X-ray investigations of PA6 in hybrid yarn composites
Eulalia Klata*, Izabella Krucińska*, Sławomir Borysiak**, Józef Garbarczyk** *Politechnika Łódzka, Katedra Metrologii Włókienniczej, ul. Żeromskiego 116, 90-543 Łódź **Politechnika Poznańska, Instytut Technologii i Inżynierii Chemicznej, pl. M. Skłodowskiej-Curie 2, 60-965 Poznań
Annals 3 No. 8, 2003 pages 332-336
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abstract Polyamide 6 (PA6)/glass fibres composites were manufactured from specially designed hybrid yarns. As thermoplastic materials, PA6 multifilament and staple polyamide fibres coated with the DT2 antielectrostatic preparation were used. The glass multifilament EC9 with an aminosilane preparation with dispersion of polyurethane resin was used as reinforcing material (Table 1). The hybrid yarns were produced by three different spinning systems: friction spinning, ring twisting and pneumatic texturing [4]. Each of these systems gives a different structure of the yarn and a different level of blending of the reinforcing and thermoplastic fibres (Figs. 1-3): - friction yarn - a core of yarn from reinforcing multifilaments and a braid from staple thermoplastic multifilaments, - twisted yarn - two multifilaments arranged parallel and twisted together, - pneumatic textured yarn - connected over the length of the multifilaments by shifting filament fibres of both components and forming loop structures in the yarn surface. It causes that distances between fibres in composites produced in the same press conditions are different (Figs. 4-6) and the impregnation of fibres by molten polymer is different. Consequently, a crystalline structure of polymeric matrix is different according to a structure of the used yarn. The different structure of the hybrid yarns leads to differences in the crystallinity of PA6 matrix in the composites. It influences on the mechanical properties of composites. With the increasing degree of crystallinity, the tensile strength, the stiffness, the modulus of resilience, the hardness of the polymer increases and the impact strength decreases [5]. The supermolecular structure of the polyamide matrix was analyzed by means of wide angle X-ray scattering (WAXS) using CuKα radiation. The X-ray diffraction pattern was recorded in angle range of 10÷30o 2Θ. Deconvolution of peaks was performed by the method proposed by Hindeleh and Johnson [7], improved and programmed by Rabiej [8]. The degree of crystallinity (Xc) by comparison of areas under crystalline peaks and amorphous curve was determined. The diffraction curves for investigated samples exhibit two crystalline peaks. The reflections at 24° and at 20,2o indicate a presence of the monoclinic α-crystal form [9, 10]. The highest degree of crystallinity of PA6 is for the composite from twisted yarn - 49%. For PA6 in the composites from friction and textured yarns the values of degree of crystallinity are smaller, 36 and 39% respectively (Table 2). Key words: x-ray investigations, composite polyamide 6, hybrid yarn