Inverse gas chromatography study of polyvinylacetate–solvent and polyethylene–solvent systems

In this article, the thermodynamic behavior of polyvinylacetate (PVAc)–solvent, and polyethylene (PE)–solvent mixtures have been studied by determining the thermodynamic sorption parameters (enthalpy, entropy, and free energy), the mass‐based solvent activity coefficients (Ω) and the Flory Huggins parameters (χ), by means of inverse gas chromatography (IGC) measurements. According to the Flory Huggins parameters of the PE–solvent mixtures, determined between 40 and 60°C the compatibility (the ability to interact with each other) of this polymer with the different types of solvents follows this order: dispersion solvents > polar solvents > association solvents. In the case of PVAc mixtures, the thermodynamic parameters were determined between 60 and 80°C, only for polar‐type and association‐type solvents due to, in the studied temperature range, the retention diagrams of dispersion solvents show that there are not bulk interactions. The Hildebrand solubility parameters of both polymers were also determined, according to Guillet procedure. The higher values of PVAc material (14.1 MPa^0.5 for PE and 19.8 MPa^0.5 for PVAc, at 60°C) are related to the strong interactions of vinyl acetate monomer. POLYM. ENG. SCI., 56:36–43, 2016. © 2015 Society of Plastics Engineers     

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     

Catalyst characterization by reversed-flow gas chromatography

A flow perturbation gas chromatographic method, used to study the kinetics of surface catalyzed reactions and for other physico-chemical measurements, can be employed as a characterization technique for various catalysts. The new method, called Reversed-flow technique, is based on reversing the direction of flow of the carrier gas from time to time, and has certain advantages over the classical characterization methods.     

Prediction of mutual diffusion coefficients for polymer–solvent systems

A new equation is proposed for relating solvent self‐diffusion coefficients and mutual diffusion coefficients for polymer–solvent systems. The formulation of the new equation avoids a friction‐coefficient formalism, and hence the new equation does not require the thermodynamic properties of the polymer–solvent system. A comparison has been made of the predictions of the proposed equation with experimental data for the benzene–rubber system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3195–3199, 2000     

Evaluation of a sorption equation for polymer–solvent systems

The predictive capabilities of a proposed sorption equation for describing the sorption behavior of glassy polymer–penetrant systems is evaluated. Factors determining the shapes of isotherms for glassy polymer–penetrant systems are considered. Data–theory comparisons are presented for three glassy polymer–penetrant systems. © 1994 John Wiley & Sons, Inc.     

Solvent and temperature effects on diffusion in polymer–solvent systems

The temperature dependence of the mutual diffusion coefficient at zero solvent concentration for a number of polystyrene–solvent systems is satisfactorily represented by an equation derived from a new version of the free-volume theory of molecular transport. The free-volume parameter which governs the temperature dependence of the diffusion rate is linearly related to the size of the solvent as estimated by its molar volume at OK. Data taken on various polystyrene–solvent systems are used to deduce information on the mechanism of solvent transfer in polymeric systems.     

Study of polymer–solvent interactions by gas chromatography. Copolymers of vinyl acetate and vinyl alcohol with hydrocarbons and alcohols

The specific retention volumes of nine hydrocarbons and 12 alcohols were measured at several temperatures within the range 120–150°C in columns whose stationary phases were poly(vinyl acetate) (PVAc) and four copolymers of vinyl acetate and vinyl alcohol with 94.8, 74.4, 60.9, and 43.4 mol % of vinyl acetate units (mol % VAc). No chromatographic retention for hydrocarbons was detected in columns loaded with poly(vinyl alcohol) (PVA) or a copolymer with 11.9 mol % VAc. The retention trends are discussed and the polymers solubility parameters (δ₂) were computed from the measured Flory–Huggins χ parameters. The copolymers δ₂ values increase almost linearly with decreasing mol % VAc; PVAc, however, has a distinct behavior. The limitations of the approach in the prediction of χ parameters are discussed.     

Determination of polymer–polymer interaction parameters using inverse gas chromatography

A modified method is discussed that is based on Farooque and Deshpande's method to obtain polymer–polymer interaction parameters using inverse gas chromatography (IGC) data. In the Farooque and Deshpande method, the ratio of the difference of probe–polymer interaction parameters between two polymers and the probe volume [(χ₁₂ ? χ₁₃)/V₁] is used as the abscissa. In the modified method, the ratio [(?₂χ₁₂ + ?₃χ₁₃)/V₁] is used as the abscissa. Experimental data previously reported for a poly(?‐caprolactone)‐polyepichlorohydrin (PCL/PECH) blend and a poly(ethyl acrylate)‐poly(vinyl propionate) (PEA/PVPr) blend are analyzed. It is found that the slopes obtained by the new method had smaller deviations from the theoretical values than the Farooque and Deshpande method. The standard deviations of both slopes and intercepts obtained from the new method are also smaller. Using the new method, the polymer–polymer interaction parameters obtained from the intercept are negative numbers for the PCL/PECH system and very small positive numbers for PEA/PVPr. Explanations are given for the probe and concentration dependency of the polymer–polymer interaction parameters that are generally observed in IGC studies. A new method for selecting the best probe for calculating the interaction parameter is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 671–680, 2003     

Heat pulse monitoring of curing and polymer–gas systems

An implantable thermal probe is used to study the reaction of molten polymers and curing systems to pulse heat release. At the heating rates T˙≥5·10⁵K/s, a polymer system shows the response to pulse heating that is confined in time and reproducible with respect to temperature. This response is related to the abrupt change in the conditions of the contact between the probe and a substance. The temperature of the response T^* is determined by the polymer properties and depends on the pressure and T˙. The pulse thermal probe method, which includes two measuring procedures, complementing each other, has been used to monitor a number of processes in polymeric systems. The variation of the values of T^* and the thermal activity of a polymer is compared with the variation of its molecular weight (M?_n～ 10²–10⁶), the molecular weight distribution, and the concentration of a low molecular weight component. The method allows one to trace the kinetics of polymerization and curing and the kinetics of dissolution of volatile impurity and polymer devolatilization, and to determine the limit of supersaturation of gas solutions in molten polymers. The pulse repetition frequency is changed from 0.1 to 1 Hz. The heated volume of a substance is 10^?4 mm³. © 1994 John Wiley & Sons, Inc.     

Spontaneous boiling up as a specific relaxation process in polymer–solvent systems

The phenomenon of spontaneous bubble nucleation in extremely supersaturated (superheated) polymer–solvent systems has been studied experimentally. Spontaneous boiling-up temperatures T^* for polystyrene and poly(ethylene glycol) solutions in a number of solvents have been measured at different values of pressure p and weight fraction of polymer c by the pulse heating method. The heating rate Ṫ varied from 10⁵ to 10⁷ K/s. For all systems studied, the values of T^* have been found to increase with increasing p and c. The T^*(p, c) dependence is discussed with the use of the data on the degree of compatibility of components. The peculiarities of polymeric solutions manifest themselves in the region c → 1, as follows: (i) an abrupt increase (by 1–2 orders of magnitude) in the slope of the T^*(c) dependence, and (ii) the appearance of the dependence of T^* values on the heating rate. Our approach to the interpretation of this result assumes a change in the initial composition of a solution in the course of heating due to polymer decomposition. An example of the extended phase diagram of a polymer–solvent system including the kinetic surface of T^*(p, c) is given. © 1996 John Wiley & Sons, Inc.     

A solution thermodynamic study of soybean oil/solvent systems by inverse gas chromatography

Inverse gas chromatography (IGC) has seen wide application in the characterization of molten polymers, fibrous materials, and natural products, such as proteins and carbohydrates, over the past fifteen years. This study describes a relatively simple IGC technique for evaluating solute-solvent interactions using a refined soybean oil as a solvent. Utilizing soybean columns that are 5–20% by weight of the inert support has allowed the determination of a number of thermodynamic solution parameters for 22 solute-solvent pairs in the temperature range of 55–125°C. Weight and mole fraction activity coefficients, along with Henry's Law constants at infinite dilution, are presented for six solute classes. In general, activity coefficients increase with carbon number for n-alkanes, alkyl-substituted benzenes, and n-alkanoic acids at all temperatures investigated, while the reverse is found for the n-alkanols. The activity coefficient data indicate that aromatic solutes, chlorinated hydrocarbons, ketones, and cyclohexane can readily dissolve soybean oil. Calculated heats of mixing for n-alkanols were found to be positive (to 2.84 kcal/mole) while recorded enthalpic interactions were weak for aromatic solutes, lower alkanes, and chlorinated hydrocarbons. The relevance of the above data to such problems as oil dissolution and solvent devolatilization are discussed. Presented at the American Oil Chemists' Society Annual Meeting in Phoenix, Arizona, in May 1988.     

Thermodynamic interaction in polybutadiene/solute systems by inverse gas chromatography

The dependence of polymer-solute interactions on temperature In the range was 66 to 96°C was studied by inverse gas chromatography (IGC). A correlation equation was developed for estimation of the specific retention volume of nonpolar and slightly polar solutes in polybutadiene (PBD). Using equation of state solution theory, thermodynamic interaction was discussed in terms of contact energy and equation of state contributions in polybutadiene/solute systems. It was found that equation of state theory serves better than the Flory-Huggins theory as a comprehensive model to describe the temperature dependence of thermodynamic interaction.     

Scaling functions of polymer‐induced turbulent drag reduction focusing on the polymer–solvent interaction

Based on turbulent drag reduction characteristics of polystyrene and polyisobutylene in a pipe flow and a rotating‐disk flow, respectively, a relationship between polymer concentration and drag reduction at a given Reynolds number was considered. The universal drag reduction equation of a three‐parameter relationship between drag reduction and polymer concentration was modified using intrinsic concentration and intrinsic viscosity, and it was then found to be the most useful formula for correlating DR data, especially for polymer–solvent interactions in a turbulent flow. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1836–1839, 2003     

A new analytical method to calculate intrinsic viscosity and viscosity constants of polymer–solvent systems

Experimental viscosities were measured by Schott Gerate viscometer at 30 °C for polystyrene–chloroform and polycaprolactum–benzene systems. These data were analyzed by a newly developed analytical method to calculate intrinsic viscosity and viscosity constants. The analytical method was compared with the graphical as well as the least squares methods and the new analytical method is better than the graphical method because it avoids personal errors that might arise in reading the intercept and slope values from the reduced viscosity versus concentration plots. Furthermore, the analytical method is as effective as the least squares method, but provides better insights while choosing the experimental viscosity values. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 283–290, 2002     

Multiparameter solution model and evaluation of polymer–polymer miscibility using inverse gas chromatography data

Inverse gas chromatography (IGC) has been widely used to determine the Flory–Huggins parameters, χ, between solutes (probes) and polymers. This study correlated the Flory–Huggins parameter data using a multiparameter model, which included dispersion, polarity, acidity, and basicity components. The parameters of poly(ε‐caprolactone) (PCL) and polyepichlorohydrin (PECH) were calculated from IGC data using a series of probes. The parameters of the polymers were used to evaluate mutual miscibility between PCL and PECH. The results predicted miscibility in agreement with the conclusion of an IGC study using blends of PCL and PECH. A method to estimate the confidence interval of polymer parameters was proposed. The anomalous solubility parameter of polymer mixtures previously reported was also explained using this model. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Numerical simulation of the self‐assembly of a polymer–polymer–solvent ternary system on a heterogeneously functionalized substrate

The spinodal decomposition of a polymer–polymer–solvent ternary blend spin coated on heterogeneously functionalized substrate is studied in a three‐dimensional numerical model. The Cahn‐Hilliard equation was used to describe the free energy profile of the domain. The mechanism of the morphology evolution was studied quantitatively. The well‐established linear relationship of the characteristic length, R(t), with t^1/3 can be observed in the simulation results. The functionalized substrate greatly affected the morphology evolution of blends with different solvent concentrations. The results indicated that a critical time can be observed, at which the evolution rate changes abruptly, also after which the compatibility of the surface morphology to the functionalized substrate pattern increases at a much lower pace in the diluted solution. In the condensed solution, the compatibility actually decreases beyond the critical time. The influence of solvent evaporation is investigated and a sharper interface was observed in the case with solvent evaporation and film thickness reduction. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Radiation-induced crosslinking in polymer–polyfunctional monomer systems

The does dependence of crosslinking yields was determined for irradiated compositions of poly(vinyl chloride) and polyethylene with an allylic polyfunctional monomer (PFM). Therewith, the notion of the differntial crosslinking yield G^*_c was used. The dose dependence of G^*_c has a maximum for the investigated systems. The current consumption of allylic groups and PFM molecules was determined. In the investigated systems, the process of network formation proceeds through chain crosslinking of graft chains of poly-PFM. © 1996 John Wiley & Sons, Inc.     

Polyurethane elastomers from post-grafted polymer–polyol systems

Certain homopolymer–polyol mixtures, after treatment with a free-radical generating agent or ionizing radiation, will produce polyurethane elastomers of nearly twice the stiffness and tensile properties compared to control elastomers made with untreated mixtures. Specific examples of these mixtures include the homopolymers of acrylonitrile and vinyl chloride with a poly(oxypropyl) triol of about 3000 molecular weight as the polyol in each case. The marked improvement in the stiffness and tensile properties of elastomers made with the treated mixtures over those of the untreated controls indicates a grafting process occurring between the polyol and homopolymer upon the generation of free radicals. In the present work, grafting could occur by a chain-transfer hydrogen-abstraction mechanism, whereby a free-radical site is generated on both the homopolymer and polyol chains. Coupling of these two free-radical sites would thus result in the establishment of a polymer–polyol graft bond.