Dependence of the strength properties of oriented linear polyethylene on the orienting conditions during stretching

Abstract

An analysis of the strength characteristics and lifetime of film-based fibres from linear polyethylene which have been subjected to orientation stretching after the development of a neck under various subsequent stretching regimes has been carried out. A regime of multistage zone stretching, carried out in four stages with a slight increase in orienting stress (by 5 MPa) after each preceding stage, is optimum from the point of view of attaining high strength, lifetime, and reproducibility of material mechanical properties. With a more abrupt increase in orienting force, the number of stretching stages can be reduced to 2 or 3. Specimens drawn in this way are not inferior in strength to specimens drawn to the same extent by regime I, but they have a lower lifetime because of intense mechanical degradation which they undergo in the extension under the larger orienting stress. Such regimes are less reproducible. A nonidentical character of failure for specimens stretched under gradual and under abrupt loading has been noted.