Effects of the processing conditions and blending with linear low-density polyethylene on the properties of low-density polyethylene films

Effects of blending low-density polyethylene (LDPE) with linear low-density polyethylene (LLDPE) were studied on extrusion blown films. The tensile strength, the tear strength, the elongation at break, as well as haze showed more or less additivity between the properties of LDPE and LLDPE except in the range of 20–40% where synergistic effects were observed. The LLDPE had higher tensile strength and elongation at break than did the LDPE in both test directions, as well as higher tear strength in the transverse direction. The impact energies of the LLDPE and the LDPE were approximately the same, but the tear strength of the LLDPE was lower than that of LDPE in the machine direction. The comparative mechanical properties strongly depend on the processing conditions and structural parameters such as the molecular weight and the molecular weight distribution of both classes of materials. The LLDPE in this study had a higher molecular weight in comparison to the LDPE of the study, as implied from its lower melt flow index (MFI) in comparison to that of the LDPE. The effects of processing conditions such as the blow-up ratio (BUR) and the draw-down ratio (DDR) were also studied at 20/80 (LLDPE/LDPE) ratio. Tensile strength, elongation at break, and tear strength in both directions became equalized, and the impact energy decreased as the BUR and the DDR approached each other.