Location: Cotton Chemistry and Utilization Research
2017 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
Under Objective 1, ARS-Cotton Chemistry and Utilization research scientists conducted a comprehensive study on the effects of fiber blends on the performance properties of needlepunched and hydroentangled nonwovens fabrics. Staple fiber used in the study included mechanically cleaned greige cotton, scoured and bleached cotton, polyester, polypropylene, tencel, viscose, and rayon. The fabrics were made with intimate blends of the greige cotton with each of the manmade/manufactured fibers in 80:20, 50:50 and 20:80 blend ratios. The study indicated the intimate blends of pre-cleaned greige cotton and certain manmade fibers can be efficiently processed on existing commercial mill equipment and hydroentangled into viable nonwoven fabrics of considerably improved properties for many end-use products. For example, a 20% cotton content of the blended fabrics made with polyester, polypropylene or Tencel provided physical and mechanical and properties, including the improved strength and absorbency which are critical in many personal care, hygienic, and medical-grade nonwoven products that presently are made mostly with synthetic fibers.
Under Objective 1, ARS-Cotton Chemistry and Utilization research scientists conducted research in which blue cotton fibers were intimately blended in specific ratios with a single variety of greige cotton. Using textile equipment a nonwovens fabric was produced which appeared whiter than the original greige cotton. The apparent increase in whiteness was a result of additive color mixing. Product blends were analyzed using colorimetric standards and it was determined that 4% of blue cotton fiber blended with 96% of greige cotton fiber produced the optimal product whiteness. This improved apparent whiteness expands the use of greige cotton in nonwovens hygiene applications where consumers associate white color with a sanitary and/or sterile product.
Under Objective 1, ARS-Cotton Chemistry and Utilization research scientists conducted research to examine the adsorption capacity and retention times of the insect repellent N,N-diethyl-3-methylbenzamide (DEET) on nonwoven hydroentangled fabrics composed of various cotton and synthetic fibers. Fiber used in the study included greige cotton, greige cotton gin motes, scoured and bleached cotton, rayon, polyester, and polypropylene. Wet pick-up of DEET and retention times were evaluated under various controlled temperatures and relative humidity levels that coincide with increased mosquito activity. Headspace gas chromatography mass spectrometry (GC/MS) was used to compare DEET evaporation over time from the different nonwoven substrates. A Fourier transform infrared spectrascope equipped with a focal plane array detector enabled visualization of the DEET uniformity over time on each nonwoven substrate.
Under Objective 2, ARS-Cotton Chemistry and Utilization research scientists selected individual recombinant inbred lines descended from a multi-parent advanced generation inter-cross (MAGIC) population for fiber traits specific for nonwovens textile applications. These fiber traits included enhanced natural flame retardancy at levels that would reduce the amount of synthetic chemical add-on for FR textile applications and high percent elongation for elastic fabrics such as diaper and adult incontinence cuffs, performance sports apparel, among others uses. Additionally, we have identified MAGIC cotton lines with extremely high yield yet very poor fiber quality not suitable for spinning and woven applications. Previous research in our unit indicated that fiber quality parameters for woven fabrics do not adversely impact nonwovens fabrics performance. With increased market demand for cotton fibers in nonwovens, this represents the first possibility to release cotton germplasm lines specifically for the nonwovens market.
Under Objective 2, ARS-Cotton Chemistry and Utilization research scientists demonstrated the natural resistance of raw cotton to heat. This unique thermal stability of raw cotton was characterized by an intensive accumulation of dehydrocellulose in solid products and the enhanced formation of water, carbon dioxide, and char as compared with in scoured cotton. The degradation of the crystalline region was accelerated in raw cotton. The activation energy for raw cotton determined under isothermal conditions at 200-300°C was significantly lower than that for scoured cotton (124 vs. 202 kJ/mol). These results indicated that naturally occurring inorganic salts present in raw cotton allowed dehydration reactions at low temperatures to proceed to a full extent to prevent a maximum yield of levoglucosan at high temperatures, which is a major constituent of flammable tar.
Under Objective 2, ARS-Cotton Chemistry and Utilization research scientists developed a bio-inspired approach to provide flame resistance with cotton. Tannins, natural phenolic compounds abundant in many plants, was found to form intumescent flame-retardant coating on cotton nonwoven fabric with an aid of sodium ions. Addition of low concentrations of sodium hydroxide enhanced the adsorption of tannic acid and catalyzed the thermal degradations of both tannic acid and cotton to increase the char formation. The produced char showed the fibrous composite structure with blown surface char layers. This intumescent char formation resulted in the reduction in heat release capacity by up to 82% as compared with control cotton and the increase of limiting oxygen index up to 30.2%.
Under Objective 2, ARS-Cotton Chemistry and Utilization research scientists conducted controlled temperature and light experiments using an environmental grow room that revealed the intensity of the brown color of Lc1 fibers is significantly reduced to a light tan color under these controlled conditions, while flame retardancy (FR) of the fibers remains the same or higher than dark brown Lc1 fibers. This phenomenon was confirmed by moving an Lc1 cotton plant from the summer field to the greenhouse over the winter. Changes in lighting conditions caused newly produced cotton fibers to exhibit a light tan color phenotype with high FR characteristics. A controlled experiment is currently being conducted with Lc1 plants grown concurrently in the growth chamber and the Southern Regional Reserch Center's field. Temperature conditions are being held constant in both locations with light intensity as the variable. Gene expression, metabolites, and FR will be examined to determine the genetic control of fiber color in response to light conditions. This is further evidence that brown color and FR can be separated to produce a white fiber cotton with enhanced FR.
Under Objective 2, ARS-Cotton Chemistry and Utilization research scientists screened the genomic DNA of Brown/red cotton varieties with enhanced fiber flame retardancy (FR) for the absence of the previously identified Lc1 genomic inversion mutation upstream of GhTT2-A07. Cotton lines were identified that lack the Lc1 mutation indicating they are possibly Lc2 plants with a currently unidentified mutation resulting in enhanced FR. Whole genome sequencing will be conducted to develop single nucleotide polymorphism molecular markers to screen mapping populations developed from crosses of putative Lc2 cotton with a conventional white cotton variety. This research will identify the Lc2 causative mutation and further our understanding of the cotton fiber proanthocyanidin pathway to facilitate genetic modifications to produce a white fiber high FR cotton line.
Under Objective 2, ARS-Cotton Chemistry and Utilization research scientists made promising progress in using a transient gene silencing approach to suppress the expression of genes involved in the development of brown color in Lc1 cotton fibers. The technique is called virus induced gene silencing (VIGS) and previously was useful only for vegetative phenotypes in cotton. Direct injection of the VIGS into a mature cotton plant allowed for systemic transmission of the VIGS into cotton bolls and fibers in fruiting branches closest to the injection site. Lc1 brown cotton fiber color was dramatically reduced, while enhanced flame retardancy was maintained. Along with the previously mentioned Lc1 brown color reduction observation, this supports our hypothesis that brown color and FR can be separated. More importantly, this separation can be controlled through genetic modifications targeting specific genes.
Under Objective 3, ARS-Cotton Chemistry and Utilization research scientists demonstrated that the stability and durability of antimicrobial silver-cotton nanocomposite fiber. The in-situ synthesis of silver nanoparticles inside cotton fibers resulted in dispersing the nanoparticle (ca. 12 nm in diameter) in the microfibrillar structure with a concentration of 7000 ppm. The silver-cotton nanocomposite fiber was stable for ten months without any changes in ultraviolet-visible (UV-Vis) absorbance wavelength, surface charge, and color of the fiber. This stability was attributed to the electrostatic interactions of nanoparticles with cotton cellulose. Along with the electrostatic binding, the physical trapping of the nanoparticles provided an effective way to control the release of silver ions - less than 8% reduction in concentration by the American Association of Textile Chemists and Colorists-61 (AATCC-61) laundering method. The silver-cotton nanocomposite fiber maintained biocidal properties against harmful bacteria (Escherichia (E.) coli and Staphylococcus aureus) after fifty accelerated launderings.
Accomplishments
1. Additive color blending to increase apparent fabric whiteness in a nonwoven textile application. ARS scientists in New Orleans, Louisiana, collaborated with a major cotton staple fiber stakeholder to expand the greige cotton fiber in nonowoven hygiene applications. This achievement is the direct result of ARS scientists developing an optimized additive color and fiber blend ratio with greige cotton using this intimate fiber blending technique that dramatically increases the whiteness of the greige fibers which are typically yellowish in color. The optimized blending can be tailored to specific greige fibers that can vary slightly in natural color. The research has resulted in an annual increase in greige cotton fiber use in nonwovens of approximately 2,000 bales. The consumption of greige cotton in this application is predicted to increase to approximately 10,000 bales in the next year.
2. The mechanisms of the thermal stability of raw cotton were characterized and verified. This verification was achieved by combining kinetic and analytical studies. According to the results, the low-temperature dehydration reactions catalyzed by inorganic salts substantially suppressed the “unzipping” depolymerization of cellulose at high temperatures and consequently reduced the production of highly volatile levoglucosan, a major constituent of flammable tar. The levoglucosan detected in raw cotton using pyrolysis gas chromatography mass spectrometry (Py-GC/MS) was two orders of magnitude less abundant than in scoured cotton. Such modified thermal reactions were supported by the chemical and structural changes in the solid substrate as well as the types of gaseous products in the entire range of pyrolysis temperature. These comprehensive analyses, conducted by ARS scientists at New Orleans, Louisiana, allowed a more complete picture of the thermal processes of raw cotton for its practical utilization as well as for its aging and deterioration at elevated temperatures.
3. The silver nanoparticle-cotton system previously developed by research scientists in New Orleans, Louisiana, showed stable and durable antimicrobial properties in laundering tests. Simply copying the nanotechnology developed in other fields, i.e., buying nanoparticles, nanotubes, or nanocrystals and applying them onto textiles, have raised environmental, health, and performance durability issues. A great deal of originality is required to develop safe and durable nanoengineered cotton. The uniform dispersion of silver nanoparticles inside the fiber was not influenced by fifty cycles of laundering, and the laundered nanocomposite fibers retained 92% of the silver nanoparticles in concentration. More importantly, powerful antibacterial activity against Escherichia coli and Staphylococcus aureus maintained after laundering. This nanocomposite fiber will continuously deliver antibacterial activity wash after wash, making it potential for antibacterial washable wipes.
4. Inspired by a previous study showing that the superior thermal resistance of brown cotton fibers was linked to naturally occurring tannins and inorganic salts, the improved flame resistance of tannic acid was achieved by the addition of sodium hydroxide. Tannins concentrated in the barks of trees are naturally fire resistant, but the use of tannins for cotton has been limited to a dyeing fixative. According to limiting oxygen index (LOI) measurement, tannic acid alone was not effective as a flame-retardant for cotton, but the addition of low concentrations of sodium hydroxide increased the LOI up to 30%. This remarkable synergistic effect of sodium ions was explained by the formation of intumescent char, in which fibrous char was embedded, more effectively hinders the transfers of heat and combustible gases. The cotton nonwoven fabrics coated with tannic acid along with sodium ions are expected by ARS scientis at New Orleans, Louisiana, to serve as a fire barrier in mattresses and furniture applications.
Review Publications
Nam, S., Condon, B.D., Liu, Y., He, Q. 2017. Natural resistance of raw cotton fiber to heat evidenced by the suppressed depolymerization of cellulose. Polymer Degradation and Stability. 138:133-141.
Hinchliffe, D.J., Condon, B.D., Thyssen, G.N., Naoumkina, M.A., Madison, C.A., Reynolds, M.L., Delhom, C.D., Fang, D.D., Li, P., McCarty Jr, J.C. 2016. The GhTT2_A07 gene is linked to the brown colour and natural flame retardancy phenotypes of Lc1 cotton (Gossypium hirsutum L.) fibres. Journal of Experimental Botany. 67(18):5461-5471.
Santiago Cintron, M., Montalvo, J.G., Von Hoven, T.M., Rodgers, J.E., Hinchliffe, D.J., Madison, C.A., Thyssen, G.N., Zeng, L. 2016. Infrared imaging of cotton fiber bundles using a focal plane array detector and a single reflectance accessory. FIBERS. 4(27):1-11. https://doi.org/10.3390/fib4040027.
Mattison, C.P., Rai, R., Settlage, R.E., Hinchliffe, D.J., Madison, C.A., Bland, J.M., Brashear, S.S., Graham, C.J., Tarver, M.R., Florane, C.B., Bechtel, P.J. 2017. RNA-seq analysis of developing pecan (Carya illinoinensis) embryos reveals parallel expression patterns among allergen and lipid metabolism genes. Journal of Agricultural and Food Chemistry. 65:1443-1455. doi:10.1021/acs.jafc.6b04199.
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.
Naoumkina, M.A., Hinchliffe, D.J., Fang, D.D., Florane, C.B., Thyssen, G.N. 2017. Role of xyloglucan in cotton (Gossypium hirsutum L.) fiber elongation of the short fiber mutant Ligon-lintless-2 (Li2). Gene. 626:227-233.
Nam, S., Condon, B.D., Delhom, C.D., Fontenot, K.R. 2016. Silver-cotton nanocomposites: nano-design of microfibrillar structure causes morphological changes and increased tenacity. Scientific Reports. 6(37320):1-10. https://doi.org/10.1038/srep37320.
