Research On The Measurement System And Test Method Of Yarn Dynamic Friction Coefficient

The surface structure of the yarn not only affects the yarn strength,appearance and weaving process,but also the performance of the woven fabric and garment processing.The static dynamic friction coefficient of yarn surface is one of the important means to characterize the surface structure of the yarn,which can provide important basis for performance evaluation and quality control of yarn.At present,the imported equipment which can make yarn dynamic performance evaluation is expensive,the friction resistance of domestic equipment is big,and the tension is unstable during dynamic operation.The lack of high stability,high precision and low cost yarn dynamic friction coefficient measuring instrument is one of the main reasons that restricts the evaluation of yarn performance and performance improvement.The entanglement method is simple and accurate to measure the friction coefficient between yarns by measuring the input tension and output tension of yarn on both sides of its own kink point.For the above-mentioned principle,we develop a set of yarn dynamic friction coefficient measurement system based on the principle of entanglement,which consists of two modules:testing system and control system.The yarn passes through the yarn guide in the test system,the input roller,the input tension measurement device,the buffer device(integrated pre-tensioning and balance detection function),the entanglement device,the output tension measurement device,the output roller,the auxiliary device,the input and output roller drive the yarn running.By measuring and controlling software on the computer in the control system,the testing process of the instrument can be control led in real time,and the curve of input tension and output tension can be displayed at the same time.It has the function of timing test and real-time displaying the friction coefficient of yarn.The system error is measured by 28tex cotton yarn and 420D polyester yarn in sequence.The results show that the average error rate(tension difference/pretension)is 6.31%and 8.88%respectively.When the yarn is entangled,the coefficient of variation(CV)of the input tension of yarn with different pretension under the same speed were lower than 10%.CVs of the yarn friction coefficients measured by the same condition did not over 10%.After five repeatability tests with 28tex cotton yarns,36tex PSF and 420D PET,the friction coefficient between the three yarns is less than 0.01,and the instrument shows good stability and repeatability.Compared with the CTT constant tension transmission system,the friction coefficient of 28tex pure cotton yarn measured by two instruments is same,and the friction coefficient CV is 6.08%and 3.92%,respectively.After 6 tests,the CV between the yarn friction coefficients was only 3.66%.With the pre-tension increases,the friction coefficient decreases gradually,after the pre-tension increases to 30cN,the friction coefficient no longer changes.Finally,according to comparison experiment of entanglement method and Rhodes method,the friction coefficient by two measuring methods showed the same changing trend.We find that there are many unstable test factors and human interference factors in Rhodes method after analyzing the measurement process of it,which reduces the test accuracy and stability.The method of entanglement is better than Rhodes method.Yarn dynamic friction coefficient measurement system improve the measurement accuracy and reduce the price of the product and had great significance for process improvement and product quality.