Preparation and Properties of Self-Crimping Polyamide-Based Side-by-Side Bicomponent Elastic Fibers

Side-by-side bicomponent fibers have a spring-like three-dimensional spiral crimp structure and are widely used in elastic fabric.The difference in thermal shrinkage between different polymers can produce an unbalanced stress during the cooling process,and this unbalanced stress can be exploited to prepare naturally crimped fibers by spinning design.In this work,different types of polyamides(PAs)were selected for fabrication of the PA-based side-by-side bicomponent elastic fibers using melt spinning,and the structure development and performance of such bicomponent elastic fibers were studied.Meanwhile,thermoplastic PA elastomer(TPAE)with intrinsic elasticity was also used as one of the comparative materials.The block structure of the PA segment and the polyether segment in the TPAE molecule is the key to providing thermal shrinkage differences and forming a good interface structure.As a result,the crimp ratio of PA6/TPAE bicomponent elastic fiber is 7.23%,which is better than that of the currently commercialized T400 fiber(6.72%).The excellent crimp performance of PA6/TPAE bicomponent elastic fibers comes from the asymmetric distribution of the stress along the radial direction of the fibers during the cooling process,which is caused by the difference in thermal shrinkage between PA6 and TPAE.In addition,the crimp formability of the PA-based bicomponent elastic fibers could be improved by expanding the shrinkage stress through wet-heat treatment.The crimp ratio of PA6/TPAE bicomponent elastic fibers reaches the maximum(33.08%)after treatment at 100℃.At the same time,the fabric made of PA6/TPAE bicomponent elastic fibers has the excellent air and water vapor permeability,with an air permeability of 272.76 mm/s and a water vapor transmission rate of 406.71 g/(m^(2)·h).

Facile and Large-scale Fabrication of Self-crimping Elastic Fibers for Large Strain Sensors

Stretchable conductive fibers offer unparalleled advantages in the development of wearable strain sensors for smart textiles due to their excellent flexibility and weaveability.However,the practical applications of these fibers in wearable devices are hindered by either contradictory properties of conductive fibers(high stretchability versus high sensing stability),or lack of manufacturing scalability.Herein,we present a facile approach for highly stretchable self-crimping fiber strain sensors based on a polyether-ester(TPEE)elastomer matrix using a side-by-side bicomponent melt-spinning process involving two parallel but attached components with different shrinkage properties.The TPEE component serves as a highly elastic mechanical support layer within the bicomponent fibers,while the conductive component(E-TPEE)of carbon black(CB),multiwalled carbon nanotubes(MWCNTs)and TPEE works as a strain-sensitive layer.In addition to the intrinsic elasticity of the matrix,theTPEE/E-TPEE bicomponent fibers present an excellent form of elasticity due to self-crimping.The self-crimping elongation of the fibers can provide a large deformation,and after the crimp disappears,the intrinsic elastic deformation is responsible for monitoring the strain sensing.The reliable strain sensing range of theTPEE/E-TPEE composite fibers was 160%-270%and could be regulated by adjusting the crimp structure.More importantly,the TPEE/E-TPEE fibers had a diameter of 30-40 pm and tenacity of 40-50 MPa,showing the necessary practicality.This work introduces new possibilities for fiber strain sensors produced in standard industrial spinning machines.