In this article we are going to talk about a problem linked to the presence of bubbles in the fabric of elasticated pair of trousers starting from a case studied in a laboratory.
The pair of trousers in the picture below was brought to the laboratory because of its “faulty” look.
In particular, what is being noticed is the presence of bubbles in the hips area near the stitching. The images below show the defect in detail:
The study of defectiveness starts from the analysis of fabrics characteristics. The above is a mixed fabric composed of cotton, polyester and elastane.
The elasticity of a pair of trousers is usually conferred to the presence of elastane, a synthetic fiber able to stretch up to three times its length and come back to the dimensions it had once the stress stops.
Elastane is a continuous and a very fine filament inside the yarn that takes a wrinkled shape. On the contrary, when the elastane is absent, the filament looks outstretched in some parts as illustrated in the image below.
Coming back to our trousers case study, the first test aimed at searching for elastomer’s presence in the area of the bubbles in order to find out whether their presence is due to the absence of elastane, which could lead to the loosening of yarn and the entire fibrous structure.
Hypothesis no 1: absence of elastomer
The extracted thread analyzed under a microscope looked regular, wrinkled, and it had a complete elastomer strain. Therefore, it can be stated that the defect was not due to the breaking of elastomer caused by e.g. stitching or packing. Hypothesis number 1 has not been proven.
Hypothesis no 2: aggressive washing treatment
The second stage of the research focused on the washing treatment the garment had undergone in order to find out whether it had been carried out too aggressively compromising, therefore the elastic performance of the fabric. To be able to carry out this test, the faulty garment’s elasticity was compared to the elasticity of a raw fabric washed regularly at 60°C. Comparing the performances allowed to understand whether the washing treatment of the garment was regular, therefore it can be possible to either confirm or eliminate the washing treatment as a possible cause of the fault.
The results of the laboratory test “Fabrics Elasticity Measurement – part 1: test on a strip width – UNI EN 14704-1” are reported below.
The comparison of results allows to state that the stretching characteristics of the faulty garment and of the fabric washed in the laboratory are actually the same. As a consequence, the treatment of the garment has not been the cause of the defect. Hypothesis number 2 has not been proven.
Hypothesis no 3: too aggressive ironing
Once verified that the elastomer is present in the fabric and it does not carry any signs of breaking nor sliding inside the yarn, and that the washing treatment has been carried out regularly, it is now possible to investigate into the last stage of garment processing that is ironing. In this stage the garment undergoes two different types of stress: heat and mechanical traction.
As underlined before, elastane is characterized by a high level of elasticity under moderate stress and it is able to come back to its original state at 100% once the stress stops. This means that the elastomer fibers do not deform when they are significantly stretched over short periods of time.
Nevertheless, in case of excessive traction, the elastane filament is not able to come back to its original dimension as the structure of the polymer gets deformed.
Such a phenomenon is particularly significant if we combine heat with traction as the elastomer fibers are very sensitive to thermal stimuli.
So, it is reasonable to say that in case of the faulty garment, the bubbles in its fabric have been created due to excessive mechanical traction during the ironing stage of the garment which was combined with the exposure to heat that “fixed” the elastomer in the stretched position. The visible consequences are the loosening of the fabric and the formation of bubbles. Hypothesis number 3 is to be considered the right one.
A= unstressed elastomer filament
B= stressed elastomer filament
By Ecochem s.r.l. and Ritex Textiles Research and Testing
DETERGO MAGAZINE
APRIL 2016
