Investigation of creep phenomena in polyethylene and polypropylene

Although creep in thermoplastics, especially for polyethylene, has been investigated throughly, not too much information exists to establish activation energies at different stress levels by the application of high stress-level, short-time creep tests. Extrapolation of data to zero stress gives a true material activation energy which is a measure of internal resistance to deformation. Descriptions of specific creep parameters and equipment with a relatively simple phototube recording device are offered along with a discussion of results and recommendations for future fields of investigation.