By Dr. John Callow Lark
In the early 1950s, production of textiles in the United States was a vibrant, growing industry. Cotton was the primary fiber utilized and demand was strong for both internally produced and purchased yarn. During this period, the industry enjoyed the attention of large chemical companies supplying products to textile manufacturing. It was in this environment that R&D company groups actively pursued new applications for the various products for utilization in our industry.
A few large chemical companies serving the textile industry were involved in the manufacture of colloidal silica. The material was polymerized from water glass and acid to a spherical 20-millimicron diameter 3D sol stabilized to a pH of 9 or higher. Colloidal silica had found use in other industries but had not found utility in textiles. Marketing personnel were assigned to correct this situation and concentrated on properties obtained from the use of colloidal silica in textiles.
The most obvious property exhibited by colloidal silica products was a frictional effect on surfaces. This prompted proposals to explore any benefit of colloidal silica on cotton fiber in yarn formation. At the time, large chemical companies supplying this sector of the industry had pilot scale equipment to evaluate product performance on fiber. This provided a convenient path to develop relevant data for presentation to the industry.
Colloidal silica was sprayed on cotton fiber during the opening process and subsequently processed to yarn. Initial evaluations presented no problems and extensive work was done to determine the effect on physical properties of the yarn produced. Improvements in tensile and elongation properties and yarn uniformity were outstanding. In addition, there were indications of reduced fiber loss during yarn formation. When colloidal silica treated yarn was put through the sizing process, warp stop levels were significantly reduced. Reduced fiber loss was also demonstrated in knitting. Application levels of colloidal silica on fiber were demonstrated to be in the range of less than 0.05 to 0.1 percent active product on fiber.
Armed with the data developed in laboratory pilot scale equipment, sales technicians approached top management of operating yarn mills. Review of the data from the in-house pilot plants was sufficient to gain approval from mill management and colloidal silica trials initiated. All data from the pilot plant trials were confirmed and/or surpassed. Approvals for full production was put into place. The news of the success of spray application of colloidal silica on fiber spread through the industry like wildfire. Spraying colloidal silica on cotton became the hot topic of the industry. Improvements in the total fabric formation process was validated by operating mills. Improvements demonstrated were:
- Improved yarn physical properties
- Higher production yields
- Improved yarn uniformity
- Reduced fiber and size shed in slashing
- Reduced warp stops in weaving
- Reduced shedding in the weave room
- Improved fabric quality
- Reduced fiber loss in knitting
- Improved knit fabric quality
A miracle additive had been introduced to improve cotton processing … until!
After widespread use of colloidal silica was adopted, mills found that machinery was being abraded at all points contacting the treated yarn. What had been ignored was the chemistry involved in stabilizing colloidal silica particles. Water in the sprayed product evaporates and leaves the process. Evaporation packs colloidal particles closer and the anionic surface pH is overwhelmed. Adjacent particles react to form an irreversible silica gel which continues to lose water to form a larger 3D inorganic particles. These particles are more commonly known as “sand”. Sand and textile machinery are not compatible. This oversight brought the use of this technology to an expensive and quick end.
What has been overlooked because of this experience have been the positive results achieved by increasing fiber cohesion (friction) within the yarn bundle. The magnitude of the failure of this specific additive completely overwhelmed the entire objective of the work.
Dr. John Callow Lark lives In Houston, Texas
January 21, 2021
