Higher quality yarn improves the weaving process. Introduction of very small non-film forming resin particles in conventional size formulations modify and provide improved fiber cohesion in the warp yarn bundle. This transient effect provides a more compact and improved yarn substrate to host conventional warp size polymers on the yarn surface. Evaluation of this technology in producing mills has provided positive results in all factors associated in the weaving process. This article Knitting fair introduces to you.
In the early 1800s, the introduction of the mechanical loom promised the potential of dramatically improved fabric production. However, the mechanical loom also introduced a level of abrasion on warp yarn that prevented this productivity potential. The abrasion problem was soon attacked by borrowing technology developed by the coatings industry. In coatings, surface protection was provided by the application of natural oils which crosslinked to form a permanent topical barrier. The concept provided the solution, but the woven fabric was not a candidate for a permanent abrasion barrier. Starch soon emerged as a suitable material to provide a transient abrasion-resistant barrier to protect warp yarn. This approach soon led to the development of the necessary machinery to apply an abrasion barrier and the concept was adopted by the industry.
During the next two centuries, significant improvements in coatings technology and materials have been adopted to accommodate continual changes in yarn composition, yarn formation, and loom technologies. Warp sizes are now designed to meet the demands of each fabric style on a case-by-case basis. Warp size suppliers and technicians have performed admirably in bridging continual changing technologies involved in the journey from fiber to fabric. We now are more secure in gauging general rules of viscosity, penetration and overall size add-on levels for optimum weaving performance. Optimization of the sizing formulation is now paired with the variables from the slasher through the greige fabric.
Advances in the use of polymer/starch surface barriers now dominate spun yarn sizing. Abrasion protection coupled with nearly 2 centuries of experience has achieved what is now regarded as the optimum in painting warp yarn. Unfortunately, this experience has fostered an attitude of complacency to the potential for improving weaving performance utilizing chemicals in the size box.
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The use of nanosize resins (oligomers) has now been evaluated as components in warp size formulations. On a theoretical basis, and the barrier coatings approach, these materials provide little optimism for improvements in weaving. Chemically, oligomer resins have the basic properties of higher molecular weight polymers of the same chemistry but are much too low in molecular weight for viable film formation. Minor adhesion and plasticization of conventional barrier film formers became the primary hope for this new technology. Initial trials with nanosize oligomers in conventional size formulations provided promising results in both adhesion and plasticization of the barrier coating. In addition, incorporation of oligomer resins provided differences that were not readily explained.
Reduction in both warp and filling stops.
Fiber and size shed at both the slasher and looms were dramatically reduced.
Increased yardage of hard yarn on the loom beam.
These results did not neatly fit into the barrier concept of warp sizing. Increased yardage on the loom beam logically indicated reduced size pick-up on warp yarn. However, multiple desize analysis of hard yarn from trials and normal production were equivalent. The repetition of these trials was consistent with the initial results. Nanosize oligomer resins were clearly providing a mechanism to complement barrier coating film abrasion resistance.
Microscopic (60X) photos were utilized to determine any visual differences between standard and trial hard yarns. Yarns containing oligomer resin in the size formulation exhibit a smoother surface with less hard fiber disruption from the sheet break. In addition, the examination of 60X photos of the sized yarn indicates a significant reduction in yarn core diameter. Sized yarn diameters exhibit near 20% reduction in comparison to normal formulation hard yarn at the same add-on.
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Examination of 1040X magnification cross-sections of yarn prior to the size box provides an explanation of the function of nanosize resins within the yarn bundle. Vacant spaces between fibers in the bundle are micron or greater in diameter and volume. Fibers in spun yarn systems are mildly anionic, natural or added, which maintain a repulsive force to keep fibers apart. As the yarn is wet-out by water, huge numbers of millimicron oligomer resin particles penetrate and adhere to fiber surfaces. Repulsive forces existing between fibers are overwhelmed and the fiber surface is modified with nanosize particles. These small resin molecules provide a like-like mutual attraction and allow fibers to be drawn closer together to partially reduce vacant spaces within the bundle. Immediate compaction of the yarn bundle occurs upon wet-out. A smaller yarn substrate is now available to host the barrier film. The count of the yarn remains constant with a smaller diameter bundle. An increase in the density of the yarn is attributed to improved fiber cohesion within the bundle.
Statamat and Uster evaluation of sized yarn at equivalent add-on provided revealing differences in properties of the sized yarns in both tensile and elongation. Although both Tensile & Elongation properties are affected, low-end values are the most important in weaving. Low-end properties are improved and the coefficient of variation reduced to provide a more uniform hard yarn. A particularly unusual benefit of fiber cohesion improvement has been in an average improvement in loss of elongation near 30% of conventionally sized yarn controls.
Years of experience with conventional size film formers have optimized penetration and encapsulation of the film barrier on yarn. Add-on levels and film locations are controlled by the viscosity of high molecular weight film formers to minimize penetration and maintain the size coating.
Adequate abrasion resistance from the barrier coating is dependent upon the surface area that must be protected. Sized yarn is a cylinder in which surface area is directly a function of the diameter of the cylinder. The new yarn created by nanosize oligomer resins in the formulation allows a reduced total size add-on to prevent oversizing and embrittlement of the hard yarn1.
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Oligomer resin effects on yarn are especially important in increasing low end tensile and elongation and reduction in coefficient of variation. This effect produces a more uniform yarn substrate for subsequent steps in the weaving process. Effects on yarn without warp size were determined through the addition of a small amount of oligomer product to the final rinse in a conventional mock dyeing procedure2.
Desize of greige fabric is accomplished utilizing conventional procedures at pH levels slightly above 7. For more knitwear knowledge, please pay attention to the knitting fair.
Source: textiles school
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As far as knitting fair knows, Growing concern over the environmental and health impacts of textiles in general and denim, in particular, are putting pressure on companies to employ more sustainable production methods.
Every closet has at least one item of denim — whether it be blue jeans, a denim jacket, or vintage overalls that our grandparents used to wear. First used in the 19th century in the form of heavy work jeans, it has since become a wardrobe staple. From 200 pairs of jeans being sold, the number produced every year has risen to 6 billion. And at the rate the fashion industry is going, we’re on track to make billions more. But just how sustainable is denim production?
Blue is not so green
The fabric used to make denim clothing is cotton or some type of cotton blend. It is first harvested, separated into fibers, then put into bales. To make a pair of jeans, our denim fabric construction guide here on Textile School explains that the material undergoes a weaving process to make yarn, which is then dyed into indigo or other colors depending on the design.
The production of denim also involves several chemical washes to make them softer or more wearable and to eliminate shrinkage. Manufacturers can then put the clothing through different processes to produce specific styles, like distressed or faded jeans.
This production cycle of denim, from harvesting the raw material to packaging the final product, makes use of vast amounts of water. In fact, The Fashion Law’s rundown of water consumption in denim production shows that it takes 1,800 gallons of water just to grow the cotton that goes into a single pair of jeans. Moreover, 1.3 trillion gallons of water are used annually to dye fabric, including denim. This doesn’t even entail the water required to wash and produce special effects in a trendy pair of denim pants.
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Aside from the enormous consumption of water, denim production is also a known culprit in water pollution. About 70% of Asia’s rivers and lakes are contaminated by garment manufacturing, of which denim is a major contributor. The production cycle involves heavy use of chemicals that produce run-offs and end up in bodies of water. These chemicals, which include lead and mercury, are also toxic to workers and communities where factories are set up. These are all issues that the textile industry is currently facing, as explored by our Textiles: Environmental Issues and Sustainability report.
Sustainable production of denim
Growing concern over the environmental and health impacts of textiles in general and denim, in particular, are putting pressure on companies to employ more sustainable production methods. One example of these environmentally responsible practices is using a micro-irrigation system that can save water usage in the early part of denim’s life cycle.
Textile manufacturers can also switch to organic pesticides to minimize the chemical exposure of workers and reduce toxic waste drained into bodies of water. As for achieving the classic denim look, C&EN reports that digital printing has become available, which can serve as a more sustainable alternative to dyeing and similar techniques. It can help solve the environmental impacts of dyeing fabric, such as producing toxic waste and human exposure to harmful chemicals.
But consumers also have a role in making denim more sustainable. Textile manufacturers can actively encourage their clients to opt for more eco-conscious fabrics from the multitude of brands that have started popping up. They can also promote ways to repurpose unused clothing, and Pretty Me’s guide to denim upcycling proves that there are many creative ways to do this. Old blue jeans can be turned into floor cushions, patchwork rugs or quilts, stylish purses, and even stuffed toys for children to enjoy.
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The bottom line is that we all play a part in bringing sustainability to denim as it is traditionally harmful to the environment. Whether it’s finding creative uses for our old pair of work jeans or supporting sustainably made denim products, our individual choices will hopefully compel textile manufacturers to turn to more sustainable practices for the sake of our planet’s future. For more knitwear knowledge, please pay attention to the knitting fair.
Source: textiles school
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