Inverse gas chromatography, IGC

Several properties of the filler are important to the compounder (279). Properties that are frequentiy reported by fumed sihca manufacturers include the acidity of the filler, nitrogen adsorption, oil absorption, and particle size distribution (280,281). The adsorption techniques provide a measure of the surface area of the filler, whereas oil absorption is an indication of the stmcture of the filler (282). Measurement of the sdanol concentration is critical, and some techniques that are commonly used in the industry to estimate this parameter are the methyl red absorption and methanol wettabihty (273,274,277) tests. Other techniques include various spectroscopies, such as diffuse reflectance infrared spectroscopy (drift), inverse gas chromatography (igc), photoacoustic ir, nmr, Raman, and surface forces apparatus (277,283—290). 

Fig. 17. A schematic of the alkane line obtained by inverse gas chromatography (IGC) measurements. The relative retention volume of carrier gas required to elute a series of alkane probe gases is plotted against the molar area of the probe times the. square root of its surface tension. The slope of the plot is yielding the dispersion component of the surface energy of...

The adsorption of gas onto a solid surface can also be used to estimate surface energy. Both inverse gas chromatography (IGC) and isotherm measurement using the BET method [19] have been used. Further discussion and detailed references are given by Lucic et al. [20] who compare the application of IGC, BET and contact angle methods for characterising the surface energies of stearate-coated calcium carbonate fillers. 

Vapour and gas sorption measurements can be performed with static or dynamic methods, either of which can provide information on equilibrium behaviour. Furthermore, the measurements can be performed using gravimetric or volumetric based instrumentation. The most common flow methods are inverse gas chromatography (IGC) [1] for volumetric studies and dynamic gravimetric instrumentation [2]. 

Inverse gas chromatography (IGC) is another technique that can be used to measure the specific surface area of a particulate material, as well as to measure a number of surface thermodynamic properties of powders. Such instrumentation operates on a different principle than traditional nitrogen/krypton adsorption using the BET isotherm. 

Inverse gas chromatography (IGC) refers to the characterization of the chromatographic stationary phase (polymer) using a known amount of mobile phase (solvent). The stationary phase is prepared by coating an inert support with polymer and packing the coated particles into a conventional gas chromatography column. The activity coefficient of a given solvent can be related to its retention time on the column. The equipment itself is commercially available, easily automated, and extremely versatile. 

Water adsorption studies are obviously indicated for the evaluation of the hydrophilic character of silica. Besides, according to our earlier studies, methylene chloride (CH2CI2), used as a probe for Inverse Gas Chromatography (IGC) measurements at Unite concentration conditions, appears to be an alternative choice for determining the hydrophobicity of silica surfaces. Indeed, earlier indications suggest that this probe, when used under appropriate conditions, is not interacting with the hydrophilic silanol groups. The present work is complementary to the study of water adsorption on fumed silica samples, described in this book [1]. 

In inverse gas chromatography (IGC), the interactions of gaseous probe molecules with a stationary phase contained within a column... 

The use of inverse gas chromatography (IGC) to study the properties of polymers has greatly increased in recent years (1,2). The shape and position of the elution peak contain information about all processes that occur in the column diffusion of the probe in the gas and the polymer phases, partitioning between phases, and adsorption on the surface of the polymer and the support. Traditional IGC experiments aim at obtaining symmetrical peaks, which can be analyzed using the van Deemter (3j or moments method (4). However, the behavior of the polymer-probe system is also reflected in the asymmetry of the peak and its tail. A method that could be used to analyze a peak of any shape, allowing elucidation of all the processes on the column, would be of great use. 

Inverse Gas Chromatography (IGC) has been used to measure solubility parameters for three polymers at 25° C using the method of Guillet and DiPaola-Baranyi. The linear relationship noted with other polymers was found and the results add further credance to the method. Solubility parameters have also been calculated for six small molecule involatile compounds of the type use as plasticizers. The original method did not yield values in good agreement with literature results but estimation of the different contributions to the solution interactions allowed calculation of more meaningful values. 

The adsorption data of different gases on various polymeric materials were obtained by using inverse gas chromatography (IGC) and compared with data available in the literature. An attempt was also made to obtain adsorption Isotherms for a binary gas mixture. IGC offers a means to obtain gas adsorption data quickly. However, some Improvements of the technique are necessary. Particularly, a high pressure IGC system must be developed to obtain adsorption data of gases under high pressures. 

By analogy to the above technique, gas chromatography is considered a useful tool to obtain data for gas and vapor adsorption on polymeric surfaces. In contrast to liquid chromatography, the general principle of the IGC technique is well established for the characterization of polymeric materials this technique called inverse gas chromatography (IGC), enables the study of various polymeric properties, including interfacial properties (15-18). 

Inverse gas chromatography, IGC, has been used to study water sorption of two poly (vinylidene chloride-vinyl chloride) and poly (vinylidene chloride-acrylonitrile) copolymers, at temperatures between 20 and 50°C and low water uptakes. It was found that the specific retention volume of water increases with decreasing amount of water injected, increases dramatically with decreasing temperature and strongly depends on the type of copolymer. Thermodynamic parameters of sorption namely free energy, entropy, enthalpy of sorption and activity coefficient were calculated. 

Most of the available data on diffusion and diffusion coefficients of volatile liquids or gases in polymers have been obtained by static sorption experiments (10, 11), which are time consuming and require extensive data analysis. In recent years, inverse gas chromatography, IGC, was found to have wide utility in measuring sorption tendency and diffusion coefficients of gases and volatile liquids in molten polymers (12-17). 

Diffusivity data are available only for a limited number of polymer-solvent systems. This paper describes research that has led to the development of the use of capillary column inverse gas chromatography (IGC) for the measurement of diffusion coefficients of solute molecules in polymers at infinite dilution. The work has resulted in a precise, rapid technique for the diffusion measurements that circumvents the many problems attendant to classical sorption methods and packed column IGC methods. Initial results of the program appeared in two recent publications (1,2)- Some of the material introduced in those papers is discussed here to present background for... 

Probing polymer-polymer interactions in miscible blends is an experimentally difficult task. Most methods available for this purpose are elaborate and limited in their applicability. In recent years, research has shown that inverse gas chromatography (IGC) offers great promise for the study of polymer-polymer interactions. Conceptually, the technique involves the following the elution behavior of volatile organic compounds (probes) is measured for one or more blend columns and compared with the retention behavior of two homopolymers studied under identical conditions. An excess retention can then be characterized and treated as a measure of polymer-polymer interaction strength. This polymer-polymer interaction is the cause of the miscibility phenomenon and is of practical interest. 

As comprehensively reviewed by Lipson and Guillet (1), inverse gas chromatography (IGC) has been used as a convenient tool to study the thermodynamic properties of polymeric systems. Despite its wide usage, all experimental and theoretical factors in this technique are not fully understood. Loading determination, usually done by means of extraction or calcination, has been considered to be the most significant source of experimental error (2.). Other factors, such as concentration effects associated with large injection sizes, slow diffusion of solute probe molecules in the stationary phase, and adsorption of probes onto the liquid-support interface, may also af-... 

Extending work done previously (1 - 2), the purpose of this paper is to examine how these characteristics could be determined using inverse gas chromatography (IGC) and to what extent these acid/base interactions are relevant to the description of the fibre-matrix interface. 

The objectives of this paper are to demonstrate how monolayer adsorption isotherms can be obtained on carbon fiber surfaces by inverse gas chromatography (IGC), and to compare results of solid/gas adsorption with those of solid/Uquid wetting. This information is correlated with independent assessments of surface chemical functionality provided by wet chemical titrations and x—ray photoelectron spectroscopy (XPS). 

Inverse Gas Chromatography (IGC) was applied to E-glass fiber surfaces modified by various silane coupling agents. Using homologous series of alcohol (acid) and amine (base) vapor... 

Since its introduction some years ago, inverse gas chromatography (IGC) has been recognized as a convenient route to the determination of thermodynamic interaction parameters for polymeric or other non-volatile stationary phases in contact with selected vapor probes (1,2). The principles of IGC experiments have also been extended to two-component stationary phases (3), thereby making it possible to specify thermodynamic interaction parameters for the components of polymer blends (4,5), as well as for filled polymers and other mu 11i-component systems. Despite these attractive features, limitations must by recognized on the general... 

Inverse gas chromatography (IGC) is used for the determination of the surface energy characteristics of silicas before and after modification by heat treatment or by grafting onto their surface alkyl, polyethylene glycol) and alcohol chains. Because of its high sensitivity, IGC reveals the nature of the grafted molecules, which may then be confirmed by independent methods. 

The examples given above indicate the necessity of having a better understanding of the surface properties of divided solids that have received a surface treatment. The objective of this paper is to demonstrate how advantageous inverse gas chromatography (IGC) is in achieving this goal. 

Previous papers (1-4 ) have documented results relating to the application of inverse gas chromatography (IGC) to coals and air oxidized coals. This paper summarizes results pertaining to the reproducibility of this IGC application, documents the use of IGC in monitoring the effect of air oxidation on coal fluidity, and compares the results via those obtained with pyrolysis mass spectrometry and Giesler plastometry. 

The conventional inverse gas chromatography (IGC) is based on equations that assume equilibrium is established during the course o the chromatograph. Consequently, those stationary phases that exhibit marked hysteresis in sorption/desorption give IGC sorption data at considerable variance with long-term gravimetric methods. A modified frontal procedure was developed that avoids the assumption of equilibrium to enable studies of interaction kinetics of gas phase components with a stationary phase, such as a biopolymer, having entropic as well as enthalpic relations affected by concentration shifts and time dependent parameters. 

Inverse gas chromatography (igc) is a useful technique for characterizing synthetic and biological polymers, copolymers, polymer blends, glass and carbon fibers, coal, and solid foods. 

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