Study on the Microstructure of Poly(Amide 6-Ether) Copolymers and Application in Elastic Fibers

Abstract

Fiber elasticity is an important property for achieving clothing comfort. The excellent resilience of poly (amide 6-ether) copolymers makes them a popular candidate material for preparing PA6-based elastic fibers. However, the low reactivity of traditional esterbonded poly (amide 6-ether) copolymers leads to the presence of partially blended polyether segments or severe microphase separation, which seriously affects the mechanical properties and processing. Herein, a series of poly (amide 6-ether) copolymers (PA6-PEA copolymers) bonded by amide bonds using polyether diamine (PEA) as the soft segment are prepared. The PA6 segment and the PEA segment exhibit high reactivity and good compatibility, making the copolymer microstructure present one kind of PA6 crystalline phase, one kind of PEA crystalline phase, and one mixed amorphous phase of PA6 and PEA. Both the improved compatibility of the soft and hard segments in the amorphous region of the copolymer and the formation of a soft continuous phase effectively improving the elastic properties of the copolymers. The elastic recovery rate of copolymers at 100 % constant elongation increases from 14.61 % for PA6 to 59.02 % for PA6-PEA-45. The elastic recovery rate of PA6-PEA elastic fiber at a constant elongation of 20 % is 93.00 %, which is 18.67 % higher than that of fPA6 fiber and higher than the elastic recovery rate of poly (trimethylene terephthalate) (PTT) fiber (86 %). The elastic recovery rate after 5 cycles of stretching and rebounding is 92.50 %, and the stress relaxation rate is 13.24 %, showing good tensile fatigue resistance. At the same time, the fiber can maintain outstanding mechanical properties (breaking strength exceeds 2.18 cN/dtex). The initial modulus of PA6-PEA elastic fiber decreased from 15.83 cN/dtex to 5.35 cN/dtex. And the introduction of hydrophilic PEA segments increases the moisture regain of the fiber to 7.23 %, improving the softness, comfort and skin-friendliness of the fiber. This work provides a new idea for the preparation of PA6-based elastic fibers with both elastic and mechanical properties.