Effect of strain rate and temperature on tensile properties of ethylene–propylene block copolymers

Tensile tests were conducted on several ethylene–propylene block copolymers with different ethylene content, over a range of temperatures (−120 to 23 °C) and strain rates, 10−4–10−2 s−1. The effect of temperature and strain rate on elastic modulus, Poisson’s ratio and yield stress has been analyzed. To determine the elastic properties, a video-extensometer was used to determine the deformation field. The experimental results about yielding are interpreted in terms of the well known principle of temperature–time equivalence. Several models have been considered to explain the significant increase in the yield stress at low temperatures or high strain rates.

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► Polypropylenes show significant variation of mechanical performance with temperature.
► This variation is accentuated with strain rate (time–temperature superposition principle).
► Highest molecular weight material exhibits more sensitivity to both parameters.
► Model to semicrystalline polymers provides reasonable results in ethylene–propylene block copolymers.