Reversible strain-induced order in the amorphous phase of a low-density ethylene/butene copolymer

Characterization of volume strain at large deformation under uniaxial tension in high-density polyethylene

“…The compaction of the amorphous phase is caused by the shrinkage of average distance between neighbouring chains while they are stretched and oriented between lamellae within the deformed spherulites. Our results confirm previous ones [20] who assessed volume variations in a low-density ethylene/ butene copolymer with another video technique during tensile tests performed at 20 8C for a stretching rate of 0.5 mm/min. Like in our work, these authors noted a net volume compaction at the beginning of deformation.…”

Filler toughening of plastics. Part 1—The effect of surface interactions on physico-mechanical properties and rheological behaviour of ultrafine CaCO3/HDPE nanocomposites

“…The decrease of volume strain with deformation for pure HDPE is probably due to the fact that the stretching of noncrystalline (rubbery) phases leads to the orientation of the amorphous chains parallel to each other to form a kind of mesomorphic structure similar to those found in liquidcrystal polymers in the smectic state, with a consequent decrease in volume strain, as suggested by Gaucher-Miri et al [30]. The decrease in volume strain on stressing pure HDPE could also be due to further crystallization.…”

“…In the case of polyethylene based polymers-and only with this type of polymers-negative volume strains have always been reported [29]. In the work of Gaucher-Miri et al [30], the measurements were made until large strains with a video apparatus instead of extensometers. In this way valid data on a low density PE copolymer could be collected even after necking.…”

New Insight on Initiation of Cavitation in Semicrystalline Polymers: In-Situ SAXS Measurements

“…But it is impossible to determine precisely the initiation of cavitation as this apparatus gives the global volume change. The latter is very complex at the beginning of the deformation and is caused by cavitations, but also by the Poisson effect, reversible densification due to a strain-induced organization of the amorphous phase, 26 and even dilatation if the temperature is not kept perfectly constant.…”