Etching of polyethylene terephthalate

A degradative etching technique has been employed with polyethylene terephthalate films to demonstrate the existence of several different structures, the size of which vary from hundreds of microns to hundreds of Angstroms. The micron‐sized structures are a function of the processing and orientation of the film and occur in regular geometric patterns. Thus, parallel stretch‐direction lines are etched into one‐way stretched film, the number of lines being dependent upon film history. Etched, two‐way stretched films reveal a lamellate composition, each layer possessing a brick wall‐like structure. This general structural pattern has been found in other types of film by similar methods. Examination of the etched areas by electron microscopy demonstrates that the micron‐sized blocks are composed of spheres, 700 A. in diameter, which are aligned over moderate distances.