Renault D47 1100 Rubber Ageing in Ozonated Air

The standard “Renault D47 1100 Rubber ageing in ozonated air”, developed by the French automobile company Renault, describes a procedure for assessing the resistance of rubber-based mixtures and parts manufactured from these mixtures to ageing in an ozone-laden atmosphere.

The test method consists of recording the appearance of test pieces after a certain period of time, kept under constant deformation in an atmosphere with a certain ozone concentration.

The main equipment used in these tests includes:

• An ozone chamber which must meet the requirements of the NF T 46-019 standard. In particular, the ozone chamber must guarantee ozone volume concentrations of 200 ppcm plus/minus 20 ppcm and 50 ppcm plus/minus 10 ppcm throughout the entire duration of the test.
• Device for continuously monitoring ozone concentration and system for sampling ozonated air close to test pieces in the test chamber.
• A microscope or other device that provides 45x and 2x magnification with illumination at 10 degrees and is equipped with a camera.
• Punch that makes it possible to obtain a test piece in accordance with the drawing in the annex of the standard (Appendix 1).
• Test assemblies for parts and test pieces (Appendix 2).
• Lint-free cloth.
• Conditioned room with a temperature of 23 degrees plus/minus 2 degrees and a relative humidity of 50 percent plus7-minus 5 percent.

The test piece shall be shaped in accordance with the NF T 46-019 standard. This test piece is defined in Annex 1. At least three test pieces shall be cut from a plate approximately 2 mm thick, using a hole punch, perpendicular to the final calendaring direction or in the injection direction before vulcanization. The test piece surfaces to be tested shall be in the form of cast molding. In case of disagreement, the plates shall be vulcanized between thin polished aluminum sheets, which shall be kept in contact with the vulcanized rubber until the test pieces are prepared. Two marking lines shall be drawn on the useful part of each test piece, at least 40 mm apart, without damaging the rubber.

The test fixture for each test piece includes two additional pieces, one of which is movable and can be locked in a position corresponding to 20 percent extension from the distance between the two marks. The fixtures should be made of a material that absorbs as little ozone as possible (e.g. steel coated with a clear coating based on methyl polymethacrylate, aluminum or polyethylene chlorosulfonate). The jaws should be designed to prevent any slippage or damage to the test pieces.

Regarding the interval between vulcanization and testing, the following time intervals must be observed, except in special cases: the interval between vulcanization and testing must be at least 16 hours and, if possible, less than 3 months.

The test assembly is adapted to the types of parts to be examined according to the indicators in Annex 2. If no indicator is provided in the Annex, the standard documents or the drawing of the part must describe assemblies that allow for a 20 percent elongation to be given to the sensitive areas of the part or another elongation specified by the conditions of use. When the geometry permits this, test pieces are taken and, except in special cases, a 20 percent elongation is applied to them.

Electrical test pieces are positioned at the selected elongation for a period of 23 to 2 hours in a conditioning chamber at 50 degrees plus/minus 5 degrees and 48 percent plus/minus 72 percent relative humidity in an ozone-free atmosphere and away from direct light.

The ozone chamber temperature should be 40 degrees plus/minus 2 degrees for the entire duration of the test. The ozone concentration in the chamber should be set at 200 ppm or possibly 50 ppm if this concentration is specified in the technical specifications or on the drawing of the part.

The air flow rate should remain between 100 l/min and 200 l/min. However, to regulate the ozone-producing lamp, a flow rate of approximately 200 l/min is recommended when the given concentration is 100 ppm. The exposure time durations are those specified in the standards.

Rubber is a polymer material. Due to its unique and excellent properties, it is widely used in the automotive industry and other fields. However, rubber is vulnerable to the comprehensive effects and accumulation of one or more of the following in the long-term use and storage processes: temperature, light, moisture, ozone, microorganisms and contact media. Under these conditions, the microstructure of rubber molecules changes, which leads to the deterioration of rubber properties.

Rubber aging is a long and continuous process. Accelerated aging tests are the main method in rubber aging research, that is, accelerated rubber aging test is carried out under laboratory conditions to study the changes in rubber during aging. Accelerated aging in an oven is considered the aging method closest to real natural aging.

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 “Renault D47 1100 Rubber ageing in ozonated air” standard with its trained and expert staff and advanced technological equipment.