Journal of Textile Research ›› 2025, Vol. 46 ›› Issue (09): 46-56.doi: 10.13475/j.fzxb.20241206601

• Fiber Materials • Previous Articles     Next Articles

Fabrication and properties of polyamide 6-based elastomers and their side-by-side elastic fibers

LI Yujie1,2, WANG Chengqin1,2, WANG Wei3, YUAN Ruchao1,2, YU Jianyong2, LI Faxue1,2()   

  1. 1. College of Textiles, Donghua University, Shanghai 201620, China
    2. Innovation Center for Textile Science and Technology, Donghua University, Shanghai 201620, China
    3. Jiangsu Textile Research Institute, Wuxi, Jiangsu 214425, China
  • Received:2024-12-26 Revised:2025-04-16 Online:2025-09-15 Published:2025-11-12
  • Contact: LI Faxue E-mail:fxlee@dhu.edu.cn

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Abstract:

Objective This study aimed to address the inherent elasticity limitations of polyamide 6 (PA6) fibers by combining intrinsic elasticity through block copolymerization and morphological elasticity through side-by-side spinning. The research is focused on developing high-strength polyether-ester-amide 6 thermoplastic elastomers (TPAEE6) and fabricating f(PA6/TPAEE6) side-by-side elastic fibers, so as to overcome the challenges of low strength and declining elasticity in existing PA6-based elastic fibers.

Method A novel TPAEE6 elastomer was synthesized using a three-step melt copolymerization process involving non-crystalline polyether-ester diols and PA6. Characterization techniques, including proton nuclear magnetic resonance spectroscopy (1H NMR), Fourier-transform infrared spectroscopy (FT-IR), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and tensile testing, were employed to verify the synthesis and evaluate the structural and thermodynamic properties of TPAEE6s. Side-by-side elastic fibers were prepared by blending PA6 with TPAEE6 elastomers at specific ratios and varying draw ratios.

Results 1H NMR and FT-IR results confirmed that TPAEE6 is composed of soft and hard segments connected by ester bonds. GPC analysis revealed that the molecular weight of the elastomer ranged from 36.5 to 45.7 kg/mol, while viscosity testing indicated a relative viscosity between 1.21 and 1.68, suggesting a high molecular weight for the elastomer. DMA exhibited dual glass transition temperatures, and structural changes in the crystalline regions observed in WAXD and SAXS demonstrated the excellent microphase-separated morphology of TPAEE6. Additionally, SAXS calculations indicated that the addition of polyether-ester segments did not alter the interplanar distance of the pure PA6 crystalline phase, confirming that the incorporation of soft segments did not disrupt the crystalline structure of pure PA6. Tensile testing results showed that the elastomer exhibited a tensile strength of 23-47 MPa and an elongation at break of 373%-758%. Cyclic tensile testing revealed a significant improvement in elastic recovery with increasing soft segment content. Beyond the first cycle, the subsequent tensile cycles showed minimal loss in elasticity. The f(PA6/TPAEE6) elastic fibers, prepared by side-by-side spinning of PA6 and TPAEE6-30 at a composite ratio of 4∶1, achieved a tensile strength of 3.12 cN/dtex, significantly outperforming previously reported PA6/TPAE composite fibers (2.14 cN/dtex), PA6/TPA6510 fibers (1.4 cN/dtex), PA6/PBTE fibers (2.4 cN/dtex), and commercial elastic fibers like T400 (2.44 cN/dtex). Under fixed elongations of 5%-20%, the elastic recovery rate and durability of the PA6/TPAEE6 fibers were significantly superior to those of T400, with recovery rates exceeding 90% in low-strain cycles and significantly reduced hysteresis losses.The microphase-separated structure of TPAEE6 balances flexibility and strength, imparting exceptional elasticity and mechanical performance to the fibers.

Conclusion The developed TPAEE6 thermoplastic elastomer exhibits excellent thermodynamic properties and a well-defined microphase-separated structure, offering new approaches and choices for the elastomer market. The PA6/TPAEE6 elastic fibers developed significantly outperform existing PA6-based and commercial elastic fibers in terms of strength and elasticity, showcasing broad application potential. This research integrates intrinsic and morphological elasticity, providing a new pathway for developing high-performance elastic fibers with the potential to enhance production and manufacturing efficiency.

Key words: polyamide 6 fiber, polyether-ester-amide 6 elastomer, microphase-separated structure, side-by-side elastic fiber, elastic recovery rate

CLC Number: 

  • TQ342.1

Fig.1

Synthesis route of TPAEE6"

Fig.2

1H NMR spectra of TPAEE6-30 and Pre-PA6"

Tab.1

Molecular structures of TPAEE6"

样品编号 MnPA6/
(kg·mol-1)		 η/η0 MnTPAEE6/
(kg·mol-1)		 PDI 转化率/
%
TPAEE6-0 2.9 1.68 43.5 5.9 -
TPAEE6-30 3.0 1.24 40.4 7.2 91.7
TPAEE6-40 3.1 1.21 36.9 8.4 85.7
TPAEE6-50 3.0 1.29 45.7 3.7 88.9
TPAEE6-60 2.8 1.25 39.0 3.3 87.5
TPAEE6-65 2.9 1.24 36.5 4.0 89.1

Fig.3

GPC curves of TPAEE6"

Fig.4

FT-IR spectra of TPAEE6 and PA6"

Fig.5

DMA curves of TPAEE6"

Tab.2

Thermal performance of TPAEE6"

样品编号 TgH/
℃		 Tm/
℃		 Tc/
℃		 ΔHm/
(J·g-1)		 Xc/
%		 T5%/
℃
PA6 51 220 175 52 27.4 355
TPAEE6-0 45 205 162 47 24.7 364
TPAEE6-30 25 166~177 123 26 19.5 352
TPAEE6-40 23 171~181 120 28 22.8 354
TPAEE6-50 17 144、166 85 24 12.6 352
TPAEE6-60 14 138、164 82 16 21.1 351
TPAEE6-65 14 133、162 74 15 14.4 351

Fig.6

WAXD spectra of TPAEE6 and PA6"

Fig.7

SAXS spectra of TPAEE6 and PA6"

Fig.8

DSC curves of TPAEE6 and PA6. (a) Secondary heating curves; (b) Cooling curves"

Fig.9

Thermogravimetric curves of PA6 and TPAEE6. (a) TGA curves; (b) DTG curves"

Fig.10

Tensile fracture curves of PA6 and TPAEE6"

Tab.3

Mechanical properties of TPAEE6"

样品
编号		 弹性模
量/MPa		 断裂强
度/MPa		 断裂伸
长率/%		 缺口冲击强度/
(kJ·m-2)		 拉伸韧
性/(J·m-3)
PA6 416 72 133 1.4 8.20×109
TPAEE6-0 281 42 373 1.8 1.35×1010
TPAEE6-30 129 41 670 27 1.60×1010
TPAEE6-40 292 47 474 38 1.64×1010
TPAEE6-50 212 33 544 42 1.49×1010
TPAEE6-60 64 23 758 74 1.10×1010
TPAEE6-65 82 29 750 52 1.54×1010

Fig.11

Cyclic tensile curves of TPAEE6"

Fig.12

Tensile fracture curves of f(PA6/TPAEE6) and T400"

Tab.4

Mechanical properties of f(PA6/TPAEE6) and T400"

PA6与
TPAEE6
质量比		 牵伸
倍数		 线密度/
dtex		 断裂
伸长
率/%		 断裂强度/
(cN·
dtex-1)		 模量/
( cN·
dtex-1)		 取向
因子
3∶1 1.2 50.0±2.1 31±5 3.11±0.13 19.38±2.87 0.624
1.3 44.5±1.9 26±4 3.37±0.18 19.69±3.03 0.681
1.4 43.4±1.8 24±3 3.30±0.17 22.60±4.12 0.709
4∶1 1.2 50.8±2.5 46±6 2.75±0.12 13.66±2.09 0.609
1.3 49.1±2.0 35±4 3.12±0.15 16.38±3.42 0.646
1.4 45.1±1.9 29±3 3.20±0.16 20.34±4.01 0.699
T400 — 56.0±2.8 21±2 2.44±0.11 22.09±2.69 —

Fig.13

Cyclic tensile curves of fibers. (a) Cyclic tensile curve of f(PA6/TPAEE6); (b) Cyclic tensile comparison curves of f(PA6/TPAEE6) and T400"

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