Short Chain Branching Effect on the Cloud-Point Pressures of Ethylene Copolymers in Subcritical and Supercritical Propane

Abstract

The cloud-point pressures of copolymers of ethylene with propylene, butene, hexene, and octene in propane were measured with a variable-volume optical batch cell to investigate the effects of the number and length of branches on the phase behavior in the temperature range from 25 to 200 °C and at pressures up to 700 bar. As the degree of branching increased in the ethylene-propylene copolymers, ethylene-butene copolymers, and ethylene-hexene copolymers, the cloud-point pressures decreased. At the same degree of branching, the cloud-point pressures decreased slightly upon increasing branch length. The copolymer SAFT (statistical association fluid theory) equation of state was found to correlate the experimental cloud-point data by adjusting the branch segment energy.

Equations of state for the calculation of fluid‐phase equilibria

“…More recently, Han et al 1998 reported that the copolymer-SAFT equation of state can be used to correlate the soft chain branching effect on the cloud point pressures of copolymers of ethylene with propylene, butene, hexene, and octene in propane. The copolymer-SAFT equation can also be used to predict phase transitions in hydrocarbonqchain Ž .…”

Phase behavior, density, and crystallization of polyethylene in n‐pentane and in n‐pentane/CO2 at high pressures

“…There is already considerable literature on the phase behavior of polyolefins in n ‐alkanes and n ‐alkane/CO 2 mixtures 1–10. However, these are mostly focused on the L–L phase boundary, with very limited data on the density and the S–F boundary.…”

“…However, these are mostly focused on the L–L phase boundary, with very limited data on the density and the S–F boundary. Some specific examples of recent work in which the S–F boundaries in polymer solutions in compressed or supercritical fluids have been reported include tetracontane in propane;10 poly(ethylene glycol) (PEG) and poly(ethylene glycol dimethylether) in CO 2 , propane, or nitrogen;11–13 copolymers of PE in ethylene, isobutane, and propane;5–10 polyester in carbon dioxide;14 polypropylene in propane and propylene;15 and PE in pentane in the presence of polydimethylsiloxane 1. The L–L phase boundaries of polyolefins in these fluids showed a lower critical solution temperature (LCST)‐type behavior, which shifted to higher P s in the presence of carbon dioxide.…”

Morphologies of blends of isotactic polypropylene and ethylene copolymer by rapid expansion of supercritical solution and isobaric crystallization from supercritical solution

“…Phase transitions of the polymer solutions were determined with a high pressure variable volume 23,24 For the cloud-point determination (liquid-liquid transition), known amounts of two polymers were inserted into the cell and then charged with propane solvent at room temperature. The solution was heated above the melting temperatures of the polymers in the preexpansion oven and pressurized by a piston to a homogeneous solution while stirring.…”

“…Han et al 24 In short, as the solubility parameters of ethylene copolymers decreased, their cloudpoint pressures decreased. The solubility parameters of EB copolymers and PP are shown in Figure 6.…”