Impact of Washing Process on the Physical Properties of Denim Fabric ( Twill and Dobby )

DOI: http://dx.doi.org/10.24018/ejers.2021.6.7.2638 Vol 6 | Issue 7 | December 2021 77 Abstract — The study was focused on investigating the impact of different washing processes (dark shade, medium shade, light shade) on various properties of denim fabric. Two different types of fabrics with twill and dobby weave constructions were produced from cotton, spandex, and polyester yarn, and different types of washing processes were applied. Dimensional stability, tensile strength, tearing strength, EPI and PPI, weight, colorfastness to rubbing, colorfastness to perspiration (acid and alkaline), and colorfastness to water was investigated and comparisons were made statistically between the before washed sample and after washed sample. It is found that the process result shows better tear and tensile strength in case of dark & medium shade wash than light shade wash. On the other hand, weight and EPI & PPI have shown better result for light wash than other wash. Colorfastness to rubbing, Colorfastness to water, and Colorfastness to perspiration (acid and alkaline medium) are similar. The shrinkage% is higher especially in the weft direction of the fabric for light wash than the dark wash.


I. INTRODUCTION
Denim is one of the predominant clothing products in the textile field recently [1]. It is a very strong, and stiff fabric constructed with weft white yarn and warp colored yarn which are fashion trend for all classes people, all seasons, all climatic conditions and all over the world [2], [3]. The weft yarn of the denim fabric enlarges alongside the entire width of the fabric [4]. Among various finishing processes in denim garments manufacturing, washing is a significant process and it's mainly applied on denim garments to modify the appearance, size outlook, comfortability, and fashion of the garments [5].
The utmost impact is made on the wear, hygienic and mechanical properties of items by washing [6]. Due to washing, insoluble matters or other impurities from the fabric are removed and it is also performed to produce effects such as color fading with or without patchiness, crinkles, puckering, hairiness softened hand feels, and stabilize dimensions in denim garment [7], [8]. Due to after wash shrinkage of some garments, it could be purchased directly from the store or shop as per required size [9]. So, garments washing especially denim garments have become popular all over the world day by day [10].
Bleach wash, stone wash, acid wash, detergent wash, silicon wash, etc are used to focusing on the finishing of denim fabric [11].
Several studies were done about the changes in physical and mechanical properties of denim fabrics in context with a PP wash, enzyme wash, bleach wash. [12], and stone & acid wash [13]. In a study, the influence of washing (enzyme wash with stone and bleach) on the tensile strength of the denimwashed fabric were investigated [14]. In another study, the changes in tear strength, fabric weight, tensile strength, dimensional stability, and different colorfastness properties were examined with different types of washing processes [15]. By using different softeners on stretch denim fabric, dimensional stability and colorfastness properties of stretch denim fabric was also studied [16].
This paper aims to determine the impact of different shade wash (dark shade, medium shade, and light shade) on various properties of twill and dobby weave denim fabric.

A. Materials
Two types of fabric were used for this research, one was slub stretch and another was regular poly stress denim. Slub stretch-denim composition is 99.15% cotton and 0.85% spandex. Regular poly stretch denim composition is 81% cotton, 18% polyester, 1% spandex.

1) Recipe for Dark Shade Wash
The detailed recipe which has been used for washing dark shade is given in Table I.

2.2) Recipe for Medium Shade Wash
The detailed recipe which has been used for washing medium shade is given in Table II.

2.3) Recipe for Light Shade Wash
The detailed recipe which has been used for washing light shade is given in Table III. Table IV illustrates the consequence of colorfastness to the water of twill and dobby denim fabric for different wash (dark, medium & light wash). Color change and color staining grade was almost unchanged for different wash. For twill fabric, an inconsiderable change was found in the color staining and slightly improved the color fastness compared to the before and after wash samples. For dobby fabric, there is no significant changes were found in the color staining.    Fig. 2 show that the weight of before wash denim fabric was 10.99 Oz/yd² and it increased upon dark wash, medium wash & light wash and values are 12.2, 12.4 and 12.6. That means samples gain more weight during light wash than dark wash and medium wash. So, we can say that different wash effect can plays a significant change in fabric weight as well as GSM.

C. Effect of Different Wash on Colorfastness to Rubbing
Colorfastness to rubbing has been affected significantly due to the wash effect. The below table is stated for details.  Table V represents about the result of color fastness to rubbing of twill and dobby denim fabric for dark wash, medium wash & light wash. It is clear that each wash shows excellent color fastness to rubbing both in dry and wet state because color fastness to rubbing was developed significantly after the treatment. The color grade of dry rubbing was relatively better in light wash & medium wash for both twill & dobby fabric and light wash was shown better color grade for wet rubbing than dark and medium wash.

E. Effect of Different Wash on Tensile Strength
Testing of samples was done after washing. Then, the result has been put on the graph and found below two graphs which represents tensile strength effect of the fabrics.  All the washes influence adversely on to the samples. Fig.  5 and Fig. 6 represent about the effect of washing process for tensile strength of twill and dobby denim fabric in the warp and weft way direction. Light wash sample shows the lowest result. On the other hand, tensile strength of dark washed sample is much better than other samples in both twill fabric as well as dobby fabric. So, light wash and medium wash should avoid in denim washing.  Table VI illustrates the consequence of dimensional stability of twill and dobby denim fabric for different wash (dark, medium & light wash). To inspect the variation in dimensional stability, the shrinkage of before and after washed samples were evaluated and got a little bit of change was found in warp direction but weft-wise shrinkage is greater for both fabrics. In both direction, light wash has shown better results compared to others wash.

G. Effect of Different Wash on EPI and PPI
After washing and testing of samples, the result has been put on the graph and found below two graphs which represent the effect of different wash on EPI and PPI.  Here in Fig. 7 and Fig. 8

H. Effect of Different Wash on Colorfastness to Perspiration 1) Colorfastness to perspiration (Acid)
There were no significant changes in the result that was found after the perspiration test at acid is given in Table VII. 2) Colorfastness to perspiration (Alkaline) There were no significant changes in the result that was found after the perspiration test at alkaline is given in Table  VIII.  Table VII and Table VIII clear the results that no significant changes occurred in colorfastness to perspiration for both Acidic and Alkaline medium of each washed samples of the fabrics. For twill fabric, a slight change in the color staining grade of light wash was observed and slightly improved the color fastness compared to the before wash sample and other wash samples. For dobby fabric, there is no significant changes were found in the color staining.

IV. CONCLUSIONS
In this study, fabric weight, tear strength, tensile strength, EPI and PPI, various colorfastness properties, and dimensional stability were analyzed by applying different wash shade on denim fabric.
The weight of both denim fabrics incremented consistently after applying different kinds of shade wash and showed the highest value for the light wash. The tear strength and tensile strength of both fabrics are decreased in both directions after wash. The EPI and PPI are also decreased. Light washed sample was shown better grade than other washed sample for dry and wet rubbing. The grade for colorfastness to perspiration (acid and alkaline) and colorfastness to water were remain unchanged with different types of wash. The dimensional stability of each sample was also changed significantly by applying different wash shade. The highest shrinkage has occurred in the weft direction for the light wash.
From this study, it is found out that light wash and dark wash have a great influence on different properties of denim fabric.