Study On The Modification In Alkali-urea System And Sizing Performance Of Linen Yarns

The linen fiber,which is known as the “fiber queen”,has good wearing performance.The linen fabric is more and more popular among consumers because of its excellent characteristics such as rough and crisp,cool and breathable,natural antibacterial,antistatic and anti-ultraviolet.However,due to the defects of hard and brittle,short and coarse of the linen fiber,which are the typical characteristics of processing fibers,the pure linen yarn made by wet spinning has a smaller elasticity and a lower breaking elongation than that of the same cotton yarn.In weaving,pure linen yarn has a brittle end because of its low breaking elongation and high strength,which affects the weaving efficiency on high-speed looms such as rapier and water jet.This limits the processing area and fabric quality of pure linen yarn and becomes a major bottleneck in hemp textile technology.To this end,in order to improve the breaking elongation of pure linen yarn and its weaving efficiency,the alkali-urea method is used to modify the linen yarn.Firstly,the 24 Nm linen yarn was modified by alkali-urea method.By comparing and analyzing the surface morphology,infrared spectrum and crystallinity of the yarn before and after treatment,it was found that alkali-urea treatment can destroy the crystalline region of cellulose.With the reduce of the fiber crystallinity and the increase of the amorphous region,the intermolecular hydrogen bond was destroyed and the intermolecular interaction force was weakened.In addition,impurities such as lignin and hemicellulose on the yarn surface can be removed to make the yarn soft.At the same time,the single-factor analysis was carried out on parameters such as alkali concentration,urea concentration,treatment time and bath ratio in modification process and the influence of various parameters on the tensile fracture properties of linen yarn was discussed.Based on the breaking strength and elongation at break of linen yarn,the treatment conditions were optimized by weight analysis method.The result showed that under the optimal condition that alkali concentration was 15%,urea concentration was 5%,treatment time was 10 min,and bath ratio was 1:10,the elongation at break of the linen yarn was increased from the original 1.93% to 4.02%.Secondly,with corn oxidized starch and polyacrylamide(XP-C)slurry as the main slurry,the single yarn sizing experiment was performed on the 24 Nm linen yarn before and after the alkali-urea modification system.The sizing quality of the linen yarn was evaluated with the sizing performance evaluation indexes such as breaking strength,elongation at break,wear resistance and regenerative hairiness index.The experimental data showed that the sizing performance of the linen yarn treated by the alkali-urea modification system is remarkably improved comparing with the untreated linen yarn.In order to determine the optimal slurry formulation,the mass fraction of corn oxidized starch in the formulation was fitted to the strength enhancement rate,the elongation reduction rate,the wear resistance increase rate and the regenerative hairiness reduction rate.The optimal compounding ratio of corn oxidized starch and polyacrylamide(XP-C)slurry was determined to be 55:45 with the uniform objective function optimization method.Finally,the optimal slurry formulation was used to carry out the single yarn sizing experiment of the treated 24 Nm linen yarn to discuss the influence of slurry concentration,grouting force and sizing speed on the sizing performance.The experimental data showed that when the slurry concentration was 6-10%,the grouting force was 0.1-0.2 MPa and the sizing speed was 30-40 m/min,the sizing performance was relatively good.In order to determine the optimal sizing process,the response surface optimization analysis method of central combined experiment was adopted to analyze the interaction among slurry concentration,grouting force and sizing speed.Through regression model fitting,variance analysis and 3D response surface analysis,the theoretical optimum sizing process parameters were determined as follows: slurry concentration was 9.98%,grouting force was 0.17 MPa,and sizing speed was 39.83 m/min.At this time,the wear resistance increase rate and the regenerated hairiness reduction rate were the best,at 292.69% and 61.06%,respectively.The optimum sizing process was modified to 10% slurry concentration,0.17 MPa grouting force and 40 m/min sizing speed.were carried out.The experimental data of several single yarn sizing experiments under the modified optimal sizing process showed that the wear resistance increase rate and the regenerated hairiness reduction rate were respectively 294.31% and 60.73%,and the relative error with the predicted value is less than 1%.