CO₂ Sorption and Dilation of Poly(methyl methacrylate)

Abstract

Sorption of CO2 in poly(methyl methacrylate) at 35−200 °C and concurrent dilation of the polymer at 35−85 °C over a pressure range up to 50 atm were studied. Dissolution and Flory−Huggins interaction parameters for the gas in the polymer, not only in the rubbery state but also in the glassy state, were estimated by analyzing the sorption data above the glass transition temperature (T g0, 105 °C). Isothermal glass transition of the polymer/gas system was observed on isotherms of sorption and dilation below T g0. Partial molar volumes of sorbed CO2 determined from the sorption and dilation isotherms increased with increasing concentration to the glass transition concentration. These isotherms were also analyzed on the basis of extended dual-mode models of sorption and dilation. From obtained parameters of the dual-mode models, nonequilibrium properties such as mean size and number of microvoids for the pure polymer and the CO2-sorbed polymer in the glassy state were evaluated. The mean size, dependent upon CO2 exposure history of the polymer, was in the range of 20−100 A3, and the number of microvoid ((1−18) × 1020 voids/cm3) was dependent upon both temperature and the exposure history.

Solubilities of sub‐ and supercritical carbon dioxide in polyester resins

“…An assumption used in the S-L EOS is that the polymer is monodisperse. The reduced parameters are defined as ϭ /* ϭ /* P ϭ P/P* T ϭ T/T* r ϭ MP*/RT** (4) where * (the corresponding mass density in the closepacked state at 0 K), * (the corresponding specific volume in the close-packed state), P* (the hypothetical cohesive energy density in the close-packed state), and T* (related to the depth of the potential energy well) are the characteristic parameters of components. These parameters are obtained by fitting PVT data of pure components using Eqs.…”

“…Phase separation [2], volumetric [3], and gravimetric [4] methods are commonly used. In the first two methods, the amount of polymer required is large compared to gravimetric methods, and hence, the time required to reach equilibrium is substantially longer.…”

“…Moreover, high accuracy in pressure sensors and volume measurements are required in the first two methods for solubility calculations. These disadvantages are overcome by a gravimetric method that uses a microbalance [4]. The principle behind the gravimetric method is the weight difference between a gas-free and a gas-sorbed polymer sample.…”

Quantifying Polymer Swelling Employing a Linear Variable Differential Transformer: CO2 Effects on SBS Triblock Copolymer

“…The complementary problem of quantifying the dissolution of CO 2 in the polymer solid state is the subject of the present paper. CO 2 solubility in polymers has often been determined by measuring gas sorption [3] by means of gravimetry, [4,5] and by spectroscopic methods. [6] Gas solubility has also been quantified by direct observation of polymer swelling.…”

Thermodynamics and Thermokinetics to Model Phase Transitions of Polymers over Extended Temperature and Pressure Ranges Under Various Hydrostatic Fluids

“…This results from the low compressibility of solvent (gas) molecules compared to the free volume compressibility induced in BC. A particular behaviour is observed with "chemically active" CO 2 where the quadrupole-dipole interactions favour the CO 2 sorption into the PMA(Az) matrix during the isotropic liquid transition (Kamiya et al, 1998;Vogt et al, 2003). The hydrostatic effect by CO 2 overcomes above 40 MPa with a CO 2 desorption at higher pressures explained by the large change of molecular motions at the isotropic transition upon the disruption of π-bounds with azobenzene moieties.…”