In current fashion trend use of stretch fabric compiled with cotton, polyester, viscose, Tencel is increasing day by day. Recent past this fiber was being used mainly to produce specially ladies skinny garments but recently it’s being widely used in ladies, gents, kids even swim and sports ware as well.
Globally, the demand of spandex is increasing day by day and many diversified spandex applications are coming out gradually. In Bangladesh, the second largest apparel exporter uses of spandex is also growing. The main reason for increasing use of spandex fabric tremendously is due to elasticity property and comfort.
Spandex breakage/damage is a severe problem and common phenomenon during stretch fabric processing. Sometimes spandex fault (called in another name Lycra missing) is not detected during fabric manufacturing or fabric processing but it comes out more prominently after garments wash. Washing is the last process of fiber to apparel processing and last stage detection mean ultimately loss of garments FOB.
Currently, global spandex consumption market is 800,000 tonnes while China alone consumes 500,000 tonnes of it. In Bangladesh, there is about 10,000 to 12,000 tonnes of spandex demand every year. Use of spandex in Bangladesh is increasing rapidly. Spandex breakage/damage is a severe problem and common phenomenon during stretch fabric processing. Sometimes spandex fault (called in another name Lycra missing) is not detected during fabric manufacturing or fabric processing but it comes out more prominently after garments wash. Washing is the last process of fiber to apparel processing and last stage detection mean ultimately loss of garments FOB. This article is the second of the author written on the topic. The first one was published in Textile Today January 2018 issue. The article was titled ‘Factors to be considered for improving stretch fabric performance’.
Following 5 major problems are generally observed during spandex fabric processing.
- Spandex/elastane missing (spandex filament missing through the width of fabric)
- Spandex /elastane damage (due to heat application during fabric processing)
- Spandex /elastane come out (spandex filament cut and come out on fabric surface)
- Tension variation in fabric i.e. core spandex not in the center position of the sheath.
- Width variation in the same roll may occur during weaving or processing.
Spandex filament is very sensitive to heat, alkali, chlorine bleach and abrasion as well. Below are some precaution suggestions that can help to improve or some case can fully eliminate this type of problems.
- Using uniform roving and good quality spandex filament during spinning.
- Using special attachment called Amsler. In a conventional system, in a core spinning while a spandex filament breaks the particular spindle not detouched from roving and sheath yarn and spinning ongoing. While using Amsler attachment particular roving atomically cut off once spandex filament break. This can avoid spandex/ lycra missing completely.
- Take care of spandex path/ guide on ring frame as if the spandex filament can keep onto the center of the yarn. i.e. maintain good core covering. This can help to improve tension variation problem in the greige.
- Ensuring uniform spandex drafting all over the ring frame, using same spandex brand also using same age spandex yarn in a lot which can improve width variation as well as elongation variation problem.
- Need to select optimum core-sheath ratio and spandex draft. Recommended draft range as table 1.
- Before spinning spandex filament storage environment should keep same. Recommended storage temp below is 300C, storage time should not exceed more than 3-4 month. Within 3-4 months spandex filament has to be used as ‘first in first out’ basis otherwise elongation /width variation problem can arise. Weaving stage:
- During weaving use maximum no of weft feeder. The more feeder the more weft mixing and minimize tension and width variation.
- For stretch fabric weaving rapier loom can produce better quality compared to air jet loom as in rapier loom pick insertion tension is more regular than air jet. Pick insertion path should be smooth.
- When weaving compact stretch fabric, a heavy bit up or bumping may occur which cause core spandex may cut off or damage. Such case to reduce bit up adjust backrest and frame height and shed angle need to be reduced as much as possible. Also do not use sharp or defected dent reed.
- Greige age is a factor to get consistent shrinkage and elasticity during processing. So, the greige fabric should be used up in processing as quickly as possible. Processing stage:
- Spandex fiber is heat sensitive. Although spandex melting temperature is 2300C, Elastane properties may be affected or be damaged at a temperature above 1800 So care should be taken on temperature from pretreatment to finishing.
- Hot alkali can damage spandex. During mercerizing, need to maintain caustic concentration not more than 250gpl or 250 Be (Baume) and impregnation time should not exceed 50 seconds.
- Care should be taken on CBR (Continuous Bleaching Range) cylinder dryer temperature as if the fabric is properly dried and not over dried.
- When heat set on stenter – heat chamber temp should be within the range of 1500C to 1750C and must not exceed 1800 In the stenter, First 4/5 heat chamber is used for drying and rest exposes heat on spandex. Precaution should be taken as if heat exposing time not exceeds 15 seconds.
- Also, stenter machine speed needs to be adjusted subject to fabric GSM and to maintain dwelling time 30 second to max 40 seconds. Garmenting stage:
- The fabric has to be kept in a relaxed system for at least a day in order to preshrunk before wash.
- When the fabric is laying for cutting, lay thickness and laying tension should be kept in optimum to avoid heat and static electricity generation in between layers.
- Use rotary knife during cutting and preciously cut curvature area of the pattern.
- During stitching use ball point needle instead of sharp needle and also change the needle after 2/3 hour of sewing. A special type of SPI fine needle is very effective for stretch fabric stitching.
- Based on fabric cover factor select appropriate swing thread, stretch type, and Compact fabric should be sewn in fine thread low SPI.
- Take care of back stitch and thick area sewing and all kind of bartack stitching (if required) should be carried on after garment washing.
- Sewing allowances should be kept as maximum as possible which will help to slip out spandex filament from the core.
- Never use a hot gun to remove potassium permanganate (PP)/contamination from finished fabric or finishing stage of garmenting. Garment washing stage:
- Chlorine bleach can damage and weaken spandex filament. Low concentrate (35%) chlorinated bleach can be used but the use of high concentrate is forbidden.
- All kind of alkali use is forbidden during desizing and scouring alternatively acid enzyme can be used. In all process, pH should be within the range of 6 to 8.
- Keep M:L ratio as maximum as possible in order to reduce beat up inside a washing
- Avoid use of stone during washing.
- Use low-temperature formaldehyde resin instead of high temperature.
- Use dummy during rubbing, destroy or any dry process.
- There is a change of spandex damage during the different dry process in washing. i.e. – during whiskering, sandblasting, destroy, PP spraying or 3D curing.End-use caring:
- Do not use hot water when washing.
- For spandex garments, hand wash is more suitable than a machine No dry cleaning.
- Never use chlorine bleach to remove the stain from the fabric.
- Use low-temperature iron and keep the iron moving on the fabric and never leave the iron on one spot for too long.