Influence of low-density polyethylene blown film thickness on the mechanical properties and fracture toughness

Recent research has shown that the resistance against crack initiation and propagation of polyethylene blown films depends on density, chain branching and crystal orientation next to the processing parameters. To assess low-density polyethylene blown film fracture toughness with different thicknesses, the essential work of fracture method has been conducted in this study. The thickness of the investigated low-density polyethylene films was regulated by the draw down ratio, which causes low-density polyethylene crystal orientation with the chain axis parallel to the machine direction at higher draw down ratios, influencing mechanical parameters and the fracture toughness. The crystal orientation was measured by X-ray diffraction. Blown films with thicknesses equal to or greater than 200 µm exhibit no preferred orientation, which is consistent with various calculated mechanical and fracture mechanics parameters. Films of less than 200 µm thickness show preferred machine direction crystal orientation and a distinct thickness influence on mechanical and fracture mechanics parameters.