Factors that affect the dimensional stability of the fabric
Hygral expansion
Hygral expansion is the moisture-absorbing properties of fabrics. The main reason behind this is the types of fibres that absorb moisture.
Especially wool fibre, the fabric has more tendency to absorb moisture.
When fabric absorbs moisture, it expands due to the swelling of constituent fibres.
When fabric release moisture, it comes back to its original dimension.
This dimension change depends on the constituent warp and weft threads type.
I.e. - In wool fabric, if warp and weft both are the same types of threads, then hygral expansion ratio of that wool fabric is equal for both directions.
Hygral expansion is generally caused by the straightening of crimped yarn as it absorbs moisture. In the case of wool fabric, wool fibres swell to 16% in diameter and 1% in length when wet.
The swelling causes fibres which have been permanently set into a curve to try to straighten out due to the imbalance of forces.
When the fibres dry out and try to come back to their original diameter and so take up their original curvature, The increase in dimensions due to hygral expansion can take place in the fabric at the same time as any shrinkage because of relaxation of set-in stresses such as occurs when the fabric is soaked in water.
The magnitude of the expansion can be greater than that of the shrinkage.
The dimensions of the fabric, when it is first wetted out and then dried, make shrinkage measurements.
A fabric often has the same moisture content during the final measurement as it had when the initial measurement was made.
Hygral expansion of fabric in a finished garment can cause problems when the garment is exposed to an atmosphere of higher relative humidity than that in which it was made.
The expansion can cause the pucker at seams and wrinkling where it is constrained by other panels or fixed interlinings.
Relaxation Shrinkage
Relaxation Shrinkage is the irreversible dimensional change of fabric dimension.
The main cause of this shrinkage is the release of fibre strains imparted during the manufacturing process, which have been set by the combined effects of time, finishing treatments, and physical restraints within the structure.
During the manufacturing of fabric from yarn, Threads are under considerable tension, particularly in the warp direction. This tension is temporarily set in the fabrics up to some extent. This fabric goes into a state of dimensional instability.
When the fabric is completely wetted, it tends to revert to its more stable dimensions which results in the contraction of the yarns, this effect is usually greater in the warp direction than in the weft direction.
In the case of wool fabric, Relaxation shrinkage is caused by stretching the wet fabric beyond its relaxed dimensions during drying.
Swelling shrinkage
Swelling shrinkage is caused by the swelling and de-swelling of constituent fibres in fabric during chemical processing and garment manufacturing process.
Swelling shrinkage is also caused by the contraction of the individual fibres which accompanies their uptake and loss of water.
Often absorption and desorption of moisture or water is the main reason for swelling shrinkage.
This shrinkage mainly occurs in cotton and viscose materials.
I.e. - Viscose fibres increase in length when absorbing moisture, by 5% and in diameter wise by 30-40% when viscose gets dryer these percentage minor changes, this variation caused swelling shrinkage.
By swelling shrinkage, the warp yarn either increases in length, or the weft threads must move closer towards ends in the fabric.
However, in some processes tension is applied to the warped way on fabric during swelling shrinkage, this will help to increase the length of the fabric or stretch the fabric.
In the absence of this tension, (which is usually the case during washing) the weft threads will therefore move closer towards warp threads and as a result, the fibre dimensions will revert to their original values on drying, the forces available for returning the fabric to its original dimensions are not as powerful as the swelling forces so that the process tends to be one way.
Felting shrinkage
Felting shrinkage is happening due to the formation of the frictional properties of the component fibres of the fabric, which cause them to migrate within the structure.
Basically, this is considered significant for fibres having scales on their surface such as wool.
In the weaving process, sometimes this shrinkage is used to increase the density of the woven structures.
Felting shrinkage is related to the directional frictional effect (DFE) which is found in wool fibres.
The coefficient of friction of wool fibres is greater when the movement of the fibre about another surface is in the direction of the tip than when it is in the direction of the root.
The felting Shrinkage effect is directly measured because it is caused by the combined effects of DFE and fibre movement promoted by the elasticity of wool.
The behaviour is promoted if the fibres are in warm alkaline or acid liquor.
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| Various fabric sample |
- Which factor affects the dimensional stability of fabric?
- What is hygral expansion?
- What is relaxation shrinkage?
- What is swelling shrinkage?
- What is felting shrinkage?
References
Booth, J. E. :. (n.d.). Principles of textile testing an introduction to physical methods of testing textile fibres, yarns, and fabrics. London: National Trade Press Ltd,1961. from https://www.abebooks.co.uk/Principles-Textile-Testing-Introduction-Physical-Methods/19989810376/bd
Cenote, M. (2015). Google Books. In The SAGE Guide to Key Issues in Mass Media Ethics and Law (pp. 847–858). SAGE Publications, Inc.
Ferreiro López-Riobóo, J. I. (2015). Long-term (2001–2012) study of a proficiency testing scheme for textiles. Accreditation and Quality Assurance, 20(4), 239–245. https://doi.org/10.1007/s00769-015-1128-1
Patwary, E. M. Z. (2012, May 30). The procedure of dimensional stability test. Textile Fashion Study; Engr. Mohammad Zillane Patwary. https://textilefashionstudy.com/procedure-of-dimensional-stability-test/
Saville, B. P. (1999). Dimensional stability. In Physical Testing of Textiles (pp. 168–183). Elsevier.
What is Fabric Dimensional Stability? How to do the Shrinkage Test? (2017, June 19). Testex. https://www.testextextile.com/fabric-dimensional-stability-shrinkage-test/
