Blends of ethylene 1-octene copolymer synthesized by Ziegler-Natta and metallocene catalysts. I. Thermal and mechanical properties

The thermal, viscoelastic, and mechanical behaviors of three binary blends of ethylene 1-octene copolymer (EOC) regarding the melt index and density, one component made by Ziegler-Natta (FA and RF in abbreviation of the commercial name) and the other by metallocene catalysts (FM, EN and PL in abbreviation of the commercial name), have been investigated to understand molecular mechanism of the blends. Thermal studies reveal that the two constituents in the three blends exclude one another during crystallization, implying a phase separation. Viscoelastic properties shaw a single beta or gamma transition in all the compositions, suggesting a miscibility in the amorphous region. The tensile modulus, yield stress, maximum strength at break, and elongation at break follow the rule of mixtures if the comonomer content does not differ too much. Otherwise, the modulus and yield stress are negatively deviated, whereas elongation at break is positively deviated from the weight-average value. The tensile properties of film at yield and break in the machine direction is increased with an addition of FM in the FA + FM blend. Although all three blends form separate crystals in the crystalline state, a correlation exists between the mechanical properties and the density of EOCs. (C) 1999 John Wiley & Sons, Inc.