BS EN ISO 22088-4:2006

Specifies a ball or pin impression method for the determination of the environmental stress cracking (ESC) behaviour of plastics by means of a constant-strain test.

1.1 This part of ISO22088 specifies a ball or pin impression method for the determination of the environmental stress cracking (ESC) behaviour of plastics by means of a constant-strain test.

1.2 The method is applicable to finished products and to test specimens prepared by moulding and/or machining, and can be used for the assessment of the ESC behaviour of a plastic product or material exposed to different environments, as well as for the determination of the ESC behaviour of different plastics materials exposed to a specific environment.

NOTE Alternative methods for the determination of environmental stress cracking by means of a constant-strain test are specified in ISO22088-3 and ISO22088-5. A method for the determination of environmental stress cracking by means of a constant-stress test is specified in ISO22088-2.

1.3 The ball and pin impression methods are both quick and sensitive procedures for assessing the ESC behaviour of plastics. The methods are well suited for amorphous plastics. They are less appropriate for materials displaying a pronounced tendency for creep and/or stress relaxation, i.e. for semi-crystalline materials. If semi-crystalline materials are tested, pins are more appropriate than balls.

1.4 The ball impression method is useful for assessing the principal ESC behaviour of the material/chemical combination under consideration. It is less influenced by the near-surface orientation state of the specimens than the pin impression method and the methods in the other parts of this International Standard, where the chemical attacks only the original surface of the material. This, depending on the manner of specimen preparation, may show a considerable degree of orientation.

1.5 The pin impression method is useful for testing specimens of small thickness and finished parts.