Elastomeric finishes

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. 

Elastomeric finishes are frequently used with swimwear, lingerie, foundation garments, athletic wear, hosiery and normal clothing. Some performance 

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Some effects are obviously contradictory, for example hydrophobic finishes and hydrophilic antistatic finishes, or stiffening and elastomeric finishes, or stiffening and softening finishes. 

Depending on their method of synthesis, silicone softeners can contain variable amounts of volatile siloxane oligomers. Together with volatile emulsifiers these oligomers can cause pollution problems in the waste air from tenter frames." In textile finishing, silicones are also used as water repellents, elastomeric finishes, coatings and as defoamers. 

All of these problems are more severe at high hand builder concentrations. Selection criteria for products that add stiffness and/or fullness include cost, ease of application, compatibility with other chemicals present in the finishing bath and, of course, the properties of the resulting finished fabrics and their degree of permanence. Hand builders provide antislip effects and can be used for antipilUng. Obviously the stiffening effect is not compatible with an elastomeric finish. 

Permanent antistatic fmishes, based on crosshnked polyamines and polyglycols, need an alkaline catalyst. Therefore the one-bath combination with finishes, which need acid catalysis, is difficult but not impossible. Examples of acid-catalysed fmishes are the easy-care and durable press fmishes, durable hydrophylic silicone softeners and elastomeric finishes, also fluorocarbon-based repellency and some flame-retardant finishes. High finish effects result from a two-bath application with of the easy-care finish first followed by the surface-related antistatic finish. 

Table 12.1 Assessment of the main effects of elastomeric finishes on woven and knitted fabrics ...

Reaction of a silane and a silanol to form an elastomeric finish. 

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. 

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. Table 12.2 shows an overview of test methods for elastomeric finishes. 

Elastomeric finishes are often combined with easy-care and durable press finishes. The silicones reduce abrasion, increase tearing strength (Ehnendorf testing apparatus - ASTM D1424), and crease recovery. For equal crease resistance and durable press performance the amount of cellulose crosslinking agents can be markedly reduced in these combinations. ... 

Ultratex [Novartis], TM for a group of silicone elastomeric finishes for natural and synthetic textile fabrics. 

Uses Fabric softener base for brushed or raised fabrics, elastomeric finishes, for cotton, rayon, acetates, wool, and nylon Properties Lt. yellowish flakes disp. in hot water pH 4 100% cone. 

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