Location: Cotton Chemistry and Utilization Research
2020 Annual Report
Objectives
1. Enable, from a technological standpoint, new commercial processes for the production of cotton-based products with enhanced flame retardant and moisture control properties.
2. Enable new commercial processes for manufacturing cotton-based body-contacting materials for use in biomedical, biosensor and hygienic applications.
3. Enable new commercial processes involving supercritical fluids, microwaves, ultrasound, or ionic liquids for the production of cotton-based products.
Approach
The U.S. cotton industry continues to face supply and demand concerns. Since cotton is used in manufactured products, the industry has been challenged by the downsizing of manufacturing facilities that traditionally provide a major underpinning to domestic cotton consumption. Thus, with the goal of giving U.S. cotton utilization a competitive edge, research emphasis will be placed in cotton fiber science and product development where consumer and industrial needs are unmet and show promise. Some of the areas of consumer need for cotton products and process potential are flame retardant durable goods and apparel, and nonwoven body-contacting materials including improved wound dressings and hygienic/incontinence nonwovens, advanced nonmaterial’s. Enabling technologies that will enhance the likelihood of success and keep pace with industrial innovations include enzymatic bioprocessing, microwave-assisted synthesis and nanotechnology. To accomplish this, a three part approach will be taken: 1) Synthesizing FR compounds will include cross-linking small molecules, binding agents and reactive electrophilic functionalities. The treated fabrics will be tested using standard FR tests and the pyrolysis mechanism and gas emissions will be assessed to develop robust FR treatments for potential commercialization. 2) A broad set of characteristics implies a varied approach to design and preparation of cotton-based prototypes as body-contacting materials. Hemostatic and chronic wound dressings, incontinence absorbents, associated top sheet(s), and contiguous acquisition and absorbent layers of these materials constitute one general group, and nanocellulosic protease biosensors still another. Structure activity relations in turn rely on structural analysis including electrokinetic parameters (fiber surface chemistry),fluorescence, colorimetry, infrared spectroscopy, x-ray crystallography, and computational chemistry to list some of the primary and pivotal technologies to enable structure activity relations. 3) Four technological processes (supercritical carbon dioxide fluid, microwave radiation, ultrasonic energy, and ionic liquids) will be collectively explored as avenues of research, leading to the development of value-added products derived from cotton cellulosic sources. This multifaceted technological approach will ensure that leads are generated in the form of novel synthetic flame retardant (FR) compounds, nonmaterial’s, extruded bioorganic fibers, moisture control fabrics, ethanolic biofuel, and bio-finished cotton fabrics.
Progress Report
Progress has been made in the final year of the project cycle to bring it to a fully successful point in meeting the five-year objectives. The objectives fall under National Program 306, Component 2, Quality and Utilization of Agricultural Products, Non-Food. Progress on this project focuses on Problem 2A to increase or protect the market demand for (or increase the value of) existing U.S.-produced non-food bio-based products derived from agricultural products and byproducts. ARS researchers in New Orleans, Louisiana, have developed new products, applications, and processes for expansion of domestic cotton in the areas of: (1) moisture control properties and hygienic and cotton fabric hand applications; (2) conversion of biomass to nanocrystals and nanofiber; (3) flame retardant cotton; (4) utilization of enabling technologies for improved flame retardant cotton, and antimicrobial protein conjugates of cotton; (5) cotton-based blood clotting (hemostatic) and antibacterial dressings; 6) hygienic diapers and pads for incontinence, and 7) chronic wound dressing sensors to detect harmful levels of wound proteases.
Moisture control applications in support of Objective 1. The specific nature of textile material absorbency is poorly understood due in part to the complex interaction of fluid transport and fabric design. ARS researchers at New Orleans, Louisiana, have investigated this problem on different cellulosic materials which possess a wide range of water absorbency. Data from the cellulosic materials indicate that variations in crystalline size and quantity affect the water retention properties of the material. The chemical modification of various cellulose substrates has provided insights into the unique and specific reactivity’s of these substrates and aided a stakeholder who sought improved absorbency from cotton fabrics.
Flame retardant cotton in support of Objective 1. Cotton contains naturally occurring chemicals that tend to confer flame retardant activity to nonwoven cotton fabrics. Research has shown how naturally occurring polyphenol compounds from plants, tannic acid, act with sodium ions to create a robust thermal barrier on cotton. Analysis of the rate of fabric burning by ARS researchers at New Orleans, Louisiana, revealed that the outer layer containing tannic acid decomposes in a two-step reaction, producing a distinctive protective barrier with post-burn surface features.
Cotton fabrics with multiple layers of intumescent nano-coatings, which are composed of phosphorus-nitrogen rich polymers, provides good flame retardant properties. The LbL (layer-by-layer) method was initiated by ARS researchers at New Orleans, Louisiana, with a flame retardant formulation containing casein, nano-clay and inorganic compounds as key constituents. By treating the cotton fabric with coatings, composed of phosphorus-nitrogen rich polymers the layer-by-layer assembly conferred anti-flammable properties to the cotton material.
Bleeding control dressings in support of Objective 2. A nonwoven dressing prototype that contains unbleached cotton to enhance clotting and absorbance for bleeding control has been developed and commercialized. The dressing is 33 percent lighter and 63 percent more absorbent than the standard crinkle-type cotton dressing made with bleached cotton. The dressing was commercialized as TACgauzeTM in 2018. Cotton dressings were used as a substrate for procoagulant formulations designed to be applied for hemorrhage control. Procoagulants were attached to cotton wound dressings designed to work when placed through a pool of blood in hemorrhaging wounds. The dressings are being developed with a formulation that adheres the procoagulants to the dressing surface without release into the bloodstream.
Antimicrobial dressing in support of Objective 2. Wound dressing that has both bleeding control properties and is antimicrobial was developed. The dressing has 99.99 percent antibacterial activity against both gram negative and gram positive bacteria and was developed for prolonged field care and treatment of pressure ulcer patients. The antimicrobial, bleeding control gauze was designed to be highly absorbent and lightweight for carrying in Individual First Aid Kits. The dressing construction is based on the simple addition of ascorbic acid to nonwoven dressings through traditional textile processing operations.
Nonwoven cotton in diapers in support of Objective 2. Cooperative Research and Development between a cotton farmer and ARS researchers has resulted in a domestic cotton-based nonwoven diaper that is now a named product sold in Target and other major vendor chains throughout the U.S. Thus, R&D on enhancing comfort and performance efficiency of diapers and hygiene pads led to products that improved domestic consumption of cotton. In collaboration with a cotton farmer, ARS researchers investigated fluid absorbency and comfort on different cotton blends composed of cotton fibers supplemented with small amounts of some man-made fibers. The results of the collaboration demonstrated cotton fabrics had improved properties of softness, smoothness, flexibility, and formability while promoting rapid passage of fluid to the diapers absorbent core. The end result of this cooperative effort has been the incorporation of cotton into commercial diapers and feminine care products.
Biosensors in support of Objective 2. Advances in nanotechnology hold promise to revolutionize healthcare through diagnosis at the point of care by using biosensors. By using highly sensitive sensors that can detect small amounts of proteins (biomarkers) associated with human disease more rapid diagnosis is possible. ARS researchers employed extremely small cellulosic particles termed ‘nanocellulose’ extracted from cotton to prepare thin, high surface area films that can be used as sensitive biosensors in chronic wounds. Thus, the films were developed into sensors with properties that allow detection of important disease biomarkers while also being useful as wound dressings. The sensor’s excellent performance in biological environments also makes them suitable for agricultural pest detection.
Microwave-assisted technology in support of Objective 3. Microwave-assisted one pot chemical treatment under minimum amounts of solvent condition is a valuable technique compared with traditional chemical treatment. The new protocol has the advantages of shorter reaction time, simple procedure and environment friendly green concept. As a result of this study, an economic inorganic flame retardant finishing treatment based on urea, diammonium phosphate, and casein has been applied to cotton fabrics. The new microwave-assisted method will be of interest and use to professionals engaged in new material design in textile industries.
Supercritical carbon dioxide for cotton in support of Objective 3. An innovative approach for preparation of flame retardant cotton fabric was obtained by utilizing supercritical carbon dioxide (scCO2). A novel phosphorus nitrogen compound was designed and synthesized with flame retardant properties, and the chemical structure characterized. Cotton fabrics were treated with the flame retardant compound using scCO2 as a solvent vehicle for the chemical reaction. The use of scCO2 enables the coating of cotton fibers as a ‘wrapping layer’ to protect the cotton fabric at a fiber level from being destroyed by heat and flame. It was determined through thermal analysis of the fabric’s reaction to fire that the mechanism of flame retardant activity may also be attributed to a sulfur heteroatom bonded to phosphorous in the cotton.
Bioprocessing in support of Objective 3. The use of proteins catalysts (enzymes) that remove unwanted constituents in cotton textiles is viewed as a viable alternative to traditional scouring approaches that utilize harsh caustic substances consuming large amounts of water and generating large volumes of waste. ARS scientists developed combinations of various enzymes that work synergistically in bio-preparation and bio-finishing of cotton textiles by using ultrasound energy to enhance the conditions. This advance represents significant cost savings and alleviates health concerns associated with implementing this technology in the textile industry. A new system of rollers was developed for continuous fabric processing.
Production of cellulose nanocrystals and nanofibers from agricultural by-products in support of Objective 3. Cotton fiber production from gin mills leaves millions of tons of agricultural by-products which have little to no value and are either buried or burned causing adverse environmental impact. ARS researchers showed that these low-value materials can be turned into value-added products through mechanical and chemical processing, transforming them into small particles termed ‘nanocellulose’, which has high value with many potential uses. ARS research has progressed from learning how to process the crude agricultural materials to fully characterizing the nanocellulose products. The impact of the work is that cotton gin waste increases in value from a valueless commodity to $2 per gram. Work on chemical modification will potentially increase their value to over $20 per gram. ARS researchers have also discovered that gin waste can be used to produce a fiber form of the nanocellulose termed nanofibers. The nanofibers are similar to nanocellulose, but with longer lengths and expanded applications. Solid-state cotton-metal catalysts with sustainable and renewable activity in support of Objective 3. A new application of brown cotton was discovered. For the first time ARS researchers demonstrated that palladium and gold nanoparticles deposited within brown cotton fibers can be used as a catalyst in chemical reactions that make sophisticated chemicals from simple ones. The cotton-metal fibers could be reused up to nine times, thus demonstrating their durability and sustainability.
Accomplishments
1. Domestic cotton use in diapers and incontinence products has significant impact on consumption. The U.S. cotton industry and cotton farmers have had continued challenges amidst a very competitive and difficult economic climate. To address this issue, ARS researchers at New Orleans, Louisiana, combined forces with domestic cotton farmers to demonstrate that highly cleaned unbleached cotton is an ideal fiber for use in the high-volume market sector of nonwoven diapers and hygiene products. The utility and comfort of using cotton fibers in baby diapers and adult incontinence products was demonstrated with fluid transport and comfort index models. The results show cottons usefulness in all functional parts of these types of skin-contacting products. The impact of the research is also reflected in a new surge in demand for domestic cotton, which is now being used as a fiber component at a 50-100 percent composition level in some diapers and incontinence pads. Moreover, cotton farmers have reported that in the last three years domestic consumption of cotton for use in diapers and hygiene products increased by sixty thousand bales annually due to demand for use in diapers and hygiene products, solely. It is predicted that a compound annual growth rate of 18.6 percent in this market sector will continue to a domestic cotton consumption level of twenty eight thousand tons by the Year 2022.
2. Wound dressing developed for prolonged field care of soldiers and pressure ulcers patients. One in five deaths worldwide has been attributed to sepsis which can often arise from infected wounds and pressure ulcers. Moreover, some harmful bacteria use acute wounds to their advantage to proliferate causing a danger of infection if the wound is not treated in a timely manner. Thus, soldiers who suffer traumatic wounds in isolated and remote parts of the world where medical care is delayed, and patients who have developed pressure ulcers in hospitals and nursing homes are at risk for developing sepsis. To address this issue, ARS researchers at New Orleans, Louisiana, have developed a special type of cotton nonwoven dressing that is treated with ascorbic acid and the outer layer of the cotton fiber retained to promote healing and prevent infection. The dressing is highly absorbent, lightweight, and sheds fewer fibers. The dressing is also designed to promote clotting and kills 99.99 percent of both gram positive and gram negative bacteria. In addition it is antiviral at the 99.99 percent level and releases small amounts of hydrogen peroxide to help mobilize wound-healing cells at the wound site. The dressing which is undergoing FDA approval will soon be made available as a Berry Amendment compliant commercial product for prolonged field care in the battlefield and in hospitals and nursing homes.
3. Layer-by-layer treatments for cotton show promise as anti-flammables. The availability of low-cost fabrics with improved thermal protection for medical, military, and large-scale emergency is an unmet need. Thus, the advantage of using an economical cotton-based approach with a wide range of short term uses has made layer-by-layer flame retardant cotton particularly attractive. To address this, ARS researchers at New Orleans, Louisiana, have pioneered a layer-by-layer self-assembly process, which is a simple method to incorporate clay particles and low cost milk proteins that are dispersed together in a repetitive layered application onto cotton fabrics. The use of clay treatments in this process provides significant physical and chemical properties to cotton that imparts favorable anti-flammable, moisture management, strength, and absorptivity applications. In addition these applications are designed to be permanently attached to the cotton and not wash off during laundering. The Berry Amendment compliant nature of these fabrics make them of potential interest to the Department of Defense. Moreover, the compound annual growth rate for layer-by-layer fabrics in the U.S. market is 6.4% by 2024, and it is thought that market demand for these types of cotton based products will increase even more as they are made more durable.
4. Antiviral cotton nonwovens. Antiviral cotton nonwovens and compounds: A study conducted during the maximal telework period by ARS researchers at New Orleans, Louisiana, in collaboration with a medical trauma wound dressing company revealed that a jointly developed cotton nonwoven product exhibited 99.999% antiviral activity after one hour of contact with the fabric. The company plans to develop the prototype for use in face masks. Further testing is being conducted. A study was also conducted where compounds were designed by ARS researchers at New Orleans, Louisiana, and synthesized (performed by a contract company) for their potential antiviral activity and use in virus detection. The compounds are based on molecular models of the Sars-Covid 2 virus mechanism of interaction with the host cell. The compounds will be studied with collaborators for their ability to inhibit and detect Covid 19.
Review Publications
Easson, M.W., Jordan, J.H., Chang, S., Bland, J.M., Condon, B.D. 2020. Investigation of bisphenol-substituted spirocyclic phosphazenes as cotton textile-based flame retardants. Journal of Engineered Fibers and Fabrics. 15:1-10. https://doi.org/10.1177/1558925020920887.
Jordan, J.H., Easson, M.W., Condon, B.D. 2019. Alkali hydrolysis of sulfated cellulose nanocrystals: optimization of reaction conditions and tailored surface charge. Nanomaterials. 9(9):1232. https://doi.org/10.3390/nano9091232.
Ling, Z., Edwards, J.V., Nam, S., Xu, F., French, A.D. 2020. Conformational analysis of xylobiose by DFT quantum mechanics. Cellulose. 27:1207-1224. https://doi.org/10.1007/s10570-019-02874-3.
