Study On Improvement Of Flax Spun Yarn Tensile Properties

Spun yarn tensile properties are.closely related to the breakage of spinning process as well as the high or low efficiency of weaving process.Therefore,it is one of the important technical indicators in spinning mills.There are several factors which influence yarn tensile performance,and the properties of scutched flax influence it directly.Firstly,this paper analyzed the relationship between physical properties,main concomitants content of scutched flax and yarn strength.From the physical performance perspective,it found that scutched flax strength had the greatest influence on yarn strength with correlation coefficient 0.7175;length had a big impact on yarn strength,correlation coefficient 0.4235;splitting degree had less impact on it,correlation coefficient 0.3044.With higher scutched flax strength,spun yarn strength was higher;with longer fiber length,yarn strength was higher;splitting degree should be moderate.From the concomitants content perspective,it found that pectin content had the greatest influence on yarn strength with correlation coefficient 0.5564;hemi-cellulose content had a big impact on it with correlation coefficient 0.4715.With more pectin in scutched flax,yarn strength was higher;with more hem-cellulose,yarn strength was higher.The lignin,fatty wax and water-soluble content of scutched flax had less impact on it.The main purpose of flax scouring and bleaching process is to remove impurities in the fiber,improve fiber splitting degree and the spinning performance.Flax scouring and bleaching process has some important influence on spun yarn tensile properties.This paper compared two processes:soda boiling-chlorite and oxygen bleaching process and flax whitening process.Roving wet strength was 504cN,whiteness was 74.16%,loss rate was 7.05%after soda boiling-chlorite and oxygen bleaching process and spun yarn breaking strength was 824cN,strength variation coefficient16.32%,elongation was 2.28%,breaking time was 1.3s,unevenness was 33.01%.While after flax whitening process,the roving wet strength was 524cN,whiteness was 66.09%,loss rate was 8.66%and spun yarn breaking strength was 722cN,strength variation coefficient19.30%,elongation was 1.84%,breaking time was 1.0s,unevenness was 35.57%.It found that yarn quality was better after soda boiling-chlorite and oxygen bleaching process.Then this paper adjusted the concentration of three key reagents in soda boiling-chlorite and oxygen bleaching process which were hydrogen peroxide,sodium chlorite and sodium carbonate.Through single experiment,it found that with the increase of hydrogen peroxide concentration,yarn breaking strength decreased,while with the increase of sodium chlorite or sodium carbonate concentration,it first increased and then decreased.When the reagent concentration was too high or too low,the strength variation coefficient was large.The breaking elongation and time were lower when the reagent concentration was low.If the reagent concentration was high,the elongation and breaking time were higher.On the basis of single experiment,orthogonal experiment was carried out in this paper.It found that the concentration of hydrogen peroxide had a highly significant effect on breaking strength and elongation.While sodium carbonate had a general significant effect on breaking strength and sodium chlorite also had a general significant effect on elongation.The effect of these three key reagents on strength variation coefficient and breaking time was not significant.The best spun yarn tensile properties could be realized when the concentration of hydrogen peroxide was 5.09g/L,sodium chlorite was 1.94g/L and sodium carbonate was 3.33g/L and yarn breaking strength was 856cN,strength variation coefficient was 16.53%,elongation was 2.35%,breaking time was 1.3s which could meet the target requirements.Quality of flax roving-after scouring and bleaching process has much effect on spun yarn tensile strength.In this paper,it discussed and analyzed the relationship between yarn strength and main concomitants content of flax roving after scouring and bleaching process.It found that pectin content of flax.roving after-scouring and bleaching process had the greatest influence on yarn strength with correlation coefficient 0.6061,it was appropriate to control the pectin content at 0.6?1.2%.Hemi-cellulose content had a big impact on it with correlation coefficient 0.4902,it was appropriate to control the hemi-cellulose content at 11?13%.Flax lignin,fatty wax and water-soluble content after scouring and bleaching process had less impact on yarn tensile strength.