Low-damage knitting of polyglycolic acid fibers through tension regulation and stitch optimization

Polyglycolic acid (PGA) is a key bioabsorbable material for load-bearing textile medical implants, but the mechanical deterioration of PGA fibers inevitably takes place in textile processing via abrasion and plastic deformation owing to high crystallinity and high moduli. This paper proposes a low-damage knitting strategy by regulating yarn tension and optimizing knit stitches. A PGA fully drawn yarn of tenacity 5.62 cN/dtex was employed to do abrasion test, knitting while recording dynamic tension, and morphological and tensile tests on the knitted fabrics. The abrasion test results show that PGA fibers have more fiber breakages and a greater extension (0.673%) than those of PET fibers (0.354%) through 100 cycles of wearing on a grinding wheel of grit size W40 ranging from 28–40 μm at a tension of 0.25 cN/dtex. Yarn knitting tension (YKT) records reveal that a yarn input tension of 2.5 cN mitigates YKT fluctuations, reducing the yarn strength loss to 18.13% for plain stitch and 10.31% for interlock stitch. The morphologies of the knitted fabrics indicate that fiber damage intensifies with decreasing loop length and is severer in plain stitch than interlock stitch. Optimization of knit stitch by adjusting sinking depth (NP value) demonstrates that the plain stitch at NP=12.0 and the interlock stitch at NP=10.5 result in high breaking force in the walewise direction, achieving a good balance between loop length and fiber damage to gain increasing fabric strength. This integrated approach of tension regulation and stitch optimization provides a reliable method for manufacturing high-strength PGA knitted implants.