Estimation of strength degradation for engineering plastic (Under elevated temperature and humidity stress test)

• Published in: Kikai Gakkai ronbunshū = Transactions of the Japan Society of Mechanical Engineers Vol. 85; no. 871; p. 18-00341
• Main Authors: SAWADA, Yuko, ECHIZENYA, Daisuke
• Format: Journal Article
• Language: Japanese
• Published: The Japan Society of Mechanical Engineers 2019
• Subjects: Accelated stress test; Arrhenius; Engineering plastic; Estimate; Humidity; Life; Strength degradation; Superheated water vapor; Temperature; Water vapor pressure
• ISSN: 2187-9761
• DOI: 10.1299/transjsme.18-00341

A large quantity of engineering plastics are used in electric industrial products. It is necessary to estimate the life of the product made of engineering plastics because of its shorter life and lower strength than some of ceramics or metals. New test device was developed for accelerated stress test. It can make the unsaturated environment above 100 oC under atmospheric pressure using superheated water vapor. Then it becomes possible to set wide range condition of temperature and humidity. Polybutylene terephthalate (PBT) is one of the hydrolyzed engineering plastics. Test pieces of PBT were submitted to accelerated stress test under some conditions of elevated temperature and humidity. Then they were provided to three point bending test. The time required for strength degradation has a good relation with water vapor pressure at each temperature. Then it became clear that the time required for strength degradation on each water vapor pressure was accelerated with temperature using the Arrhenius type equation.