Tensile properties of linear low density polyethylene (LLDPE) blown films

Various linear low-density polyethylene (LLDPE; density similar to (0.920 g/cm(3)) resins that encompass those polymerized using Ziegler-Natta, metallocene, and chromium oxide based catalysts were blown into film at similar process conditions, and the tensile properties of the resulting films were investigated in relation to their orientation characteristics. The tensile properties of the subject blown films were observed to be significantly different from those of isotropic/un-oriented polyethylene specimens of similar density (crystallinity). Further, the tensile properties were different in the machine and transverse directions. These were explained in terms of the orientation and lamellar organization characteristics of the LLDPE blown films. Investigation of the temperature dependence (between -50 degreesC and +50 degreesC) of these tensile properties indicated an increase in modulus, yield stress and break stress with decreasing temperature pointing to the possible role played by the decreased mobility of the non-crystalline phase at lower temperatures. Excellent correlation between the Elmendorf tear properties of the LLDPE blown films and their tensile yield characteristics was observed. This added substantial credibility to previous hypotheses that specimen stretching plays a significant role in Elmendorf tear tests and further supported the previously identified structural features and microstructural deformation mechanisms that are deemed responsible for the discernment of LLDPE blown film tear resistance.