Phase behavior of binary and ternary mixtures of poly(ethylene‐co‐octene)–hydrocarbons

Poly(ethylene-co-octene) (PEO) is a new thermoplastic elastomer that has the wide variation in mechanical, thermal, optical, and elastomeric properties. The variety of PEO properties results from incorporation octene comonomer in polyethylene backbone. Because of the wide difference in the copolymer properties, it is important to know the phase boundary to optimize the copolymerization and separation processes of PEO. The cloud-point and bubble-point curves for poly(ethylene-co-15.3 mol % octene) (PEO 15 ), which has 15.3 mol % octene repeat unit in the backbone structure, were determined in n-pentane, n-hexane, n-heptane, and n-octane. The miscibility of PEO 15 in normal alkane enlarges with the size of the normal alkane because of the increasing dispersion interactions related to polarizability. The phase behavior for the ternary systems of PEO 15 -ethylene-octene was also investigated, where ethylene and 1-octene are monomer and comonomer of PEO. As the concentration of ethylene in the ternary mixture increases, the miscibility of PEO 15 dramatically decreases. Adding 64 wt % ethylene into the ternary mixture increases the pressure, dissolving PEO 15 up to 1000 bar. In pure ethylene, PEO 15 was not dissolved up to 1900 bar, 160°C.