Abstract
Pressure exerted to resin during trial closure and polymerization was measured with a strain gage transducer. Further, internal stress of heat-curing resin during polymerization in the flask was investigated.
When load of 1, 750 kgf was employed at trial closure, the highest value of the pressure to resin was about 40 kgf/cm2. Though the pressure to resins during polymerization in water bath at 70℃ and in boiling water went up to 10 kgf/cm2 and 17 kgf/cm2, respectively, the pressures to resins were 0 kgf/cm2 before the exothermic heat was evolved.
The internal stress of the resin during polymerization in water bath at 70℃ for 240 min. and at 70℃ for 60 min. and then in boiling water for 30 min. increased with an increase in polymerization time, and was 300 kgf/cm2 and 350 kgf/cm2, respectively, after the termination of polymerization. On the other hand, the internal stress of the resin during polymerization in boiling water for 40 min. decreased from 60 kgf/cm2 to 0 kgf/cm2 when the temperature of the resin was about 120℃ after 20 min, and was 250 kgf/cm2 after the termination of polymerization.
