Water vapour transmission tests

Laminated tapes In more general use now than pressure sensitive tapes are tapes consisting of polyvinyl chloride or polyethylene films in conjunction with butyl rubber. These tapes are applied with an adhesive butyl rubber primer. Thicknesses of up to 0-75 mm are in use and loose protective outer wraps of p.v.c. or polyethylene sheet are commonly applied. Tape quality control is exercised with reference to ASTM standard test methods and may include water vapour transmission rate and elongation. 

The permeability measured by water vapour transmission rate is given in Table 4. It is seen that HOPE showed a superiority among other materials, PVC geomembrane was the worst in permeability among the samples tested. Bitumen contents adversely affect the permeability of ECB. 

The ASTM standard E96, Standard Test Method for Water Vapor Transmission of Materials provides a method for determination of water vapour transmission of materials such as paper, plastic films, other sheet materials, fibreboards, gypsum and plaster products, wood products, and plastics. This method has also been used for textiles for quite some time, although it does not simulate the actual wearing conditions of clothing. 

The water vapour permeability index can also be calculated by expressing the water vapour transmission (WVT) of the fabric as a percentage of the WVT of a reference fabric which is tested alongside the test specimen. The main drawback of this method is that the still air layer inside the cup between the water surface and the fabric offers higher water vapour resistance than the fabric itself. 

WVT = water vapour transmission rate, g/mVday =mass of test body after test, g a =mass of test body before test, g A=test area,... 

ASTM Standard F 1249-90 (1995) Standard Test Method for Water Vapour Transmission Rate Through Plastic Film and Sheeting Using a Modulated Infrared Sensor. 

Swelling or sorption test of liquids and vapours through the rubber is obtained by the standard method of ASTM D 814 and ISO 6179 2010 as a general method for various types of rubber. Other standard methods to test liquid and water vapour transmission rate are displayed in Table 27.1. Gas permeation test is obtained by the standard method of ASTM D 1434-82 and ISO 2782 as a general method, especially for oxygen gas mostly using ASTM D 3985 as a protocol for measurement. Table 27.2 exhibits the standard methods of gas permeability test. 

Physical testing of rubber, Method for determination of the transmission rate of volatile liquids Plastics. Determination of water absorption Determination of the water vapour transmission rate of plastic film, rubber sheeting, paper, board and other sheet materials by gravimetry... 

Using various model dispersions, acrylic/styrene and pure acrylic copolymer dispersion binders for masonry paints were investigated by studying the way in which chemically different monomers affected the film properties and those of formulated paints. The test methods used were for water resistance, water vapour transmission, tensile properties, colour variation, UV transmittance, UV stability, artificial weathering and weathering-induced chalking. 12 refs. 

Testing of plastics and elastomer films, paper, board and other sheet materials — Determination of water vapour transmission, 2001... 

Standard Test Method for Rubber Property - Vapour Transmission of Volatile Liquids Standard Test Method for Water Absorption of Plastics Standard Test Methods for Water Vapor Transmission of Materials... 

Instead of putting the desiccant inside the dish, with a controlled humidity outside, the dish could contain water which is then transmitted out into a dry atmosphere and the amount transmitted measured by weight loss. By inverting the container, the transmission rate when the water is in contact with the test piece can also be measured. The transmission rates measured by the various alternative procedures will be different because different vapour pressure gradients across the test piece are being used and, logically, the conditions most relevant to service would be chosen. 

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