Technical Tuesdays

REF:TT/July 2011/ WK 1

Possible causes and precautions To be taken care to Reduce/Control the Shrinkage of 100% Cotton Woven bottom weight fabric before sanforising –

Shrinkage :

Shrinkage is a complex interaction of different parameters.It depends on type of fibre, EPI, PPI, thread count, twist, crimp, type of weave and nature of finish applied to it.

Possible causes right from fibre :

SPINNING - Here lies rare root cause for shrinkage faced in final finished fabric

  • Fibre Quality
  • Crimp
  • Staple length of fibre and its proportion of mixing (short and long)
  • Nature of yarn (Combed / Carded)

-in Combed yarn the Fibres are evenly arranged because of which the tension is evenly distributed

-in carded yarns mostly there are irregular in position

these are considered as the most important parameters as the shrinkage is highly depended on the the structural arrangement of fibres and micro fibrils with in the construction of yarn

WEAVING -Fabric construction has to be balance

Some of the parameters to be watched closely are:

  • Total cover factor
  • Ratio of warp to weft cover factor to ensure construction of the fabric is balanced
  • Even distribution of pick density mainly in case of slub yarns

WET PROCESSING –

Desizing :
- very good and thorough de-sizing will ensure a proper relaxing at early processing stages

Mercerisation & Drying :

-One must do mercerization no causticicingpreferebly in a chain mercer after desizing.

-Fabric stretching at mercerization process is very important, almost in all the cases mercerized fabric width is most relaxed in terms of shrinkage..

-Winding of fabric on Frame should not be done with too much of tension, here preferably one should have positive driver etc...

-While processing warp wise elongation takes place which can be controlled by less tension at drying /batching process.

Finishing :

-Final step in controlling the Shrinkage

-Addition of resin based system (glyoxal/DMeDHEU) along with a good silicone and PE helps to reduce the shrinkage to a considerable extent with minimal strength loss..

Last but not Least above all the process,final stage sanfo after finishing also provides good dimensional properties to the end fabric,

- advisable only after checking the potential shrinkage under standard test conditions after finishing as sonfo is the final stage of processing to control shrinkage.

“Have a happy week ahead”


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