This standard provides a method for determining the environmental stress resistance (ESC) of plastics in the presence of chemical media under constant tensile force. It is suitable for molding and machining samples. It is used to evaluate the ESC of plastics exposed in different environments, determine the ESC of different plastics under specific environmental conditions, and evaluate the influence of molding conditions on the performance of products. The relationship between the measurement results of the sample short boat and the actual performance of the product cannot be evaluated by sub-evaluation.
1 Scope of application
This standard provides a method for determining the environmental stress resistance (ESC) of plastics in the presence of chemical media under constant tensile force. It is suitable for molding and machining samples. It is used to evaluate the ESC of plastics exposed in different environments, determine the ESC of different plastics under specific environmental conditions, and evaluate the influence of molding conditions on the performance of products. The relationship between the measurement results of the sample short boat and the actual performance of the product cannot be evaluated by sub-evaluation.

ISO 6252-1992 “Determination of the Resistance of Plastics to Environmental Stress Cracking (ESC) – Constant tensile stress method”

2 Principles
The specimen is subjected to a constant tensile force below the yield stress and immersed in a condition at a selected temperature. The time or stress of the specimen when breaking is recorded and the stress-cracking of the specimen is measured by one of the following methods:

Method A: To determine the new tensile stress caused at 100h, which can be obtained by interpolating the tensile stress with the American series diagram at the time of fracture.

Method B: determination of breaking time under specified tensile stress.

Method c: Measure the tensile stress against the new time curve until the specified time.

3 Instruments
 

ISO 6252-1992 “Determination of the Resistance of Plastics to Environmental Stress Cracking (ESC) – Constant tensile stress method”

3.1 Test device, which can make the sample bear tensile stress and chemical environment at the same time. See Figure l and Figure 2 for details.

3.2 Thermostatic control bath or chamber can keep the test system at (23±1)℃ or higher test temperature, up to (100±0.5)℃.

3.3 Automatic timer, used to measure the sample failure time.

3.4 Suitable sample preparation equipment.

4 Chemical environment
The chemical environment used in the test is generally specified by the standards related to materials. If not specified, the following chemicals can be used in the application of materials:

a.95%(volume fraction) ethanol, pharmaceutical grade;

b.1% aqueous solution of nonylphenoxyl polyoxyethylene oxide monoethanol;

C. Refined linseed oil.

ISO 6252-1992 “Determination of the Resistance of Plastics to Environmental Stress Cracking (ESC) – Constant tensile stress method”

5 Test conditions
5.1 test temperature, 23 soil (1) ℃, priority (55 + / – 0.5) ℃, also can choose (40 + / – 0.5) ℃ and (70 + / – 0.5) ℃ and (85 + / – 0.5) ℃ and (100 + / – 0.5) ℃.

5.2 The test stress should be less than the maximum allowable stress of the material at the test temperature, that is, the stress that produces 2% elongation after 1h. The test temperatures and applied stresses used for different materials are shown in Table 1.

6 Operation steps

ISO 6252-1992 “Determination of the Resistance of Plastics to Environmental Stress Cracking (ESC) – Constant tensile stress method”

7 Result representation
7.1A method, calculate the arithmetic mean of the measured failure time. The logarithmic value of time was plotted against the tensile stress, and the same stress corresponding to 100h failure was determined by interpolation method.

7.2B method, calculate the arithmetic mean of the failure time obtained from the five samples.

7.3C method, calculate the arithmetic mean of the failure time of each stress used, and plot the tensile stress with the logarithm of the failure time.

Standard RESUME and bid acquisition status
This standard was formulated by IS0/TC6l/SC6 in 1981 and revised for the first time in l992. Now it is the second edition, cancelled and replaced by the first edition (IS06252; 1991), the technical content is consistent with IS06252,1981.

There is no corresponding standard in our country.