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An Argon Plasma Etching Method for the Investigation of Craze Microstructure in PVC Gas Pipes

 

Testing and Processing # 1985 York

The gas industry in the Netherlands uses not only PE and metal but also unplasticized and impact modified PVC as pipe material for the distribution of natural gas.
For a number of years the phenomenon of crazing in PVC and impact modified Pvc

gas pipes caused by the combined action of mechanical stresses and certain gas components has received attention. In this contribution an argon plasma etching method is presented that is very well suited for the investigation of craze microstructure using Scanning Electron Microscopy. The reason for this is that craze material that has absorbed certain gas components is not or only to a minor extent attacked by the argon plasma, whereas the surrounding material is strongly attacked.

It can be shown by means of this preparation method that many crazes formed in

PvC in natural gas environments do not show fribrillation but merely show signs

of localized absorption, swelling and de-gelation behaviour. This is probably due to the low mechanical stresses that are present during craze formation in many practical situations. In other crazes produced in the laboratory using higher stresses a high extent of fibrillation can be made clearly visible by the argon plasma treatment. Another conclusion this preparation method allows is that crazes caused by different chemicals show different microstructures.

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