A New Perspective to Improve Warp Sizing

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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Cleaning ensures sanitization and thus the safety of the artefact itself and others stored/displayed in its vicinity. At the same time, the process invariably alters the character of textile to a certain extent. Cleaning ensures removal/deactivation of soil and harmful organic matter from the artefact. However, a small number of surface molecules from the textile might be eroded in the process as well. This leads to weakening of the textile and might cause alteration in colour spectrum/ depth etc. Controlled cleaning techniques in conservation laboratories focus on minimizing this damage. However, not much scientific data is available on the efficacy of present cleaning techniques employed in conservation laboratories. Presently aqueous cleaning and solvent cleaning are primary modes utilised as next step to dry tools. Additionally, novel cleaning technologies like enzyme wash and ultrasonic wash provide soil specific methodology that would reduce the threat to the base fabric. This article Knitting fair introduces to you.

The present paper is a systematic analysis of these cleaning techniques and their impact on aged museum fabrics, i.e., cotton, wool and silk. Change in tensile strength parameters, whiteness index and yellowness index have been used as indicators to test the efficacy of different cleaning techniques on aged museum textiles. Numerical data generated by laboratory experiments clearly indicate that there is no standard cleaning treatment available for the three natural fibres. Each fibre has exhibited suitability to different cleaning treatment while balancing between restored whiteness and minimizing strength loss.

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METHODOLOGY

Cotton, wool and silk samples were selected for research. The samples were tested for determination of tensile strength and Whiteness Index and yellowness index. Samples were subjected to accelerated ageing as per the method suggested in the AATCC Test Method 26-1994. This ascertained that samples were brought to a condition of approximately 20years of ageing. Aged Cotton, Wool and Silk samples were taken for Tensile Strength testing and Spectroscopy. Standard testing procedures were followed to measure the indicators. Thereafter, the aforesaid samples were divided into 4 groups for wet cleaning i.e., home laundry, enzymatic cleaning, dry cleaning and ultrasonic cleaning. The samples were subjected to treatments as appropriate for their fibre content. For example in the home laundry group cotton was exposed to the detergent, temperature and conditions prescribed for selected fabrics. After wet treatment, the samples were again tested for loss in tensile strength and removal of yellowness. Recorded values for whiteness Index and tensile strength were then compared to determine the best possible method.

A Home Laundry

Home laundry techniques are probably the oldest and simplest means of sanitizing fabrics. The primary merit of this method is that the worker gets to closely interact with fabric at every stage of treatment. This ensures the possibility of simultaneous improvisation, while the fabric is still under treatment. A crucial advantage of this technique stands that professionals can modify the procedure as per suitability to the textile while retaining absolute control over the artefact at the same time. For the purpose of this study AATCC test method 61-2007 was followed. Test no 1A- was used as specimens subjected to this test should show colour change similar to that produced by five typical careful hand launderings at a temperature of 40+/-30C. Laundering machine was adjusted to maintain the designated bath temperature of 40+/-20C. The wash liquor was prepared with total liquor volume of 200ml and detergent concentration at 0.37%. The test was run in lever lock stainless steel canisters of size 75X125 mm with 10 steel balls in each canister. The laundering machine was run for 45mins after which each test specimen was rinsed in a separate beaker. Each specimen was rinsed three times in distilled water at 40+/-20C with occasional stirring and hand squeezing. To remove excess water, flat specimens were pressed between folds of blotting paper. Thereafter, specimens were air-dried, placed flat on a blotting paper. A commercial detergent was used for cotton fabrics whereas a neutral soap was used as ‘non-ionic’ detergent for wool and silk.

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Dry Cleaning/ Solvent Cleaning

A synonym of solvent cleaning, this technique has been widely used for cleaning of sensitive textiles like wool, silk, chiffons. Most sensitive fabrics that behave adversely to aqueous medium stand comfortable to dry cleaning. For the purpose of this research AATCC test method, 158-1995 was used where samples were dry-cleaned at a commercial workshop with perchloroethylene. Drycleaning machine with a commercial rotating cage was used. The sample fabric was placed in the machine and perchloroethylene was introduced. The machine was run for the specified period of time. The solvent was thereafter drained and centrifuged. The load was dried in a drying tumbler by circulating in warm air for an appropriate time. The specimens were removed from machine immediately and placed on a flat surface for drying.

Enzymatic Cleaning

Literature about the use of enzymes is available from the late ’60s. In 1988, Segal published a paper reporting important factors affecting enzyme activity and various immersion and non-immersion techniques of application. Contemporary studies have repeatedly noted the efficiency of Cellulase enzyme as an effective bio-polishing agent for cotton fabric which considerably preserves the strength and weight parameters of the fabric in contrast to other chemical techniques (Bhat, 2000). The primary advantage of using enzymes is that enzymes are substrate-specific. Thus if proven useful, they stand superior to all parallel techniques of achieving a desirable result. The concept utilized in this section of the study is that of bio-polishing. The phenomenon talks about removing the damaged superficial layer of the fabric and restoring the fresher subsequent layers (Doshi et. al, 2001). Since the fabrics used in this section of the research were both cellulosic and protein in nature Cellulases and Proteases were the enzymes used for the purpose.

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Ultrasonic Cleaning

The potential of ultrasonic cleaning in conservation has been recognized for some time. Barton et. al. (1986), reported that archaeological conservation in Europe has resorted to this type of cleaning in dealing with waterlogged wood, textiles and leather artefacts. The principle of ultrasonic cleaning is the generation of mechanical impulses through a liquid at high frequencies. These impulses create minute bubbles of vacuum which implode against the immersed object, creating shocks which clean its surface (Dallas, 1976). Thus ultrasonic cleaning technique is effective while remaining gentle in terms of time and handle. Therefore the possibility of using ultrasonic cleaning technique for removal of a superficial damaged layer of aged fabrics was explored to restore whiteness without considerable strength loss. For the purpose of the present study, samples were cleaned in ultrasonic cleaning machine at North India Textile Research Association, Ghaziabad (Figure 1). Three cotton samples were washed at a temperature of 50oC with a commercial detergent at a concentration of 5gpl (IS: 5785: 2005). The first sample was taken out of the machine after 5mins, second after 8mins and third after 11mins (Sethi, 2012). The samples were then dried on a flat surface. Whiteness Index and tensile strength of these samples were recorded thereafter. Similarly, silk and wool samples were treated at a temperature of 40oC with a non-ionic washing detergent at 5gpl. Again the samples were dried flat and values for Whiteness Index and Tensile Strength noted thereafter. Thus the samples in all three fibres were subjected to the above-mentioned cleaning treatments. Whiteness Index and tensile properties for these samples were noted before and after the cleaning treatments. Comparison of these values provided insight into the utility of these treatments for each fibre.

For more knitwear knowledge, please pay attention to the knitting fair.

Source: textiles school

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Personal protective equipment (PPE) is used in a wide range of industries to protect workers from exposure to workplace hazards and is designed to address requirements specific to the context of its use. In healthcare, the goal of PPE is to protect healthcare personnel (HCP) from body fluids and infectious organisms via contact, droplet, or airborne transmission. This article Knitting fair introduces to you.

The ideal face mask blocks large respiratory droplets from coughs or sneezes – the primary method by which people pass the coronavirus to others – along with smaller airborne particles, called aerosols, produced when people talk or exhale. The World Health Organisation recommends medical masks for healthcare workers, elderly people, people with underlying health conditions, and people who have tested positive for the coronavirus or show symptoms.

Types of Masks

Two medical-grade masks, N99 and N95, are the most effective at filtering viral particles. N99 masks reduced a person’s risk of infection by 94 to 99 per cent after 20 minutes of exposure in a highly contaminated environment. N95 masks offered almost as much protection – the name refers to its minimum 95 per cent efficiency at filtering aerosols. N95 masks offered better protection than surgical masks.

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Disposable surgical masks are a close second. Surgical masks are made of nonwoven fabric, so they’re usually the safest option for healthcare workers who don’t have access to an N99 or N95 mask. Surgical masks reduced the transmission of multiple human coronaviruses through both respiratory droplets and smaller aerosols. In general, surgical masks are about three times effective in blocking virus-containing aerosols than homemade face masks.

Hybrid masks – combining two layers of 600-thread-count cotton with another material like silk, chiffon, or flannel – filtered more than 80 per cent of small particles (less than 300 nanometres) and more than 90 per cent of larger particles (bigger than 300 nanometres). A combination of cotton and chiffon offered the most protection, followed by cotton and flannel, cotton and silk, and four layers of natural silk. These options may even be better at filtering small particles than an N95 mask, though they weren’t necessarily better at filtering larger particles. Two layers of 600-thread-count cotton or two layers of chiffon might be better at filtering small particles than a surgical mask. Three layers of cotton or silk are also highly protective.

Mask Specification Requirements

WHO recommends that fabric masks have three layers: an inner layer that absorbs, a middle layer that filters, and an outer layer made from a non-absorbent material like polyester. Three layers of either a silk shirt or a 100 per cent cotton T-shirt may be just as protective as a medical-grade mask. Silk, in particular, has electrostatic properties that can help trap smaller viral particles.

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Masks have very specific performance requirements. Standard Test Method for Evaluating the Bacterial Filtration Efficiency (BFE) of Medical Face Mask Materials, using a Biological Aerosol of Staphylococcus aureus by using ASTM F2101 has been summarised below:

This test method offers a procedure for evaluation of medical face mask materials for bacterial filtration efficiency.

This test method does not define acceptable levels of bacterial filtration efficiency. Therefore, when using this test method it is necessary to describe the specific condition under which testing is conducted.

This test method has been specifically designed for measuring bacterial filtration efficiency of medical face masks, using Staphylococcus aureus as the challenge organism. The use of S. aureus is based on its clinical relevance as a leading cause of nosocomial infections.

This test method has been designed to introduce a bacterial aerosol challenge to the test specimens at a flow rate of 28.3 L/mm. (1 ft3 /min). This flow rate is within the range of normal respiration and within the limitations of the cascade impactor. Unless otherwise specified, the testing shall be performed with the inside of the medical face mask in contact with the bacterial challenge.

Testing may be performed with the aerosol challenge directed through either the face side or liner side of the test specimen, thereby, allowing evaluation of filtration efficiencies which relate to both patient-generated aerosols and wearer-generated aerosols.

Degradation by physical, chemical, and thermal stresses could negatively impact the performance of the medical face mask material. The integrity of the material can also be compromised during use by such effects as flexing and abrasion, or by wetting with contaminants such as alcohol and perspiration. Testing without these stresses could lead to a false sense of security. If these conditions are of concern, evaluate the performance of the medical face mask material for bacterial filtration efficiency following an appropriate pre-treatment technique representative of the expected conditions of use.

Consider preconditioning to assess the impact of storage conditions and shelf life for disposable products, and the effects of laundering and sterilization for reusable products. If this procedure is used for quality control, perform proper statistical design and analysis of larger data sets. This type of analysis includes, but is not limited to, the number of individual specimens tested, the average per cent bacterial filtration efficiency, and standard deviation.

Data reported in this way help to establish confidence limits concerning product performance. Examples of acceptable sampling plans are found in references such as ANSI/ASQ Z1.4 and ISO 2859-1.

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Scope of Tests

This test method is used to measure the bacterial filtration efficiency (BFE) of medical face mask materials, employing a ratio of the upstream bacterial challenge to downstream residual concentration to determine filtration efficiency of medical face mask materials.

This test method is a quantitative method that allows filtration efficiency for medical face mask materials to be determined. The maximum filtration efficiency that can be determined by this method is 99.9 %.

This test method does not apply to all forms or conditions of biological aerosol exposure. Users of the test method should review modes for worker exposure and assess the appropriateness of the method for their specific applications.

This test method evaluates medical face mask materials as an item of protective clothing but does not evaluate materials for regulatory approval as respirators. If respiratory protection for the wearer is needed, a NIOSH-certified respirator should be used.

Relatively high bacterial filtration efficiency measurements for a particular medical face mask material does not ensure that the wearer will be protected from biological aerosols since this test method primarily evaluates the performance of the composite materials used in the construction of the medical face mask and not its design, fit, or facial-sealing properties. The values stated in SI units or inch-pound units are to be regarded separately as standard.

The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance of the standard. This test method does not address the breathability of the medical face mask materials or any other properties affecting the ease of breathing through the medical face mask material.

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This test method may also be used to measure the bacterial filtration efficiency (BFE) of other porous medical products such as surgical gowns, surgical drapes, and sterile barrier systems.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

There are some other methods which are also useful for combating COVID – 19 viruses for medical professionals. This may be either in the form of medical gowns or other protective textiles useful for doctors, nurses and other staff members associated with the profession. For more knitwear knowledge, please pay attention to the knitting fair.

Source: textiles school

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