Linear low-density polyethylene, LLDPE, has increased its market share in the packaging industry due to its excellent mechanical properties. These properties are the result of its molecular structure due to its short chain branching, SCB, and their distribution, DSCB. Together with the molecular weight and the distribution of molecular weights, the SCB affects the blown film process because it interferes in the film solidification and crystallization kinetics up to the freezing line. The objective of this work was to verify the influence of the DSCB of LLDPE in the rheological and optical properties of blown films. Three LLDPE, synthesized with Ziegler-Natta and metallocene catalysts, were studied, all with similar weight average molecular weight, Mw, but with different DSCB. It was observed that the DSCB influenced the rheological properties that reflect the material elasticity, such as the first normal tension difference, N1(<FONT FACE=Symbol>g</font>), the storage modulus G'(w) and the recoverable strain gammar; however, the rheological properties that reflect the viscosity, such as the shear viscosity eta(gamma) and the loss modulus G"(w), were not affected. In addition, the higher the gammar of the LLDPE, the lower the crystalline structures of the films, which decreased their opacity. However this proportionality was kept up to a given value of gammar above which the melt fracture dominated the recoverable strain and the opacity increased again.
LLDPE; blown films; recoverable strain; opacity
