Pultrusion of a flax/polypropylene yarn

Institut für Allgemeinen Maschinenbau und Kunststofftechnik, Technische Universität Chemnitz, 09107 Chemnitz, Germany
Composites Part A Applied Science and Manufacturing (Impact Factor: 3.01). 05/2007; 38(5):1431-1438. DOI: 10.1016/j.compositesa.2006.01.024

ABSTRACT The present work reports the pultrusion of a flax reinforced polypropylene commingled yarn containing discontinuous flax and polypropylene fibers. This was the first attempt to pultrude this material. Rectangular cross-sectional profiles have been successfully produced using a self-designed pultrusion line. In a series of experiments carried out with yarns of two different flax fiber contents, the pultrusion parameters were varied. In particular, the preheating and die temperatures and also the pulling speed, which are the most relevant parameters regarding the potential future pultrusion of natural fiber composite profiles at industrial scale. A complete characterization of each profile was conducted in order to examine the influence of processing parameters on the profile quality. The mechanical properties were evaluated by performing three point bending as well as Charpy impact tests.

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    ABSTRACT: Fundamental mechanisms of the pultrusion process using commingled yarns of polypropylene matrix and discontinuous flax fiber to produce thermoplastic profiles were investigated in numerical and experimental manners. Essential issue is the fact that all natural fibers are discontinuous by nature, which may negatively influence the processability. The pultrusion process will be only successful if the pulling force exerted on the solidified pultrudates can be transmitted to the regions of unmelted commingled yarns by “bridging over” those melted regions within the die. This can be realized by applying a sufficient number of small yarn bundles of high compactness rather than a thicker single bundle of lower compactness as the raw material. Furthermore, the possibility of adding extra melt into the yarn bundles by side-fed extrusion has been investigated showing that the impregnation can be improved only for the outer layers of yarns, which is owed to the high viscosity of the thermoplastic melt and the limited length of the die.
    Research Letters in Materials Science 01/2007; DOI:10.1155/2007/37123 · 0.50 Impact Factor
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    Advanced Composite Materials 01/2011; 20(3-3):231-244. DOI:10.1163/092430410X547047 · 0.48 Impact Factor