Development of An Automatic Air-permeability Tester

Abstract

A new system for precise and speedy measurement of air permeability of textile fabrics is developed and reported in this paper. A constant rate of air flow is generated by the piston motion of a plunger/cylinder mechanism and passed through a specimen from and into atmosphere by the piston motion of the plunger. The suction and the discharge periods of air are 5 seconds respectively to complete a cycle within ten seconds. The air pressure loss caused by the air resistance of the specimen is measured by a semiconductor differential-perssure gauge with high accuracy and high sensitivity, and the air resistance of the specimen “R” is directly indicated on a digital panel meter after the completion of one-cycle piston motion. The pressure losses in the suction and the discharge periods are at first measured separately by averaging the pressure output for the period of 3 seconds in each of the suction and the discharge periods, then thse two averaged pressures are averaged again to obtain a reliable value of pressure loss. The time required for the one measurement is therefore, only ten seconds. The measurements of R are carried out for various kinds of textile fabrics using this new system to inspect the performance of the system. It has been found that the proportional relation between the air flow rate and the pressure loss is obtained in a wide range of air flow rate for many kinds of the fabrics inspected here except a few exception. This result is, however, different from the result which has been obtained with the conventional Frazier air permeability tester which does not show the proportionality. Some discussions are made with respect to this difference. It is domonstrated that this new tester is also applicable to the measurement of air permeability of fiber assembly bodies such as mattress materials by using a simple adapter to hold the specimen, and also that air permeability of fiber assembly body depends on fiber diameter very sharply, these experiments have been made by using nonwoven fabrics made by different denier fiber and some random assembly bodies of different kinds of fiber.