Location: Cotton Chemistry and Utilization Research
2018 Annual Report
Objectives
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.
Approach
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.
Progress Report
Progress was made on all three objectives, all of which fall under National Program 306, Component 2 Product Quality and New Uses, Non-food. Progress on this project focuses on developing knowledge and enabling commercially-viable technologies to (1) measure and maintain/enhance post-harvest product quality, (2) harvest and process agricultural materials, and (3) create new value-added products.
Under Objective 1, significant progress was made toward the goal of enabling new commercial products with cotton-containing nonwoven materials. ARS-Cotton Chemistry and Utilization researchers collaborated with a major cotton staple fiber manufacturer and supplier for the nonwovens industry. Nonwovens textiles can be quickly manufactured directly from fibers without the need for converting fibers to yarns and weaving or knitting that are required processing steps for woven textiles. The functionalities imparted to technical nonwovens were examined and optimized by varying cotton staple fiber blend ratios with man-made fibers, modifying processing parameters, and modifying structural characteristics of the fibers. The nonwovens fabrics were all produced by orienting the fibers lightweight webs in a continuous process known as carding. This was followed by crosslapping the webs to a desired basis weight and needlepunching to impart integrity to the fabrics produced. The needlepunched fabrics were then processed through a hydroentanglement system and converted into spunlaced nonwoven fabrics. Hydroentanglement strengthens the nonwoven fabrics by using high pressure water jets to further compress and entangle the fibers. Critical processing parameters affecting functionalities of the fabrics were fabric weight and the cumulative amount of energy (a function of water pressure, processing speed, and other variables) applied to the fabrics during hydroentanglement. Nonwovens production trials were conducted with several stakeholders to produce prototypes for non-sterile hygiene applications including diapers and incontinence products among others. Under Objective 1, ARS-Cotton Chemistry and Utilization researchers collaborated with a Georgia Athletic Association Professor of Fibers and Textiles at the University of Georgia, Athens, to study the production and performance properties of elastic nonwovens containing cotton fibers. Several composite nonwoven samples were produced by hydroentangling cotton fiber webs with elastomeric webs that produced a stretchable cotton nonwoven fabric. The elastic webs consisted synthetic man-made polymers including meltblown thermoplastic polyurethane and spunbond polypropylene/polyester. The meltblown/spubond process uses heat to melt pellets composed of the polymer(s) that is then extruded as filaments of polymer to produce a synthetic nonwoven web onto a moving belt in a continuous process. The samples were characterized for thickness, weight, permeability, barrier properties, tensile properties, porosity and absorbency. Also, the structure is further being characterized using scanning electron microscopy and optical microscopy. The relationship between the structure and properties observed are being evaluated. To further understand the usefulness of these fabrics, stretchability and stretch recovery of these composite webs are being evaluated using cyclic testing procedure.
Under Objective 2, significant progress was made on the development of a new cotton variety with inherently flame retardant white fibers. ARS-Cotton Chemistry and Utilization researchers conducted extensive flame retardancy (FR) testing on cotton fibers from a genetically diverse and unique cotton population. Microscale combustion calorimetry was used to examine combustion properties of cotton fibers and cotton lines with enhanced fiber FR characteristics were selected. Microscale combustion calorimetry requires small fiber samples and obtains measurements that correlate with flammability of a material. Cotton fibers exhibiting an enhanced FR property remained stable when grown in different years and environments that included Stoneville and Starkville, Mississippi, and Florence, South Carolina. The genomes of the cotton lines were sequenced and analyzed for molecular markers. Two independent locations on two cotton chromosomes were identified by a genome wide association study as potentially important to the fiber enhanced FR property and converted into DNA markers. The markers successfully predicted FR characteristics of fibers from untested cotton lines and selections were made for enhanced and minimal fiber flame retardancy. Nonwoven fabrics were produced from fibers of cotton lines with and without enhanced FR and subjected to standardized flammability testing. The fabrics from a selected enhanced FR selection self-extinguished whereas the fabrics produced from typical fibers were completely consumed by open flame. Also under Objective 2, ARS-Cotton Chemistry and Utilization researchers deployed a mapping population consisting of approximately 550 individual cotton plants developed by a cross between a white fiber cotton line and a brown fiber cotton line designated as Lc2. As we demonstrated in previous years with Lc1 fibers, the fibers of Lc2 cotton exhibit enhanced flame retardancy (FR) but are a lighter shade of brown color sometimes described as tan or khaki in the literature. The cotton mapping population will allow researchers to correlate DNA markers with fiber color and FR and will be used in a genome wide association study to identify the gene(s) that are the causative mutation of Lc2. This knowledge will provide greater insights into the regulatory mechanisms of fiber color and enhanced fiber FR toward the goal of developing white fiber cotton lines with superior flame retardancy.
Under Objective 3, significant progress was made using nanotechnology to enable the development of new commercial cotton products. ARS-Cotton Chemistry and Utilization researchers developed a new water-based binary polyol process to synthesize silver nanoparticles. Although the polyol process is a widely used strategy for making nanoparticles from various reducible metallic precursors, it involves a bulk polyol liquid reaction, which requires high reaction temperatures and the addition of protective agents. Based on the UV/Vis adsorption intensity as a function of reaction time and the dependence of the concentration of ethylene glycol on the UV/Vis adsorption intensity, the following consecutive mechanism of the particle formation was proposed: (1) seeding and surface growing, (2) combining of small particles, and (3) growing of large particles at the expanse of small particles. Under Objective 3, ARS-Cotton Chemistry and Utilization researchers developed an in-situ synthetic method of copper nanoparticles. Although copper nanoparticles are antimicrobial, their use in cotton products has been limited by a lack of stability due to their oxidation. The direct formation of copper nanoparticles onto cotton demonstrated the significant improvement in their stability. The results of UV-Vis absorbance, surface charge, and the color of fabrics indicated that the stabilizing capability of cotton fiber along with the use of ascorbic acid effectively prevented the oxidation of copper nanoparticles. The applied copper nanoparticles exerted the 99% antibacterial reduction of two pathogenic bacteria, E. coli and S. aureus, via the release of copper ions, expanding the utility of cotton (with copper nanoparticles) for antimicrobial wipes, curtains, and mops used in medical facilities as well as a water purifier.
Under Objective 3, ARS-Cotton Chemistry and Utilization researchers developed a new approach to uncover the thermally induced structural transitions of cotton fiber at low and intermediate temperatures by modeling the temperature dependence of the fiber tenacity distribution. As the temperature increased, the probability density of tenacity developed a unique pattern—periodic evolution/degeneration of bimodality. This pattern was successfully parameterized by using the mixed Weibull model. The crystallographic and thermogravimetric analyses suggested the coexistence of thermal crystallization during the thermal decomposition. The decomposition of the crystalline cellulose was found to be predominant along the fiber axis.
Accomplishments
1. A cotton-based specialty wipe that meets criteria for use on sensitive precision machine parts. ARS scientists in New Orleans, Louisiana, conducted a comparative study to evaluate the possibility of utilizing cotton-based nonwovens for specialty wipe applications such as aviation maintenance. The aviation industry has specific acceptance guidelines for precision wipes used on sensitive aerospace components including pH, residue quantification, and linting induced contamination. Since this market is primarily dominated by synthetic materials, the volume of information regarding the use of cotton-based nonwovens in this particular arena is limited. Several cotton-based and non-cotton-based nonwovens were subjected to a battery of standardized tests in addition to environmental scanning electron microscopy and tensile testing. This study demonstrated the feasibility of using cotton-based wipes composed of 100% raw cotton staple fibers for sensitive precision applications and promotes the expanded use of cotton fibers in nonwovens applications.
2. A white lint cotton variety with enhanced flame retardancy. Textile produced from cotton fibers are flammable and require the addition of chemical additives to achieve the level of flame retardancy (FR) required for specific applications. A cotton line with fibers that possess enhanced flame retardancy would be of great benefit to the cotton industry for the production of fire-safe cotton textiles with reduced chemical additives. ARS scientists in New Orleans, Louisiana, utilized a cotton multi-parent advanced generation inter-cross (MAGIC) population to screen for enhanced fiber FR characteristics by microscale combustion calorimetry. Looking at the entire genetic make-up of cotton, researchers were able to identify two independent regions of the genome as potential candidates for enhanced FR. Nonwoven fabrics produced from fibers of a cotton line selected for enhanced FR were subjected to standardized apparel flammbility tests and self-extinguished, whereas the fabrics produced from typical fibers were rapidly and completely consumed by open flame. A cotton MAGIC population can be used to select for enhanced nontraditional cotton fiber properties and expand cotton fiber use in specialty applications. Fabrics produced from genetically enhanced FR fibers may reduce the quantity of chemicals required to produce flame retardant textiles.
3. Making size-controlled silver nanoparticles for antibacterial cotton. The biocidal performance of silver nanoparticles is strongly dependent on the particle size, i.e., the smaller the size, the greater the antibacterial activity; however, they easily aggregate into large particles, which negates the antibacterial efficacy associated with the nanoscopic dimension. There is a critical need for developing methods that control the synthesis of nanoparticles. ARS scientists in New Orleans, Louisiana, developed an easy, low cost, and controllable water-based method using low concentrations of polyethylene glycol and ethylene glycol. The obtained nanoparticles were smaller than those produced by polyol process in a similar condition. Their minimum inhibitory concentrations (MIC) against Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus enterica, and Escherichia coli (4.7, 2.3, 2.3, and 1.2 ug/mL, respectively) were smaller than those in the literature, confirming the particle size effect. The reduced MICs obtained by controlling the particle size demonstrated that silver nanoparticles are suitable as a targeted disinfecting tool for healthcare and food packaging nonwoven cotton products.
4. Creating bifunctional cotton by the in-situ synthesis of stable copper nanoparticles. The direct synthesis of copper nanoparticles onto textiles has been a long time challenge due to the oxidation of these nanoparticles. Such poor stability of copper nanoparticles has hampered their applications in a long-term usage or storage. ARS scientists in New Orleans, Louisiana, demonstrated that the oxidation of the nanoparticles is preventable by the in-situ synthesis onto the surface of cotton fiber with the aid of ascorbic acid. Due to their high surface area to volume ratio and copper-ion release, the applied copper nanoparticles imparted powerful antibacterial activities against both Gram positive and negative bacteria. Nano copper-cotton fabric exhibited a high degree of hydrophobicity that results in the retention of water droplets on the surface of the fabric. This hydrophobicity renders cotton surface stain-repellent and thus easy to clean. The bifunctionality—biocidal activity and hydrophobicity—of the nano copper-cotton will raise its potential as a cleaning tool for oleophilic dirt or oil spills.
5. Identifying the thermally induced structural transitions of cotton fiber. Due to the complexity of cotton structure, identifying its transitions under heat treatments is not a trivial task. In particular, the glass transition (i.e., thermal softening) of cotton fiber has been a controversial topic. ARS scientists in New Orleans, Louisiana, developed a statistical method to identify the stepwise thermal response of cotton fiber by parameterizing the periodic pattern of bimodality in the tenacity distribution of the heated fibers at elevated temperatures using a mixed Weibull model. The results demonstrated that a mixture Weibull model not only fully described the complex statistical behavior of the tenacity of heated cotton fibers but also revealed the thermal responses of the fiber and their characteristics. Identification of the thermally-induced structural alteration of cotton fiber will contribute to enhancing the thermal processing efficiency, and the determined glass transition temperature will be exploited in the annealing process to improve the mechanical property of cotton fiber.
Review Publications
Nam, S., Alhassan, D.A., Condon, B.D., French, A.D., Ling, Z. 2018. Thermally induced structural transitions in cotton fiber revealed by a finite mixture model of fiber tenacity distribution. ACS Sustainable Chemistry & Engineering. 6:7420-7431. https://doi.org/10.1021/acssuschemeng.7b04919.
Nam, S., Condon, B.D., Xia, Z., Nagarajan, R., Hinchliffe, D.J., Madison, C.A. 2017. Intumescent flame-retardant cotton produced by tannic acid and sodium hydroxide. Journal of Analytical and Applied Pyrolysis. 126:239-246. https://doi.org/10.1016/j.jaap.2017.06.003.
Santiago Cintron, M., Fortier, C.A., Hinchliffe, D.J., Rodgers III, J.E. 2016. Chemical imaging of secondary cell wall development in cotton fibers using a mid-infrared focal-plane array detector. Textile Research Journal. 87(9):1040-1051. https://doi.org/10.1177/0040517516648505.
Hinchliffe, D.J., Condon, B.D., Madison, C.A., Reynolds, M.L., Hron, R.J. 2017. An optimized co-formulation minimized quaternary ammonium compounds adsorption onto raw cotton disposable disinfecting wipes and maintained efficacy against MRSA, VRE, and Pseudomonas aeruginosa. Textile Research Journal. 0(00):1-10. https://doi.org/10.1177/0040517517720505.
Nam, S., Park, B., Condon, B.D. 2018. Water-based binary polyol process for the controllable synthesis of silver nanoparticles inhibiting human and foodborne pathogenic bacteria. RSC Advances. 8:21937-21947. https://doi.org.10.1039/c8ra01823e.
