Gas polymer interactions

The gas-polymer-matrix model for sorption and transport of gases in polymers is consistent with the physical evidence that 1) there is only one population of sorbed gas molecules in polymers at any pressure, 2) the physical properties of polymers are perturbed by the presence of sorbed gas, and 3) the perturbation of the polymer matrix arises from gas-polymer interactions. Rather than treating the gas and polymer separately, as in previous theories, the present model treats sorption and transport as occurring through a gas-polymer matrix whose properties change with composition. Simple expressions for sorption, diffusion, permeation and time lag are developed and used to analyze carbon dioxide sorption and transport in polycarbonate. 

Another model for the sorption and transport of gases in glassy polymers at super atmospheric pressures is the gas-polymer-matrix model, proposed by Raucher and Sefcik (1983). The premise of this model is that the penetrant molecules exist in the glassy polymer as a single population and that the observed pressure dependence of the mobility is completely due to gas-polymer interactions. In the mathematical representation of this model the following expression for sorption and transport is used ... 

Gon9alves et al. also studied the addition of different quantities of a-TOC to PLA films prepared by casting but focused their attention on the effects on functional properties. No significant changes were found in PLA thermal or mechanical properties by the addition of the antioxidant. Nevertheless, sorption of Oj increased with higher a-TOC content and the convex shape of the isotherms indicates strong gas-polymer interaction. However, there does not seem to be any significant effect on CO2 absorption. 

Gas-Polymer Interactions Key Thermodynamic Data and Thermophysical Properties... 

Scanning transitiometry has been used to determine the gas-polymer interaction energy, for instance upon CO2 sorption in MDPE and in PVDF samples (Fig. 9). 

Three differential modes were investigated, taking into account the differential principle of the instrument (Fig. 10) thermal I differential without reference sample, thermal 11 differential with reference sample, and thermal II differential comparative mode. With the thermal I differential mode, in an initial experiment the polymer sample is placed in the measuring cell, which is connected to the gas line. The reference cell, not connected to the gas line, acts as a thermal reference. An additional blank experiment (under identical conditions) is performed in which the polymer sample is replaced by an inert-metal (stainless steel) sample of similar volume. Then, the difference in the heat effects between polymer and blank experiments allow quantification of the thermal effect due to the gas-polymer interactions. In the thermal II differential mode, the polymer sample is placed in the measuring cell while an inert-metal sample of equal dimensions is seated in the reference cell, both cells being coimected to the gas line which serves to pressurize. Then, under gas pressure, the calorimetric differential signal is proportional to the thermal effect due to the gas-polymer interactions. The third and last mode... 

BOY Boyer, S.A.E., Klopffer, M.-H., Martin, J., and Grolier, J.-P.E., Supercritical gas-polymer interactions with applications in the petroleum industry. Determination of thermophysical properties, J. Appl. Polym. Sci., 103, 1706, 2007. 

Abstract Gas polymer interactions play a pivotal role in the formation of different molecular organizations/reorganizations of polymeric structures. Such structural modifications can have a negative impact on the material properties and should be understood in order to prevent them or these modifications are of engineering interest and they should be purposely tailored and properly controlled. Two newly developed techniques, gas-sorption/solubility and scanning transitiometry, are shown to be well adapted to provide the necessary (key) data to better understand and monitor the polymeric modifications observed under the triple constraints of temperature, elevated pressure, and gas sorption. This article illustrates the major contribution of gas polymer interactions in different intercoimected applied and engineering fields of the petroleum industry, polymer science, and microelectronics. 

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