The Indentation and Scratch Hardness of Plastics

Static and sliding indentation tests on vinyl chloride-acetate copolymer and nylon 66 are described, and form part of a study of the deformation and wear of gramophone records. The vinyl was unusual in showing considerable work softening. Static indentation tests covered the whole range from the fully elastic to the fully plastic condition, and behavior was consistent with the Hertz equations, but the accuracy of the Meyer law is doubtful. Sliding indentation tests included measurement of the depth of track under load on flat and curved surfaces, and observations on the onset of instability, and the formation of a chip. These data will be used for the calculation of distortion on record playback due to deformation of the groove wall under load.