Morphology and Mechanical Properties of Reactive and Non-Reactive COC/EOC Blends

Blends based on metallocene cycloolefin copolymer (COC) and ethylene-octene copolymer (EOC) have been studied as a function of the blend composition, mixing technology and chemical reactions initiated between the components. In order to examine the effect of reactive blending on the interfacial adhesion as well as on the size of the dispersed phase domains a suitable peroxide was used. The investigated blends exhibited complete phase separation forming a matrix-droplet type morphology as observed by scanning electron microscopy (SEM). Co-continuous morphology was found in the composition range of 70-25 wt.% cycloolefin copolymer in dependence on the method of blending. This was predicted by the rheological study and confirmed by the mechanical tests. The interfacial adhesion between the two copolymers was improved by addition of peroxide, and a refinement of the morphology as well as an improvement of the mechanical performance was observed for reactive blends with EOC content in the range of 30-60 wt.%. A glass transition temperature depression of the ethylene-octene copolymer depending on the composition was detected by DMA in the nonreactive as well as in the reactive blends when COC forms the matrix.