Gas Chromatographic Determination of Thermodynamic Properties of Polymer Solutions. I. Amorphous Polymer Systems

Abstract

A gas chromatographic (gc) method has been developed to measure solubility isotherms of a low molecular weight solvent in a high polymer. This method depends on the elution of the injected solvent on a concentration plateau of the same solvent in nitrogen carrier gas. The measured solubility is used to calculate the vapor-solid equilibrium ratio (Q = a~/ w~) , along with the solvent-polymer interaction parameter X, as a function of solution composition. Based on the Flory-Huggins and Maron theories, a mathematical correlation permits computation of Q values, usually with less than 5 deviation from those measured experimentally. The following polymer-solvent systems have been studied: polystyrene with benzene and ethylbenzene at 120" and with ethylbenzene at 185", polyethylene with n-decane at 185", and atactic polypropylene with hexane at 80". The computed i2 values range from about 4 to 5 .he urgent need for reliable process design data has led

Surface and kinetic effects in gas chromatographic studies of polystyrene

“…The size of the injectionmay alter the measured retention volume for a variety of reasons (27), of which the most important for the polystyrene system are non-linearity of the partition isotherms (with p or p, no longer independent of c) and adsorption effects on uncoated support. The small but significant increase in retention volume with Y increasing injection size above T, may be due to a curved isotherm which is anti-kangmuir in form (concave away from the vapour pressure axis when sorbed vapour is plotted against vapour pressure) as has been observed for ethylbenzene on polystyrene (14). The more pronounced effect below T,, where injection size causes a decrease in retention volunle, implies that the adsorption isotherm is of the oftenobserved kangmuir type.…”

“…Their technique has been used by Brockmeier et ai. (14,15) to measure solubility isotherms of several hydrocarbons in amorphous and semicrystalline polymers. The most recent development (16,17) has been the extension of the gas chromatographic method to three compoaent systems, where the stationary phase consists of a blend of polymers or a polymer-plasticizer mixture, in order to determine the interaction parameters betbeen the two components of the stationary phase.…”

Sorption of solutes by poly(ethylene oxide). II. Benzene at finite concentrations

“…Each term in eq. (1) has been discussed in detail by Conder and P~r n e l l l l -~~ and by Brockmeier et al 17 Solute sorption in the PEO causes a residence t i h e difference between solute and air. The relative retention volume is given by…”

Solubility of gases and liquids in molten polystyrene

“…Chromatographic measurements of solubilities in molten polystyrene at low pressures were obtained by Brockmeier et al (1972) for benzene and ethylenebenzene at 393°K and ethylbenzene at 453"K, by Newman and Prausnitz (1972) for a number of soluble organic liquids for 423" to 473"K, and by Covitz and King (1972) for organic liquids for 397" to 483°K. In this study a similar procedure has been utilized to determine solubilities in molten polystyrene for a number of organic solutes.…”

“…The previous chromatographic measurements of solubilities in molten polystyrene were obtained by Brockmeier et al (1972) with 47 cm long columns, low coverage ratios, and Chromasorb-W as the substrate; by Newman and Prausnitz (1973) with 24 cm long columns, various coverage ratios, and Fluoropak-80 as the substrate; and by Covitz and King (1972) with columns 1 m long, high coverage ratios, Chromasorb-P substrates, and polystyrenes with various molecular weight distributions. Brockmeier et al (1972) found no dependence on flow rate for a 1% loading of polystyrene, with some dependence for a 5% loading.…”