Abstract:

Objective Basalt fiber (BF), as an environmentally high-performance fiber, exhibits great potential in flame protective clothing. Compared to commercially available flame-retardant materials, BF's inherent flame-retardant properties are more environmentally friendly. However, the BF's disadvantages, such as poor toughness, high modulus, and brittleness, lead to easy fiber fracture during textile production and processing. Consequently, addressing the issue of BF twist fracture is critical to fulfill yarn and fabric preparation.

Method In this work, waterborne polyurethane (WPU)/nano silica (SiO₂) sizing agent (WS) was prepared by blending WPU with SiO₂, and scanning electron microscopy and FT-IR spectra confirmed the successful application of the sizing agent. The effects of WPU content, SiO₂ content, twists, and drying temperature on yarn strength, abrasion resistance and hairiness were analyzed to identify the optimal spinning process for modified yarn production. Finally, WPU/SiO₂/BF yarn (WSBF) was blended with commercially available flame-retardant viscose fiber (CV) and meta-aramid fiber (PMIA) to prepare double-layer knitted fabrics (WSBF/CV,WSBF/PMIA). These blended fabrics demonstrate the weavability and wearability of modified basalt yarns, followed by an analysis of the fabric’s comfort, flame retardancy, and fire resistance were discussed.

Results WPU/SiO₂ exhibited a visible covering layer and uneven roughness on the fiber surface, and the FT-IR absorption bands confirmed its successful incorporation. When 8% WPU was added, WSBF strength reached 58.83 N, which is 51.7% higher than at 2%, and it withstood 406 abrasion cycles with minimal hairiness. As SiO₂ content increased gradually to 1%, yarn abrasion resistance was improved, and hairiness reduced, although yarn strength was slightly dropped. Based on overall yarn performance, 1% SiO₂ was selected. Analogously, 90 twists/m and 100 ℃ were selected. These blends with CV and PMIA were used to weave WSBF/CV and WSBF/PMIA double-layer knitted fabrics, which have air permeabilities of 1 992 mm/s and 2 024 mm/s, respectively, 116.3% and 21.3% higher than the pure knitted CV and PMIA fabrics. For fabric moisture permeability, although the increased fabric thickness expanded water transport channels, the relative effect of the increased porosity kept it above 92%. For fabric hairiness, the entangling effect of WSBF on CV and PMIA reduces the hairiness of blended fabrics below 0.2 mm. During vertical combustion test, the damage length of WSBF/PMIA has declined to 5.6 cm. During 5 s of flame heating, the fabric surface is within safe temperature ranges for humans. At 1 300 ℃ high-temperature damage, combustible materials were protected by WSBF/PMIA structural integrity, and fireproofing improvement.

Conclusion The sizing of WPU/SiO₂ is proven to enhance the yarn properties, and the WSBF is successfully prepared by investigating WPU content, SiO₂ content, twisting, and drying temperature. WSBF is blended with CV and PMIA yarns to create WSBF/CV and WSBF/PMIA fabrics, which maintain the comfort of pure fabrics. During combustion, the damage to blended fabric is reduced, fabric integrity is improved, and flame-retardant properties are enhanced. When exposed to direct flame, WSBF/CV and WSBF/PMIA achieve short-time flame fetch, with excellent fireproof performance at temperatures up to 1 300 ℃.

Key words: waterborne polyurethane/nano silica, sizing agent, basalt fiber fabric, flam-retardant viscose fiber, aramid fiber, flame retardant, inorganic fiber, high-performance fiber