Objective 1: Enable, from a technological standpoint, new commercial products and market applications for cotton containing nonwoven materials. Objective 2: In collaboration with the ARS Cotton Fiber Bioscience Lab, enable a new commercial variety of white cotton exhibiting improved flame retardancy. Objective 3: Use nanotechnology to enable new commercial cotton products.
Through fiber selection and blending combined with modification of nonwoven bonding processes, specialty and commodity cotton-based nonwoven fabrics can be produced which are suitable for new disposable or semi-durable applications. The approaches primarily include the following. Procure the required raw materials from commercial sources and using the in-house, commercial-grade production equipment and procedures, sufficient quantities will be prepared of the required fibrous batts for the downstream needlepunch and hydroentanglement of the fibers into nonwoven fabrics. The research products will be comprehensively tested for the required pertinent information to closely assess their values for the targeted end-use products. Based on the process and fabric evaluations, the most promising research fabrics/products will be selected for duplicate confirmation before embarking on their pilot operations. Offer the selected fabric(s) and explore industrial partners for mutual cooperation to take the research product to industrial trials. The development of new cotton fibers with unique properties, and novel chemical applications for cotton-based nonwovens will be explored. Cotton fibers with specific inherent properties such as natural increased flame resistance (FR) observed in brown cotton fibers will reduce the need for external applications of chemical additives to achieve the desired functionality. The scientific approach will attempt introgression of improved FR from brown cotton fibers into fibers of conventional white cotton varieties through traditional breeding approaches while attempting to identify and characterize the compound(s) responsible for the increased FR. The molecular mechanisms of FR in brown cotton fibers are unknown and a comparative chemical analysis between selected brown and white fiber cotton varieties has the potential to identify novel biomolecules or other molecular components that can be adopted as naturally occurring additive chemistries to existing nonwoven textiles. The production of durable antimicrobial cotton products using nanotechnology will be explored. Since silver (AG) nanoparticles (NPs) formed inside the cotton fiber are expected to be stable and to release antimicrobial ions in a controlled manner for the protection against harmful microorganisms, Ag-cotton nanocomposite fiber can find new technical nonwoven applications, such as wound dressings and biomedical devices. To verify the continuous and long-lasting antimicrobial activity of Ag NPs caged inside cotton fiber, the kinetic study on the Ag ion release in aqueous environment will be examined, and the variation of the antimicrobial properties of the resulting cotton will be monitored. This research will also focus on the incorporation of other multifunctional NPs into cotton fiber. The production of nano-sized metal or transition metal particles inside cotton fiber would provide the increased flame retardant performance as well as durability. As one of non-halogenated flame retardant solutions, this research will focus on transition metal elements that have known flame retardant effects and the synthetic methods of their NPs.
In support of the Cotton-based Nonwovens Project Plan 6054-41000-106-00D which operates under National Program 306, “Product Quality and New Uses, Component 2: Non-food, Problem Statement 2.B – Enable technologies to produce new and expand marketable nonfood, nonfuel biobased products derived from agricultural feedstocks, ARS researchers at New Orleans, Louisiana, conducted experiments over a five-year period that promoted and increased the market share of cotton fibers in nonwovens textiles. Objective 1, significant progress was made by ARS researchers at New Orleans, Louisiana, to facilitate the release of new commercial products and market applications for cotton containing nonwoven materials. Extensive research was conducted that incorporated raw cotton fibers into the nonwovens production process with emphasis on hydroentanglement machinery that utilized high pressure water jets to form fabrics. Processing variables that effected the structural and performance properties of the resultant fabrics included speed, water pressure, hydraulic energy, jet diameter, and number of jets per inch. These variables were extensively studied to optimize processing parameters to achieve cotton fabric properties for specific nonwoven end-use applications. Nonwoven fabric properties that were examined included absorbency which could be directly increased or decreased as a function of processing parameters. In this manner nonwoven fabrics produced from raw cotton fibers could be made absorbent for hygiene applications or hydrophobic for improved fluid handling and moisture management properties where moisture is moved away from contact with the body rather than being absorbed (e.g. diapers, menstrual pads, incontinence briefs, etc.). Given the recent increased usage of cotton fibers in nonwovens textile applications, these findings served as processing guidelines for stakeholders including roll goods manufacturers, converters, and brand name owners. During the course of this five year project, ARS researchers at New Orleans, Louisiana, collaborated extensively with stakeholders based in part on cooperative research agreements that initially facilitated the development of cotton-containing nonwoven prototypes, and ultimately the release of commercial processes and products that increased the market share of cotton fibers in nonwoven textiles. Specific examples of impactful progress that resulted from collaborative research with stakeholders and scientists within the USDA included: 1) Successful transfer of technology enabling the use of greige cotton in a commercially available disposable diaper; 2) Successful transfer of technology enabling an optimized fiber blending process that provides for a “whiter” appearance of 100% greige cotton nonwovens for use in hygiene, medical, and other applications where consumer response to product appearance is critical; 3) Successful development of an optimized disinfecting solution compatible with cotton applicators such as rags and disposable wipes that was efficacious against gram positive and gram negative bacteria that included Pseudomonas aeruginosa, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant enterococcus; 4) Demonstrated feasibility of using cotton-based wipes composed of 100% raw cotton staple fibers for sensitive precision applications such as aviation wipers; and 5) Successful transfer of technology that resulted in a commercially available hemostatic wound dressing composed of US grown cotton fibers for use by military and first responders. Objective 2, significant progress was made to characterize the physical and flammability characteristic of nonwoven fabrics produced from brown and white cotton fibers. ARS researchers at New Orleans, Louisiana, determined the previously unknown mechanisms by which brown cotton fibers exhibited enhanced flame retardant properties, which was the result of the synergistic accumulation of condensed tannins and naturally occurring inorganic salts. Extensive genetic and gene expression studies on brown fiber cotton varieties provided the first report that identified the mutation resulting in brown fiber color and enhanced flame retardant properties. These research findings were utilized to create a new environmentally friendly, bio-based flame retardant application for textiles using the naturally abundant biomolecule tannic acid together with sodium ions. It was further demonstrated that the enhanced flame retardant properties of brown cotton fibers existed during fiber development well before the fibers matured and bolls opened. During fiber development, brown cotton fibers are white and indistinguishable from the fibers of conventional cotton varieties. The brown color of the fibers does not start to appear until late in development and closer to boll opening. ARS researchers at New Orleans, Louisiana, also determined that colorless precursor molecules were present in the developing fibers prior to appearance of brown color. Taken together, these findings demonstrated the feasibility of manipulating the condensed tannin metabolic pathway to develop a white cotton variety with inherent enhanced flame retardant properties. Under Objective 2 and in collaboration with National Program 301, ARS researchers at New Orleans, Louisiana, utilized a genetically diverse population of cotton plants to identify unique fiber properties that resulted from genetic rearrangements known as transgressive segregation. All the individual cotton plants that comprised this population possessed conventional white fibers that were used to examine natural variations in flame retardant properties using a technique known as microscale combustion calorimetry. In this manner, individual plants were identified that possessed fiber with enhanced flame retardancy that were used to produce nonwoven textiles that self-extinguished during flammability testing. Objective 3, ARS researchers at New Orleans, Louisiana, selected a silver nanoparticle-embedded cotton system and demonstrated its washing durability for the production of permanent antibacterial textile products. The developed embedding technology, which utilizes the natural chemistry and structure of cotton, allows the direct formation of nanoparticles within cotton fibers. The resulting advanced cotton demonstrated superior nanoparticle-leach resistance with 20% and 42% of total silver lost into water and detergent solution, respectively, after 50 launderings, whereas commercial silver nanoparticle-treated textile products lost up to 77% and 93%, respectively, after only 20 launderings. A test collaborated with U.S. Army showed the persistent antibacterial activity of the system after 50 launderings, i.e., 99.99% reductions of Gram-positive and Gram-negative bacteria. Under Objective 3, ARS researchers at New Orleans, Lousiana, developed a practical analytical method for quantifying silver nanoparticles in a washing solution to evaluate the durability of silver nanoparticle-treated textiles using surface-enhanced Raman spectroscopy. This method is based on utilizing the “coffee ring effect”, that is, the formation of a ring pattern after a particle-laden liquid drop dries. The nanosized gap between silver nanoparticles aggregated to the ring was found to generate a “hot spot,” i.e., dramatically enhanced Raman signal, that strongly correlates with the concentration of nanoparticles. In addition to its remarkable sensitivity, the developed method is advantageous over conventional methods by differentiating silver nanoparticles from other silver forms, which conventional methods cannot. This additional function revealed the silver release behaviors of textiles and the fate of silver when silver nanoparticle-treated textiles are washed. Under Objective 3, ARS researchers at New Orleans, Louisiana, developed a new surface-enhanced Raman spectroscopic method to characterize silver nanoparticles in textiles. The conventional analytical method for textiles requires destructive and laborious preparatory work, but the developed method is rapid and non-destructive. Using a common dye that produces a distinct Raman spectral signal, this method not only measures the concentration of silver nanoparticles in textiles but also maps their distribution. Objective 3, ARS researchers at New Orleans, Louisiana, developed raw cotton varieties equipped with hydrophilic properties and heat resistance using biomineralization. Due to their environmental and economic benefits, raw cotton products are gaining increased attention; however, the inherent hydrophobicity of raw cottons limits their application. By mimicking the natural mineralization process, the cotton surface was mineralized with calcium carbonate polymorphs. The mineralized cotton varieties immediately absorbed water and reduced heat release capacity by up to 40%, showing their potential in the application of absorbent and protective nonwoven products.
1. Wash-durable antibacterial cotton by embedding technology. With nanotechnology advancements, silver nanoparticles are popularly applied in the production of antibacterial textile products, e.g., odor-inhibiting socks and anti-infective masks. However, as currently available technologies are based on surface coating, most of nanoparticles applied leach out during washing. ARS researchers at New Orleans, Louisiana, developed silver nanoparticle-embedded cotton fibers by the direct formation of nanoparticles inside cotton fibers. Since the nanoparticles are anchored within the fiber, they are leach-resistant. About 80% and 58% of the total silver nanoparticles introduced were retained in cotton after 50 launderings in water and detergent solution, respectively. A test collaborated with the U.S. Army demonstrated the permanent antibacterial performance of the 50-laundered cotton fabrics. The antimicrobial textile market is rapidly growing, with a forecasted value to reach $1,076.1 million by 2026. The wash-durable antibacterial cotton is currently garnering great interests from national and international textile companies, and its patent application was filed.
2. New analytical techniques to characterize silver nanoparticle-treated textiles. To develop safe and reliable nanoparticle-enhanced products, it is essential to have proper analytical techniques that evaluate the developed technologies and products. However, currently available techniques are complicated, destructive, expensive, and time consuming. ARS researchers at New Orleans, Louisiana, developed two simple, cost-effective, fast, yet accurate surface-enhanced Raman spectroscopic methods to quantify silver nanoparticles. The first method, which utilizes plasmonic hot spots of aggregated nanoparticles, measures silver nanoparticles in a (washing) solution. The second method, which uses a dye to generate a distinctive Raman signal, measures silver nanoparticles in a solid (textile) material. These methods are highly sensitive, accurate, and moreover advantageous over conventional methods by distinguishing silver nanoparticles from other silver species and mapping the distribution of nanoparticles in textiles. They verified the uniformity of the developed silver nanoparticle-embedded cottons and their washing durability. The first method was supported by the ARS Innovation Fund and the National Science Foundation, and its novelty was highlighted as a featured article on the front cover of the journal Analytical Methods.
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