LLDPE Resin Granules

Processing

 

Both LDPE and LLDPE have excellent rheology or melt flow. LLDPE Resin Granules has less shear sensitivity because it has a narrow molecular weight distribution and short branched chains. LLDPE maintains greater viscosity during shear, making it more difficult to process than LDPE with the same melt index. In extrusion, the lower shear sensitivity of LLDPE results in faster stress relaxation of the polymer molecular chains and the resulting reduced sensitivity of the physical properties to changes in the blow-up ratio. In melt extension, LLDPE typically has a lower viscosity at all strain rates. This means that it will not strain harden on stretching as much as LDPE.

 

As the deformation rate of polyethylene increases, LDPE shows a striking increase in viscosity, which is caused by molecular chain entanglement. This phenomenon is not observed in LLDPE because of the lack of long branched chains in LLDPE to keep the polymer from entangling. This property is extremely important for film applications, and LLDPE films are easier to make thinner films while maintaining high strength and toughness.

 

The rheological properties of LLDPE Resin Granules can be summarized as "rigidity in shear" and "softness in extension". When replacing LDPE with LLDPE, film extrusion equipment and conditions must be modified. The higher viscosity of LLDPE requires the extruder to have more power and to provide higher melt temperatures and pressures. Typical die gap dimensions for LDPE and LLDPE are 0.024 to 0.040 and 0.060 to 0.10, respectively.