Difference Of LDPE And LLDPE Materials

Low density polyethylene degree polyethylene (LDPE) is a plastic material that is suitable for various molding processes of thermoplastic molding processing and has good moldability. LDPE is mainly used for film products, also used in injection molding products, medical equipment, pharmaceuticals and food packaging materials, blow molding hollow molding products.

    Linear Low Density Polyethylene (LLDPE) is ethylene with small amounts of higher alpha-olefins (such as butene-1, hexene-1, octene-1, tetramethylpentene-1, etc.) under high pressure Or a low pressure polymerized copolymer with a density of 0.915 to 0.9 for low density polyethylene applications of 40 g/cm3. The molecular structure of conventional LLDPE is characterized by its linear main chain, with little or no long branches, but with some short branches. Without long chain branching, the crystallinity of the polymer is higher.

    LLDPE products are non-toxic, tasteless, odorless and have milky white particles. Compared with LDPE, it has the advantages of high strength, good toughness, strong rigidity, heat resistance, cold resistance, etc. It also has good resistance to environmental stress cracking, tear strength, and is resistant to acids, alkalis, organic solvents, etc.

    Both LDPE and LLDPE have excellent rheological or melt flow properties. LLDPE has less shear sensitivity because it has a narrow molecular weight distribution and short chain branching.

   During shearing (eg, extrusion), LLDPE maintains greater viscosity and is therefore more difficult to process than LDPE with the same melt index. In extrusion, the lower shear sensitivity of LLDPE makes the stress relaxation of polymer molecular chains faster, and thus the sensitivity of physical properties to changes in blow-up ratio is reduced.

   In melt extension, LLDPE generally has a lower viscosity at various strain rates. This means that it will not be strain hardened when stretched like LDPE. With the polyethylene deformation rate increases. LDPE shows a surprising increase in viscosity, which is caused by the application of molecular chain entanglement to low density polyethylene.