Solubility and diffusivity of solvents by packed column inverse gas chromatography

Inverse gas chromatography was used with solid polymer particles in packed columns to measure polymer-solvent solubility and diffusion. A new model for this IGC technique has been developed and used to obtain experimental results for n-pentane, isopentane, 1-hexene, n-hexane, and 1-octene solvents in polymer beads of polyethylene. The conditions were measured for solvents at infinite dilution, and experimental data were obtained for the binary polymer-solvent systems in a temperature range from 70 to 100 °C.     

Study of the change of crystallinity of polyethylene on oxidation by inverse phase gas chromatography

Inverse-phase gas chromatography has been used for monitoring the oxidative degradation of low density polyethylene, which has great industrial importance. Polyethylene was oxidized in a gas chromatographic column at 145°C with an oxygen flow of 10 mL/min for different periods. After oxidation for a specified period, the crystallinity and solvent interaction parameters were monitored. For crystallinity studies, the solvent probe was n-decane, and for solvent interaction these were n-decane, o-xylene, n-butanol, and n-butyl acetate. With oxidation there was a gradual fall in crystallinity, and after 15 h the crystallinity was practically nil. Total loss of crystallinity also occurred at 175°C with 1 h passage of oxygen. This has also been confirmed by differential scanning calorimetry. The specific retention volumes of polar solvents showed a sharp increase with oxidation. The results, which are different from that reported in the literature, have been explained.     

Study of some sulphur-group solvents for aromatics extraction by gas chromatography

Nineteen organosulphur solvents have been studied by gas chromatography as potential solvents for the extraction of aromatics. The activity coefficients of nine typical hydrocarbon solutes have been determined in these solvents at three temperatures. From the activity coefficient data, the selectivities of all the solvents have been calculated for benzene with respect to each of the other hydrocarbons in order to screen them for extraction studies. Solvent losses in the g.c. column were also studied.     

Study of some sulphur-group solvents for aromatics extraction by gas chromatography

Nineteen organosulphur solvents have been studied by gas chromatography as potential solvents for the extraction of aromatics. The activity coefficients of nine typical hydrocarbon solutes have been determined in these solvents at three temperatures. From the activity coefficient data, the selectivities of all the solvents have been calculated for benzene with respect to each of the other hydrocarbons in order to screen them for extraction studies. Solvent losses in the g.c. column were also studied.     

Acid–Base interactions in filler characterization by inverse gas chromatography

Glass beads as model fillers were characterized by inverse gas chromatography (IGC) according to the Lewis acid–Lewis base (donor–acceptor) concepts as adapted by Fowkes. A range of organic probes (acidic chloromethanes, neutral n-alkanes, and basic acetone and diethylether) was used to elucidate the acid–base nature of the glass bead surface. The untreated glass bead surface was found to contain predominantly acidic sites while the treated glass bead (treated with an aminopropyltriethoxysilane coupling agent) was more basic than its unmodified counterpart. Calculation of the enthalpies of acid–base interactions (ΔH^ab) form the retention behavior of the basic probes with the two glass beads produced at least an 8-kJ/mol difference between the two glass types, the ΔH^ab of the untreated glass being greater than the treated glass. A difference of this magnitude is sufficient to produce a corresponding difference in the interfacial behavior of the two glass types. Therefore, IGC can be used as a quantitative technique for characterizing filler surfaces.     

反气相色谱法研究增塑剂-探针分子的热力学性能

利用凝胶色谱(GPC)、热重分析(TGA)、表面张力仪和差示扫描量热(DSC)法等对增塑剂环烷油的分子结构及其基本性能进行了表征。以不同种类的溶剂作为探针分子,采用反气相色谱(IGC)法对增塑剂的热力学性能进行了研究。结果表明:在试验温度(50～80℃)范围内,正戊烷、正己烷、正庚烷、环己烷、氯仿、苯和乙醚是环烷油的良溶剂,甲醇和丙酮是环烷油的不良溶剂;IGC法测得随着温度的升高,环烷油的溶度参数从50℃的13.94(J/cm3)1/2逐渐降至80℃的13.21(J/cm3)1/2;利用相互作用参数与温度的关系,采用外推法可得到25℃时环烷油的溶度参数为14.38(J/cm3)1/2,这与14.50(J/cm3)1/2(根据表面张力-溶度参数关系式计算而得)基本一致。     

Determination of exchange enthalpy and entropy parameters of the equation‐of‐state theory for poly(dimethyl siloxane) and some aromatic solvents by inverse gas chromatography

The specific retention volumes, V_g^o of toluene, ethyl benzene, n‐propyl benzene and isopropyl benzene on poly(dimethyl siloxane)(PDMS) were measured at temperatures between 333 and 403 K by inverse gas chromatography. The parameters of hard‐core interaction, χ_t^∞, effective exchange energy, X ₁₂, exchange enthalpy, X₁₂, and exchange entropy, Q₁₂ in the equation‐of‐state theory were determined. The parameters χ_t^∞ of the isopropyl benzene‐PDMS pair decreased from 0.65 to 0.60 while those of others decreased from around 0.77 to 0.69 with increasing temperature. The values of the parameters X₁₂ also decreased as molecular weight of the substituted aliphatic group on the benzene ring of the solvent increased, ie 15 J cm⁻³ in toluene and 5 J cm⁻³ in isopropyl benzene. Both X₁₂ and Q₁₂ show negligible dependence on temperature. © 2000 Society of Chemical Industry     

Thermodynamic interactions of EVA copolymer‐solvent systems by inverse gas chromatography measurements

The solubility parameter and the Flory–Huggins interaction parameter of two EVA (ethylene–vinyl acetate) copolymers, each one with different vinyl acetate content, are calculated by using inverse gas chromatography technique. The influence of the vinyl acetate percentage is analyzed and indicates that the polymer–solvent interactions are stronger in the case of the copolymer with the highest vinyl acetate percentage. The results also point to the fact that the most favorable solvents for the studied materials are the aromatic‐type ones. Finally, from the calculated values of the polymer solubility parameter (16.3 MPa^0.5 for EVA 460 and 15.1 MPa^0.5 for EVA410, at 50°C), it can be noticed that the solubility parameter of the EVA copolymer with the largest vinyl acetate content is the closest to the solubility parameter of pure vinyl acetate. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Determination of physicochemical properties of some fatty acid methyl esters by gas liquid chromatography

Physicochemical data such as vapor pressures (p⁰), heats of vaporization (ΔH_v), activity coefficents at infinite dilution (γ^∞) and excess partial molar entropy (ΔS _e ⁰ ) are considered important for conducting unit processes and designing reactor equipment. Scanty information regarding such data is available in the literature for the higher fatty acid methyl esters. The objective of this research was to determine the physicochemical properties of higher fatty acid methyl esters (C₁₁–C₂₃) by a gas-liquid chromatographic technique with SE-30 and diethylene glycol adipate as stationary phases. Correlations between carbon numbers and various thermodynamic properties have indicated definite trends, which could be useful in predicting the properties of unknown fatty acid methyl esters. The data generated may be useful to chemical engineers in the construction of storage tanks, solvent extractors and distillation columns. IICT communication no. 2993.     

用反气相色谱测定碳纤维表面能

详细阐述和分析了反气相色谱法的原理、仪器和测试方法。根据国内外碳纤维生产厂商应用该方法对其碳纤维表面能测试事例表明,该方法测定碳纤维表面能以及建立起来的软件处理系统,使得测定精度显著提高。指出该新测定方法值得推广应用。     

Surface characterization of polyethersulfone by inverse gas chromatography

Summary In this work, the surface properties of polyethersulfone (PES) were analyzed by inverse gas chromatography (IGC). Five n-alkanes (n-C₆, n-C₇, n-C₈, n-C₉, and n-C₁₀) were chosen as apolar probes to characterize the surface dispersive free energy at different temperatures. Acetone (Acet), dichloromethane (DCM) and tetrahydrofuran (THF) were chosen as polar probes to detect the Lewis acid-base parameters, i.e. the Lewis acidic number K_a and Lewis basic number K_b. It was found that the surface dispersive free energy was 32.09, 30.41, 28.52, and 27.21 mJ/m² at 60, 70, 80, and 90 °C, respectively. The Lewis acidic number K_a is 0.086 and Lewis basic number K_b is 1.523. Compared with other polymers characterized by IGC, the PES belongs to a strong basic polymer material.     

Characterization of polynuclear aromatic and aliphatic hydrocarbon fractions of solvent-refined coal by glass capillary gas chromatography/mass spectrometry

Separation and identification of the polynuclear aromatic and aliphatic fractions of solvent-refined coal and its recycle oil were performed using a combination of solvent partition and Chromatographic fractionation procedures with glass-capillary gas chromatography (g.c.)/mass spectrometry (m.s.). Chromatographic profiles were generated for each fraction, and some semiquantitative data were also obtained. In total, 146 polynuclear aromatic components of SRC were tentatively identified by their molecular weights, as indicated by the mass spectra of the g.c. peaks. In addition, whereever possible specific isomers have been indicated, based on comparison of spectral characteristics and retention data.     

反相气相色谱法测定小分子溶剂在聚乙烯粒子中的无限稀释扩散系数

基于经典线性非平衡色谱过程的矩分析理论,用反相气相色谱法测定了323.15～358.15 K温度范围内二氯甲烷、三氯甲烷、四氯甲烷3种不同相对分子量的同系物小分子及正己烷在聚乙烯粒子中的无限稀释扩散系数。采用聚合物粒子直接填充的色谱柱,考察了温度、同系物小分子分子量及聚乙烯结晶度对扩散系数的影响。实验结果表明,对同一种小分子溶剂/聚乙烯体系,扩散系数均随温度升高而增大。不同相对分子量的同系物小分子在同一种聚乙烯中扩散系数随分子量增加而减小,聚乙烯结晶度增加也会导致扩散系数减小。采用文献中所报道的Krevelen扩散系数预测模型的计算值与实验测量值较为吻合,表明本文所采用的以聚合物粒子直接填充色谱柱的反相气相色谱扩散分析具有一定的可靠性。     

Study of solvents for butadiene extraction by gas chromatography

Six solvents have been studied by GLC for separation of 1,3-butadiene from C₄-olefins having close boiling points. Infinite dilution activity coefficients and partition coefficients of five olefins have been determined in these solvents by conventional GLC-technique at 30 °C. Relative volatilities of olefins in solvents have been calculated and on this basis the solvents have been compared.     

毛细管气相色谱测定芳烃组成

利用气相色谱快速、准确的分析特点，建立以SP-3400气相色谱仪及聚乙二醇毛细管柱快速分析芳烃类样品组成的方法，对同一样品测定的相对标准偏差为2.54％。此方法与叫/NL08-59-89芳烃组成测定方法对不同的样品进行分析对比，结果表明，误差范围符合要求，分析速度快，操作简便，可以用于日常分析工作。     

Use of inverse gas chromatography to quantify interactions in amine cured epoxy resins

Flory–Huggins interaction parameters, λ, were determined for a series of probes in an amine cured epoxy resin matrix (433–493 K) and its precursors (324–363 K) by inverse gas chromatography (IGC). Hildebrand–Scatchard theory was combined with Flory–Huggins theory in order to estimate infinte dilution solubility parameters (δ₂) for the matrix and its precursors at 298 K. It was shown that the value of the solubility parameter for the cured resin matrix lies between those of its precursors. Compared to the majority of published work, an unusual aspect of this application of IGC is that solubility parameters have been determined when the stationery phases are (i) small molecules and (ii) a highly crosslinked polymer. Moreover, all possible attempts have been made to ensure equilibrium conditions between probe and stationary phase, and compensation for asymmetry of peak profile has been applied in determining δ₂. The solubility parameters estimated by IGC are in good agreement with those calculated by other methods.     

Determination of infinite dilution diffusion and activity coefficients of solvents in polystyrene by inverse gas chromatography on a capillary column

Infinite dilution activity and diffusion coefficients of several solvents in polystyrene have been measured by inverse gas chromatographic on a capillary column for temperatures between 110 and 170°C. Chromatographic data have been treated according to Khan's model, evaluating the contribution to the peak broadening due to radial and axial molecular diffusion in the mobile phase, radial diffusion in the stationary phase, and interfacial mass transfer resistance. Four capillary columns have been prepared with coating thickness ranging from 0.5 to 3.3 microns in order to determine the minimum thickness necessary to obtain reliable measurements of the diffusion coefficient of the solvent in the polymer in every possible experimental condition. Our experimental data are in considerable agreement with the data already available in the literature, obtained by static and chromatographic methods. © 1994 John Wiley & Sons, Inc.     

Surface characterization of intact fibers by inverse gas chromatography

Inverse gas chromatography (IGC) was used to determine adsorption isotherms and isosteric heats of adsorption for several normal alkanes on a number of intact textile fibers and to determine the specific surface areas of these fibers. Surface areas obtained by IGC were in excellent agreement (except for cotton) with those calculated from the geometric dimensions of circular cross-section fibers and with those obtained by the adsorption of krypton. Heats of adsorption were found to be only slightly higher than the corresponding heats of liquefaction of the probes. The effect of fiber surface purity on adsorption behavior as well as computerized data reduction are briefly discussed.