Research Project: Chemical Modification of Cotton for Value Added Applications

Location: Cotton Chemistry and Utilization Research

2016 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
This is the first report for 6054-41430-004-00D. Agricultural Research Service (ARS) Cotton Chemistry Utilization (CCU) 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; and 6) Flame retardant materials. Moisture Control Properties. Moisture Control Properties: 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 modify cotton fibers and hydroentangled fabrics, man-made rayon fibers and hydroentangled fabrics, and man-made viscose fibers. A series of standardized absorbency tests examined the water retention properties of each material type. This provided a greater understanding of the moisture management properties of these materials. A better understanding of material science will lead to improved material selection and enhanced moisture control properties. Hygienic Applications. Currently, consumer demand is driving the market for cotton-containing hygienic products that are white in appearance. Mechanically cleaned greige cotton, which is raw non-bleached cotton fiber with a high standard of cleanliness, has been found to be marketable in hygienic products as a functional material. However, mechanically cleaned greige cotton suffers from a slightly off-white, yellow appearance which consumers do not like. In order to address consumer demands, greige cotton fibers were mixed with blue dyed fibers to produce a product that appears whiter than the original greige cotton. A statistics-based approach to the determination of optimal fiber ratios of blue-dyed fibers with greige cotton was used to determine the highest index of fabric whiteness. Mixed combinations of fibers were examined for color properties using standard methods and instrumentation. These experiments will lead to the expanded use of greige cotton in hygienic applications and gain greater market share through increased consumer demand. Bio-processing. In order to lessen the intensive natural resource demands and the environmental impact of current textile processing methods, research is being undertaken on an alternative processing method which is more sustainable. Over the past year, research has focused on improving the use of enzyme based bio-processing by introducing improved 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. This bio-based processing method accomplishes scouring of the greige cotton fabric without the need for harsh caustic substances that consume large amounts of water and generate large volumes of waste. Hemostatic Dressing Materials. With a goal of developing a battlefield or first responder dressing for wound blood control a series of greige cotton-based materials blended with synthetic fibers were prepared as nonwoven dressings that represent new leads for product development. Fibers from these materials were tested for their ability to promote clotting using a method that measures the rate of clot formation upon mixing fiber samples with blood (thromboelastography), and also evaluated for absorption capacity properties by use of a method to evaluate fiber moisture absorption. Material compositions consisting of a mix of greige cotton, bleached cotton fibers, and synthetic fibers produced varying degrees of blood clotting acceleration. The result of this study produced several lead materials containing greige cotton that show developmental promise for a dressing that can accelerate blood clotting. Analysis of the effect of the blend composition on absorption capacity demonstrated that the bleached fibers influenced higher absorption capacity in the nonwoven materials. A combination of the results of the two approaches of absorption capacity assessment and thromboelastograpy was used to develop lead prototypes for further development. Chronic wound dressing materials. It was discovered that greige cotton fibers are a source of low level hydrogen peroxide generation, and brown cotton fibers examined for hydrogen peroxide production were found to produce higher amounts than white cotton fibers. Both brown and white cotton fibers were processed into hydrogentanlged nonwoven materials that were examined for hydrogen peroxide production. It was found that brown cotton-containing nonwoven materials produced levels of hydrogen peroxide commensurate with levels that stimulate and enhance fibroblast proliferation in wounds. Both brown and white cotton types were compared from field to mill processing for hydrogen peroxide generation properties, and the mechanism of action investigated by examining molecular constituents i.e. carbohydrates (pectin), metals, enzymes (super oxide dismutase) and plant-containing molecules that are retained in the cotton fiber and are associated with hydrogen peroxide production. It was found that brown cotton had much higher levels of plant-containing chemicals (polyphenolics) that give rise to hydrogen peroxide oxidation. On the other hand levels of hydrogen peroxide levels were increased in all cotton materials upon the addition of copper and ascorbate (vitamin C), which independently generate hydrogen peroxide. Subsequently further examination of a larger library of white cotton fibers has revealed some cotton varieties produce levels of hydrogen peroxide sufficient to stimulate fibroblast proliferation. Cotton-Based Sensors. Nanocellulosic aerogels are lightweight highly porous materials with high specific surface area having high utility for use in sensors. A natural source of greige cotton fibers was employed to generate nancellulosic aerogels as sensors for the detection of human neutrophil elastase, which is a destructive enzyme found in chronic wounds and numerous inflammatory diseases. Nanocellulosic aerogels were prepared by employing a process that transforms the greige cotton into a gel that can be cast into a lightweight highly porous homogeneous material. Characterization of the cotton-based aerogels revealed they contained small amounts of pectin. Protease sensors were prepared from the aerogels by attaching a fluorogenic elastase peptide substrate to the aerogel. The elastase sensor activity of the nanocellulosic aerogels demonstrate the effectiveness of a cotton-based approach as a good substrate to assemble sensors for sensitive detection of human neutrophil elastase levels found in chronic wounds. Layer-by-layer approach to flame retardant semi-durable materials. Cotton fabrics were coated with phosphorous-nitrogen rich clay formulations and prepared through a method that is termed layer-by-layer (LbL) since one layer is assembled over another to form a cohesive. These treatments were found to confer flame retardant properties to cotton fabrics. The LbL method was implemented by an aqueous solution of casein, nano-clay, poly ethyleneimine, and inorganic compounds. The novel approach provides a low cost alternative to flame retardant materials. These materials are designed to be permanently attached to the cotton to circumvent wash off during laundering. The commercial use of this approach to fire retardant treatments has the best potential where safe and semi-durable finishes with simple, low-cost applications are in demand. A new approach to a rapid and high add-on chemical treatment method of cotton fabrics was developed using microwave-assisted technology. The combination of phosphorous and nitrogen containing compounds when applied to cotton fabrics offers several advantages including char formation from phosphorous and incombustible gas without toxic smoke from nitrogen. These advantageous thermal properties together enhance the ability to retard flame propagation on the cotton fabric. The approach shows promise in the design and development of novel environmentally friendly small molecules and formulations that confer flame retardant properties to commercial cotton-based textiles.

Accomplishments
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 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. A greater understanding of fluid transport through these composite materials will lead to the development of new absorbent materials with greater fluid retention properties and will expand the role of cotton in absorbent applications.

2. Hygienic applications. Current greige cotton fiber processes uses caustic bases to scour and bleach to whiten, generating hazardous waste streams which require further neutralization and costing additional time, money and water resources. ARS scientists have found that greige cotton fibers can be mixed with blue dyed cotton fibers to yield a product that appears whiter than the original greige cotton, without the need for caustic scouring or bleaching. This research confirmed the principles of additive color mixing in textile fiber applications. Additionally, a statistics-based approach to experiments optimized additive color mixing of fibers to yield the whitest possible blend of greige and blue dyed fibers. This research will enable industry stakeholders to process greige cotton in a more cost-effective manner while employing a more sustainable, greener process method.

3. 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 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.

4. 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. 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.

5. 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 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. The availability of nonwoven cotton dressings that enhance wound healing properties would be of interest for commercial development and a low-cost, economic approach to state of the art advanced chronic wound care.

6. Lightweight highly porous materials from cotton as sensors. High tech applications of cotton have the ability to increase cotton’s market share. Aerogels are light weight materials that feature very low density, high specific surface area and consist of a coherent open-porous network of loosely packed, bonded particles or fibers. Aerogels based on nanocellulose have attracted interest for use in different materials from biocompatible scaffolds for tissue engineering to biodegradable packaging foams and sensors. Cotton-based nanocellulosic aerogels were prepared as sensors for harmful proteins found in chronic wound, and can also be interfaced with chronic wound dressings. The cotton-based aerogel sensors have a high specific surface area, porosity and fluid uptake capacity. They function well as sensitive detectors of protease activity when derivatized with fluorescent protease substrates. The potential impact of the may be realized as an application in bedside wound care, and other biomaterial areas where biocompatible porous substances are needed.

7. The availability of low-cost simple approaches that confer flame retardant and moisture control properties to semidurable cotton textiles (fabrics that can be used multiple times without discarding) has been developed through Layer-by-layer (LbL) coating. LbL coating is a simple method to incorporate different forms of clay-based formulations into cotton fabrics using clay particles as a dispersing matrix. These clay treatments provide a variety of different physical and chemical properties to cotton including moisture management, strength, and absorptivity. By treating the cotton fabric with nano-coatings, composed of phosphorous-nitrogen-rich polymers prepared via layer-by-layer (LbL) assembly, the cotton fabric can be rendered anti-flammable. The coatings, which also include nonmaterial’s are thought to have intumescent (initiated swelling due to an increase in thermal contact) properties that render them flame retardant when applied to cotton. The novel approach provides a low cost alternative to flame retardant materials. The commercial use of layer-by-layer self-assembly processing would provide an excellent thermal protection for medical, military, and large scale emergency material use demands where a low cost, semi-durable product is desired. These materials are designed to be permanently attached to the cotton to stop the process wash off during laundering. The commercial availability of this approach to fire retardant treatments would confer a safe and semi-durable finish.

8. Microwave-assisted technology. Recently, ARS scientists have developed an efficient method for the chemical treatment of a series of flame retardant compounds such as commercially available inorganic and novel compounds on cotton fabrics. A microwave-assisted one-pot chemical treatment of cotton fabrics that minimizes the use of auxiliary agents affords an economical alternative to the age old traditional chemical treatments of textiles i.e. pad-dry-cure method. The new protocol has the advantages of shorter reaction time, a simple procedure and an environmentally friendly green concept. Our preliminary results also revealed that most of the flame retardant textile products prepared using this approach demonstrated better activity. The microwave-assisted products were confirmed by standard flame retardant test methods standard test methods. The new Microwave-assisted method will be of interest and use to professionals engaged in new material design in textile industries to create new marketable uses as firefighter apparel, institutional draperies and upholstery, carpet, transportation blankets and seat covers, children’s sleepwear, and bedding, etc.

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Review Publications
Edwards, J.V., Sawhney, A.P., Bopp, A., French, A.D., Slopek, R.P., Reynolds, M.L., Allen Jr, H.C., Condon, B.D., Montalvo Jr, J.G. 2015. An assessment of surface properties and moisture uptake of nonwoven fabrics from ginning by-products. In: Poletto, M., Ornaghi, Jr., H.L., editors. Cellulose-Fundamental Aspects and Current Trends. Croatia: InTechOpen. p.45–61. doi.org/10.5772/61329.
Fontenot, K.R., Edwards, J.V., Haldane, D., Graves, E.E., Santiago Cintron, M., Prevost, N.T., French, A.D., Condon, B.D. 2016. Human neutrophil elastase detection with fluorescent peptide sensors conjugated to cellulosic and nanocellulosic materials: part II, structure/function analysis. Cellulose. 23(2):1297-1309.
Edwards, J.V., Fontenot, K.R., Haldane, D., Prevost, N.T., Condon, B.D., Grimm, C.C. 2016. Human neutrophil elastase peptide sensors conjugated to cellulosic and nanocellulosic materials: part I, synthesis and characterization of fluorescent analogs. Cellulose. 23(2):1283-1295.
Fontenot, K.R., Nguyen, M.M., Al-Abdul-Wahid, M., Easson, M.W., Chang, S., Lorigan, G.A., Condon, B.D. 2015. The thermal degradation pathway studies of a phosphazene derivative on cotton fabric. Industrial and Engineering Chemistry Research. 120:32-41.
Edwards, J.V., Ningtao, M., Stephen, R., Edmund, C., Condon, B.D., Hinchliffe, D.J., Gary, L., Graves, E.E., Bopp, A., Wang, Y. 2016. Fluid handling and fabric handle profiles of hydroentangled greige cotton and spunbond polypropylene nonwoven topsheets. Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications. 230(4):847-859.