fibers can be manufactured with drastically improved tensile properties. None of these methods, however, is currently in production but a few shall be named here. On a pilot plant scale, fibers with 1.3 GPa strength and 45 GPa modulus were developed by Acordis (Fibre B, NL) at the beginning of this century, spun from an anisotropic super phosphoric acid solution [1]. The poster presents the results of investigations on enhancing the supermolecular structure by alkalization of the dissolving pulp used for NMMO technology in order to enable stable spinning at high solid content of 18 wt.-%. The focus of the work was on achieving the textile-physical properties within the range of high-modulus cellulose fibers which were only available by various alternative methods up to now. Rheological and X-Ray investigations as well as tensile test show the effect of pulp treatment on the spinning solution and the fiber properties. Highly oriented fibers with a modulus of 37 GPa and a tensile strength of 700 MPa could be stable spun by common airgap spinning technology.