Comparing accuracy of the methods of polytetrafluoroethylene fiber linear density measurement

Abstract

There are various test methods applied to measure mean linear density of PTFE split-film fibers. The measured results vary with respect to computation mechanisms, measurement parameters, and morphology and inherent properties of fibers. Five test methods and an assumption calculation were introduced to evaluate the linear densities of PTFE fibers. The experimental results show that the gravimetric method generated the highest linear density, followed by the cross-section method, theory calculation, airflow measurement, assumption calculation, and vibration method. Statistical analyses indicated that actual mean linear density of the PTFE split-film fibers is in the effective range between the maximum and minimum fineness obtained from the theory and assumption calculation, respectively. Linear density of the PTFE split-film fiber tested via the gravimetric method, cross-section method, and vibration operation were significantly different to the effective range. In the case of the airflow experiment, mean linear densities measured at high porosities are in high accordance with the actual fineness. The airflow method offers a short time to reliably measure mean linear density of PTFE split-film fibers under appropriate test conditions.