1a. Objectives (from AD-416):
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.
1b. Approach (from AD-416):
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.
3. Progress Report:
Agricultural Research Service (ARS) Cotton Chemistry Utilization scientists at Southern Regional Research Center (SRRC), New Orleans, Louisiana, have developed new products, applications, and processes for expansion of domestic cotton in the areas of: 1) Moisture Control Properties; 2) Hygienic Applications; 3) Bio-processing; 4) Rapid blood clotting wound dressings; 5) Chronic wound dressing materials; 5) Cotton-based nanomaterial sensors; 6) Flame retardant materials; and 7) Microwave assisted technology. 1) Moisture Control Applications for wearable fabrics related to objective #1. Sports apparel is constructed using a wide range of moisture management materials that are poorly understood. In order to better understand these materials, a comparative study was completed on the derivatization of the cellulosic materials used in sports apparel using a water-binding functionality. In this study, water retention properties were examined after chemically modifying cotton fibers. Absorbency tests examined the water retention properties of cotton-based materials. In a surprising discovery, reaction conditions used to improve moisture control resulted in a broad range of moisture properties, depending upon the cellulose substrate. It was found that an optimal ratio of isopropanol and water yielded the highest degree of substitution and highest level of moisture retention. In a separate project, cottonseed protein was used as a binding material in moisture management textile applications for a non-petroleum-based material which is sustainable and environmentally-friendly. Cottonseed protein was added to nonwoven greige cotton and tensile strength, and was found to increase fabric strength and while retaining water-repellant properties. This research provided a greater understanding of the moisture management properties of these materials and their reactivity’s. A better understanding of material science will lead to improved cotton material selection and enhanced moisture control properties. 2) Bioprocessing to replace caustic scouring of cotton related to objective #3. In order to lessen the intensive natural resource demands and the environmental impact of current textile processing methods to remove waxes and pectin from cotton needed for bleached fabrics used in apparel and upholstery, research is being undertaken on an alternative processing method which is more sustainable. Enzyme based bio-processing was coupled with ultrasound technology to enhance the efficacy of the enzyme treatment of greige cotton. Optimization of a pilot-scale approach has allowed for several yards of greige cotton fabric to be continuously fed into the ultrasound reactor. Experimental products were analyzed and data trends were correlated from research results, which furthered the development of this sustainable bioprocessing method. New processing equipment, consisting of a system of rollers for continuous fabric feed and uptake, was successfully designed, manufactured and tested. It was found that this new equipment could be inserted into the existing equipment set-up without impinging upon the effectiveness of the ultrasound-enhanced bio-scouring process. 3) Cotton-based Blood Clotting (Hemostatic) Dressings which relates to objective #2. Mitigation of battlefield injury and hemorrhage is the highest priority of U.S. military trauma surgeons and researchers, and hemorrhage control is an important first-line measure of treatment by medics or emergency medicine personnel. Prototype cotton-based materials were prepared as nonwoven dressings, and the material’s fibers were tested for their ability to promote clotting using a method that measures the rate of clot formation upon mixing fiber samples with blood (thromboelastographic). From a series of one hundred different blended material compositions consisting of varying mixes of cotton and synthetic fibers, lead materials were identified that gave improved accelerated blood clotting. The lead materials were tested at Virginia Commonwealth University, Department of Reconstructive Surgery, in platelet-fresh whole blood for their effect on clotting times (Lee White Clotting Assay). Cotton-based samples with clay mineral formulations attached revealed blood clotting times in whole blood consistent with hemorrhage control properties. Untreated compositions of fiber blends were also found to yield improved acceleration of clotting when compared with commercial standards. 4) Chronic wound dressing and protease sensor materials. The removal of harmful proteases helps prevent damage to growth factors and the extracellular matrix essential for completion of healing in non-healing wounds, and the stimulation of cell proliferation is equally as important. Cotton-based nanocellulosic materials were developed that remove proteases from mimicked wound fluid as a function of increasing negative charge conferred to the material in its preparation. In a separate approach to stimulating wound healing in chronic wounds the concept of low levels of hydrogen peroxide to stimulate wound healing was applied to cotton. In previous work we characterized the role of copper and ascorbic acid supplemented to unbleached cotton to produce therapeutic levels of hydrogen peroxide that would stimulate wound healing. A new procedure to affix copper to materials using ascorbic acid was developed as a green alternative. This approach to treating unbleached cotton with nontoxic agents is useful both to prevent leaching of the reagents from the material, and as a source of hydrogen peroxide that is generated at therapeutic levels for as much as two days. 5) Intelligent Cotton Dressings. Cellulosic and nanocellulosic materials derived from cotton were evaluated as protease sensors to interface with a protease-modulating wound dressing for chronic wound treatment. The ‘intelligent dressings’ detect and remove proteases from a simulated wound-like fluid solution via the use of woven and nonwoven materials prepared from varying ratios of different forms of nanocellulose. Dressing properties including water vapor transmission rates, porosity, pore size, and increase in absorption capacity were determined, and found to be within the range suitable for use in minimally to moderately exudative wounds. Materials in this study were found to be compatible with a wide range of dressing types including gauze, films, and hydrogels, and hydrocolloids. 6) Flame Retardant Cotton Materials which relates to objective #1. Flame retardant coatings that swell to protect a fabric by sealing gaps of exposure during a fire are referred to as intumescent. Treating cotton fabrics with intumescent nano-coatings, composed of phosphorous-nitrogen rich polymers and prepared via layer-by-layer (LbL) the cotton fabric provided good flame retardant properties. The LbL. method was initiated with a flame retardant formulation containing casein, nano-clay and inorganic compounds as key constituents. By treating the cotton fabric with coatings, composed of phosphorous-nitrogen rich polymers the layer-by-layer assembly conferred anti-flammable properties to the cotton material. All coated fabrics passed standard 45 degree angle and vertical flammability tests which demonstrated the flame retardant efficacy of the materials. 7) Microwave-assisted preparation of flame retardant cotton relates to objective #3. A chemical treatment method for flame retardant cotton fabrics was found to achieve the attachment of high amounts of flame retardant agent to the cotton fabrics by using Microwave-assisted technology. The combination of phosphorous and nitrogen offers several advantages including char formation from phosphorous, incombustible gas without toxic smoke from nitrogen, and above all, synergistic property from both that enhances the ability to retard flame propagation. It is mainly useful to design and develop novel environmentally friendly small molecules and formulations that allow textiles of commerce to be flame resistant. Recently, we have developed an efficient method for the chemical treatment of a series of flame retardant compounds such as economically commercial available inorganic compounds (urea and diammonium phosphate) and transition metal compounds (zinc, silver, magnesium, and iron) on cotton fabrics. Our results demonstrate that iron sulfate hydrate treated textile products show better flame retardant activity so far.
1. Moisture control applications. The specific nature of textile material absorbency is poorly understood due in part to the complex interaction of fluid transport and fabric design. ARS scientists at New Orleans, Louisiana, have investigated this problem on different cellulosic materials which possess a wide range of water absorbency. The absorbent properties of control and derivatized cellulose material were examined using sophisticated technologies. Data from the cellulosic materials indicate that variations in crystalline size and quantity affect the water retention properties of the material. The chemical derivatization of various cellulose substrates has provided insights into the unique and specific reactivity’s of these substrates. These insights have led to shorter experimental reaction times and the conservation of chemical resources in the preparation of the derivatized substrates. Experiments with cottonseed protein have determined that it is a viable alternative to non-sustainable petroleum-based additives for moisture management in textile applications.
2. Cotton-based Blood Clotting (Hemostatic) Dressings. Uncontrolled blood hemorrhage from traumatic wounds is the leading cause of death on the battlefield, and the second leading cause of death in the civilian trauma setting. Thus, rapid blood clotting is essential for initial survival and optimal recovery. Cotton dressings are carried by armed forces soldier’s first aid kit. Cotton-based materials have been developed by ARS scientists in New Orleans, Louisiana, for these types of applications where hemorrhage or excessive bleeding is treated. The potential impact of these cotton-based hemostatic dressings is to be found in improved dressings used by the armed forces and first responders.
3. Flame retardant cotton. Pioneering layer-by-layer self-assembly process would provide an excellent thermal protection for medical, military, and large scale emergency uses where a low cost, short-term product is desired. Layer-by-layer (LbL) is a simple method to incorporate various polymers, colloids, or nano-disperse clay particles onto cotton fabrics. These clay treatments provide significantly different physical and chemical properties to cotton including moisture management, strength, and absorptivity. By treating fabric with intumescent nano-coatings, composed of phosphorous-nitrogen rich polymers and prepared via layer-by-layer (LbL) assembly, ARS scientists at New Orleans, Louisiana, found that the cotton fabric can be rendered anti-flammable. These materials are designed to be permanently attached to the cotton so as to not wash off during laundering. There is little doubt that if fire retardant treatments can be made safer and more durable the market for cotton will increase greatly.
4. Microwave-assisted technology. Microwave-assisted one pot chemical treatment under minimum amounts of solvent conditions, developed by ARS scientists at New Orleans, Louisiana, is a more valuable technique compared with traditional chemical treatment on textile, thus pad-dry-cure method. The new protocol has the advantages of shorter reaction time, simple procedure and environment friendly green concept. The new Microwave-assisted method will be of interest and use to professionals engaged in new materials designing in textile industries to create new marketable uses such as firefighter apparel, institutional draperies and upholstery, carpet, transportation blankets and seat covers, children’s sleepwear, and bedding.
5. Cotton-based blood clotting (hemostatic) dressings. Uncontrolled blood hemorrhage from traumatic wounds is the leading cause of death on the battlefield, and the second leading cause of death in the civilian trauma setting. Thus, rapid blood clotting is essential for initial survival and optimal recovery. Cotton dressings are carried by armed forces soldier’s first aid kit. However greige cotton fibers initially demonstrated enhanced clotting ability over bleached cotton fibers taken from cotton gauze. ARS scientists at New Orleans, Louisiana, found that fibers taken from nonwoven materials composed of greige cotton and synthetic fibers demonstrated a further improvement in accelerated clotting based on blood clotting measurements as a function of material composition and structure. These materials represent leads in the R&D of hemostatic wound dressings that would likely be suitable for accelerating clotting in treatment of vascular trauma. The potential impact of these cotton-based hemostatic dressings is to be found in improved dressings used by the armed forces and first responders.
6. Functional chronic wound dressings that stimulate healing. Human skin wounds have been termed a ‘major and snowballing threat to the economy.’ It is estimated that chronic wounds affect around 7 million patients in the United States and the wound management market is estimated to reach a value of $4.4 billion in 2019. Thus, excessive resource utilization could be improved by the availability of low cost highly functional dressings that would actually stimulate wound healing. Bleached cotton dressings have been a staple of wound care for hundreds of years. Recently ARS scientists at New Orleans, Louisiana, have found that highly cleaned greige cotton, which still retains waxes and pectin, generates levels of hydrogen peroxide commensurate with those found to enhance cell growth in wounds. Nonwoven forms of both brown and white cotton were compared, and it was found that brown cotton contained higher levels of molecular constituents associated with higher levels of hydrogen peroxide than white cotton. More recently we have found that some varieties of white cotton also appear to generate similar levels of hydrogen peroxide, thus making them lead candidates for further development of chronic wound dressings.
7. Bioprocessing. 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 at New Orleans, Louisiana, 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. Statistical software analysis of bio-processing experiments determined that ultrasound can be safely applied to enzyme-based scouring of fabrics when used in an industrial setting, and without the need for expensive sound-attenuating enclosures for the equipment or hearing protection for the textile workers. 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 successfully designed, manufactured and tested, allowing for the continuous fabric feed into the ultrasonic bath. The ability to continuously feed fabric is a significant improvement over previous equipment designs and is an important step towards large-scale commercialization.
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Edwards, J.V., Prevost, N.T., Nam, S., Hinchliffe, D.J., Condon, B.D., Yager, D. 2017. Low-level hydrogen peroxide generation by unbleached cotton nonwovens: implications for wound healing applications. Journal of Functional Biomaterials. 8(1):1-13. doi:10.3390/jfb8010009.
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