Thermal cycling procedure using water bath of 5 C and 55 C is a commonly used method to stress and age test specimens in laboratory testing. Typically, test specimens are kept in each of the water bath for 20 sec with 3 sec transfer time using 5000 – 10 000 cycles. After the thermal cycling, specimens are cut into smaller specimens and exposed to various forces to determine physical properties. To reduce intra specimen variation in such cases, uniform temperature changes must be obtained in the thermal cycled specimens. The present study measured temperature changes in test specimens with different size and dwell time in the water baths.
Test specimens were made from resin based composite material and thermal couples were placed in the middle of the specimens having the size of 10x10x10 mm and 5x10x10 mm. The specimens were transferred between thermostatically controlled water baths of 5 C and 55 C and kept in the bath for 20 sec, 40 sec and 60 sec, respectively. Transfer time was 3 sec. The temperature was measured digitally and the lowest and highest temperature in the specimens recorded.
After 20 sec the difference in temperature (low to high) was 30 C in middle of the large samples and 44 C in the small samples. None of the specimens reached the temperatures in the cold and warm water baths after 20 sec. To obtain a 50 C uniform temperature difference in the specimens, the small specimens needed 40 sec in the water baths and the large ones 60 sec
The temperature changes in test specimens during thermal cycling is dependent on specimen size and dwell time in the water baths.
Jon Dahl (Presenter), NIOM Nordic Institute of Dental Materials
Sigfus Eliasson, University of Iceland
This poster was presented at the 2018 IADR conference in London, UK.