Abstract:

Objective Glass fiber is an important material for the preparation of tubular textile reinforcements because of its high strength, high modulus and high cost performance, but its brittleness, small fracture elongation and poor torsion resistance limit its textile processability. In order to obtain glass fiber weft-knitted biaxial tubular (WKBT) fabrics with stable and compact structure to meet industrial requirement for integrated tubular fabric formation with high strength, high modulus and low ductility, glass fiber WKBT fabric with warp and weft lining yarns constructed using 1×1 rib structure was designed and discussed, and the tensile properties of WKBT fabric were evaluated.

Method Four types of WKBT fabrics, i.e., PET₁-GF-GF, PTFE-GF-GF, PE {\mathrm{T}}_2^{\mathrm{F}\mathrm{B}}-PET₁-GF-GF, and PTFE^FB-PTFE-GF-GF, with different stitch structures and binding yarns were prepared by plaiting technology and spreading device, and their appearance morphology, transverse and longitudinal density and tensile properties were analyzed. The shrinkage was introduced to discuss the dimensional stability of WKBT fabric influenced by the stitch structure and the binding yarns. The strength efficiency of lining yarn was defined to describe the influence of different stitch structure and binding yarns on the strength efficiency of glass fiber.

Results According to the definition of "binding yarn-warp yarn-weft yarn", three types of WKBT fabrics were prepared by different binding yarn and insertion yarns, which were PET₁-PET₁-PET₁、PET₁-GF-GF、PTFE-GF-GF, respectively. The WKBT fabric was stretched in the 0° direction on the machine, and the diameter of the WKBT fabric was approximately equal to the diameter of the weft yarn along the circumferential direction of the fabric. Under the pulling force, the sinker loop transfer to leg causing loops to shrink and densely arranged along the circumferential direction, and the diameter of the WKBT fabric becomes smaller. The weft lining yarns were bent and arched on the front of the fabric under the shrinkage force of the adjacent binding loop, resulting in the phenomenon of "lining yarns buckling". "Plaiting yarn-binding yarn-warp yarn-weft yarn" was defined to describe the WKBT fabric, and the plaiting yarn on the front side of fabric (F), back side (B), and front and back (FB), respectively. Two WKBT fabrics were prepared, which are PE {\mathrm{T}}_2^{\mathrm{F}\mathrm{B}}-PET₁-GF-GF and PTFE^FB-PTFE-GF-GF. The dimensional stability and appearance of fabric was improved by the plaiting yarn, but the buckling of lining yarns still existed. Compared to the 1+1 rib, the plaiting yarn prevented more effectively the shrinkage of fabric along the circumferential direction. The total shrinkage of the WKBT fabric was small, and the fabric was stable and compact. The weft lining yarns were straightened after the WKBT fabrics were spreading, the buckling of lining yarns decreased. The WKBT fabric was more compact which was bond by the PTFE fiber. The elasticity of PTFE fiber was smaller and the fabric shrank along the 0° direction after spreading. Compared with 1+1 rib structure, the longitudinal density of WKBT fabric increased which was bond by the plaiting structure and the fabric is more compacter. Four WKBT fabrics had good tensile properties, and the strength efficiency of warp lining yarn were 70.48%, 69.14%, 63.88% and 46.02%, respectively, and the strength efficiency of weft lining yarn were 70.50%, 81.40%, 84.68% and 62.09%, respectively. The structure and tightness of stitch structure were shown to be important factors affecting the elastic modulus of WKBT fabric.

Conclusion The plaiting stitch can prevent the circumferential shrinkage of the binding stitch structure, but there is still the lining yarns buckling. The buckling of lining yarns can be solved by using the spreading device. Combined with the plaiting technology, the WKBT fabric with stable and compact structure can be prepared. The lining yarns of the four WKBT fabrics still have high elastic modulus and strength efficiency, meaning that the WKBT fabrics with excellent performance can be prepared by plaiting technology and spreading device while eliminating shrinkage.

Key words: weft-knitted biaxial tubular fabric, spreading device, shrinkage, tensile property, strength efficiency of lining yarn