Development of a new low-cost instrument for dynamic friction coefficient measurement of yarns based on the entanglement method

The surface dynamic and static coefficient of friction of yarns is one of the most important means of characterizing the surface structure of yarns and can provide an important basis for yarn performance evaluation and quality monitoring. The lack of highly stable, high precision and low-cost instruments for measuring the dynamic coefficient of friction of yarns is a major constraint to yarn performance evaluation and performance improvement. The entanglement method calculates the coefficient of friction between yarns by measuring the input and output tensions on both sides of the yarn at its own kink point, which is easy to use and highly accurate. Based on this, a yarn dynamic friction coefficient measurement system was developed based on the kink principle and the measurement error was evaluated using 28tex cotton yarn and 420 D polyester yarn in turn. After five repeatability tests using 28tex cotton yarn, 36tex aramid and 420 D polyester, the coefficient of friction between the three yarns themselves fluctuated by less than 0.01 and the instrument showed good stability and repeatability. In six comparative tests with the CTT constant tension transfer system from Lawson, USA, the inter-group CV of the coefficient of friction between the yarns themselves was only 3.66% after six tests. A final comparison of the data from the entanglement and the Rhodes method tests shows that the coefficients of friction obtained show the same trend. The yarn running speed and pre-tension are adjustable and the system has a timed test function, which allows the input and output tensions of the yarn and the dynamic coefficient of friction between the yarn and the yarn to be measured and displayed in real time. This improves the measurement accuracy, reduces the price of the product and helps to evaluate the surface properties of yarns and improve product quality.