Thermo-Rheological Characteristics of Low-Density Polyethylene /Linear Low-Density Polyethylene (LDPE/LLDPE) Blends and their Processibility in Blown Film Extrusion
Low-density polyethylene (LDPE) is cost effective and widely used in the blown film industry for its flexibility, toughness and optical properties.However,film strength and optical properties are a major concern for many packaging applications. Linear low-density polyethylene (LLDPE) is utilised for its better mechanical strength although its processibility is challenging. To meet necessary film properties for packaging applications and ease of processing, LLDPE is blended with LDPE. The LDPE/LLDPE blend is suitable to process in the conventional LDPE film blowing apparatus with only minor modifications. Therefore, it is vital to study the thermal and rheological characteristics of LDPE/LLDPE blends before they are processed. The objective of this paper is to study the thermo-rheological properties of LDPE/LLDPE blends and make recommendations for their processing in blown film extrusion. Branching characteristics of the LDPEs and their effect on LLDPE will also be discussed with respect to their flow activation energy.Two different commercial grades of LDPE were blended with LLDPE using a brabender twin screw extruder, producing four different compositions. Modulated differential scanning calorimetry (MDSC) and an Advanced Rheometric Expansion System (ARES) rheometer were used to determine thermal and rheological properties of the blends.