This project directly addressed the immediate need for developing safer multifunctional textiles through a simple and versatile combination of surface chemical functionalization, plasma deposition processes involving more sustainable materials. Nylon/cotton (Nyco) is one of the widely used fabric for soldiers' Army combat uniforms. Nyco combines excellent mechanical properties, abrasion resistance and comfortable to wear. However, Nyco is not flame resistant and does not provide adequate vector protection. There are very few reliable cost-effective solutions that impart durable flame retardancy and vector protection to Nyco. Current flame retardant protective materials (e.g. flame retardant Army combat uniforms [FRACU]) are expensive have deleterious environmental impacts and in many cases, are not produced in the U.S. Although permethrin is used for vector protection, lack of durability of the coating and safety is still of concern. In this work, cost-effective and environmentally benign waste byproducts such as phytic acid were utilized to introduce durable flame retardancy. In addition, plasma-assisted deposition of insect repellents such as permethrin to make a multifunctional Nyco fabric was demonstrated.
Combination of activation of hydroxyl groups on cotton to facilitate chemical surface functionalization followed by plasma assisted deposition of an insect repellent (permethrin) was the approach successfully developed over the course of the project. The insect repellent is locked in position using acrylic monomers followed by crosslinking it under plasma. Extensive characterization of functionalization, thermal and flammability behavior of the multifunctional fabric as well as an assessment of the efficacy of insect repellency of the fabric have been carried out to demonstrate the success of the approach.
Multifunctional Nyco fabric with combination flame retardant properties and insect repellency was successfully demonstrated. The flame retardancy was imparted to the fabric by covalently functionalizing bio-based phytic acid. The treated Nyco fabric successfully passes the standard vertical flame test in accordance with American Society for Testing and Materials D6413. The multifunctional fabric also exhibits excellent thermal stability, improved char formation and a significant reduction in heat release characteristics. The plasma deposited permethrin coating imparts excellent insect repellency with >98% mosquito mortality rate in the World Health Organization Susceptibility Test for Adult Mosquitoes.
This research has provided proof-of-concept data on the efficacy of novel low cost, safer and durable multifunctional coatings for Nyco fabric that imparts both Flame retardancy and insect repellency. This multifunctional fabric will have a direct impact the safety, comfort and operational success of the U.S. Soldiers in harsh environments. These functionalization techniques described are simple, sustainable and readily scalable to large scale manufacturing.