Warp Sizing: Taking Advantage of A Necessary Process

The addition of low levels of nanotechnology based additives in conventional warp size formulations has been studied in commercial operations. Fiber cohesion improvements within the yarn have provided multiple benefits in woven fabric formation. The nanotech species studied is a complex of a resin protected silica colloid used to enhance fiber cohesion in the bundle.

In the 1960’s, introduction of polyester/cotton permanent press fabric into the apparel market was an immediate marketing success. However, this success presented severe problems in manufacturing fabric for the no-iron finish. Traditional starch based warp sizes developed for cotton were incompatible with polyester fiber in the blend yarn and would not adhere to the warp yarn. Abrasive forces developed by the loom quickly destroyed the warp yarn and the weaving industry could not begin to supply demand. Looms in mills were idle and collecting dust.

In the midst of this panic, size suppliers began evaluating polyvinyl alcohol (PVA) as the primary film former in their formulations. PVA forms a strong film around the yarn and does not rely on adhesion to the fiber bundle to provide abrasion resistance. PVA was an answer to the problem and was quickly adopted by the industry.  Both warp size suppliers and the industry soon regarded PVA based formulations as the ultimate solution for weaving polyester/cotton spun yarn fabric.

Primary film formers, urea, waxes, and synthetic polymer binders have been the extent of what has been considered research in this area for many years. Modification of surface size films and chemical effects were the primary focus of chemical suppliers and technicians. This situation led to an approach practiced by nearly all industries.

*Commissioner of the United States Patent Office, 1899.  Reportedly proposed ending the United States Patent Office because everything that could be invented had already been invented.

As a result of this approach, variations in size formulations have been only dictated by the particular style under consideration and formulation cost. With all suppliers employing the same raw material base, size cost has become the primary driving factor in the majority of weaving mills. 

Nanotechnology has presented the opportunity to investigate and exploit unique characteristics of selected chemical additives within warp yarn. The small size and huge surface areas of these chemicals in the yarn dramatically alters yarn properties. The interior areas in the yarn bundle are not readily available to the high molecular weight polymeric sizing chemicals currently in use. Adhering to the topic of this study, the effects of nanosize materials in sized warp yarn have been evaluated.

The problem of low quality yarn has been a continual concern in weaving performance. Efforts to improve yarn properties with traditional warp sizes have not enjoyed any consistent success. The current study has concentrated on nano materials that can penetrate the yarn bundle and improve sized yarn properties. Warp sizing is the only water based process in spun yarn fabric formation that allows this possibility. 
It is important to note that this extended study has taken advantage of size formulations and practices developed by current size chemical suppliers. This work has been designed to demonstrate improvements to these formulations. Evaluations could not have been accomplished without these established standards and supplier cooperation.

Studies with current size formulations with and without low levels of nano based products were conducted.  The nano materials were added to the standard size bath and used the standard formulations as the controls. Additions of the nano product were based on total dry size solids. All evaluations were adjusted to provide equal size add-on. No changes in current practices were made.

Laboratory Tests:

  • Microscope evaluation of yarns from each trial demonstrated a more compact sized yarn than the control with significantly less protruding hard sized fiber.
  • Tensile data of hard yarn demonstrated a lower coefficient of variation than the control.
  • Elongation data of hard yarn demonstrated a lower coefficient of variation than the control.
  • Abrasion resistance of the sized yarn was improved.

At The Slasher:

  • A smoother break at the bust bar section.
  • Lower levels of size and fiber shed at the bust bar section.
  • More sized yarn on the loom beam.

On the Loom:

  • Reduced warp stops;
  • Reduced fill stops;
  • Reduced size shed; and
  • Reduced fiber shed.

Nano materials are readily removed with conventional sizing materials in normal desize procedures.

Incorporation of nano based materials into conventional warp size formulations have provided very positive results.  Nanosize materials have been shown to penetrate to the interior of warp yarn in the sizing process to provide a more compact and uniform yarn. This treatment improves the coefficient of variation in both tensile and elongation properties.  Nano material penetration into the bundle improves fiber cohesion and promotes improved weaving performance.   

For more information, please contact Dr. John C. Lark, johnlark@bellsouth.net

August 18, 2015