Commonly in plastic and rubber testing process, material’s performance under low temperature is always needed to test, such as low temperature impact test, brittleness temperature test, TR test and so on, that would desire testing machines to be with good and stable low temperature testing circumstance. At present, major refrigerating system includes dry ice, liquid nitrogen and refrigerator, and the former two are more common, but these two methods have a lot of inconvenience. On the one hand, it’s very inconvenient to product, store and carry dry ice or liquid nitrogen, and it will produce much gas by volatilization that would be potential safety hazard. On the other hand, generally the testing temperature down to minus 70℃ is enough for the low temperature test of materials. The refrigerating temperature of dry ice is -70℃, and liquid nitrogen is -198℃, too much low temperature will lead to property changes when it exceeds the testing temperature during cooling, that will restrict the accuracy of the test to some extent, at the same time, thermoregulation will not easy to be stable.

    Since the reasons above, the new refrigerating method refrigerator is now getting recognized and more attention, its biggest advantage is adopting built-in refrigerator and provide an environment with stable temperature control, safety, environment protection and convenient operation. For instance, Yasuda’s brittleness temperature tester, impact tester and TR tester adopt R-404A as refrigeration medium. The cooling is by refrigerator to keep a stable low temperature environment during the test. The use of built-in refrigerator realizes that the test can be conducted in a low temperature and closed environment from the beginning to end which avoids the outside influence, take low temperature impact for example, in liquid nitrogen method, it would be took out from the low temperature oven and transfer to the testing machine when the temperature reached the requested, this process would have much effect on the test precision due to the environment change and personal factor. But the built-in refrigerator integrated impact tester realizes the specimen operated and tested under a closed low temperature environment, which avoids the testing error fundamentally.

    Another role of the refrigerator is that the temperature could be down to initial testing temperature when it is high, for example generally the testing temperature of VICAT and HDT exceeds 100℃, while the initial testing temperature is 23℃, commonly the temperature is to be cooled down by circulated water, but when the temperature is down to 50℃, the cooling speed would be very slow, especially in summer, it would take several hours and could not get to the desired initial temperature. Yasuda’s VICAT-HDT tester adopts circulated water and refrigerator working together, and the refrigerator will start automatically when the temperature is down to 50℃, it will take only 20min from 300℃ down to 23℃, it will greatly improve working efficiency. With the same principle, the built-in refrigerator can be used for the test of high temperature creep property as well.

 

2012年12月20日

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The Application of Built-in Refrigerator in Plastic and Rubber Testing Machine

Commonly in plastic and rubber testing process, material’s performance under low temperature is alw

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