Flory's Equation Of State Theory Research Articles

Upper critical solution temperature (UCST) phase behaviour and pressure-sensitive adhesive properties in blends of poly(vinyl ) with hydrogenated terpene resin

Abstract Pressure-sensitive adhesive ( PSA ) properties of blends of poly-vinyl ethylene -co-1,4- butdiene ), V-BR , with hydrogenated terpene resin were examined using blend films prepared at 70 and 140°C. Since the blend has an upper critical solution temperature of ∼133°C, significant differences between PSA properties of miscible and immiscible blends were indicated. These differences were explained in terms of the dynamic mechanical behaviour. Cohesive failure of the adhesive layer was also discussed with reference to the surface tensions of the V-BR and the hydrogenated terpene resin, these parameters being estimated according to the Flory equation of state theory.

Mean-field lattice equations of state: 5. Influence of pressure on liquid-liquid phase behaviour of polymer blends

The semi-phenomenological (SP) treatment and a modified form of the mean-field lattice-gas (MFLG) model were used to investigate the influence of pressure on the phase behaviour of polymer blends. It was shown that the peculiar phase relations of the system poly(ethyl acrylate)/poly(vinylidene fluoride) could be reproduced in a qualitative way. Positive and negative signs for the excess volume could be predicted in accordance with the observed pressure-temperature-weight fraction relations. Furthermore the effect of pressure on the location of binodals for oligomeric mixtures of polybutadiene and polystyrene was represented quantitatively with the MFLG model and the SP treatment. It was shown that end group contributions cannot be neglected if polymers of low molar mass are involved. It was further demonstrated that the SP approach only requires one interaction function to represent all critical data whereas in the MFLG model different interaction terms, one for each system, are necessary in order to obtain good descriptions. Both descriptions are found to be superior to a modified version of the Flory equation of state theory.

Thermodynamic properties of chain liquid mixtures with strong, local interactions

AbstractThis paper addresses the effect in chain liquids on thermodynamic behavior of a large charge in the strength of local interactions on mixing. We classified real systems according to the ability of the Flory equation of state (FES) theory to prodict the excess volume. The FES theory enables reliable estimates provided the mixture is nearly athermal and the pure components obey the Flory equation of state. These requirements arise from Flory's approximations for the lattice part of the configuration integral, ZL, and the cell part, ZC, respectively. We revised ZL without adding adjustable parameters by the quasichemical perturbation method to account for local ordering in the mixture because of a large change in the strength of binary interactions on mixing. The modification improves the predictions of the thermodynamic functions for systems where Flory's ZL is inadequate.

Thermodynamics of oligomeric binary mixtures of polyethylene glycol and polypropylene glycol methylethers

Measurements are reported of the heats of mixing and cloud point curves of binary mixtures of methoxylated polyethylene glycol with methoxylated polypropylene glycol. The data are discussed in terms of the Flory equation of state theory and it is shown that both a temperature and concentration dependent X 12 parameter and a Q 12 term are required.

The compatibility of poly(butyl acrylate) with chlorinated polyethylene

AbstractThe compatibility of poly(butyl acrylate) (PBA) with chlorinated polyethylene (CPE) was studied using dynamic mechanical measurements and light scattering turbidimetry. For around 50 wt.‐% and above chlorination of CPE they were found to be miscible and show a lower critical solution temperature upon heating. It was found that a favourable heat of mixing of oligomeric analogues could not be taken as a guarantee of the compatibility of the corresponding polymers: the heat of mixing of PBA with cereclor 45 (chlorinated paraffin, 45, 7 wt.‐% CI) is negative, but the corresponding polymers PBA/CPE3 (48,0 wt.‐% CI) are immiscible. When the Flory equation of state theory is applied to the system, a large negative interaction entropy parameter Q12 must be introduced to counterbalance the large negative interaction energy parameter X12, obtained from the heats of mixing of PBA with cereclor. The simulated spinodals are flat‐bottomed. However, if a much smaller negative X12 is adopted, the spinodal calculated will have more curvature. Kinetic constraints on the migration of molecules during phase separation were observed when the molecular weight exceeded certain limits and this could affect the observed cloud point diagram.