Elastomeric fabrics

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. 

The manufacturing machines are usually equipped with positive feeding devices to control the stretch, recovery, and modulus of the completed elastomeric fabric, especially a design for one-pound or two-pound weights to control the elastic yam draft in elastomeric fabrics. The final percentage of elastic yams in each constmction can also be accurately controlled by the feeding devices for producing consistent fabrics. 

Raschel Warp knit raschel fabrics are produced in a similar way as tricot fabrics except for their stitch motions. The motion results in elastic yams being put into raschel construction as lay-in-yams versus knit-in yams on tricot constractions as shown in Figure 3.7. This lay-in stmcture leads to the raschel fabrics with elastic stretch in the length direction. Other elastic bar movements are possible to increase stretch and modulus in width. Raschel machines can have up to 64 yam guide bars to produce fabric patterns as extensive as jacquard lace. Elastomeric fabrics made by raschel showed good elastic stretch, recovery, and modulus in both length and width directions as elastic yam lap increases. 

Special requirements for warp knitting include the following (1) a device is required for proper density and even tension of elastomeric yams in producing elastomeric fabrics with repeatable results in stretch, recovery, modulus, shrinkage, and elastic fiber content (2) yam let-off must be electronic or electromechanical for best fabric control and reproducibility (3) special selvage holders (pullers), fabric hot-wire slitters. 

Interlock machines Interlock elastomeric fabrics are produced by adding a lay-in feeder for the elastic yams positioned between the cylinder and the dial yam feeds, as shown in the feeds stmctures in Figure 3.8. Therefore, the yams are trapped... 

Double jersey machines The elastomeric fabrics produced by double-knit machines show distinct face and back stmctures. The fabrics with double or triple layers in some end uses can also be produced by the machines. All double-knit stitches, including double jersey, pique, French pique, ottomans, twills, needle outs, and flat back rib stmctures can be produced using elastic yams. The stitches have width or both width and length stretches using lay in, knit in, or plaiting carrier systems as mentioned above for the elastic yams in bare and covered types. 

Testing for elastomeric fabrics is not similar to that used for rigid fabrics because the slight tension variation of elastomeric yams affects the final fabric properties. Normally, an ahysteresis curve is produced when a force is applied to an elastomeric fabric... 

Figure 3.9 Hysteresis curve of elastomeric fabric elasticity...

Elastic stretch and recovery of elastomeric fabric is tested using ASTM D 4964-96 (2012) method. Fabric slippage will be more for elastic fabrics, which will affect the end results. This can be controlled by using band clamps at both the edges. Kielty et al. (2002) recommended that the stretch properties are better tested by deformation of a sample clamped all around, as in a burst tester. 

Uses Intermediate solvent humectant coating resin raw material in paints crosslinking agent in polyurethane elastomers polyurethane chain extender intermediate for plasticizers, pharmaceuticals mfg. of tetrahydrofuran, terephthalate plastics elastomeric fabric coatings in food-pkg. adhesives Regulatory FDA 21CFR 175.105... 

These include elastomeric fabrics, high temperature webs, such as those based on ethylene/chlorotrifluoroethylene copolymers (E-CTFE), water soluble webs based on polyvinylalcohol (PVOH) and others [5],... 

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