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

The ISO 22088 standard, developed by the International Standards Organization (ISO), consists of the following subsections under the main title of "Plastics - Determination of resistance to environmental stress cracking (ESC)":

ISO 22088-1 Part 1: General guidance
ISO 22088-2 Part 2: Constant tensile load method
ISO 22088-3 Part 3: Twisted strip method
ISO 22088-4 Part 4: Ball or pin pressing method
ISO 22088-5 Part 5: Constant tensile deformation method
ISO 22088-6 Part 6: Slow strain rate method

When a plastic material is stretched in air below its yield point, stress cracking occurs after a very long time. These voltages can be internal or external, or a combination of both. Simultaneous exposure to a chemical environment and stress or strain results in a significantly shorter downtime compared to an inert environment. Environmental stress cracking (ESC) is exhibited by many materials, including plastics. Allowable long-term strain or strain can be significantly reduced.

In general, environmental stress cracking occurs through the following processes:

Formation of micro-voids in samples with microscopic stress concentrations after stress 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 cracks due to fibrillar breakage due to applied stress and contact with a chemical medium.

Cracks can penetrate completely through the thickness of the material, split the material into two or more pieces, or be stopped when they reach regions of lower stress or different material morphology.

Determining environmental stress cracking is complex because it is affected by many parameters, including:

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

Keeping all but one parameter constant, the relative effect of the variable parameter on environmental stress cracking is evaluated. The main purpose of these measurements is to determine the relative effect of chemical exposure on plastics.

The ISO 22088-1 standard provides information and general guidance regarding the selection of the test method used to determine the environmental stress cracking of thermoplastic materials. The test methods described in other sections are applicable only to thermoplastic materials. These are essentially sequencing tests and are not intended to provide data to be used for design or performance prediction.

For the purposes of this standard,

Test temperature refers to the temperature at which test specimens are in contact with the test environment while under stress.
Trial period refers to the time that test specimens are in contact with the test environment while under stress.
Test medium refers to the liquid, gas, paste, solid, or other chemical medium chosen for contact with test specimens during testing.
The ESC index expresses the ratio of the value of the error indication feature determined in the test environment to the value determined in a reference environment (usually air) measured at the same test temperature after the same test period.
The ESC index expresses the ratio of the breaking voltage value determined in the test environment to the value determined in the reference environment (usually air) for the same exposure time.
The ESC index refers to the normalized value of shear stress, which measures the environmental stress cracking susceptibility of different materials to a given environment.

The ISO 22088-2 standard describes test methods for the determination of environmental stress cracking of thermoplastics when subjected to a constant tensile load in the presence of chemicals. This standard is applicable to test specimens prepared by molding or machining and is used for the assessment of environmental stress cracking of both plastic materials exposed to different environments and different plastic materials exposed to a specific environment. This is primarily a ranking test and is not intended to provide data to be used for design or performance prediction.

The ISO 22088-3 standard describes a test method for determining the environmental stress cracking resistance of thermoplastics when subjected to a constant bending stress in the presence of chemicals. Environmental stress cracking is indicated by the change of an appropriately selected indicator property of specimens stressed in the environment for a given period of time. This test method is suitable for determining the resistance of plates and flat test specimens, especially the susceptibility of localized surface regions of specimens to environmental stress cracking.

The ISO 22088-4 standard describes a ball or pin pressing method for determining the environmental stress cracking behavior of plastics through a constant stress test. This method can be applied to finished products and test specimens prepared by molding or machining, and can be used to determine environmental stress cracking as well as to evaluate the environmental stress cracking behavior of a plastic product or material exposed to different environments.

The ISO 22088-5 standard describes a method for determining the environmental stress cracking behavior of thermoplastics when subjected to a constant tensile deformation in the presence of a chemical environment. It can be applied to test specimens prepared by molding or machining, and can be used to evaluate the environmental stress cracking behavior of plastic materials exposed to different environments, as well as to determine the environmental stress cracking behavior of different plastic materials exposed to a particular environment.

The ISO 22088-6 standard describes a procedure for evaluating the environmental stress cracking susceptibility of polymeric materials in chemical environments by slowly increasing the stress applied to a tensile specimen at a constant rate. It can be applied to test specimens prepared by molding or machining and can be used to evaluate the relative environmental stress cracking susceptibility of a material exposed to different environments or the relative environmental stress cracking susceptibility of different plastics exposed to a particular environment.

Among the numerous tests, measurements, analyses, and evaluations our organization provides for businesses in various sectors, we also offer testing services for determining the resistance of plastics to environmental stress cracking, in accordance with the ISO 22088 standard, thanks to our trained and expert staff and advanced technological equipment.