Dimensional Stability test by ASTM D1204 measures changes in linear dimensions when a material is subjected to a specific temperature condition. The measurement determined by Dimensional Stability ASTM D1204 identifies the direct dimensional change occurring from exposure to temperature. The test is extremely useful as it provides a lot of conformity about the internal stress introduced during processing. Dimensional Stability is highly used for sheeting or film made by extrusion or calendar processes.
For the ASTM D1204 test dimensional change and dimensions of the specimen are noted at reference marks before starting the test. After that, a talc dusted paper is used to make a sandwich around the specimen, and these sandwiched specimens are kept in an oven at a specified temperature for a fixed time. After that, the specimens are taken out from the oven and restored to room temperatures for at least an hour. After the specimens cool down, the differences between the reference marks are recorded.
Usually, 100 mm × 100 mm specimen is cut from the plastic sheet.
Percent linear change equals the difference of the final length and the original length divided by the original length and the whole multiplied by 100.
% change = (final length – original length)/ original length × 100
ASTM D1204 is a standard test method for linear dimensional changes of nonrigid thermoplastic sheeting or film at elevated temperature.