INTRODUCTION

Over the last few decades various garment washing techniques have been used on different material types to create a large variety of attractive fashions in garments. Since denim constitutes the largest portion of the garments that are washed, the term wash has come to mean the finishing of denim garments (Chong, 1994). Denim washing is generally divided into the following categories:

Today, use of enzymes and bleaching agent to stonewash has become increasingly popular because use of stones alone has several disadvantages. For example, stones used in the process causes wear and tear on the machinery, they cause environmental waste problems due to the grit produced and result in high labor costs associated with the manual removal of the stones from pockets of garments. Consequently, reduction or elimination of stones in the wash may be desirable.

In view of that fact, ultrasound appears to be a very promising alternative technique to provide a far more efficient stirring/mixing mechanism for the immediate, border layer of liquid at the fiber’s surface. Generally, sonication of liquid causes two primary effects, namely, cavitation and heating. When microscopic cavitation bubbles collapse at the surface of the solid substrate, they generate powerful shock waves that cause effective stirring/mixing of the adjusted layer of liquid (Blanchard et al., 2004). The common features of using ultrasound is: Cutting and sewing (Dermott, 2001), textile wet processing (Michielsen and Beckham, 2004), elimination of polyester fiber oligomers (Cunko et al., 2001), preparation of non-woven fabric reinforced polyacrylonitrile (Hirata, 1992), low temperature dyeing of polyester (Bhatlacharya, 2000), dyeing polyamide/lycra blend (Merdan, 2004), enzyme treatment of cotton fabric (Yachmenev, 1999) and etc.

According to the literature survey and the history of ultrasonic, it has been very useful in a wide variety of applications, including textile treatments such as washing, dyeing and etc. The objective of the presented paper is to investigate the effectiveness of ultrasonic environment in making a different worn out appearance on denim fabrics, which can be used as a complementary measure for reducing chemicals in the treatment and for making a various look on the fabric.

EXPERIMENTAL

All the tests were done in Islamic Azad University Research and Science Campus and Iran Color Research Center in 2006.

Samples of two kinds of blue and black denim fabrics (Table 1) with two neutral cellulase enzymes and sodium hydrosulphite (Table 2) were treated as depicted in Table 3. Time, temp, L:R were the same for all the samples 60 min, 50°C, 1:100 orderly and twenty four series of samples were treated.

In 1 step method 4.5 g L^-1 of cellulase enzyme with 2.5 and 5 g L^-1 hydrosulphite lonely or simultaneously together were used and in 2 step method, first the same amount of enzyme as before applied then 2.5 or 5 g L^-1 of hydrosulphite were added to the samples (Table 3).

To observe and take pictures of produced changes on the appearance of samples a Projectina microscope (No. 4014 Swiss made) and a Fujitsu scanner (No. Fi-4010, resolution = 100) used.

Color coordinates L*, a* and b* of treated samples determined by a reflective spectrophotometer (COLOUREYE 7000A of Macbeth brand with view angle of 60°C and the light source D₆₅ in dye standard of CIELAB) and by using 1 and 2 relations the ΔE*and W were obtained.

The Abs and λ_max of samples determined by an absorption spectrophotometer (CECIL2021 Single Beam in the range of 200 to 700 nm).

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