Development of Cross-linked/Antibacterial Lyocell Fiber: A Breakthrough in Sustainable Textile Materials

Baoding, Hebei – April 2025​ – A new study published in Artificial Fibre(Vol.52, No.1) details a successful experimental research on the preparation of cross-linked/antibacterial Lyocell fiber. Conducted by Gao Bing from Baoding Swan New Fiber Manufacturing Co., Ltd., this research introduces an innovative, eco-friendly process that significantly enhances the functional properties of Lyocell fiber, positioning it as a leading sustainable material for the textile industry.

Introduction: The Promise of Lyocell Fiber

Lyocell fiber, recognized as a fully sustainable fiber throughout its lifecycle, is produced from renewable wood pulp using a recyclable green solvent. Its manufacturing process is clean and environmentally friendly, with biodegradable waste, making it a representative green fiber product. Known for excellent mechanical and wearable properties, Lyocell is widely used in apparel, home textiles, hygiene materials, and special applications like filter materials and battery separators. However, Lyocell fiber’s tendency to fibrillate in wet conditions—where fibers split into microfibrils—has limited its use in smooth, bright fabrics due to issues like uneven dyeing and poor luster. Domestic research has made significant strides in developing low-fibrillation Lyocell through cross-linking technologies. Concurrently, functional modifications, including antibacterial properties, have become a key focus for enhancing Lyocell’s applicability.

Experimental Preparation of Cross-linked/Antibacterial Lyocell Fiber

The study outlines a two-step preparation process: first, cross-linking Lyocell staple fiber with a selected non-aldehyde cross-linking agent, followed by antibacterial modification using a bio-polysaccharide antibacterial agent.

Step 1: Cross-linking Lyocell Staple Fiber

The cross-linking process utilizes a fiber gel modification technique. Wet Lyocell fiber, spun from cellulose/NMMO solution, is treated with a cross-linking bath before drying and densification. The primary cross-linking agent used is 1,3,5-Triacryloyl-hexahydro-1,3,5-triazine (TAHT). Key Process Parameters for Cross-linking:

• Cross-linking bath concentration (cross-linker + catalyst): 2.0~4.0%
• pH of cross-linking bath: 10.0~12.0
• Cross-linking temperature: 45~70°C
• Cross-linking time: 4~8 minutes
• Fiber liquid expression rate: 65~85%
• Cross-linking fixation temperature: 90~130°C
• Cross-linking fixation time: 20~30 minutes

The research optimized these parameters to achieve a high degree of cross-linking, measured by the wet abrasion resistance​ (number of rotations until fiber breaks). Results showed that cross-linked Lyocell staple fiber achieved a wet abrasion count of over 500 cycles, indicating excellent anti-fibrillation performance. While cross-linking slightly reduced dry tensile strength (by 14.83%), wet tensile strength (by 21.63%), and dry elongation at break (by 30.87%), the mechanical properties still met the top-grade criteria of the industry standard T/CCFA01026-2016 for fully cross-linked Lyocell staple fiber.

Step 2: Antibacterial Modification of Cross-linked Fiber

Following cross-linking, the fiber underwent antibacterial modification using a reactive bio-polysaccharide antibacterial agent. This agent reacts rapidly with cellulose molecules at room temperature, forming stable ester bonds for durable antibacterial effects. Optimized Antibacterial Modification Parameters:

• Antibacterial bath concentration: 0.15~0.25%
• Antibacterial bath pH: 5.0~8.0
• Antibacterial bath temperature: 20~40°C
• Antibacterial treatment time: 2~3 minutes

Testing revealed that the antibacterial treatment had a minimal impact on the fiber’s mechanical and cross-linking properties. Crucially, after 50 standard washes, the cross-linked/antibacterial Lyocell fiber demonstrated exceptional antibacterial rates: 91% against Staphylococcus aureus, 98% against Escherichia coli, and 92% against Candida albicans, far exceeding the required standards.

Analysis of Key Technologies

The study highlights several critical technological innovations:

1. Catalyst System:​ A novel, cost-effective, and environmentally friendly phosphorus-free alkaline catalyst was developed to replace traditional Tripotassium Phosphate (TSP) for TAHT, reducing environmental impact and cost.
2. Bath Preparation and pH Control:​ Precise control of the TAHT mother liquor concentration and bath pH was essential to ensure solubility, stability, and effective cross-linking reaction with cellulose hydroxyl groups.
3. Thermal Fixation:​ Heating the fiber after cross-linking bath treatment solidified the network structure formed between cellulose and the cross-linker, enhancing structural integrity and minimizing performance loss.
4. Processing Method:​ A refining method with online淋洗 impregnation on a moving chain plate was employed, allowing for efficient and uniform treatment. A secondary cross-linking treatment was used to ensure thorough reaction.
5. Molecular Structure:​ The process constructs a stable composite structure within the fiber. TAHT forms ether bonds with cellulose via a Michael addition reaction, creating a cross-linked network. The bio-polysaccharide antibacterial agent forms ester bonds, anchoring antibacterial groups firmly to the fiber.

Conclusion and Significance

This research successfully demonstrates an integrated preparation technology for low-fibrillation, antibacterial Lyocell fiber.

• Using the non-aldehyde cross-linker TAHT with a tailored catalyst system, the team produced Lyocell staple fiber with a wet abrasion count exceeding 500 cycles, meeting top-grade standards for fully cross-linked fiber.
• Subsequent modification with a reactive bio-polysaccharide antibacterial agent resulted in fibers with outstanding and durable antibacterial properties (>90% inhibition after 50 washes), without compromising the core mechanical or cross-linked performance. This agent also maintains the biodegradable nature of Lyocell.
• The chemical bonding (ether and ester bonds) formed during modification effectively addresses the fibrillation issue while imparting robust antibacterial functionality.

This development of cross-linked/antibacterial Lyocell fiber represents a significant advancement in the functional modification of sustainable fibers, offering new possibilities for high-performance, eco-friendly textiles in medical, hygiene, and apparel markets.

Source:​ Artificial Fibre, Vol.52, No.1, April 2025. “Experimental Study on Preparation of Cross-linked/Antibacterial Lyocell Fiber” by Gao Bing. Keywords:​ Lyocell Fiber, Cross-linking, Wet Abrasion Resistance, Antibacterial Modification, Antibacterial Rate, Sustainable Materials, Green Fiber, Textile Innovation.