Characterization of Areal Density and Uniformity in Nonwovens Using Capacitive Method Part I: General Approach and Preliminary Results, 1990 Nonwovens Conference Proceedings

One of the most important requirements of fibrous assemblies which determine their success in commercial application of products is that they be uniform in properties. A close second is that the average areal or linear density lie near the target value. These chacteristics are particularly difficult to achieve in the manufacture of nonwoven fabrics because the speeds are high and the conversion of fiber to fabric direct. A possible solution to this problem lies in developing a method which could be used to monitor and control the linear density of the web as it is produced.

Explored in this paper is the potential offered for achieving this objective by the method based on measuring capacitance of the web. A parallel plate capacitor available in Uster evenness tester was used for making the measurements. Fabrics of different weights, structures, and fiber content were evaluated for their areal densities and uniformity. The latter were also characterized independently by a gravimetric method for comparison. The data were analyzed to determine the effects of various factors and to determine the nature of the correlation that existed between the capacitance and the gravimetric results. The feasibility of utilizing this method for characterizing areal density and uniformity in the production of nonwovens is discussed.