POLYETHYLENE FILM AND METHOD FOR THE MANUFACTURE THEREOF

摘要

The present invention pertains to a polyethylene film which has a ratio between the strength in a first direction in the film plane and the strength in a second direction in the film plane perpendicular to the first direction in the range of 0.1-10:1, the strength in at least one direction in the film plane being at least 0.2 GPa, wherein the polyethylene has a weight average molecular weight of at least 500 000 gram/mole and a Mw/Mn ratio of at most 6. The invention also pertains to a process for manufacturing such film, wherein a starting UHMWPE polymer with a weight average molecular weight of at least 500 000 gram/mole, an elastic shear modulus determined directly after melting at 160°C of at most 1.4 MPa, and a Mw/Mn ratio of at most 6 to a solvent-free compacting process and a stretching process under such conditions that at no point during the process the temperature of the intermediate polymer film is raised to a value above its melting point, wherein in the stretching process a force is applied onto the intermediate polymer film in a first direction and in a second direction which is perpendicular to the first direction.