High Stretch Denim - Processing made Simple !

High Stretch fabrics are becoming very popular these days, but at the same time it is a challenge for a conventional Denim Mill to manufacture & process these fabrics, with their conventional machinery setup.

New mills have installed the wider width machines to weave wider width fabrics, but still they struggle to make a proper high stretch denim fabric.

As per my experience, majority of the problems can be solved if care is taken at the fabric construction and designing stage, and if a 'fabric relaxing machine' is installed as a process just before sanforizing.

What are the expectations from a customer for High Stretch Denim?

• Stretch in the fabric should be 40% to 50%

• Residual Shrinkage in the Fabric should be -10% to -12%

• Fabric Growth should be 4% to 6%

• Fabric Recovery should be 85% to 90%

What are the challenges faced in manufacturing High Stretch Denim?

• How to relax and process the fabric without curling or creasing?

• How to achieve lower shrinkages with high stretch and excellent recovery properties in the final finished fabric?

What should be the approach to find a smart & simple solution?

The fabric mill should install a continuous fabric relaxing machine on the concept of steam tumbling. This will help eliminate the cumbersome procedure of wet processing. This also makes the process sequence very short, smart and simple, resulting in increased fabric yields of first quality goods free from defects like creases.

The second most important aspect should be to use technical & creative skills to construct a right fabric at weaving stage itself. This will solve majority of subsequent problems faced in processing like bundling, creasing and high residual shrinkage. To solve these issues, most of the technicians in processing, adopt the process of heat-setting the fabric; but this results in collateral damage of inferior stretch and poor recovery.

Different weaves and different fabric optics will require different parameters to be decided in weaving. However, I will list down some concepts for deciding the 'on-loom' weaving construction parameters for the most conventional basic 3/1 twill Denim Fabric. These tips are from my personal experience on the shop floor.

Some practical tips to design 3/1 twill High Stretch Denim Fabrics:

• High Stretch fabrics are generally used in the weight range of 8 Oz to 10 Oz.

• As far as possible, count of weft yarn should be same or coarser than the count of warp yarn. Such fabrics using coarser weft would generally never curl or bundle.

• Ensure the weft cover factor lies between 12 to 14. This will ensure that the fabric handle is not limp, at the same time give sufficient air space to develop high stretch.

• Over all cover factor of the fabric should be kept below 35.

• Reduce the warp density in comparison to a conventional rigid fabric of the similar weight.

• Lesser the warp density, more the air space leading to higher stretch levels in the weft direction.

• Use grey fabric boil test procedure to decide the correct warp density.

• Instead of using cotton spandex core spun yarn in the weft, replace it with polyester cotton blended spandex core spun yarn. This will give a fabric with better 'flat look' optics, superior stretch and recovery at the finished fabric stage.

• Use of a micro-filament polyester stretch yarn in the weft, also gives excellent results. Microfilaments helps subside the harsh feel on fabric back side.

• Use a finer denier of spandex filament in the core. This will help eliminate the heat-setting process, which will help retain the excellent stretch & recovery in the final finished fabric.

• The fabric relaxing machine will allow to shrink the fabric to the required width needed to meet the 'residual shrinkage' standard promised to the customer. Compute this target 'finish width' backwards from the boil test result.

In short, it is possible for a conventional Denim mill to make High Stretch Denim fabric without opting for a costlier and riskier wet processing route. Always remember, keep the process sequence steps to the minimum. As in practice, every additional process step is a potential risk for the increased downgradation in the fabric.

In case any further assistance is required, contact me on my website www.astuteconsult.in or write to me a mail at atul.singh@astuteconsult.in