Mechanical and transport properties of drawn low‐density polyethylene

Quenched, quenched and annealed, and slowly cooled branched low‐density polyethylene films were drawn at 25, 40, and 60°. The true draw ratio λ L of the volume element was obtained and used to characterize the dependence on plastic deformation of the density, drawing stress, and work of plastic deformation, and the sorption and diffusion of methylene chloride. The effects observed are similar but less drastic than on linear high‐density polyethylene. In particular, the transformation from the original lamellar to the final fibrous structure seems to be fastest for λ L between 3 and 4. But the changes of vapor transport clearly indicate that the transformation is not yet complete even at the highest draw ratio λ L = 6, just before the sample breaks. Annealing at 90°C of the drawn samples with free ends restores or even increases the transport properties beyond those of the undrawn sample without causing the fibrous structure to revert to the original lamellar structure.