ISO 22088-1 Plastics - Determination of Resistance to Environmental Stress Cracking (ESC)

Developed by the International Standards Organization (ISO), this part of the ISO 22088 standard provides information and general guidance regarding the selection of the test method to use to determine environmental stress cracking (ESC).

When a plastic material is stretched or stretched in air below its yield point, stress cracking can occur after a time that can be too long. These voltages can be internal or external, or a combination of both. Simultaneous exposure to a chemical environment and stress or strain can result in significantly shorter downtime compared to an inert environment.

This phenomenon is called environmental stress cracking (ESC) and is exhibited by many materials, including plastics. Allowable long-term stress or strain can be significantly reduced by this phenomenon.

It is generally believed that ESC occurs through the following processes:

• Formation of micro-voids in samples with microscopic stress concentrations after tension is applied.
• The formation and subsequent growth of macrocavities, resulting from the breakdown of intermolecular bonds in the cavities formed by the action of a chemical environment, and the formation of cracks consisting of interconnected cavities and fibrils.
• Growth of frenzy resulting from the breakdown of fibrils due to applied stress and contact with a chemical environment.
• Finally, a crack begins at the tip of the frenzy, leading to brittle failure.

Cracks can penetrate completely through the thickness of the material, split it into two or more pieces, or be stopped when they reach regions of lower stress or different material morphology. Determining the ESC is complex because it is affected by many parameters, including:

• test sample dimensions,
• Test specimen condition (orientation, structure, internal stresses),
• Sample preparation,
• The thermal history of the sample,
• stress and strain,
• test temperature,
• the duration of the test,
• chemical environment,
• Stress and strain application method,
• Failure criterion.

By keeping all but one parameter constant, the relative effect of the variable parameter on the ESC can be evaluated. The main purpose of ESC measurements is to determine the relative effect of chemical environment exposure on plastics (test samples and articles).

Measurements can also be used to evaluate the effect of molding conditions on the quality of an article when the failure mode corresponds to that achieved in actual service.

However, it is almost impossible to establish any direct relationship between the results of short-term ESC measurements on test samples and the actual service behavior of the articles, since the behavior of the latter will be more complex than that of the test samples.

Among the services provided by our organization within the framework of material testing services, there are also ISO 22088-1 standard tests. Do not hesitate to contact our laboratory EUROLAB for your testing and certification requests.