VALUE ADDED AND HIGH-VOLUME COTTON PRODUCTS AND PROCESSES
Location: Cotton Chemistry and Utilization Research
Title: Advent of Greige Cotton Nonwovens Made By Hydro-Entanglement Process
Submitted to: Textile Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2010
Publication Date: March 11, 2010
Citation: Sawhney, A.P., Reynolds, M.L., Slopek, R.P., Condon, B.D., Hui, D. 2010. Advent of Greige Cotton Nonwovens Made By Hydro-Entanglement Process. Textile Research Journal. 80(15):1540-1549.
Interpretive Summary: The use of cotton in the nonwovens sector of textile manufacturing has been limited mainly because of economics and certain technical factors in context with the prevailing end-use products. Most of the cotton fiber ever used in the nonwovens sector predominantly has been bleached cotton, especially for the medical- and hygiene- care end-use applications. Bleached cotton is relatively expensive, difficult to process, and environmentally sensitive. The problem with the use of greige (scour/bleach-less) cotton is that the latter requires substantial cleaning of its foreign and contaminating matter, which consequently requires specialized processing equipment and technical expertise that the existing nonwovens companies generally do not have in their existing plants. Results of initial, preliminary research conducted at the Southern Regional Research Center, ARS, USDA, in New Orleans, Louisiana, have shown that a run-of-the-mill greige cotton, which has been conventionally opened, cleaned and carded on existing equipment, can be successfully made into certain nonwoven structures [for subsequent conversion (with or without chemical treatment, depending on the end-use application) into certain end-use products, such as wipes.
Using greige (scour/bleachless) cotton, a few nonwoven fabrics have been successfully produced by adopting conventional fiber opening, cleaning and (modified) carding machines followed by cross-lapping, pre/light needling, and hydro-entanglement (H-E) on modern commercial machinery and equipment. Using standard test methods and procedures, the fabrics were evaluated for their weight, thickness, tensile and tear failures in both machine (MD) and cross (CD) directions, and absorbency. Dimensional characteristics of the fabrics were determined before and after an ordinary wash. Microscopic examinations of the fiber/fabric surfaces before and after various conditions/degrees of hydro-entanglement were conducted. Results of these preliminary research investigations have shown that a run-of-the-mill greige cotton, processed on a conventional cotton cleaning and preparatory system, can indeed be efficiently processed on the downstream nonwovens production equipment. Additionally, it has been shown that different processing conditions, especially the high-pressure (HP) hydraulic energy of the H-E system, considerably influence properties of the fabrics produced. At the nominal fabric production rates deployed in the research trials, the HP greater than 100 bars (at the system’s two high-pressure jet-heads) produces a fabric that is partially hydrophilic – a desirable attribute for many end-use applications of cotton nonwovens. Based on a previous in-house investigation, it seems that the HP (hydraulic energy) at certain levels partly removes some of the greige cotton fiber’s natural hydrophobic defensive membrane (outer-surface barrier) of heavy hydrocarbons, such as waxes, pectins, etc., thus making the fiber/fabric partially hydrophilic. It has also been observed that the high water pressures (HP), under otherwise similar processing conditions, tend to fracture some cotton fibers into tiny fibrils, as evidenced by SEM pictures. These ruptured fibers, by way of exposing their inner (hydrophilic) walls, could also partly contribute to the fabric’s improved absorbency at elevated hydraulic energy levels. Also, a unique fabric structure composed of well-defined “strands and channels” observed at elevated HP pressures could partly attribute to the greige fabric’s improved wick-ability.