Study of the effect of themolecular architecture of the components on the melt rheological properties of polyethylene blends

The influence of the molecular architecture of linear low-density polyethylene on melt miscibility with low-density polyethylene was investigated. Different LLDPE resins with variable type and content of branches were blended at a given composition with the same LDPE. The rheology and different data-treatment methods based on mixture models suggest that the melt blend morphology is strongly dependent on the molecular architecture of the matrix, particularly on the amount of short chain branches. The properties of the blends in which the LLDPE sample possesses a high content of branches can be predicted by the miscible blend additivity rule. The blends in which the LLDPE had the lowest branch content were completely immiscible. In these cases the rheological properties showed values that are higher than expected for miscible blends, as predicted by the Palierne model. The molar mass and the type of comomomer in LLDPE do not play an important role in the melt morphology of the blends at the composition studied. Thus the level of branching in LLDPE is revealed as the molecular feature with the strongest influence on melt miscibility with LDPE.