What are the shrinkage types of knitted fabrics?

① Elastic contraction

When the fabric can relax freely, elastic contraction occurs in each processing process. Theoretically, the fabric shrinks elastically in both wet and dry state, but the fabric is less stable in wet state and is easier to be stretched. Therefore, in most cases, the elastic contraction can be caused by applying mechanical kinetic energy (such as expansion, vibration) to the fabric. Because the friction between the loops of the dry fabric is very high when it is stretched, it is easy to shrink, so there is almost no elastic shrinking effect when mechanical kinetic energy is applied to the dry fabric. It can be seen that the elastic shrinkage mainly occurs in the first half of the drying process of the wet cloth.

 ② Drying shrinkage

When the residual moisture content of the fabric reaches about 30% to 40% and then dried, the shrinkage produced is the drying shrinkage; when the moisture content of the fabric is 6% to 8%, the shrinkage ends. The drying shrinkage depends on the mechanical kinetic energy exerted on the fabric during the re-drying process, and the drying shrinkage occurs in the second half of the drying process of the fabric.

③ Pre-shrinkage

Dry or slightly damp fabric loops will produce shrinkage after being compressed, that is, the fabric will shrink when it is pre-shrunk through the felt, and the fabric will get better residual shrinkage after shrinking.

④ Washing shrinkage

When the fabric is not completely shrunk, when the garment made of the fabric is washed by the washing machine, washing shrinkage will occur. It appears in the form of elastic shrinkage and drying shrinkage. The method of detecting the shrinkage rate of the finished fabric is to detect the degree of shrinkage of the fabric after washing. Usually different in the way of drying. There are two testing standards: the hanging drying standard in the form of static drying and the tumble dryer drying standard in the form of kinetic energy drying. Generally, the difference in shrinkage between these two standards is about 5%.