Study On The Plying Of Coarse Jute Yarn And Fine Viscose Yarn

Jute yarn has high strength but also high coarseness and hairiness,which seriously restricts its application.Blending with fine yarn is an effective method to reduce its surface hairiness,which can improve the comprehensive performance of jute yarn without significantly increasing the fineness of resultant ply yarn.The performance of single yarn and the twist coefficient ratio of plied yarn to the average of two single yarns determine the strand performance.In this paper,jute yarn and viscose yarn are used as raw materials,and the effects of the twist coefficient ratio on the hairiness index of more than 3mm,breaking strength and elongation,the number of snarling and other properties of plied yarn are explored through reverse plying experiment and theoretical derivation.Theoretical derivation was carried out by twist amplitude analysis.On the basis of the hypothesis yarn cross section is circular,the twisting process of plied yarn is divided into three stages and four cases and analyzed respectively.Then the distribution function of twist amplitude and the theoretical torque of plied yarn were obtained,and the theoretical unevenness of twist amplitude and the torque of plied yarn were further deduced,which provided theoretical support for the analysis of strength and number of snarling of plied yarn.Furthermore,jute yarn of 214.5tex and viscose yarn of different specifications were used as experimental materials,and the single factor experiment was carried out on the twist coefficient ratio,viscose yarn density and viscose twist coefficient.According to the above experimental results,a three-factor and three-level orthogonal experiment was designed,and the optimal process parameters were obtained and verified combing with range analysis and variance analysis,so as to further optimize the process of jute yarn and viscose yarn.The research results of this project are as follows:（1）In the reverse plying experiment of jute single yarn of 175.93tex（5.6 Nm）and 287.20 Tex（3.5 Nm）and viscose single yarn with linear density of 31tex and twist coefficient of 358 and 416,the twist coefficient ratio was set to 0.2～2.0.The test results showed that,when the twist coefficient ratio was 1.4,the breaking strength of jute/viscose yarn was the highest,and the harmful hairiness was reduced by 65%.When the twist coefficient ratio is 1.0,the breaking strength of jute/viscose yarn is the minimum.In the experimental range of twist coefficient ratio,the number of yarn snarling increased with the increase of twist coefficient ratio,but too much snarling would cause yarn distortion and feel hard,affecting its normal use.Overall consideration,the jute/viscose yarn performance is the best when the twist coefficient ratio is 1.4.（2）Assuming that yarn cross section is circular,it can be obtained through twist amplitude analysis that:the theoretical radial twist amplitude y of the plied yarn can be expressed as y₁=_2r1^2P1-P0-ΔPx+P₁-ΔP（-2r1≤x<0）,y₂=_2r2^2P2-P0+ΔPx-P₂-ΔP（0≤x≤2r2）(In which P0 represents strand twist,r₁ represents coarse yarn radius,P₁ represents its surface twist amplitude,r₂represents fine yarn radius,and P₂ represents fine yarn surface twist amplitude,ΔP=₀^1-2₀).And the theoretical torque of plied yarn can be expressed as T=r₁（P₀-ΔP）+r₂（P₀+ΔP）.Combined with the performance test data,it was found that the amplitude distribution function of plied yarn could explain the appearance of maximum strength point of plied yarn to a certain extent--as a result of the minimum CV of twine twist amplitude,but it could not explain the appearance of minimum strength point.In addition,the torque function of plied yarn derived from twist amplitude analysis can explain the phenomenon of increasing torque of reverse plied yarn to a certain extent.（3）On the basis of single factor test,a series of orthogonal experiments were carried out in the range of yarn twist coefficient ratio of 0.2～2.0,viscose yarn density of 20～60tex and viscose yarn twist coefficient of 260～420.The optimal process of 214.5tex jute single yarn and viscose single yarn was explored as follows:yarn twist coefficient ratio 1.4,viscose yarn density 20tex,viscose twist coefficient 340.Under this condition,the plied yarn had the suboptimal hairiness index and residual torque,the breaking strength was also well.Moreover,the viscose yarn density is selected as 20tex,which can reduce the raw material cost to a certain extent.