In this report, Dr. Wright aims to explain both the causes of environmental stress cracking (ESC) and its implications.

ESC is the premature initiation of cracking and embrittlement of a plastic due to the simultaneous action of stress and strain and contact with specific fluids. This definition provides the key to the problem of predictability. Failure is due to a combination of influences, which would not cause the same problems if encountered individually.

Approximately 15 of all failures of plastics components in service are caused by ESC. Such failures may be costly or life threatening, and consequently the phenomenon has been the subject of intensive research for more than 40 years. This research has revealed a great deal about the casual mechanism, but has not yet brought us to the ideal position of being able to predict and prevent the occurrence of ESC in all situations.

The report is divided into three sections:

PREDICTION OF ESC AND ASSESSMENT BY TESTING

In the absence of comprehensive data for all possible combinations of mechanical influences and fluid there are a number of predictive pointers, together with testing techniques, which may prove invaluable when selecting materials for particular applications and situations.

FACTORS THAT INFLUENCE ESC

An understanding of the theory of plastics failure, and the influence of fluids upon it, will also enable the reader to evaluate the problems which are likely to occur in specific instances.

DATA ON SPECIFIC PLASTICS

There has been extensive experimental work carried out on a number of plastics in frequently encountered environments. Some of the data produced are clearly of relevance in a wider context, and Dr Wright has presented these findings. The bulk of the work has been concerned with the commonly used amorphous thermoplastics, which are particularly sensitive to ESC due to their structure. However, there has been some interest in semi-crystalline plastics, particularly polyethylene, and data on these materials are also presented and discussed.

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