Abstract:

Objective Cotton fabrics are popular among consumers due to its good breathability, moisture absorption and wearing comfort. However, cotton fabric elasticity is poor, prone to wrinkles during the washing process. In order to improve the anti-wrinkle properties of cotton fabrics, reactive dyes with different reactive groups were used to dye cotton fabrics by cold pad-batch process to improve anti-wrinkle properties of cotton fabrics while dyeing.
Method In this study, the chemical properties and surface morphology of dyed cotton fabrics were characterized with the help of X-ray diffraction, Fourier infrared spectroscopy and scanning electron microscopy. In addition, the effects of the number, type and distance of reactive dye groups on the anti-wrinkle properties of dyed cotton fabrics were investigated by testing the wrinkle recovery angle and K/S value of dyed cotton fabrics.
Results The wrinkle recovery angle of cotton fabrics dyed with Reactive Blue 19 did not change significantly with the increase of dye mass concentration (Fig. 1). The wrinkle recovery angle of cotton fabrics dyed with Reactive Red 198 and Reactive Black 5 increased with the increase of dye mass concentration, and the wrinkle recovery angle of cotton fabrics dyed with Reactive Black 5 was higher than that of cotton fabrics dyed with Reactive Red 198. Among the four two vinyl sulphone groups, i.e. Reactive Black 5, Reactive Orange 131, Reactive Blue 203, and Reactive Red AS, reactive dyed cotton fabric obtained darker apparent color, and their K/S maximum values were 25.2, 23.8, 24.1, 23.3 respectively (Fig. 3). The wrinkle recovery angle of the cotton fabrics dyed with the four dyes increased rapidly with the increase of the dye mass concentration. When the dye mass concentration reached a certain value, the wrinkle recovery angle of the fabric remained unchanged (Fig. 4). The wrinkle recovery angles of cotton fabrics dyed with Reactive Black 5, Reactive Orange 131, Reactive Blue 203 and Reactive Red AS increased from 165° to 210°, 208°, 205° and 198°, respectively, representing increases of 27%, 26%, 24% and 20% respectively, corresponding to the distance between the two vinyl sulphone groups in the reactive dyes (Tab. 1). The X-ray diffractograms of cotton fabrics dyed with Activated Black 5 were basically the same as the untreated ones, all of which showed four crystalline surfaces, exhibiting the form of cellulose I (Fig. 5(a)). The absorption peaks of benzene ring and C=C at 1 609 and 1 567 cm^-1 appeared in the cotton fabric impregnated with Reactive Black 5 dye dried immediately relative to the untreated cotton fabric (Fig. 5(b)). However, the absorption peak of C=C at 1 567 cm^-1 disappeared in the cotton fabric impregnated with Reactive black 5 after cold pad-batch process. In addition, the cross-section of cotton fabric changed from flat waist-like to elliptical after Reactive Black 5 dyeing (Fig. 5(c)).
Conclusion Compared to single reactive groups, double reactive group dyes can improve the wrinkle resistance of cotton fabrics. Compared with the Reactive Red 198 dyed cotton fabric containing isobutyl groups, the Reactive Black 5 dyed cotton fabric containing two vinyl sulphone groups has better anti-wrinkle properties. By comparing the Reactive Black 5, Reactive Orange 131, Reactive Blue 203 and Reactive Red AS, the 4 two vinyl sulphone group dyes, the greater the distance of the reactive group, the better the anti-wrinkle properties of the dyed fabrics. Among them, the Reactive Black 5 dye dyed fabric has the best anti-wrinkle effect. The cross-section of cotton fabrics becomes round from a flat waist-like shape after dyeing. The dye reacts covalently with the hydroxyl groups on the macromolecular chain mainly in the amorphous region of the fiber, and the cross-linked structure formed enhances the anti-wrinkle property of the cotton fabric.

Key words: cotton fabric, anti-wrinkle property, reactive group, reactive dye, dyeing property, cold pad-batch