| Cotton fabric is widely popular by consumers because of its comfortable wearing,excellent air permeability and soft hand feeling.However,cotton fabric is prone to wrinkle and has poor shape retention,which affects the wearability of cotton fabric to some extent.Therefore,it is necessary to carry out crease-resistant finishing in the post-finishing process of cotton fabric to improve the shape retention and crease resistance of cotton fabric.However,before crease-resistant finishing,cotton fabric should be pretreated to remove impurities in grey fabric and meet the requirements of subsequent processing.Anti-crease finishing methods mainly include resin finishing and liquid ammonia finishing.Anti-crease finishing can improve the anti-crease performance and shape retention of cotton fabrics.At the same time,it will have an impact on the polymerization degree and crystallinity of cotton fabrics.In this paper,the effects of different printing and dyeing processes on the polymerization degree and crystallinity of cotton fiber are compared,which provides reference for the selection of printing and dyeing procedures in factories.In order to test the molecular weight of cotton fabric accurately,the influence of different solvent systems on the molecular weight of cellulose was studied,and the solvent system suitable for the molecular weight test of cotton fabric was selected.The main research contents and conclusions are as follows:Viscosity method is generally used to test the molecular weight of cotton cellulose.The disadvantage of viscosity method is that the solvent easily leads to cellulose degradation in the process of dissolving cellulose,which makes the measured molecular weight lower than the actual value.In order to reduce the degradation degree of cotton cellulose in the determination process,and avoid affecting the accurate characterization of the molecular weight of cotton cellulose,the mixed solvents BMIMAC/DMSO and copper ethylenediamine were used as cellulose solvents,respectively.And the viscosity of the cellulose solution was measured to explore the effects of different solvents on cellulose degradation.The results showed that the molecular polymerization degree of cellulose measured by dissolving cotton fabric with BMIMAC/DMSO was higher than that measured by dissolving cotton fabric with copper ethylenediamine.With the extension of storage time of cellulose solution,the viscosity of cellulose/copper ethylenediamine solution decreased continuously,while the viscosity of cellulose/BMIMAC/DMSO solution remained basically unchanged,which indicated that copper ethylenediamine had obvious degradation effect on cellulose,while cellulose had good stability in BMIMAC/DMSO solution.The intrinsic viscosity[η1]of cotton fiber after first dissolving in BMIMAC/DMSO is 12.1362（100 ml/g）.The regenerated cellulose was obtained by adding water into the cotton fiber/BMIMAC/DMSO solution,and the intrinsic viscosity[η2]of regenerated cellulose after second dissolving is 11.7677（100 ml/g）.The difference of intrinsic viscosity obtained by two dissolution is only 3.0%,which indicated that cotton cellulose molecules did not degrade obviously in BMIMAC/DMSO solution.The molecular weight changes of cotton fabrics before and after desizing,mercerizing,liquid ammonia finishing and resin finishing were measured by viscosity method using Bmim Ac/DMSO as solvent.The results showed that compared with grey cloth,the polymerization degree of cotton fabric after desizing decreases by 0.87%.After mercerization,the polymerization degree of cotton fabric decreased by 2.89%.After finishing cotton fabric with liquid ammonia,the polymerization degree of cotton fabric after liquid ammonia-alcohol treatment-air drying decreased by 2.99%.After liquid ammonia-air drying,the polymerization degree of cotton fabric decreased by 6.95%.After liquid ammonia-drying,the polymerization degree of cotton fabric decreased by 8.99%.And after resin finishing,the polymerization degree of cotton fabric decreased by 26.07%.Cotton fabrics processed by different printing and dyeing processes were tested by XRD,and the crystallinity was calculated by XRD diffraction data.The results showed that compared with grey cloth,the crystallinity of cotton fabric after desizing decreases by 3.23%.After mercerizing,the crystallinity of cotton fabric decreased by 6.12%.After finishing cotton fabric with liquid ammonia,the crystallinity of cotton fabric after liquid ammonia-alcohol treatment-air drying decreased by 19.91%.After liquid ammonia-air drying,the crystallinity of cotton fabric decreased by 24.67%.And after liquid ammonia-drying,the crystallinity of cotton fabric decreased by 15.73%.The crystallinity of cotton fabric after resin finishing decreased by 10.96%.The crystallinity of cross-linked cotton fabric with liquid ammonia moisture decreased by 14.16%. |
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