ISO 8339 Building Construction - Sealants - Determination of Tensile Properties (Elongation to Break)

The “ISO 8339 Building construction - Sealants - Determination of tensile properties (elongation to fracture)” standard, developed by the International Organization for Standardization (ISO), describes a test method used to determine the tensile properties of sealants used in joints in building construction.

For the purposes of this standard, the terms and definitions given in “ISO 6927 Sealants for construction and civil engineering - Glossary” apply.

When starting the tests, in principle the test specimens are prepared so that the sealant to be tested adheres to two parallel contact surfaces. The test specimens are extended to failure and the tensile properties are recorded on a force/extension diagram. The test results are used to calculate the shear modulus and the extension to failure.

The main equipment used in these tests includes:

• The substrate materials used in the preparation of test specimens are as defined in the ISO 13640 standard. The substrate materials are chosen from mortar or anodized aluminium or glass. Other substrate materials may be used as agreed by the parties concerned. Two substrate pieces of the same material with a cross-section of the dimensions shown in the figures given in the standard are required for each test specimen. Test substrates of other dimensions may be used, but in this case the dimensions of the sealing bead and the area of ​​adhesion must be the same as those shown in the figures.
• Non-stick surface sectioned (12 mm × 12 mm) spacers. For the preparation of test samples, the figures given in the standard should be consulted.
• Anti-adhesive substrate (for preparation of test samples, e.g. polyethylene film, preferably according to the sealant manufacturer's recommendation).
• Tensile testing machine with recorder. This machine can stretch test specimens at a rate of 5,5 mm/min plus/minus 0,7 mm/min.
• Refrigerated enclosure. This enclosure can hold test samples at a temperature of minus 20 degrees plus/minus 2 degrees extended.
• Ventilated convection type oven. This oven can be kept at 70 degrees plus/minus 2 degrees for conditioning according to method B.
• Vessel. This vessel is used to immerse test specimens in distilled water for conditioning according to method B.

When preparing test samples, the sealant and test substrates should be brought to 23 degrees plus/minus 2 degrees. Three test samples should be prepared for each substrate type and each test temperature. For each sample, two substrates and two spacers should be bonded and placed on the non-adherent substrate. For example, the sealant manufacturer's instructions regarding whether to use primer and the mixing procedure for multi-component sealants should be followed. The space created by the substrates and spacers should be filled with sealant.

In the meantime, the following precautions should be taken:

• The formation of air bubbles must be prevented.
• The sealant should be pressed into the inner surfaces of the substrates.
• The sealant surface should be cut flush with the surfaces of the substrates and spacers.

Test specimens should be placed on the edge of one of the supports. The non-adherent substrate should be removed as soon as possible. Specimens should be placed in this position to allow the sealant to cure or dry optimally. Spacers should be kept in place during conditioning.

Test samples are conditioned in accordance with method A or method B, as agreed upon between the parties involved.

When applying Method A, test samples are conditioned at 28 degrees plus/minus 23 degrees and 2 percent plus/minus 50 percent relative humidity for 5 days.

When applying method B, test samples are conditioned in accordance with method A and then subjected to the following storage cycle three times:

• 70 degrees plus/minus 2 degrees in the oven for three days
• One day in distilled water at 23 degrees plus/minus 2 degrees
• Two days in the oven at 70 degrees plus/minus 2 degrees
• One day in distilled water at 23 degrees plus/minus 2 degrees

Alternatively, this cycle may be carried out in steps three, four, one and two. After conditioning according to Method B, the test specimens shall be stored at 24 degrees plus/minus 23 degrees and 2 percent plus/minus 50 percent relative humidity for 5 hours prior to testing. Method B is a normal conditioning procedure using the effects of heat and water. It is not suitable for giving information on the durability of the sealant.

The test procedure is carried out at temperatures of 23 degrees plus/minus 2 degrees and minus 20 degrees plus/minus 2 degrees. Three test specimens are tested at each temperature.

• When performing the test procedure at 23 degrees plus/minus 2 degrees, the spacers are removed to prepare the test samples and the test sample is placed in the tensile testing machine, then extended at a speed of 5,5 mm/min plus/minus 0,7 mm/min at a temperature of 23 degrees plus/minus 2 degrees until rupture occurs. The force/extension diagram is recorded.
• When performing the test procedure at minus 20 degrees plus/minus 2 degrees, the test samples are stored at minus 4 degrees plus/minus 20 degrees for at least 2 hours before the test begins. To prepare the test samples, the spacers are removed and the test sample is placed in the tensile testing machine, then extended at a speed of 5,5 mm/min plus/minus 0,7 mm/min at minus 20 degrees plus/minus 2 degrees until rupture occurs. The force/extension diagram is recorded.

Our organization has a strong staff that closely follows the developments in science and technology in the world and constantly improves itself. Among the numerous test, measurement, analysis and evaluation studies provided for businesses in various sectors, there are also test services in accordance with the “ISO 8339 Building construction - Sealing materials - Determination of tensile properties (elongation to break)” standard.