Textile Finishing; Light Reftectant and Light Resistant Finishing

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Textile finishing is complex procedure. There are two types of fabric finishing. Light-Reftectant Finishing and Light-Resistant Finishing are one kind of chemical finishing. Those fabric finishing process are used to make textiles lightproof for particular end use. Some of the chemical change their form in presence light. In that case the chemical must preserve in light protected area. We can easily produce ultraviolet protected fabric using the light reflectant and resistant finishes. Ultraviolet protection is now being built into fibers and fabrics. 

Light-Reftectant Finishes 

Light-reflectant finishes are created by the application of microscopic reflective beads to the surface of a fabric. The increased number of persons who jog or ride bicycles after dark is probably responsible for the application of this finish to a variety of garments for sports and to other items such as backpacks. A reflective finish called Scotchlite is produced by the 3M Company. The manufacturer notes that the finish does not alter the color or appearance of the garment by day, but after dark the fabric “lights up” when directly in the path of the lights of an oncoming vehicle. 

Light-Resistant Finishes

Many textile fabrics are deteriorated by exposure to sunlight, so attempts have been made to protect fabrics from light damage. Of all the types of rays in the sun’s spectrum, ultraviolet rays are the most destructive of fibers. Although antilight finishes have yet to be perfected, those that are being tried either coat the fabric or impregnate the fibers with materials that absorb ultraviolet rays but are not themselves damaged by or removed by exposure to these rays. Such finishes are particularly important in olefin fabrics, which are degraded by sunlight unless ultraviolet stabilizers are added. Such additives to olefin fibers are permanent and are not lost during usage. 

Synthetics that have been delustered with titanium dioxide are especially subject to damage from sunlight. This chemical apparently accelerates damage to the fiber and fading of dyes. The addition of certain chemical salts to the melt solution before spinning can ameliorate this problem. The relationship between exposure to the ultraviolet light of the sun and skin cancer is well known. Many people assume that fabrics prevent exposure to any part of the body that is covered; however, research shows that fabrics do allow passage of ultraviolet light. Knitted fabrics, which usually have a more open structure, generally allow more ultraviolet light through than woven fabrics; lightweight summer fabrics allow more ultraviolet light to reach the skin than heavier fabrics with more opaque yarns. Ultraviolet protection is now being built into fibers and fabrics. Most of the techniques are proprietary processes, so details of how the protection is provided are limited. Kuraray, a Japanese firm, produces Esmo, a polyester staple fiber to which powdered ceramics have been added to absorb and reflect ultraviolet rays. A similar fiber called Aloft is produced by the Japanese firm Toray, and other Japanese firms produce fabrics that are given special protective finishes Australian researchers have developed a chemical finish called Rayosun that is said to be washfast, colorfast, and lightfast. The finishing material contains a “two part molecule,” one part of which absorbs ultraviolet rays while the other part reacts with the fabric, thereby making the finish durable (Sun-proof clothing 1993, 72).

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Textile Finishing; Flame Resistance Temperature Regulating Heat Reflectant Finishing

Flame Resistance finishing:

Flame resistance finishing is modern process of finishing. The terminology employed in a discussion of flame resistance finishing can be confusing. The following definitions and descriptions are currently accepted, although usage may vary, particularly from country to country.

1. Flame resistance finishing is defined by American Society for Testing and Materials (ASTM) (1998, 23) as “the property of a material whereby flaming combustion is prevented, terminated, or inhibited following application of a flaming or non-flaming source of ignition, with or without the subsequent removal. of the ignition source.” The material that is flame resistant may be a polymer, fiber, or fabric.

2. Use of the terms flame retardant and self-extinguishing is discouraged (ASTM 1998, 23, 40). Flame-retardant treated and flame-retardant treatment are, however, acceptable terms and flame retardant is used in other countries. ASTM does not approve the use of the term self-extinguishing to describe a textile product because it is meaningful only when applied to specific circumstances.

3. A thermally stable material (fiber or polymer) is one that has a high decomposition temperature and is thus inherently flame resistant because of chemical structure (rather than through the presence of added flame-retardant treatments) (Clark and Tesoro 1974).)

Temperature Regulating Finishes

Temperature-regulating fabrics are sensitive to the surrounding temperature or to body heat. Finishes that provide this adaptation include substances called phase change materials (PCMs) (Lennox-Kerr 1998). These substances change from solid to liquid or liquid to solid depending on the temperature. The example we are probably most familiar with is ice changing to water when the temperature rises and then changing back to ice again when cooled. Ice absorbs heat to melt and water gives off heat when it becomes solid. PCMs work the same way but are selected to undergo this phase change around normal skin temperature.

One such finish is polyethylene glycol (PEG), which is applied to fabrics along with a methylol agent such as DMDHEU. The result is a network polymer that is insolubilized on the surface of the fibers. The polymer absorbs and holds heat energy at high temperature, and then releases the stored energy under cooler conditions. The finish is durable to wear and laundering, because it is cross linked on the fabric.

Not only do these finishes help to warm or cool the body, but they also increase the moisture absorbency of fabrics, thereby further enhancing comfort. Other improved properties are resistance to static, wrinkling, abrasion, pilling, and soil. The PEG finish has been used on T-shirts, underwear, socks, activewear, and biomedical products.

In another form, PCMs have been applied to fabrics as microcapsules in coatings, used in nonwoven bonding materials, or included in spinning solutions of manufactured fibers. Outlast Technologies, Inc. produces the microcapsules. Acordis Fibers has produced a version of their Courtelle acrylic fibers with the PCM embedded in them. The fabrics made with these fibers are targeted for outdoor apparel, particularly for cold climates. PCM-containing textile fabrics are expensive because the encapsulation process is technology intensive.

Heat Reflectant Finishes

An increased level of insulation can be provided in garments and draperies by the addition of heat-reflectant finishes. Most of these products are treated with a spray coating of metal and resinous substances. The heat-reflectant material is sprayed onto the surface of a closely woven fabric. The finish is designed to keep heat either on one side or the other side of the fabric. The finish is effective only with radiated heat.

Lining fabrics are usually constructed so that the finish is applied to the inside of the fabric. The finish reflects the body heat back toward the wearer, thus providing added warmth. In protective clothing to be worn under hot conditions, the finish is worn to the outside to deflect heat away from the body.

Draperies may also be treated to provide greater insulation for homes. Treated draperies placed inside windows may serve to keep heat inside the home or to reflect heat outward, preventing it from warming the house. Some of the processes designed to produce heat reflectance use aluminum in the finish, because it provides excellent reflectancy. A variant of this principle is utilized in fabrics coated or laminated with a thin layer of aluminum, foams, resins, or synthetic rubber.

Flame Resistant Textiles by Flame Resistance Finishing

F1ame-Resistant Textiles 

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Textile products can be made flame resistant by using fibers that are inherently flame resistant or by application of a flame resistant finish. Modacrylic fibers offer adequate flame resistance at a moderate cost and have some use in carpets, curtains, and children’s sleepwear. Many other synthetic fibers shrink from ignition flames, providing some protection. Untreated polyester and nylon, for example, will pass the test for children’s sleepwear based on this characteristic. 

The more thermally stable materials such as asbestos, glass fiber, the aramids, PBI, and PBO could be called fireproof substances that will not burn. Glass fiber has many industrial uses and may be used to a limited extent in household textile products such as window shades or lamp shades. Thermally stable synthetic fibers have not been developed for general use but rather are intended for specialized protective clothing for industrial and military uses. Not only are they expensive, but they also lack the aesthetic features that would make them useful in consumer products. 

For fibers that are not flame resistant, a flame-retardant treatment can be applied. Durable finishes for cotton and cotton blend fabrics contain phosphorus which reacts chemically with the fibers and inhibits the production of compounds that fuel the flame. Commercial flame-retardant finishes are Pyrovatex, Proban, and Pyron, the latter produced by Ciba Chemicals. 

Finishes for synthetic fibers have bromine that quenches the flame by reducing the generation of flammable gases. Tris-2, 3- dibromopropyl phosphate (TRIS) was used for several years to impart flame resistance to nylon and polyester, but was suspected of causing cancer in laboratory animals. Since its removal from the market, and modifications in the test procedure for children’s sleepwear, nylon and polyester are not usually finished with a flame-retardant treatment. 

A particular problem in textile flammability is the burning of cotton/polyester blends. Since polyester is less flammable than cotton, one would expect blended fabrics to be less hazardous than all cotton fabrics. This is unfortunately not the case, because the char left as the cotton burns serves to hold the melting and dripping polyester in the flame. This is referred to as a “scaffolding” effect that prevents the polyester from dripping away, as it would do in a 100 percent polyester fabric. 

The polyester remains in the flame and contributes to the burning. Wool is inherently moderately resistant to burning and provides some protection in apparel and interior furnishings. For more stringent uses such as airplane seats, however, wool is given a flame-retardant treatment. A common finish for wool is Zirpro. performance standards that materials are required to meet are set forth in the CFR. These tests described above usually have a single pass/fail criterion. A wide variety of additional tests for flammability can be conducted to provide information on burning behavior and effectiveness of finishes. 

Many of these methods require test samples of considerable size or even whole garments. DuPont, Eastman Kodak, and the University of Minnesota have developed thermal testing manikins with heat sensors located in various parts of the figure. Tests performed using these figures can determine not only the combustibility of the fabric being tested but also the location of hot spots and can furnish data about the transfer of heat. They can also assess effects of fabric layers such as a cotton dress worn over a nylon slip. 

There are tests for carpets other than the pill test required by the federal standard. The Flooring Radiant Panel Test is said to simulate conditions of interior fires more effectively than other carpet tests. As a result, it is likely to be used by governmental and other regulatory agencies that require the more extensive product evaluation that carpeting installed in hospitals and facilities participating in Medicare and Medicaid programs must meet. 

An area of considerable interest in flammability testing of interiors is computer simulation or virtual tests to determine the hazards of real-life situations. For example, data on the furnishings in a prototype room can be used to predict the results of a fire (Gorman 1994). More realistic measures of fire hazards can be obtained and used in such predictive models. 

These measures, including total heat release, rate of heat release, and toxic gases evolved, are the real dangers from fires involving textiles. resin holds yarns together at the points where the yarns interlace. Resin antis lip finishes are durable. Other antislip finishes can be created by coating silica compounds on fabrics. However, these finishes are only temporary.

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Textile Finishing; Stain Repellency and Stain Resistant Finishing

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There are some textile products or fabric those used long time without any types of wash. So some special care must be taken for those materials. Stain Repellency finishing and Stain-Resistant Finishing are those special treatment whish ensure the proper care of the textile material. This types of finishing also cares from oil and wax. 

Stain Repellency finishing: 

Scotchgard and other finishes that repel water and oil may be classified as stain resistant finishes. These finishes decrease the surface energy of the fabric so that water or oil beads up rather than penetrating the fiber. Illustrates this principle with two different stain-repellent finishes: fluorochemical and silicone. The fluorochemical finish, like DuPont’s Teflon finish on cookware, prevents both oil and water from penetrating the fabric surface. The silicone finish, which also coats the fabric, repels water but not oil.Soil-Release Finishes 

Soil-release finishes were developed largely as a result of the tendency of durable press and polyester fabrics to absorb and hold oilborne stains. The soil-releasing finish should not be confused with stain-repellent finishes, although Scotchgard is both stain resistant and soil releasing. Soil-release finishes alter the characteristics that cause soil to bond to the fibers. Agents such as polyethylene glycol derivatives may be added to the polymer solution before extrusion to make the nonabsorbent fibers more hydrophilic (“water loving” or having a strong affinity to water). Other finishes may form hydrophilic grafts on the fiber resulting in improvements in soil release and soil redeposition. Most soil-releasing finishes are applied during the finishing of the fabric and are compatible with durable pres; finishes. 

Some fluorochemical finishes are dual-acting. They are block copolymers of fluorocarbons and polar segments such as esters. In air the fluorocarbon sections come to the surface to repel oily substances. When the finished fabric is immersed in water, however, the polar hydrophilic sections predominate on the surface, attracting water to help release soils. At the same rime that soil-releasing finishes increase the receptivity of fibers to water, a second benefit is gained. Static electricity buildup is decreased as absorbency is increased. 

Increased absorbency also increases the comfort of the garment in warm weather. Fuzzing and pilling seem to be decreased by soil releasing finishes as well, because the finish also lubricates the fabric. Effective soil-releasing finishes should result in fabrics from which common soil is removed during home laundering with normal detergents. Oily stains, often hard to remove from durable press fabrics, should be removable in home laundering. The disadvantage of most of these finishes is that they are gradually diminished through laundering. 

Stain Resistant Finishing: 

Stain-resistant finishes for nylon carpets were developed to increase the resistance of these carpets to food and other common stains. The finishes are generally sulfonated aromatic condensation (SAC) compounds that function essentially as colorless dyes. The stain blockers, which have negative charges, are attracted to the positive sites in the nylon fibers, tie up the dye sires, and set up a barrier layer to staining materials. Many food stains, for example, which are negatively charged like the stain resist molecules, are not absorbed as easily. Today, stain-resistant finishes are used on most nylon carpets for residential use. One trademark is DuPont’s Stainmaster.

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Textile Finishing; Waterproofing finishing, Soil and Water Repellency finishing

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Textile Finishing and Fabric finishing is very important terms in textile manufacturing area. We need some special task with textile material to meet the buyer requirement. We know that natural fibres as well as textile fabric manufactured with natural fibre absorb the water. So it easily passes water with their surface. If we want to protect passing water or making the water proof fabric surface, we need to do some special treatment to surface of the fabric. This could be known as water proofing finishing. This is similar for Soil and Water Repellency finishing. The term water repellent should not be confused with the term waterproof Water-repellent fabrics resist penetration by water but are not completely waterproof. Such fabrics represent a practical alternative to fabrics that keep out water and air.

Waterproofing finishing: 

For a fabric to be truly waterproof, it must be completely sealed with a substance that is insoluble in water. The familiar rubber coated garb of police officers and firefighters is a good example. Modern waterproofing materials include the vinyl resins, which do not oxidize and crack as readily as rubber. Synthetic rubbers are also more durable to outside influences than natural rubber. The fabrics used in most of today’s waterproof materials are cotton and nylon. The latter, coated with vinyl resins, has largely superseded the heavy canvas tarpaulins used to protect merchandise in transit. A fabric that is waterproof allows no water to penetrate from the surface to the underside. Coatings made from rubber or synthetic plastic materials can create fabrics that are completely waterproof; however, these fabrics tend to be warm and uncomfortable because they create a barrier that traps air and perspiration close to the body.

The dilemma of providing protection and comfort was resolved by the development of fabrics that are described as waterproof and breathable (WP/B). The general principle behind these fabrics is that they keep out water from rain and snow but allow the passage of moisture vapor from perspiration. They are promoted for use in outdoor clothing and for active sports. One of the first of these products was Gore- Tex, made by placing a membrane of fluoropolymer underneath a layer of outer fabric. The membrane is porous.

The pores are smaller than a drop of water that contains many water molecules, but they are larger than a molecule of water vapor. This structure keeps out rain but allows moisture from perspiration to escape.

The success of Gore- Tex has led to the production of other products using similar principles. Many of these use polyurethane coatings with microscopic pores. Sympatex, a polyester membrane for lamination, is nonporous but breathable. A charged outer surface attracts polar water molecules which are drawn through the membrane. Also helping to “push” moisture vapor through is the high vapor pressure on the body side (Sympatex 1988).

Soil and Water Repellency finishing:

Soiling results when a textile comes into contact with soiled surfaces or with air- or waterborne soils. Soil is retained either by mechanical entrapment of soil particles within the yarn or fabric structure or by electrostatic forces that bond the soil to the fabric. One way to approach the problem of soiling is to prevent its deposition on the fabric. Another is to seek ways to facilitate its removal. Special finishes have been developed that have taken both of these approaches.

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Fabric Shrinkage Control by Textile Finishing

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Fabric finishing is most effective procedure to maintain the fabric property. Most of the fabric property could be maintained by textile finishing. There are different types of textile finishing. Such as Mechanical finishing, Chemical finishing or other special finishing. 

Fabric shrinkage is one of most important fabric property. Shrinkage property is depending upon the fibre property. It effects in finished garments shape. We know that every style of garments have particular size. The most popular sizes are Small(S), Medium(M), Large(L), Extra Large(XL) etc. size of particular garment indicate by pattern grading. Most probably 1cm to 2 cm varies from one size to another size. Due to shrinkage the size of the garment could be change abnormally. For example Length of a garments increase but chest does not change. So it will be subjected as size mistake but the size was ok during fabric cutting. That’s why shrinkage property of fabric must be controlled by particular finishing method before cutting the fabric. 

A reduction in the length or width of a fiber, yarn, or fabric is known as shrinkage. If fabrics shrink after they have been made into garments or household items, they may decrease in size to such an extent that the item is no longer serviceable. For example, a garment with a 25-inch waist size will decrease by 11\4 inches if it shrinks 5 percent. Growth occurs when a fabric increases in dimension. Some fibers such as wool, cotton, and rayon swell more in water than do others. Fabrics made from these fibers are less dimensionally stable than fabrics made from fibers with lower moisture absorbance. Wetting a fabric causes the tension that has been applied during its manufacture to be relaxed, so that fabrics generally shrink after the first and subsequent launderings. This type of shrinkage is known as relaxation shrinkage. It occurs because the moisture within the fibers allows them to return to the dimensions they occupied before they were stretched during processing. The amount of relaxation shrinkage depends on the amount of stretching the fibers underwent during manufacturing. 

Wool fibre and rayon fibre, which are more extensible, will stretch more and therefore have greater potential for relaxation. Successive heating and drying cycles may produce progressive shrinkage, where the fabric continues to shrink. Woven fabrics generally shrink more in the warp than in the filling direction because the warp yarns are under greater tension during weaving. When the fabric is later subjected to moisture, or heat in the case of thermoplastic fibers, the stresses within the fibers are relieved, and the fabric relaxes. Fibers that are moisture-absorbent absorb a significant amount of water and swell. Accordingly, the yarn diameter increases, and the yarns in each direction must move closer together to accommodate the yarns in the opposite direction. This is a less strained position for the yarns and results in a permanent increase in crimp, especially in warp yarns. 

Knit goods tend to stretch more during manufacture than woven goods, and therefore knit goods are likely to shrink and change shape even more than woven goods. Procedures and solvents used in commercial dry cleaning, as a rule, do not permit fabrics to relax, as washing does, so that items that are dry cleaned may not shrink as readily. Shrinkage in dry cleaning generally results from the high moisture content in the solvent or from steaming the fabric during pressing.

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TEXTILE FINISHING; CONVENTIONAL AND SPECIAL FINISHES FOR TEXTILE FABRICS AND YARNS

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Textile or Fabric Finishing

The textile finishing is an important process for production of finished textile fabrics and garments. Textile finishing usually includes treatments such as scouring finishing, bleaching finishing, dyeing and/or printing, the final mechanical finishing or chemical finishing operations of textiles, that during this stage are carried out on textile products (staple, sliver or top, yarns or filaments, woven or knitted fabrics to enhance their basic characteristics like dye penetration, printability, wettability, colour, hand, and appearance of textile material.

By special textile finishing, we also mean all the processing operations that, though included in the so called finishing stage, are generally applied to the textile fabrics to improve their appearance, hand and properties, at times in accordance with their field of application.

The textile finishing stage plays a fundamental role in the excellency of the commercial results of textiles, which strictly depend on market requirements that are becoming increasingly stringent and unpredictable, permitting very short response times for textile manufacturers. The latest finishing machines on the market used for textile finishing operations generally offer multi-purpose applications; the flexibility and versatility features of these finishing machines are uninterruptedly evolving to grant excellent consistency of the results in finishing process.

The making of a marketable consumer-usable textile fabric is not completed after fabric formation, dyeing, or printing. Fabrics usually still need to undergo and additional processing know as textile finishing, which is the final processing before the fabric is cut into apparel or made into articles such as towels, curtains, or draperies. Finishing is what makes fabrics more suitable for their intended end use. Final inspection to ascertain fabric quality is performed at the completion of finishing. There are many types of finishes; some make fabrics softer after finishing, some stiffer after finishing, some water-repellent after finishing, and some shrink-resistant after finishing. Some fabrics may have two or more finishing treatments at a time in the finishing machine. Certain finishes are so temporary that they completely lose their effectiveness after one laundering. Therefore, understanding textile finishes and the properties they impart, the fibers and fabrics to which they may be applied, and their limitations and shortcomings is important to an overall understanding of textiles.

Most textiles finishing processing are performed in the same plants as dyeing or printing. Most dyers and printers are also finishers, with finishing being considered a separate but integrated department of the dyeing or printing organization.

Classification of textile Finishes and finishing process:

Textile finishing operations can be carried out by means of discontinuous, continuous and semi continuous systems according to the finishing machine.

Discontinuous or batch-type systems of finishing:

A single or individual finishing machine is used to complete all the finishing stages.After taking all types of preparation the finishing machine is loaded with the textile material. Predetermined cycles are carry out according to the finishing process. After completing the process the machine is unload and finally wash it thoroughly before starting a new cycle. This process is suitable for small batch and the working procedures are most easy and flexible. for example, it is easy to a carry out a bleaching process on a single machine, and then a scouring one followed by a dyeing process. The discontinuous process is labour-intensive for the production of large production because it necessary more man power to handle and transport the textile material; it is also a time oriented process and results that can change  from one lot to another.

Continuous systems of finishing: 

 A series of machines are required for continuous finishing system. Each machine carries out always and solely the same process.According to production requirements each finishing machine are arranged. Initial cost of this system is higher and the machine set up very much complex.but once the system has developed according to proper plane, it requires a smaller manpower and grants excellent repeat ability and high production rates; So it is stat that the continuous system is beneficial for producing large batch of textile material with the highest cost-efficiency and productivity.

Semi-continuous systems of finishing: 

Semi continuous finishing system is modern and result oriented method. In this system the continuous finishing machine and discontinuous finishing machines are used for better performance.For explain the procedure it is said that a continuous finishing machine is used to wet the textile material. The machine could be continuous pad batch machine, The small and medium lots are suitable for these mixed systems of finishing. In that process the quality of the product is higher but the cost is medium but more manpower is required.

Textile finishes and finishing are classified in several ways, the most common classifications being aesthetic finishes, which modify the appearance and/or hand or drape of fabrics, and functional finishes, which improve the performance properties of fabrics. The textile finishes discussed in this articles are presented in these two categories.

Finishes are also classified as chemical finishes and mechanical finishes. Those finishing are also called wet finishing and dry finishing, respectively. Wet finishes are normally used to textile material by padding, followed by drying or curing.Mechanical finishing are special types of process used to change change the  appearance by changing the surface the fabric or any textile material. It related to specific physical treatment . Finishes are also categorized by their degree of permanence. These finishes are called durable,semi durable temporary and permanent finish. Permanent finishes do not change or alter throughout the life of a textile material. usually involve the change in structure of fibre structure by special chemicals.

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