The leather is elastic, and the non-elastic fabrics have a lower elasticity than the leather. By adding a small percentage of elastane from 2 to 5% to the garment, it acquires a significant elasticity, easily adapting to the body movements and always returning to its original size. The elastane is a synthetic polyurethane fibre used to give elasticity to the fabrics. In North America and Australia it is known as spandex. Better known among the consumers with the commercial brand names like: Lycra, Dorlastan, etc. Even if in appearance it looks like a single continuous thread, in reality it is composed of several thin threads. Up to 33 dtex, the thread count can be produced as a single filament, while the bigger ones are produced as multifilament (from 2 to several dozen).
Cross-section of elastane fibre Fibre longitudinal view
The most frequent defects after dry-cleaning:
1. Defect (most frequent): loosen loops or white threads
Light loosen loops or light hanging filaments on the surface of the fabric, highlighted by the colour contrast: the fabric most at risk is viscose/elastane fabric.
General fabric appearance Detailed view of elastane loops
Elastane loosen loops
Elastane threads coming out of the edges Frosted appearance after dry-cleaning
We will try to explain the causes of elastane spillage from the fabric, during washing and after being worn. The elastomer is embedded in the fabric and covered by the yarn. There are several types of coverings with different benefits for the items A, B and C.
Usually version A is preferred for cost reasons
Low coverage
As it can be seen from the photos, the cover is normally not strong enough to hold the inner elastane core to its place, as shown in the photo. In addition, during the dyeing and finishing processes of the elastic fabrics, a thermofixation treatment is necessary (heat-fixing for 20-30 sec at 170°C) to stabilise the elastomer. If the fabric is not thermally fixed, the drying temperature causes the elastomer shrinking, which scarcely covered externally, it comes out of the fabric and seams, making loops and white filaments. Using the B or C version and thermofixation, the problem will not arise anymore, but this solution is more expensive.
2. Defect: creases and corrugations especially near the seams
The garments gauging located at the seams along the weft and the crotch area are caused by the spillage of the elastane threads from the seams due to the low coverage of the elastane core and the absence of thermofixation; the elastane spills out of the seam for a few centimetres. The covering yarn remains trapped in the seam, while the elastomer comes out, getting wrinkled the fabric that remained without elasticity.
Types of creases
Elastomer spillage from the seam
3. Defect: low elastic recovery after washing
Often, when wearing the garment and after washing, the most stressed areas (knee) become puffy or loosen due to the low elastic recovery of the elastane, that reaches a maximum limit of 95%.
Corrugations due to a low elastic recovery
For improving the elastic recovery that is often missing in the case of the elastomer, it is used instead or in addition, the elastomultiester that has less elasticity, but that is close to 100% elastic recovery.
Elastic recovery chart
The elastic recovery is measured with a dynamometer by applying 5 hysteresis cycles to the material and checking the deformation at the end
4. Defect: total elasticity loss during washing
The chlorine used in washing ( bleaching) or finishing treatments can cause the elastane breakage.
Elastane breakage Detailed view of the breakage
5. Defect: blue stains due to optical bleaching
Sometimes we can find on the garments small blue or yellow/ pink stains after washing with optical bleachers. As shown in the photos, the optical (which is usually a blue or pink colour) is settled or rather, absorbed by the elastane; elastane absorbs the colour of the optic due to the high percentage (9-10%) of silicone oil that it contains. Placing the garments with such defects on other garments, the colour is transferred as the silicone oil acts like a conductor for the dye.
Various blue stains caused by optical bleaching
Therefore, we obtain stretch garments without using elastane or adding it. The elasticity is slightly lower while the stretch recovery is much higher.
6. Defect: colour difference (non-homogeneity) not detected in acceptance
The elastane contains a significant percentage of silicone oil, which if it is not previously removed through dry-cleaning, it can prevent the proper color distribution during the dyeing process, creating a non-uniform color as shown in the picture below.
Non-homogeneity defect
In order to avoid this defect on all garments containing elastane, it is therefore necessary to dry-clean the garment before dyeing it, in order to remove the oil contained by the elastomer. •
by ING. VITTORIO CIANCI
Director LART – Textile Research and Analysis Laboratory
LART
Laboratorio Analisi e Ricerca Tessile
Textile Research and Analysis Laboratory
Via Vasco de Gama 2 41012 CARPI (MO)
Tel. 059 645279
lart@lartessile.it – www.lartessile.it
DETERGO Magazine # January 2023
