Features
Login | Register 
Clip this Page |Discuss this Page |Email this Page |Print this Page
Garments, Fashion & Retail
  Application of elastomeric finish in apparels

Elastomeric finishes have beneficial properties; they are easy to process, permeable to air, non-adherent to wounds and have excellent sewability, very good softness, desirable stretchability and recovery, aver S Sakthivel, Dr B S Dasaradan, R Chandhanu, J Padmapriya, P Vadivel and R Vignesh.

Elastomeric finishes are also referred to as stretch or elastic finishes and are particularly important for knitwear. These finishes are currently achieved only with silicone-based products. The main effect is durable elasticity, because not only must extensibility be enhanced, but recovery from deformation is of crucial importance. After all stresses and disturbing forces have been released, the fabric should return to its original shape. An alternative approach to providing fabrics with elastomeric finishes is to incorporate a few per cent of elastic fibres (mostly segmented polyurethanes) into the yarn making process prior to fabric manufacture.

Depending on the content of elastic fibres the resulting elasticity of the fibre blend can be much greater (eg, power stretch) than with elastomeric finishes. But these finishes avoid the typical problems correlated to weaving or knitting, dyeing or printing of fabrics from elastic fibre blends. Elastomeric finishes are preferred when a lesser degree of elasticity, combined with other useful performances, is desired. For this reason, even the combination of elastomeric finishes and elastic fibre blends is common.

Elastomeric finishes are frequently used with swimwear, lingerie, foundation garment, athletic wear, hosiery and normal clothing. Some performance enhancements provided by elastomeric finishes include very soft handle, improved crease recovery, better sewability, higher abrasion resistance and some stain-repellency. The table shows the importance of the main effects of elastomeric finishes on woven and knitted fabrics. Silicone products, including elastomers, are used for the preparation of wool, creating shrink resistance and soft handle, often in combination with polyurethane pre-polymers (eg, blocked isocynates). In the textile-related silicone market elastomers are very important.

Assessment of the main properties of elastomeric finishes on woven and knitted fabrics

Properties Woven Knitted
Elasticity * ***
Crease recovery ** *
Handle *** **
Sewability * ***
* = Important, ** = Very important, *** Extreme important

Elastomeric mechanism

The individual fibres of an elastomeric fabric must be completely covered with a thin film of an elastic material without any fibre-to-fibre bonding. The film causes a high degree of recovery from deformations owing to its particular structure of widely spaced crosslinks.

Chemistry of elastomeric finishes

The mesh structure responsible for elasticity is achieved by the condensation of a mixture of silicone pre-polymers on the fabric surface. This mixture may often consist of a terminal silanol (α, ω-dihydroxy polydimethylsiloxane), methyl hydrogen silane and a metal salt catalyst. Some hydro-silane groups can be oxidised by air to silanol groups. Condensation of the silanol groups of neighbouring molecules generates cross-linked structures that are necessary for elasticity.

The incorporation of a small content of tri- or tetra-functional silanols, hydroxysilanes, acyloxy or ester derivatives is another approach that yields wide-meshed networks with high permanence. The molar ratio of terminal silanols and cross-linking multifunctional compounds determines how widely spaced the resulting silicone film and the corresponding elasticity will be the permanence of these silicone films on hydrophilic fibres, such as cellulosics, is restricted by mechanical stress caused by repeated laundering and related swelling.

Therefore reactive fixation of epoxy-modified silicones was developed. The epoxy groups react with the hydroxyl groups of cellulose or the amino groups of wool and silk generating stable ether or amino bonds between the silicone film and the fibre surface. In addition to their high wash permanence these epoxy-modified silicone finishes have low yellowing properties, but their softness is less than that of the amino silicones. As with all highly reactive compounds, the handling of epoxides needs special care. They are potentially physiologically dangerous. Nonionic elastomeric silicones are best applied by padding, while cationically modified silicone products may also be applied by exhaustion techniques.

Evaluation of elastomeric finishes

The simplest, but not necessarily the best, way of evaluating elastomeric finishes is the ‘template’ method. The fabric is stretched by hand with, it is to be hoped, constant force in both warp and fill or weft and wale directions. The residual elongation is determined by the fabric’s dimensional change. This method suffers from difficulties in repeatability owing to the variable stretching forces. A more reliable extension tester is a machine has hydraulic damping and constant tension controls to provide reproducible stretching forces to the fabric. Fabrics can be tested in the wet or dry states. Another suitable method for evaluating elastomeric finishes is ASTM D 4964-96: ‘Standard Test Method for Tension and Elongation of Elastic Fabrics (Constant-Rate-of-Extension Type Tensile Testing Machine)’. Fabric samples are formed into loops and are placed through several extension–recovery cycles under controlled conditions.

Troubleshooting for elastomeric finishes and particularities

Elastomeric finishes that have been completely reacted cannot be easily removed, so reworking of fabric seconds can be a problem. Other potential difficulties with elastomeric finishes include increased pilling and flammability (the silicate residue prevents thermoplastic fibres from melting away from the flame). Silicone elastomers can attract dirt. The fabric shade after treatment with elastomeric finishes may be significantly altered from the original shade, therefore good communications between the dyeing and finishing departments are necessary.

Elastomeric finishes are often combined with easy-care and durable press finishes. The silicones reduce abrasion, increase tearing strength and crease recovery. For equal crease resistance and durable press performance the amount of cellulose crosslinking agents can be markedly reduced in these combinations. Silicone films have a relatively low light reflectance and therefore cause more depth of colour both dry and wet fabrics. In contrast the high reflectance of polyester, especially of polyester micro fibres, impedes their dyeing and printing to deep shades. Here silicone finishes are used as ‘black improvers’. But silicones increase the thermomigration of disperse dyes, causing lower wash and crocking fastness. This disadvantage is especially marked with micro-emulsions of silicone softeners, containing high concentrations of emulsifiers, which also increase dyestuff migration.

Application of elastomeric finishes

The following applications are made with elastomeric finishes:

• Premium “hand”
• Very good softness
• Excellent fibre-fibre lubrication
• Substantive to fibres
• Good stretch and recovery
• Improved elasticity and resiliency
• Excellent drape
• Good durability
• Excellent sewability

Conclusion

Elastomeric finishes are used in various fields due to their inherent properties. They are easy to process, permeable to air, non-adherent to wounds and excellent sewability, very good softness and good stretch and recovery. A basic understanding of how these should be selected and used to their maximum benefit can help the swimwear, lingerie, foundation garment, athletic wear, hosiery and normal clothing, achieve the desired elastomeric finish.

References

1. Hardt P: Silicon-Textilhilfsmittel, Textilveredlung, 1984, 19 (5), 143–146.

2. Gysin H P: Moderne Textilausrüstung mit Silikonelastomeren, Textilveredlung, 1981, 16 (12), 475–479.

3. Guise B and Jones F W: Shrink-resisting Wool with Silicones, Textile Chemist Colorist, 1977, 9 (3), 65–69.

4. Geubtner M and Hannemann K: Waschbare Wolle durch moderne Pflegeleichtausrüstung, Melliand Textilberichte, 2001, 82 (7/8), 598–602.

5. Liebiger M: Silikone zum Ausrüsten von Textilien, Deutscher Färberkalender, 1989, 93, 132–151.

6. Mooney W: Chemical Softening in Textile Finishing, D Heywood (ed), Bradford, Society of Dyers and Colourists, 2003, 283–291.

7. Poppenwimmer K and Schmidt J: Ausrüstung von Synthesefaserstoffen, Teil 2, Textilveredlung, 1999, 34 (7/8), 4–8 © 2004.

Note: For detailed version of this article please refer the print version of The Indian Textile Journal September 2011 issue.

S Sakthivel,
Department of Fashion Technology,
Angel College of Engineering and Technology,
Tirupur, Tamil Nadu 641 665.

Dr B S Dasaradan,
Department of Fashion Technology,
Angel College of Engineering and Technology,
Tirupur, Tamil Nadu 641 665.

R Chandhanu,
Department of Fashion Technology,
Angel College of Engineering and Technology,
Tirupur, Tamil Nadu 641 665.

J Padmapriya,
Department of Fashion Technology,
Angel College of Engineering and Technology,
Tirupur, Tamil Nadu 641 665.

P Vadivel
Department of Fashion Technology,
Angel College of Engineering and Technology,
Tirupur, Tamil Nadu 641 665.

R Vignesh
Department of Fashion Technology,
Angel College of Engineering and Technology,
Tirupur, Tamil Nadu 641 665.

published September , 2011
back to Features   |   back to Garments, Fashion & Retail
ViewpointFeaturesFeatures
A Raw Deal
China, the world's largest cotton importer, accounting for more than 60 per cent of total raw cotton exports from India, has upset the calculations of Indian cotton sector following a marked fall in demand from that country. Cotton exports from India have been
Testing the world's favourite fibre
Cotton is the world's favourite fibre, and a superb raw material for many textile end-uses. But it is by no means easy to work with - as a natural product, its many variabilities present some extremely complex challenges.
Arvind's fire protection solutions
Since 1931, Arvind Ltd stands tall as the flagship enterprise of the $14 billion Lalbhai group. Arvind has marked its presence throughout the apparel value chain - from fibre to retail. The company has recently made a strong foray
full viewpoint... more... more...
Table of Contents Most Recent Issues Write to Editor
Subscribe to ITJ | Write to the Editor | Rate Card | ITJ Ads | Tell A Friend | About Us | Contact Us  | Login | Register  | Home
Associated Portals:  | www.ipfonline.com | www.automotiveproductsfinder.com
IPFonline Limited, 2nd Floor, Shafika Building, 17/7 Kodambakkam High Road, Nungambakkam, Chennai - 600 034.
Tel: +91 44 42991234 (30 Lines). Fax: +91 44 42108441. Email: admin@ipfonline.com