PPの疲労破壊特性に及ぼす射出成形速度の影響

抄録

The effect of injection speed on the fatigue fracture property of polypropylene has been mainly investigated from a low temperature of -40°C to a high temperature of 50°C. Results show that, (1)The thickness of the skin layer(with low hardness)and the intermediate layer(with high hardness)decreases but the thickness of core layer(with middle hardness)increases as the injection-molded speed increases. The ductile property of all specimens becomes better. (2)In the all fatigue fracture test, the origin of crack from intermediate layer of high hardness and propagation of the crack leads the specimen to rapture. (3)Under the condition that the temperature(20°C, 50°C)is over the room temperature, fatigue tests show that the life of specimen becomes longer as the injection-molded speed increases. (4)Under a lower temperature(-40°C, -10°C), fatigue tests show that the value of tanσ decrease but the E does not in the fatigue process of all specimens. There is a tendency of brittle fracture. The fatigue life of specimes made with the injection-molded speed of 22cm³/s is the shortest for the thickness and hardness distributions in each layer of specimen sections are strongly interrelated. (5)Under all the test temperature, the status of fatigue crack took placed in a layer in closely related to the injection-molded speed. It has great influence on the specimen fracture mechanism.