Showing papers on "Miscibility published in 1987"

Rapid measurement of minimum miscibility pressure with the rising-bubble apparatus

Abstract: The minimum miscibility pressure (MMP) for a gas/oil pair can be measured within 1 hour with the rising-bubble apparatus (RBA). Development of miscibility between a gas bubble and an oil can be observed visually. The measurements of the MMP with the RBA compare favorably with those based on slim-tube experiments and predictions from phase-behavior studies.

Blends of polycarbonate and poly(methyl methacrylate) and the determination of the polymer-polymer interaction parameter of the two polymers

Abstract: Melange polycarbonate du bisphenol A/PMMA prepare par coulee d'une solution ou extrusion a vis

Entropically Driven Miscibility in a Blend of High Molecular Weight Polymers

Abstract: Molecular miscibility between cis-1,4-polyisoprene and atactic poly(vinylethylene), as evidenced by their spontaneous interdiffusion, is reported. It is suggested that miscibility arises in this blend of nonpolar hydrocarbons, not from specific interactions between moieties on the respective chains, but merely from the small combinatorial entropy accompanying mixing. This is made possible by fortuitous near equivalence of the dispersive energy densities of the respective chain subunits. The customary single glass transition is observed in the mixtures, at a temperature whose composition dependence is quantitatively in accord with theory for random arrangement of the statistical segments. No UCST was observed in this system, even for the least stable compositions, at temperature down to the onset of glassy behavior (ca. -45 "C). Crystallization of the polyisopropene is inhibited by the presence of the poly(vinylethy1ene); the latter, moreover, is apparently unable to disentangle from the crystallizing chains of the polyisopropene.

Partial miscibility of poly(butylene terephthalate)/BPA polycarbonate melt blends

Abstract: Differential scanning calorimetry (DSC) measurements have been carried out on a number of poly(butylene terephthalate) (PBT)/BPA polycarbonate (PC) blends prepared by melt compounding and solution casting from hexafluoroisopropanol (HFIP). The results clearly indicate that appreciable mixing of the two polymers takes place in the melt phase whereas complete separation is observed in cast films. The failure of the casting procedure to mimic the melt blending results is related in part to liquid-liquid phase separation and to crystallization of both polymers from the casting solvent.

Phase Relations and Miscibility in Polymer Blends Containing Copolymers.

Abstract: This article reviews the reported work on thermodynamics of polymer blends in which at least one of the components is a copolymer. Theoretical and experimental studies of miscibility and phase transition and separation behaviors in such systems are summarized. Chapter 2 deals with blends involving random copolymers, including the cases in which a random copolymer AB is mixed with either a homopolymer A, or a homopolymer C, or two homopolymers A and B. Chapter 3 deals with blends involving a block copolymer, and after giving a brief overview of systems containing a pure block copolymer alone, it reviews the blend systems containing a block copolymer AB mixed with a homopolymer A or two homopolymers A and B.

The importance of enthalpic interactions in polymeric systems

Abstract: Enthalpic interactions between blend components primarily determine the state of miscibility and many of the physical properties of the blend. Recent applications of these thermodynamic considerations are reviewed for a variety of systems, including binary and ternary blends of homopolymers, binary blends of copolymers with homopolymers, and polymer-solvent mixtures. Recent advances toward predicting polymer blend miscibility through use of a modified quasichemical thermodynamic model and heats of mixing data for liquids are also discussed.

Isomorphic behavior of poly(aryl ether ketone) blends

Abstract: Blends of various poly(aryl ether ketones) have been found to exhibit a range of miscibility and isomorphic behavior. This range is dependent on molecular weight; however, for poly(aryl ether ketones) with number-average molecular weight of 20,000, this range is about ±25% difference in ketone content. All miscible blends exhibit isomorphism, and all immiscible blends exhibit no evidence of isomorphism. The dependence of the glass transition temperature Tg versus composition exhibits a minimum deviation from linearity whereas the melting temperature Tm versus composition exhibits a pronounced maximum deviation from linear behavior. The crystalline melting point versus composition for isomorphic blends is considerably different than for random copolymers with isomorphic units. Homopolymers and random copolymers exhibit a melting point that is a linear function of ketone content (increasing ketone content increases Tm). For blends, the melting point is essentially the same as that of the higher melting constituent until high levels of the lower melting constituent are present. The observed melting point versus composition behavior will be interpreted using classical theory to calculate the components of the liquid and crystalline phase compositions. As a miscible blend is cooled from the melt, essentially pure component of the highest melting point crystallizes out of solution, as predicted by calculated solid-liquid phase diagrams. This occurs until the crystallization is complete owing to spherulitic impingement. At high concentrations of the lower melting constituent, lower melting points will be observed because the highest melting constituent will be depleted before the crystallization is complete. In many miscible blends involving addition of an amorphous polymer to a crystalline polymer, the degree of crystallinity of the crystalline polymer has been shown to increase. On the basis of evidence presented here, it is hypothesized that dilution by a miscible, amorphous polymer allows for a higher level of crystallinity.

Gas permeation in miscible blends of poly(methyl methacrylate) with bisphenol chloral polycarbonate

Abstract: The miscibility of poly(methyl methacrylate) (PMMA) with bisphenol chloral polycarbonate (BCPC) has been studied using differential scanning calorimetry (DSC), optical indication of phase separation on heating (ie, lower critical solution temperature (LCST) behavior), density measurement, and gas permeation All evidence indicates that PMMA is miscible with BCPC over the whole blend composition range Single composition-dependent glass transition temperature and LCST behavior have been observed for each blend The specific volumes of the blends follow closely the simple additivity rule indicating the interaction between PMMA and BCPC is weak Gas permeability coefficients for He, H2, O2, Ar, N2, CH4, and CO2 measured at 35°C under 1 to 2 atm upstream pressure are lower than those calculated from the semilogarithmic additivity rule The difference between this calculated permeability and the measured one increases with gas molecular size As a result, the ideal gas separation factors for He/CH4, CO2/CH4, and O2/N2 gas pairs estimated from the ratio of pure gas permeabilities are higher than predicted from the semilogarithmic additivity rule These permeation results were interpreted in terms of the free volume theory and the activated state theory, which have been proposed to describe gas transport behavior in polymer mixtures

Miscibility and phase separation in poly(vinyl methyl ether)/poly(bisphenol A hydroxy ether) blends

Abstract: Les melanges du polyester avec un copolymere bisphenol A/epichlorhydrine sont miscibles a toute composition au-dessous de 420°K. A temperature plus elevee, separation en deux phases

Polymer-polymer miscibility determination via CP-MAS NMR in blends of deuteriated and protonated polymers

Abstract: Methode applicable lorsque le melange (PS/PUME, PMMA/PVC et PS/PMMA) contient meme entre 5 et 10% de l'un des polymeres

Miscibility of poly(p-vinyl phenol) with polymethacrylates

Abstract: Poly(p-vinyl phenol) is miscible with poly(methyl methacrylate), poly(ethyl methacrylate), poly(n-propyl methacrylate), poly(isopropyl methacrylate), and poly(tetrahydrofurfuryl methacrylate), but is immiscible with poly(n-butyl methacrylate). Except for poly(p-vinyl phenol)/ poly(methyl methacrylate) blends, the other miscible blends show pronounced positive deviations in their glass transition temperatures. The Tg-composition curves of the five miscible blend systems can be described by the Gordon-Taylor and the Kwei equations.

Calculation of Minimum Miscibility Pressure

Abstract: An algorithm is presented for the calculation of the thermodynamic minimum miscibility pressure (TMMP) consistent with an equation-of-state (EOS) -based fluid description. This algorithm handles both condensing and vaporizing miscibility mechanisms. TMMP calculations are included for a ternary mixture of pure components, as well as a reservoir-oil/CO/sub 2/ system.

Gas permeation in miscible homopolymer–copolymer blends. I. Poly(methyl methacrylate) and styrene/acrylonitrile copolymers

Abstract: Gas transport properties in homogeneous blends of PMMA with each of two SAN random copolymers, containing 13.5 and 28% by weight of acrylonitrile respectively, have been measured at 35°C for He, H2, O2, N2, Ar, CH4, and CO2. For all cases, the permeability and diffusion coefficients are higher than that expected from the semilogarthmic additivity rule. On the other hand, the solubility coefficients and the ideal gas separation factors follow this rule well. These results for PMMA/SAN blends differ from those observed recently for other miscible blend systems; however, they agree well with recent theories proposed to describe gas sorption and permeation behavior in polymer mixtures. The composition dependence of gas transport properties observed in PMMA/SAN blends is attributed to the very weak net interactions between PMMA and SAN produced by repulsions between styrene and acrylonitrile units in the SAN random copolymers. Gas transport properties in phase-separated PMMA/SAN blends have also been studied. The phase-separated blends show sorption and permeation properties very similar to the corresponding homogeneous blends which can be explained by an isotropic, interconnected, two-phase model proposed by Kraus and Rollmann. Gas permeabilities for the solution cast PMMA films used here are compared with melt-extruded specimens used previously, and the differences are attributed to molecular orientation.

Phase Behavior of Ternary Polymer Blends

Abstract: The effect of varying interaction parameters on the phase diagrams of ternary polymer blends was explored by simulating spinodals through use of the Flory-Huggins lattice theory. Results indicate that miscibility is favored for the case of ternary mixtures of marginally miscible or marginally immiscible pairs where all pair interactions are nearly athermal. Miscibility is restricted for asymmetric ternary blends when one of the polymer pairs is either strongly miscible or strongly immiscible. For symmetric blends of partially immiscible pairs, both two-phase and three-phase miscibility gaps are predicted.

The morphology and deformation behavior of poly(butylene terephthalate)/BPA polycarbonate blends

Abstract: In this communication the results of a series of recent studies of the morphology and deformation behavior of toughened poly(butylene terephthalate) (PBT)/BPA polycarbonate (PC) blends are briefly summarized. Several papers containing a more detailed account are currently in press (1–3). Among the unique morphological features of these blends are the consistent isolation of the core/shell impact modifier (IM) in the PC phase and the crystallization and phase separation of the PBT from the partially miscible PBT/PC melt on slow cooling. DSC studies provide corroborating evidence for melt miscibility of the two resins. The blends deform through a combination of cavitation and shear processes. In all cases cavitation occurs exclusively within the IM particles and is suppressed at higher PC concentrations and elevated temperatures.

Structure‐property‐processing relationships of polypropylene‐polybutylene blends

Abstract: In this paper we discuss PP-PB blends in which both components are highly crystallizable. It was our intention to try to prepare homogeneous PP-PB blends, assuming miscibility in the melt, by using the ultraquenching technique and to study the properties of the resulting blends following crystallization from the glass. Due to the possibility of preparing homogenous blends by ultraquenching, it should be interesting to compare the morphology, properties, and crystallization of the glass-crystallized blends with the melt-crystallized blends. We conclude that, in general, the above results suggest there is a considerable degree of compatibility, possibly even miscibility, of PP and PB in the melt, but that miscibility is difficult to obtain by ordinary melt mixing processes.

Effect of Oil Composition on Minimum Miscibility Pressure-Part 1: Solubility of Hydrocarbons in Dense CO2

Abstract: This paper examines the effect of oil composition on the phase behavior of CO/sub 2//hydrocarbon mixtures and, hence, on the development of miscibility in a CO/sub 2/ flood. Results of component-partitioning measurements are reported for mixtures of CO/sub 2/ with five synthetic oil systems: normal alkanes, branched alkanes, naphthenes, aromatics, and a mixture of all four molecular types. The results of the experiments indicate that unsubstituted ring structures are less soluble in dense CO/sub 2/ than branched or normal alkanes with the same number of carbon atoms, but that the addition of alkyl side chains to ring structures improves their solubility. Also reported are component-partitioning measurements for mixtures of CO/sub 2/ with three crude oils: Rock Creek (paraffinic), Maljamar (more aromatic), and Rock Creek plus 15 wt% of a mixture of aromatic components. The experimental results suggest that of the many factors that influence extraction of hydrocarbons by dense CO/sub 2/, the distribution of molecular weights present in the oil is the most important.