PSA D45 1234 Parts Containing Plastic Elements - Reaction to Heat in Non-Radiant Dry Oven

The purpose of the method described in the standard “PSA D45 1234 Parts containing plastic elements - Reaction to heat in a non-radiant dry oven” developed by the French automobile company Renault is to evaluate the response of thermoplastic parts to prolonged exposure to dry heat in terms of shrinkage, deformation and change in appearance. This test method should be performed only for the examination of molding stresses.

This standard applies to all parts containing plastic elements fitted to vehicles (dashboard, steering wheel, radiator grille, lamps, door handles and similar parts).

In principle, this method consists in placing the parts to be examined in a ventilated oven, which has been raised to a pre-selected temperature, for a certain period of time. The temperature and the duration of the test are specified in the documentation.

Equipment used in this test method includes:

• Oven: A forced air device that ensures that the temperature is uniform throughout the available space and that the selected temperature is maintained throughout the test period. The oven shall include a regulating device so that the temperature does not vary more than plus/minus 2 degrees around the selected value during the test and does not vary more than plus/minus 1 degree from one end of the part to the other. The internal dimensions of the oven shall be such that the part under test does not, under any circumstances, come into contact with the walls or bottom of the oven and does not disrupt air circulation.
• Grill: Placed at the middle height of the oven, it prevents the parts from coming into contact with the oven floor.
• Calibrated thermometers: graduated to 0,5 degrees, placed in Erlenmeyer flasks filled with vaseline or thermocouples connected to a temperature recorder.
• Fixture for fixing the part to be examined: It should be in conditions as close as possible to the fixing method used in the vehicle.
• Equipment required to create visible marks on the part to be inspected
• Suitable measuring instruments (e.g. rulers, marking tools, calipers, ray compasses and others)

Test samples or specimens should be representative of the scale to be characterized. To ensure this representation, it is necessary to find out the basic characteristics of the population under study. Selection criteria for test samples or specimens should be stated in the test report in accordance with the PSA A10 0156 standard. In case of doubt about the sampling, the PSA service should be contacted to obtain the guidelines to be followed.

The steps of the procedure to be applied are as follows:

• The part to be inspected is fixed in the fixture under the conditions specified in the standards or, if not, under known usage conditions (especially tightening torques for fastening screws).
• Reference marks are drawn on the part at a specified distance in the cardinal directions (e.g. length and width), measured to the nearest 0,1 percent using a suitable instrument, and the part is previously conditioned at 2 degrees plus/minus 23 degrees for at least 2 hours.
• In addition, using the most appropriate tools depending on the shape of the part, the dimensions that play an important role in its strength in use (e.g. speedometer on a dashboard, dimensions of the opening for the ashtray housing) are measured to the nearest 1/2 mm.
• If the possible deformation of a part between the fixing points needs to be evaluated, its relevant dimension is measured with a beam compass.
• The temperature of the oven is adjusted to the value defined in the standards.
• Wait for the temperature to stabilize before placing the part to be examined into the oven.
• If the part to be examined contains several areas exposed to various temperatures during use, the part is, if possible, subjected to a test at each of these temperatures, in increasing order, in 10 degree steps. In this case, it is also advisable to perform a test on another part, taking it directly to the maximum temperature.
• The part is placed in the furnace under appropriate conditions without exposing it to stresses not specified in its function. If there are parts that are passed freely, they are positioned in a way that reduces the stresses associated with their weight. It is observed whether there are any defects.
• The duration of the test is as specified in the standards.
• The part is removed from the oven and allowed to return to ambient temperature.
• Its appearance is observed, then the dimensions between the reference marks and the dimensions of the part are measured again.

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