scope:

This part of ISO 899 specifies a method for determining the tensile creep of plastics in the form of sta ndard t est specimens under spe cified conditions such as those of pretreatment, t emperature and humidity.

The metho d is suitabl e for use with rig id and sem i-rigid non-rein force d, fille d and fibre-rein forced plastics materials (see ISO 472 for definitions) in the form of dumb-bell-shaped test specimens moulded directly or machined from sheets or mould ed articles.

The method is intended to provide data for engineering-design and research and development purposes. Data for engineering-design purposes requires the use of extensometers to measure the gauge length of the specimen. Data for research or quality-control purples may use the change in distance between the grips (nominal extension).

Tensile creep may vary significantly with diff^^^^ces in specimen preparation and dimensions and in the test environment. The thermal history of the test specimen can also have profound effects on its creep behaviour (see Annex A). Consequently, when precise comparative results are required, these factors must be carefully controlled.

If tensile-creep properties are to be used for engineering-design purposes, the plastics materials should be tested over a broad range of stresses, times and environmental conditions.