ISO 2782-2 Rubber, Vulcanized or Thermoplastic - Determination of Permeability to Gases - Part 2: Equal Pressure Method

The standard "ISO 2782-1 Rubber, vulcanized or thermoplastic - Determination of permeability to gases - Part 2: Equal pressure method" developed by the International Organization for Standardization (ISO) describes a method for determining the gas transmission rate and gas permeability coefficient of vulcanized or thermoplastic rubber under conditions where the overall pressure on both sides of the rubber test piece is the same. This method uses gas chromatography to determine the amount of gas passing through the rubber.

This method is applicable to vulcanized and thermoplastic rubbers with a hardness of not less than 35 IRHD (international rubber hardness rating) and to both single gases and gas mixtures.

For the purposes of this standard, the terms and definitions described in ISO 2782-1 apply.

In this test, a test cell maintained at constant temperature is divided by a test piece into a gas supply side and a gas transmission side. The test gas is introduced into the gas supply side and a carrier gas is passed through the gas transmission side. The pressure on both sides of the cell is equal (atmospheric pressure), but since the partial pressure of the test gas is higher on the gas supply side, it diffuses from the test piece to the gas transmission side. The amount of test gas passing through the test piece is measured using a gas chromatograph.

In this method, measurements can be made on test gases containing water vapor, and it is also possible to analyze gas mixtures to determine the components.

The equipment used in this test method consists of the test cell, a gas chromatograph, test gas and carrier gas supply systems, and associated piping and valves:

• The test cell is such that the gas transmission area is clearly defined when a test piece is inserted into it, including a gas supply side and a gas transmission side. The gas supply side has a test gas inlet port and an exhaust port, and the gas transmission side is connected to the carrier gas supply and the gas chromatograph via a sampling loop. The material of the test cell should be inert to the test gas and should not absorb the gas used. The surfaces of the two halves of the cell in contact with the test piece should be smooth and flat to prevent any gas leakage. A seal such as an O-ring may be used between these areas and the test piece, in which case the gas transmission rate of the seal should be significantly lower than the gas transmission rate of the material being tested and thus should not affect the result of the test. The diameter of the gas transmission area should be in the range of 10 mm to 150 mm, depending on the expected gas transmission rate. The cell should be equipped with a heating system capable of raising the temperature to 80 degrees. The temperature accuracy should be for temperatures between 40 degrees and 80 degrees plus/minus 1 degree. An example of a heating system is an electric heating jacket and an oven designed to hold the test cell and the test gas source.
• The gas chromatograph must have a detector such as a thermal conductivity detector or a hydrogen flame ionization detector. The detector and column must be suitable and of the required sensitivity for the test gas used.
• The test gas controller must comply with the ISO 2782-1 standard.
• One of the two temperature sensors is placed in the test cell to measure the test temperature, and the second is placed in the carrier gas flow to measure the temperature of the carrier gas. The sensors must be capable of reading to 0,1 degrees or better.

A single gas such as nitrogen, oxygen or hydrogen or a mixture of gases such as air, liquefied petroleum gas or coal gas is used as the test gas. The purity of a single gas or each component in a gas mixture shall be 99,5 percent by volume or higher unless otherwise agreed upon by the parties concerned. In this case, a gas of lower purity may be used. The test gas shall not contain any impurities that may affect the measurement.

When a gas mixture is used, the purity of each component should be verified beforehand with a suitable instrument such as a gas chromatograph.

When a toxic or flammable gas is used, all necessary precautions must be taken in its use and recovery or disposal.

Among the numerous tests, measurements, analyses and evaluation studies that our organization has carried out for businesses in various sectors, it also provides testing services defined in the standard “ISO 2782-2 Rubber, vulcanized or thermoplastic - Determination of permeability to gases - Part 2: Equal pressure method” with its trained and expert staff and advanced technological equipment.