How do you test water vapor permeability?
A testing container’s opening is covered by the sample. Using the desiccant method, it is filled with a desiccant that absorbs the water during the permeation time. Following the water method, the container is filled with water that evaporates through the specimen. The permeated amount of water is detected by weighing.
Why water vapour permeability testing is required?
Water vapor permeability is a measure of the passage of water vapor through a membrane. It is the rate of water vapor transmission per unit area per unit of vapor pressure differential under test conditions. It is also known as water vapor transmission rate (WVTR) or moisture vapor transmission rate (MVTR).
What does water vapor permeability mean?
Often referred to as breathability, vapor permeability describes a material’s ability to allow water vapor to pass through it. Unlike bulk water holdout, which refers to water in its liquid form, vapor permeability concerns water in its gas form.
Why water vapour permeability and gas permeability testing is required?
The purpose of these tests is to obtain, by means of simple apparatus, reliable values of water vapor transfer through permeable and semi permeable materials, expressed in suitable units. These values are for use in design, manufacture, and marketing.
What is ASTM E96?
Water Vapor Transmission ASTM E96. Scope: The test evaluates the water vapor transfer through semi-permeable and permeable samples. The data can be used by manufacturers and designers and is often important in packaging applications.
What is the unit of water vapor permeability?
The metric perm (not an SI unit) is defined as 1 gram of water vapor per day, per square meter, per millimeter of mercury. The equivalent SI measure is the nanogram per second per square meter per pascal. The base normal SI unit for permeance is the kilogram per second per square meter per pascal.
What is the temperature and humidity of water vapour permeability test?
The permeability of the films to water vapour was assessed, at 38°C and 90% relative humidity, using a gravimetric method according to ASTM E96-80.
Is vapor barrier permeable?
Class I and II vapor retarders are, for all intents, considered non-permeable as defined by Code.
What is the standard test for water vapor?
The simplest and most widely used test of the rate of water vapor transmission is the dish or the cup method. The specimen is sealed to the mouth of an impermeable test dish containing water or a desiccant, and placed in a controlled atmosphere.
What is ASTM E154?
ASTM-E154 › Standard Test Methods for Water Vapor Retarders Used in Contact with Earth Under Concrete Slabs, on Walls, or as Ground Cover.
What is the difference between permeance and permeability?
Permeance is the moisture transmission rate of the membrane. It is a performance test and is stated in perms. Lower numbers indicate better performance. Permeability is another term used to describe moisture transmission of a material.