The purpose of this study is to explore the effect of dyeing kinetics of direct dyes on cotton fabrics which have been pretreated by the one‐step method. The results indicate that as the dip temperature or curing time is decreased, the equilibrium absorption and rate constant increase, while the activation energy decreased, Furthermore, all the measures of dyeing indicated poorer results with the one‐step method than the conventional method, although there was no significant difference observed in terms of the structural diffusion resistance constant.

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ABSTRACT:The influence of pregrafting of cotton fabrics with mixed monomer on the dyeing kinetics of direct dyes was investigated. The results of this research show that the equilibrium absorption (a e ) and activation energy (DE*) in the dyeing of grafted fabrics are smaller than those of ungrafted fabrics. The experimental results show that the value of the equilibrium absorption is smallest when the molar ratio of MAA/MAM (methacrylic acid/methylacryl amide) is 4/6. However, the rate constant ( k) is larger for grafted fabrics than for ungrafted fabrics. No significant difference was observed between the structural diffusion resistance constant ( n) of grafted and ungrafted fabrics.

SYNOPSISCotton fabrics were pregrafted with mixed monomer of methacrylic acid (MAA) and Nmethylolacrylamide (MAM) before undergoing finishing with 1,3-dimethylolethylene urea. Experiments show that when the molar ratio of MAA and MAM is 4 : 6 the finished fabric has the maximum nitrogen content (N%) and crosslinking density. The pregrafting can improve the wet crease recovery angle and the moisture regain, can reduce the tensile strength retention, and has little effect on the dry crease recovery angle. In addition, at a pregrafting ratio of 4 : 6, the finished fabric has the highest crease recovery angle and moisture regain. I N T R O D U C T 1 0 NIn the past there are many reports on using vinyl monomer to graft cotton fabrics for modifying chemical properties.'-" Most of these reports are based on single monomer grafting, with a few using mixed monomer to pregraft before resin finishing. In addition, Hebeish et al. reported about first finishing cotton with N-methylolacrylamide (MAM) and then grafting.12 On the other hand, Negishi and Reinhardt et al. used various single vinyl monomers to first pregraft the cotton fabrics and then finish with MAM.l3,l4 The results show that when the fabrics are pregrafted first and then finished with resin, the finished fabric shows great improvement of its physical properties. However, these reports concern only the physical changes in the finished fabrics. There is no research report on the crosslinking and physical properties of pregrafted fabrics, nor the use of mixed monomers for pregrafting and then resin finishing. Thus in this work, two monomers, methacrylic acid (MAA) and MAM, were mixed in different molar ratios to pregraft cotton fabrics for resin finishing. In addition, the relationship between the physical properties and crosslinking structure of the fabrics, after pregrafting and resin finishing, was studied . EXPERIMENTAL MaterialsThe cotton fabric, 40s * 40s ends (100) and picks (80), was desized, scoured, and bleached. MAM and MAA were purified according to the standard proc e d u r e~.~~~'~ Sodium hydroxide, ferrous ammonium sulfate, hydrogen peroxide, selenium mixture catalyst, sulfuric acid, boric acid, pyridine zinc nitrate, etc., were of reagent grade. The finishing agent 1,3-dimethylolethylene urea (DMEU) was synthesized according to the Hoover and Voals method. Methods Grafting ProcedureThe sample of cotton fabric was first impregnated in freshly prepared aqueous ferrous ammonium sulfate (0.03%) for 15 min at 25°C under a materialto-liquor ratio of 1 : 100. The sample was then squeezed, washed thoroughly with distilled water, and dried. Accurate weight of the Fe2+-containing sample was immersed in an aqueous solution containing the monomer or the mixture monomer, hy- 625