Ultrasonic testing of the hardening kinetics of epoxy resins used for foundry patterns

Abstract The study presents the results of investigations on the hardening kinetics of modern pattern materials which, among others, include also epoxy resins. Tests were carried out using a new ultrasonic technique developed by the author of the present study. On the example of the EPO 999 resin, the run of the hardening process at temperatures of 10, 20 and 30 o C was shown. This is the temperature range applied during production of foundry patterns. The time of the preliminary hardening amounted to 800 min at a temperature of 10 o C, and to only 180 min at a temperature of 30 o C. Using ultrasonic technique, the effect of temperature on the modulus of elasticity E d of the examined resin was determined. The temperature has been observed to exert a linear effect on the value of the modulus E d . When the resin pattern is preheated in the range of temperatures from 20 to 50 o C, the value of the modulus E d decreases by 30%. The drop in the value of the modulus E d , as well as the resin hardness decreasing from 18 to 9,0HB at the increasing temperature reduce the applicability of this material for patterns operating at high temperatures (moulding sands)