Abstract:

Objective As a natural polymer of high molecular weight, cotton fiber has advantages in wide availability, rich reactive chemical sites, good natural non-toxic properties, softness, and high comfort. It is widely used in the development of superhydrophobic and other composite functional textiles. Currently, the prepared superhydrophobic and other composite functional cotton fabrics demonstrate the disadvantages in low chemical durability of cotton fabrics, large impact on the wearability of cotton fabrics during the modification process, and failure to meet the wear requirements. This research aims to improve the durability of antibacterial superhydrophobic cotton fabrics while maintaining their wearability, which is a research challenge.

Method This study works on the modification of cotton fiber by using L-cysteine (L-Cys) as crosslinking agent. The carboxyl groups of L-Cys molecules underwent esterification with the hydroxyl groups of cotton fibers, resulting in the grafting of L-cysteine onto the surface of cotton fabrics. This provides thiol groups for the subsequent introduction of silver nano particles. At the same time, the thiol group of L-Cys molecules chelated silver nano particles (AgNPs) through coordination bonds, enhancing the binding force between AgNPs and cotton fibers, which further increases the surface roughness of cotton fibers, laying the foundation for the preparation of superhydrophobic cotton fabrics. After this step, the surface energy of cotton fabrics is further reduced by a polydimethylsiloxane polymer coating (PDMS), resulting in the preparation of cotton fabrics with antibacterial superhydrophobic multifunctional properties. In order to further explore the potential mechanism of this synergistic effect existing between cotton, AgNPs and PDMS, the modified cotton fabrics for chemical structure, microstructure, superhydrophobic, antibacterial properties, and durability were tested. In the practical application of antibacterial super-repellent cotton fabrics, apart from the keen consideration and assessment of the durability property of the fabric, it is also necessary to consider the wearing performance of the antibacterial superhydrophobic cotton fabrics. Therefore, the influences of these finishing processes on the pemeability and softness of the fabric were evaluated, aiming at maintaining the comfort of the fabric while enhancing antibacterial superhydrophobic properties.

Results Experimental results showed that untreated cotton fabric (OCF) fibers were flat and smooth with no attachments. The modified cotton fibers were covered with granular-shaped AgNPs. However, after PDMS coating, a dense film was formed on the surface of the fibers covered with AgNPs. This led to the reduction in the surface energy of the cotton fabrics which further improved the load retention of AgNPs. The antibacterial superhydrophobic cotton fabric (P-AgCF) prepared by grafting AgNPs and PDMS coating met the standard of superhydrophobic. The static contact angle of the antibacterial superhydrophobic cotton fabric surface reached 154.6°, demonstrating excellent self-cleaning functionality. It effectively removed different solution stains due to liquids, such as orange juice, milk, cola, and dye commonly encountered in daily life. Additionally, the antibacterial rate of the antibacterial superhydrophobic cotton fabric (P-AgCF) against Escherichia coli and Staphylococcus aureus reached 98.67% and 97.44%, respectively, indicating excellent antibacterial performance. The durability of the samples was tested by gradually increasing the number of washing cycles. The static contact angle and antibacterial rate against both bacteria species showed slight decreases with increasing washing cycles. However, after 40 washing cycles, the static contact angle still exceeded 150.6°, and the antibacterial rate against both bacteria species was higher than 95.25%, indicating excellent durability. Additionally, this finishing process did not affect the pemeability and the softness of the cotton fabrics.

Conclusion A synergistic method of grafting and coating finishing is adopted to prepare cotton fabrics with both antibacterial and superhydrophobic functions. The static contact angle of the multifunctional cotton fabric surface reaches 154.6°, and it has excellent self-cleaning performance. It has excellent antibacterial properties against both Escherichia coli and Staphylococcus aureus. In addition, after 40 washing cycles, the static contact angle still exceeded 150.6°, and the antibacterial rate against both bacteria species was higher than 95.25%, indicating excellent durability, indicating excellent durability. Additionally, this finishing process did not affect the pemeability and the softness of the cotton fabrics. In summary, this study provides an effective method for preparing cotton fabrics with antibacterial, superhydrophobic, durable and other multifunctional properties. This fabric has broad application prospects in medical care, home furnishings, sports and other fields, and it is expected to bring more convenience and comfort to people's lives. Additionally, this preparation method also provides new ideas and references for functional modification of other fiber materials.

Key words: cotton fabric, antimicrobial, superhydrophobic, durability, self-cleaning, functional textiles