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) (PEO15), 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 PEO15 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 PEO15- ethylene- octene was also investigated, where ethylene and I-octene are monomer and comonomer of PEO. As the concentration of ethylene in the ternary mixture increases, the miscibility of PEO15 dramatically decreases. Adding 64 wt% ethylene into the ternary mixture increases the pressure, dissolving PEO15, up to 1000 bar. In pure ethylene, PEO15 was not dissolved up to 1900 bar, 160degreesC. (C) 2004 Wiley Periodicals, Inc.