Phase equilibria of poly(ethylene-co-vinyl acetate) copolymers in subcritical and supercritical ethylene and ethylenevinyl acetate mixtures

Single‐stage fractionation of poly(ethylene‐co‐vinyl acetate) in supercritical ethylene with saft

“…For example, SAFT was found to account for phase transitions in binary and ternary systems of PEP-a-olefin (Gregg et al, 19931, PVT data for pure PEP systems (Chen et al, 1994b), and for the associating effects in binary systems of monohydroxyl and dihydroxy telechelic PIB in nonpolar and polar solvents (Gregg et al, 1994). Recently, SAFT was successfully used to model the cloud points of EVA in supercritical ethylene and ethylene-VA mixtures (Folie et al, 1996). SAFT was found to account for the effect of the polymer MW and VA content, and solvent composition on the CPP and on the size of the fluid-liquid miscibility gap over a broad range of temperatures and polymer concentrations.…”

“…In order to extend S A F T to real fluid mixtures, mixing rules are required only for the dispersion term since the three reference terms can be extended to mixtures based on rigorous statistical mechanics. The van der Waals one-fluid (vdW1) mixing rules are used for the two parameters in the dispersion term that require mixing rules, u/k, the temperaturedependent segment-segment interaction energy, and m. As explained elsewhere (Folie et al, 1996), only one binary interaction parameter k i j per pair of components was used in this work. k i j is a correction factor to the geometric mean rule used to estimate the unlike-segment interaction energy uij which appears in the vdWl mixing rule for u/k For an n-component system, the number of kijs ideally required is equal to (n2 -n)/2 if k,, = kji and kii = 0.…”

“…Hence, only three k,s were used in this work: one for the ethylene-VA interaction (k12), one for the ethylene-EVA interaction (kI3), and one for the VA-EVA interaction (k,,). These kijs were determined by Folie et al (1996) by fitting SAFT to vapor-liquid equilibrium (VLE) data for the ethylene-VA binary, and to cloud point data for the parent EVA-ethylene pseudo-binary and the parent EVA-ethylene-VA pseudo-ternary systems. Furthermore, since all three kijs were found to be only slightly dependent upon temperature, three temperature-independent kijs were used throughout this work: k,, = 0.15340, k,, = 0.06198, and k,, = 0.08583.…”

“…The pure component parameters for the ten nearlymonodisperse EVA pseudocomponents were estimated as detailed by Folie et al (1996). Following Huang and Rodosz (19901, we set voo equal to 12 mL/mol-seg, and estimate m and uo/k from the n-alkane corollaries 0).…”

“…Later, the same LDPE-ethylene system was modeled by Liu and Prausnitz (1980) and Jungermann and Luft (1987) using an EOS based on the perturbed-hard chain theory, and by Sako et al (1989) who developed a simple cubic EOS from the generalized van der Waals partition function. More recently, the S A F T EOS was used with success by McHugh (Lee et al, 1994) and by Folie et al (1996) to model the cloud point curves of LDPE copolymers including EVA and poly(ethy1ene-co-methyl acrylate) (EMA) in supercritical ethylene. In those studies, the polymer was always treated as a monodisperse component.…”