GB/T 7759-1996 in English

《GB/T 7759-1996硫化橡胶、热塑性橡胶 常温、高温和低温下压缩永久变形测定》由TC35（全国橡胶与橡胶制品标准化技术委员会）归口，主管部门为中国石油和化学工业联合会。
本标准规定了硫化橡胶、热塑性橡胶在常温、高温和低温条件下，在规定的压缩率，经一定的压缩时间后，测定橡胶的变形量。本标准也规定了橡胶国际硬度值为10～80时压缩率为25%，当橡胶国际硬度值大于80时，80～89和90～95时其压缩率分别为15%和10%。本标准也适用于在液体作用下，橡胶压缩永久变形的测定。

Scope

This standard specifies the deformation of vulcanized rubber and thermoplastic rubber after a certain compression time at a specified compression rate under normal temperature, high temperature and low temperature conditions. This standard also stipulates that when the rubber hardness value is 10-80, the compression rate is 25%. When the rubber hardness value is greater than 80, the compression rate is 15% and 10% when the rubber hardness value is 80-89 and 90-95, respectively. This standard is also applicable to the determination of rubber compression set under the action of liquid. Note: When rubber is in compression, physical and chemical changes will inevitably occur. These changes prevent the rubber from returning to its original state when the compressive force is removed, and compression set occurs. The size of the compression set depends on the temperature and time in the compressed state, and the temperature and time in the recovery height. At high temperatures, chemical changes are the main cause of compression set in rubber. Compression set is measured after removing the compressive force applied to the sample and recovering its height at standard temperature. At low temperatures, changes due to glass hardening and crystallization are dominant. These effects disappear when the temperature rises. It is therefore necessary to measure the specimen height at the test temperature.