Fabrication of aramid 1313–UHMWPE composite yarns and investigation of the thermal performance of its knitted fabrics

Heat setting is crucial for knitted fabric finishing but poses challenges for ultrahigh-molecular-weight polyethylene (UHMWPE) knits due to their low melting point (130–148°C). This study presents a ring-spun core–sheath yarn design featuring UHMWPE filaments as the core and aramid 1313 staple fibers as the sheath. This configuration provides thermal protection for the core while enhancing interfiber cohesion and improving knittability. The optimized yarn was knitted into air-layer fabrics and subjected to heat treatments at 110–150°C. Performance was evaluated against pure UHMWPE controls using tensile and tear tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), and transient radial heat-conduction simulations. Results demonstrated superior thermal stability: the composite yarn maintained structural integrity with minimal property changes (wale-direction tensile 1.6%, course-direction 4.7%; tear strength 4.4% and 3.5%), while the control exhibited significant degradation (16%, 34.7%, 24.1%, and 31.8%, respectively). SEM analysis confirmed intact UHMWPE cores, and XRD revealed preserved crystallinity. Heat-conduction simulations showed the sheath extended thermal equilibrium time from 0.015 to 0.31 s, effectively delaying heat transfer to the core. This innovative yarn architecture enables successful heat setting of UHMWPE knits, advancing their potential in protective and functional textile applications.