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 The latter, coated with vinyl resins, has largely superseded the heavy canvas tarpaulins used to protect merchandise in transit.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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