Shrinkage force studies of oriented polyethylene terephthalate

Shrinkage force measurements on drawn polyethylene terephthalate fibres have been evaluated in terms of the elastic behaviour of a molecular network. It is shown that for low network deformations the classical theory of Kuhn and Grün describes the stress‐optical behaviour very well. For high deformations, the recent theory of Edwards and Vilgis has been found to give a satisfactory description of the data. It also provides some tentative insights into the structure of the spun yarns.