ORIGINAL PAPER Journal of Textile Engineering (2006), Vol.52, No.3, 107-112 2006 The Textile Machinery Society of Japan Structure Variations of High Tenacity Nylon 6 Fiber on Cyclic Temperature Changes SHIBAYA Miaki a, TSUJI Yoshihiro b, SAKURAI Shinichi b, ISHIHARA Hideaki a,*, YOSHIHARA Nori c a Division of Advanced Fibro-Science, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606 8585, Japan b Department of Polymer Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606 8585, Japan c TOYOBO Co., Ltd., 1-1 Katata 2-chome, Otsu, Shiga 520 0292, Japan Received 2 September 2005; accepted for publication 3 December 2005 Abstract Nylon 6 fibers are used as tire cord in carcass of automobile tire for rubber reinforcement to keep internal pressure. During run state, the internal part of tire is heated up to 100 C and cooled by stopping, resulting in the same thermal history of Nylon 6 tire cord. It has been reported that crystal phase of Nylon is transformed to other phase under high temperature condition. In room temperature, two reflection peaks assigned to α phase were observed by wide angle X-ray diffraction measurement for Nylon 6 fiber. On heating, these two peaks became one peak of pseudohexagonal phase at around 70 C. This transition referred as the Brill transition took place repeatedly by heating and cooling. Also, tensile strength decreased with increasing temperature by heating and increased by cooling. For higher-order structure measured by small angle X-ray scattering, the long period of Nylon 6 lamella was constant on cyclic temperature changes. On the other hand, it was observed that the slope against fiber direction and the size of lamella were irreversibly changed at around 70 C. It has been reported in former study that the Brill transition was observed at higher temperature region than 150 C because samples were Nylon 6 pellets and films. Accordingly, the Brill transition temperature changed much lower in high oriented Nylon 6 fiber. Key Words: Nylon tire cord, Nylon 6, Brill transition, Wide angle X-ray diffraction, Small angle X-ray scattering 6 a b b a,* c 95% 93% [1] 100 C [2] * REC (Ryukoku Extension Center) 520-2194 1-5, E-mail: h-ishihara@rnoc.fks.ryukoku.ac.jp Tel: +81-77-544-7297, Fax: +81-77-543-7771 107
SHIBAYA Miaki, TSUJI Yoshihiro, SAKURAI Shinichi, ISHIHARA Hideaki, YOSHIHARA Nori 6 2127dtex 304 20 C 3.55 Fig. 1 Crystal modification of Nylon 6; (a) α crystal form and (b) γ crystal form. 6 ε [3] 6 5 66 Fig. 1 α γ [4 8] γ H O α 3% 6 α γ α β [9 12] 66 210 C X Brill [13] Brill 6 X Brill [14 16] 6 X γ γ α [14] 6 6 6 6 20 C 65%RH 300 mm/min 50 mm 20 100 C 100 C 20 C (Tenacity) X (WAXD) X RU3 (CuKα) 45 kv 40 ma PSPC50 (Position Sensitive Proportional Counter, PSPC) 20 100 C 0.05 C/s 0.2 C/s 100s X (SAXS) SPring 8 BL40B2 0.1 nm 1.0 m CCD II CCD 2 SAXS Fig. 2 100 C 1.0 cn/dtex 10% Fig. 2 Temperature dependence of Nylon 6 fiber on tenacity. 108
Journal of Textile Engineering (2006), Vol.52, No.3, 107-112 6 Fig. 3-1 3-3 PSPC Fig. 3-1(a) (d) Fig. 3-2(e) (h) Fig. 3-3(i) (l) 27 C 2 69 C 1 27 C 2θ 20 24 69 C 21 1 Fig. 3-3 WAXD intensity profiles of Nylon 6 fiber on 2nd heating and cooling process; (i) 34 C, (j) 72 C, (k) 93 C and (l) 34 C. Fig. 3-1 WAXD intensity profiles of Nylon 6 fiber on heating process; (a) 27 C, (b) 51 C, (c) 69 C and (d) 94 C. 2 1 2 Fig. 4 (200) (002) (202) 70 C 4.2Å α Brill 70 C 100 C 70 C 4.2Å 2 α 4.2Å 2 α Brill 6 Fig. 3-2 WAXD intensity profiles of Nylon 6 fiber on cooling process; (e) 64 C, (f) 51 C, (g) 39 C and (h) 34 C. Fig. 4 d spacing changes of Nylon 6 crystal in fiber on 1st and 2nd heating and cooling processes. 109
SHIBAYA Miaki, TSUJI Yoshihiro, SAKURAI Shinichi, ISHIHARA Hideaki, YOSHIHARA Nori Brill 150 200 C Brill 70 C 4 L 4 2 Fig. 7 Fig. 5 2 SAXS (2d-SAXS) 2d-SAXS 4 25 C Fig.5 (a) (e) 100 C 4 2 100 C Fig. 5 (f) 2d-SAXS 2d-SAXS Fig. 5 2d-SAXS (q, φ) Fig. 6 2d-SAXS q (1) q = (4π / λ) sin (θ / 2) (1) λ X θ φ qm I(q) q * Fig. 6 Parameters in 2d-SAXS pattern of Nylon 6 fiber. q: scattering vector, qm: peak position, q * : distance between peaks and φ: angle of aperture. Fig. 5 SAXS patterns of Nylon 6 fiber in terms of temperature change; (a) to (e) show heating processes and (f) shows cooling process. Fig. 7 1d-SAXS profiles on cross-streaks, converted from the 2d-SAXS patterns shown in Fig. 5. 110
Journal of Textile Engineering (2006), Vol.52, No.3, 107-112 2d-SAXS I(q) I(q) [17] Fig. 7 qm (2) L L = 2π / qm (2) Fig. 8 L 2d-SAXS 4 Fig. 6 2 M 2 1 1 0 Fig. 9 70 C 0 0 2d-SAXS 4 q * qm (3) φ φ = 2 sin 1 (q * / 2qm) (3) Fig. 10 4 X 2 4 Fig. 7 I (q) Fig. 11 4 70 C 2 70 C Fig. 8 Long period calculated by the Lorentz-corrected profiles of Nylon 6 crystal in fiber. Fig. 10 Relationship between peak angles of scattering intensity and temperature. Fig. 9 Intensity difference between two peaks of line profiles shown as broken line in Fig. 6 2d-SAXS patterns. Fig. 11 Peak area change as the index of lamella size in 1d-SAXS profiles shown in Fig. 7. 111
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