Study On Improving Cotton Yarn Properties By Means Of The Adhesive-aided Ring Spinning

Ring spinning occupies an important position in various spinning technologies,accounting for more than 80%of yarn production.Various modified technologies such as compact spinning and siro spinning have been proposed to further improve yarn properties through reducing spinning triangular space or fiber modulus during spinning process.An adhesive-aided ring spinning（AARS）was reported according to the theory of ring spinning and the character of cotton fiber in this study.The AARS offers liquids on the fibrous strand during yarn formation zone through direct contact.The fiber ends can be attached on the surface of fibrous strand and be twisted into the fibrous strand through the wetting and adhesion effect of solutions on cotton fiber and mechanical action,then the yarn properties can be improved.First of all,the principle of AARS was studied.The AARS,taking full advantage of the wetting and adhesion between cotton fiber and the liquid,makes fibers be better controlled.The fiber ends can be attached on the yarn body through direct contact.In addition,the direct contact and the liquid viscosity redistribute the twist of yarn formation zone between the front roller nip and the yarn guide,making the attached fiber ends twisted into the yarn body after passing through the AARS to improve yarn properties.The wetting and adhesion effect between liquids and cotton fibers is the foundation of AARS.Through the analysis of the wetting and adhesion between liquids and cotton fiber,the adhesion work is stronger when the adhesive has the similar structure with cotton fiber and the surface tension is close to 98m N/m.Combining with a better wetting effect when the surface tension and viscosity are lower,the better wetting and adhesion effect can be obtained.In order to explore the essence of the AARS on improving yarn properties,the relative movement and force analysis of fibers on the fibrous strand during spinning process was studied to deduce the mechanism of AARS.The theoretical analysis states that the stronger wetting and adhesion effect and the mechanical action are two keys for improving yarn properties.In addition,the mechanical action should be limited because it can affect spinning efficiency to some extent.Second,two kinds of systems with rotating wheel or fixed pipe were designed to realize this technology.The rotating wheel in the system can bring liquids on the surface of the wheel to complete the AARS process.It can produce different relative speeds between the system and fibrous strand.The other system with a fixed pipe makes liquids overflow to contact the fibrous strand through increasing the pressure and it can control the overflowing quantity of liquids and is more stable.The relative speed is also fixed between the system and fibrous strand.According to the hydrophilia of cotton fiber,water is used as the medium to conduct the experiments.The observation of AARS process through high-speed camera shows that different relative speeds can change the movement of fibers on the surface of fibrus strand,therefore,the distribution of fibers on yarn surface are also different.The reduction rate of harmful hairiness for 14.5 tex yarns is 5%when spinning without water.The harmful hairiness reduces 34%at most when using the system with rotating wheel.Because the fiber ends pointing to the spinning direction account for the most of the hairiness,the rotating speed of the wheel little faster than the output speed of the yarn is more beneficial to the reduction of yarn harmful hairiness.When using the system with a fixed pipe,the reduction rate of harmful hairiness is about 25%.Therefore,both systems have their advantages.It also states that the reduction of yarn hairiness depends on the wetting and adhesion of water on cotton fiber.On the other hand,the adhesive solutions using sodium carboxymethyl cellulose（CMC-Na）with the concentration of 1-7‰were matched because CMC-Na has the similar structure with cotton fiber.Higher concentration can increase the surface tension and viscosity of solution（20-272 m Pa·s）,so the adhesion work increases and the wetting ability decreases.Spinning with CMC-Na solution,higher concentration can reduce yarn diameter,the reduction rate of yarn diameter is up to 8.6%and keeps stable when the concentration is5‰.The attachment amount of solution on fibrous strand will not increase when the concentration reaches 5‰as well through fluorescence labeling method.Through the observation and calculation of online twist and shape through high-speed camera,the twist loss rate is amongst 10-14%and this twist stop effect has little effect on the spinning efficiency.The fiber ends can be attached on the surface of fibrous strand effectively.The bringing quantity of adhesive solutions during AARS process is about 0.7 g/1000m.The yarn moisture regains of ring spun yarn and AARS yarn are the same and the AYRs of AARS yarns are small.It states that only little content of solution touches the fibrous strand and the effect of AARS is significant.The properties of yarns spun with two systems show that AARS can significantly reduce yarn hairiness indicated by the hairiness S₃ value reducing more than 65%with higher CMC-Na concentration for 14.5 tex yarns.The hairiness reduction rate of cone yarns is similar.Meanwhile,the growth rate of breaking strength reaches 15%and the abrasion resistance also shows an improvement more than 12%.The AARS cannot change yarn twist and yarn evenness.There is no obvious difference between two systems,and the yarn properties tend to stable when the concentration reaches to 5‰.In addition,it has been found that a slightly faster linear surface velocity of the wheel is only beneficial to the reduction of yarn hairiness S₁₊₂ value.Therefore,the system with a fixed pipe is more appropriate for the AARS.Last,on the basis of CMC-Na,PAM and PVA were used as auxiliary adhesives to match composite solutions.The analysis of solution performance shows that PAM can increase the surface tension and viscosity of solution（110-280 m Pa·s）,therefore,it can increase the adhesion work and decrease the wetting effect of solution.Spinning with CMC-Na/PAM solution,the twist loss rate is amongst 12-14%.Higher PAM concentration can not further decrease yarn diameter.Due to the analysis of the fluorescence labeling during AARS,PAM can increase the attachment amount of solution on the surface of fibrous strand.Using the adhesive-aided system with a fixed pipe in the experiments,the results state that CMC-Na/PAM solutions can make the reduction rate of hairiness S₃ value more than 90%for14.5 tex yarns.The growth rate of abrasion resistances is more than 20%,and the growth rate of breaking strength is not obvious.The twist loss rates of different solutions are similar,and it states that the higher reduction of yarn harmful hairiness is based on the stronger wetting and adhesion effect when the twist stop effect is formed.PVA can decrease the adhesion work and increase the wetting effect of solution It can not decrease the yarn diameter,however,it will decrease the attachment amount of solution.The yarn properties show that the yarn breaking strength improved by PVA increases by over 25%.The growth rate of abrasion resistance of yarns reaches more than 40%,and it can not affect yarn hairiness S₃ value.Central composite design was adopted to achieve the predicted models of yarn properties and the optimal match of composite solution in suitable concentration ranges.Overall,the models indicate that composite solution with CMC-Na concentration of 5.46‰,PAM concentration of 0.16‰and PVA concentration of 0.44‰will achieve the desired effect on yarn properties.In addition,the predicted values and the experimental values achieve an agreement.Comprehensively,AARS can substantially improve cotton yarn properties,taking advantage of the wetting and adhesion effect of solution on cotton fiber and the mechanical action coming from the direct contact.When a little twist stop effect is formed,the wetting and adhesion effect is the key point for improving yarn properties.The AARS yarn of 14.5tex spun with composite solution including CMC-Na,PAM and PVA can achieve a 89.6%of reduction in harmful hairiness（reduction rate of 87.4%in harmful hairiness of cone yarn）,a28.5%of growth in breaking strength and a 50.6%of growth in abrasion resistance.