GB/T 1683-2018Rubber,vulcanized - Determination of compression set at constant strain (English PDF)

1 Scope

GB/T 1683-2018 is the Chinese national standard on rubber,vulcanized - determination of compression set at constant strain, in the field of rubber and plastic industries. The /T suffix marks it as a recommended standard: it is not compulsory by itself, but it becomes binding as soon as a contract, a tender or a customer specification calls it up - which in practice is how most foreign buyers meet it. It was issued on 6 February 2018 by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China; Standardization Administration of China, and has been in force since 1 September 2018. Classification: ICS 83.060, CCS G40. This page is published from the official record of the standard held by the Chinese standards administration: the identification, the dates, the classification and the issuing body are taken from there. The clause text, the tables and the numeric limits are in the document itself, which is delivered complete in English translation.

This Standard specifies the methods of determining the characteristics of compression set of vulcanized rubber at constant strain. This Standard is applicable to the evaluation of vulcanized rubber's capability of maintaining its elasticity after continuous compression under the condition of stipulated temperature and compression ratio.

2 Normative References

The following documents are indispensable to the application of this Standard. In terms of references with a specified date, only versions with a specified date are applicable to this Standard. The latest version (including all the modifications) of references without a specified date is also applicable to this Standard.

GB/T 2941-2006 Rubber - General Procedures for Preparing and Conditioning Test Pieces for Physical Test Methods

GB/T 3512-2014 Rubber, Vulcanized or Thermoplastic - Accelerated Ageing and Heat Resistance Tests - Air-oven Method

GB/T 7759.1-2015 Rubber, Vulcanized or Thermoplastic - Determination of Compression Set - Part 1. At Ambient or Elevated Temperatures

3 Principle

In this test, vulcanized rubber test piece is compressed to a stipulated height. After a certain temperature and a certain period of time, or after infiltration with medium, determine the compression set of the test piece at constant strain.

6 Test Conditions

6.1 Selection of Constant Compression Ratio In accordance with the hardness (Shore A) of the test pieces, there are the following options.

---When the hardness is below 50, 40 % compression ratio can be selected;

---When the hardness is between 50 ~ 75, 30% compression ratio can be selected;

---When the hardness is above 75, 20% compression ratio can be selected. on the compression surface of the fixture.

7.2 Adjust the thickness gauge to point at zero, then, measure the initial height (h0) of the test piece before compression.

7.3 Select a suitable limiter; place the test piece and the limiter in an appropriate position in the fixture, then, evenly compress it to a stipulated height (h1). During the compression, the test piece and the limiter shall not contact each other.

7.4 During the liquid medium-resistant test, the fixture shall be placed in a sealed container. The test piece shall be completely soaked in the liquid medium. Liquid medium for tests cannot be used repeatedly.

7.5 In terms of tests at a stipulated temperature, the time of test shall be calculated since the fixture or the container is placed into the test chamber.

7.6 After the stipulated time, take out the fixture or the container from the test chamber. Select one of the standard laboratory temperatures that are stipulated in GB/T 2941- 2006; cool down for 2 h. Then, open the container and the fixture; take out the test piece. At the same standard laboratory temperature, place the test piece in a free state for 1 h, then, measure the recovered height (h2) after compression.

7.7 After the test with less volatile liquid medium, before opening the fixture, certain solvents, for example, gasoline, can be used to rinse it. The duration of rinsing shall not exceed 30 s.

8 Test Result

8.1 Compression set value K (%) shall be calculated in accordance with Formula (1). Where. h0

---height of test piece before compression, expressed in (mm); h2

---recovered height of test piece after compression, expressed in (mm); h1

---height of limiter, expressed in (mm).

8.2 When test piece is ruptured after the test, the test data shall be abolished.

8.3 The arithmetic mean value of 3 test results shall be deemed as the test result.