Showing papers on "Miscibility published in 1999"

Confinement-induced miscibility in polymer blends

Abstract: The use of polymer thin films in technology is increasingly widespread—for example, as protective or lithographic surface coatings, or as active (electronic or optical) elements in device architectures. But it is difficult to generate films of polymer mixtures with homogeneous surface properties, because of the tendency of the polymers to phase-separate1,2. Copolymer compatibilizers can induce miscibility in polymer blends, but only with chemical components that are either close to a critical point in the phase diagram3 or which have an attractive interaction between them4,5. Instead of manipulating the chemical composition of the blend, we show here that complete mixing can be obtained in polymer blends by the physical effect of confinement in thin films. The compatibilization results from entropic inhibition of phase separation into micelles, owing to confinement. The result is an intimately mixed microemulsion with a perfectly flat surface and a two-dimensional maze-like structure with columnar domains that extend through the film.

Polymer Blends and Alloys

Abstract: Compatibilization and miscibility: compatibilization of polymer blends compounding and compatibilization of high-performance polymer alloys and blends miscibility and interfacial behaviour in polymer-polymer mixtures miscibility and relaxion processes in blends thermoplastic rubbers via dynamic vulcanization thermosetting polymer blends - miscibility, crystallization, and related properties computer simulation of spinodal decompositon in polymer mixtures interactions and phase behaviour of polyester blends miscibility of nylon 66/santoprene blends. Characterization: high-performance polymer blends and alloys - structure and properties natural polymer alloys - PC/ABS systems properties of thermotropic LCP blends polymer liquid crystals in high-performance blends structure-property relationship in poly (aryl ether ketone) blends applications of x-ray photoelectron spectroscopy and secondary ion mass spectrometry in characterization of polymer blends emulsion models in polymer blend rheology. Morphology: microstructure of multiphase blends of thermoplastics study on morphology and toughening mechanisms in polymer blends by microscopial techniques deformation mechanisms in toughened PMMA impact toughening mechanisms in glassy polymers. Recent developments: new strategies for the tailoring of high-performance multiphase polymer-based materials developments in reactive blending developments in poly (vinyl chloride)/epoxidized natural rubber blends development of oil palm-based lignocellulose polymer blends.

Miscibility behavior and single chain properties in polymer blends: a bond fluctuation model study

Abstract: Computer simulation studies on the miscibility behavior and single chain properties in binary polymer blends are reviewed. We consider blends of various architectures in order to identify important architectural parameters on a coarse grained level and study their qualitative consequences for the miscibility behavior. The phase diagram, the relation between the exchange chemical potential and the composition, and the intermolecular paircorrelation functions for symmetric blends of linear chains, blends of cyclic polymers, blends with an asymmetry in cohesive energies, blends with different chain lengths, blends with distinct monomer shapes, and blends with a stiffness disparity between the components are discussed. We investiagte the temperature and composition dependence of the single chain conformations in symmetric and asymmetric blends and compare our findings to scaling arguments and detailed SCF calculations. Two aspects of the single chain dynamics in blends are discussed: the dynamics of short non--entangled chains in a binary blend and irreversible reactions of a small fraction of reactive polymers at a strongly segregated interface. Pertinent off-lattice simulations and analytical theories are briefly discussed.

Blends of ethylene 1‐octene copolymer synthesized by Ziegler–Natta and metallocene catalysts. I. Thermal and mechanical properties

Abstract: The thermal, viscoelastic, and mechanical behaviors of three binary blends of ethylene 1-octene copolymer (EOC) regarding the melt index and density, one component made by Ziegler–Natta (FA and RF in abbreviation of the commercial name) and the other by metallocene catalysts (FM, EN and PL in abbreviation of the commercial name), have been investigated to understand molecular mechanism of the blends. Thermal studies reveal that the two constituents in the three blends exclude one another during crystallization, implying a phase separation. Viscoelastic properties show a single β or γ transition in all the compositions, suggesting a miscibility in the amorphous region. The tensile modulus, yield stress, maximum strength at break, and elongation at break follow the rule of mixtures if the comonomer content does not differ too much. Otherwise, the modulus and yield stress are negatively deviated, whereas elongation at break is positively deviated from the weight-average value. The tensile properties of film at yield and break in the machine direction is increased with an addition of FM in the FA + FM blend. Although all three blends form separate crystals in the crystalline state, a correlation exists between the mechanical properties and the density of EOCs. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1169–1177, 1999

Liquid−Liquid Equilibria of the Ternary Systems Water + Acetic Acid + Ethyl Acetate and Water + Acetic Acid + Isophorone (3,5,5-Trimethyl-2-cyclohexen-1-one)

Abstract: Liquid-liquid equilibria for the ternary systems water + acetic acid + ethyl acetate and water + acetic acid + isophorone (3,5,5-trimethyl-2-cyclohexen-1-one) were measured over the temperature range (283 to 313) K. The results were used to estimate the interaction parameters between each of the three compounds of the systems studied for the NRTL and UNIQUAC models. The estimated interaction parameters were successfully used to predict the equilibrium compositions by the two models; experimental data were successfully reproduced. The UNIQUAC model was the most accurate in correlating the overall equilibrium composition of the studied systems. Also the NRTL model satisfactorily predicted the equilibrium composition. Isophorone experimentally resulted in a better extraction capacity for acetic acid and in a lower miscibility with water.

Crew-cut aggregates from self-assembly of blends of polystyrene-b-poly(acrylic acid) block copolymers and homopolystyrene in solution

Abstract: The formation and morphological characteristics of crew-cut aggregates from blends of polystyrene-b-poly(acrylic acid) diblock copolymer and polystyrene homopolymer in solution were studied by static light scattering, transmission electron microscopy and size exclusion chromatography. The crew-cut aggregates, consisting of a polystyrene core and a poly(acrylic acid) corona, were prepared by direct dissolution of the polymer blends in a selective solvent mixture consisting of 93 wt % dimethylformamide and 7 wt % water. It is found that the aggregation behavior depends strongly on the relative volume fractions of the block copolymer and homopolymer in the blends. This is a result of the difference in solubility between the copolymer and the homopolymer in solution which, in turn, influences their miscibility and mutual solubility and consequently the morphology of the formed crew-cut aggregates. Specifically, when the homopolymer fraction is low, it is mainly dissolved in the cores of the crew-cut aggregates formed by the block copolymer. When the homopolymer fraction exceeds its solubility limit in the copolymer micelles, aggregates of another type are formed which contain a major fraction of the homopolymer. These aggregates are usually much larger than the primary micelles and have an internal structure due to the formation of reverse micelles from the dissolved block copolymer chains. The importance of thermodynamic vs. kinetic aspects during the formation of the crew-cut aggregates is also discussed.

Rheology and miscibility of thermotropic liquid crystalline polymer blends

Abstract: Steady and dynamic rheological properties of a thermotropic liquid crystalline polymer (TLCP), HIQ45, its blend with a polycarbonate (PC) and with another TLCP (Vectra A950) are presented in this work. Due to the biphasic nature of HIQ45, both complex and steady shear viscosities increase with temperature after 350°C. According to a three-zone model, the dynamic rheological behaviour of HIQ45 is assigned to terminal and plateau zones. Relaxation times derived from the crossover frequencies of G′ and G″ decrease with temperature and show a sharp reduction between 320°C and 340°C. Dynamic rheology of PC shows terminal zone characteristics, and its blends with HIQ45 display PC-dominant dynamic behaviour. These blends were found to be miscible, which is unusual for blends of a TLCP and a thermoplastic. The Cox-Merz rule is followed by PC and HIQ45, but not by the blends. HIQ45 and Vectra A950 form a miscible blend system and its dynamic behaviour, both in the solid state and molten state, is dominated by HIQ45 component. The Cox-Merz rule is not obeyed by Vectra A950 but is for blends with HIQ45. Under steady shear, the blends show a strong negative deviation from the existing models proposed for miscible and immiscible blends. This enhanced synergistic flow behaviour is explained in terms of enhanced alignment and lubrication of the TLCPs on a molecular level.

Miscibility and Specific Interactions in Blends of Poly(4-vinylphenol) and Poly(2-ethoxyethyl methacrylate)

Abstract: The properties of the hydrogen-bonded polymer blends of poly(4-vinylphenol) and poly(2-ethoxyethyl methacrylate) are presented. Spectroscopic techniques such as 13C solid-state NMR and FT-IR are used to probe specific interactions of the blends at various compositions. Spectral features from both techniques revealed that site-specific interactions are present, consistent with a significant degree of mixing of the blend components. Changes in chemical shift and line shape of the phenolic carbon and carbonyl resonances in the 13C CPMAS spectra of the blends as a function of composition are interpreted as resulting from changes in the relative intensities of two closely overlapped signals. A quantitative measure of hydrogen-bonded carbonyl groups using 13C NMR has been obtained which agreed well with the results from FT-IR analyses. It is also shown that 13C NMR can be used to measure the fraction of hydroxyl groups associated with carbonyl groups, which was not possible previously using FT-IR due to extensi...

Design of morphology in PMMA‐modified epoxy resins by control of curing conditions. I. Phase behavior

Abstract: Rheokinetic and phase separation behavior of diglycidylether of bisphenol-A–4,4′-diaminodiphenyl methane epoxy mixtures, modified with a constant amount (15 wt %) of poly(methyl methacrylate) (PMMA), have been investigated. Stoichiometric epoxy/amine mixtures precured at 80°C several times presented various levels of miscibility. Differential scanning calorimetry (DSC) and dynamic mechanic thermal analysis were used for rheokinetic studies of curing and also for testing the thermal behavior of the fully cured mixtures. Phase separation, through curing, was simultaneously studied by transmission optical microscopy and DSC, showing an excellent correlation between the results obtained with both techniques. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 772–780, 1999

Control of phase separation behavior of PC/PMMA blends and their application to the gas separation membranes

Abstract: Gas transport and thermodynamic properties for the blends of polycarbonate (PC) and polymethylmethacrylate (PMMA) were studied. To explore glass transition temperatures of blends and their phase separation temperatures due to a lower critical solution temperature, LCST, a type of phase boundary, transparent blend films that are miscible and do not contain solvent-induced PC crystals were prepared by controlling molecular weights of each component. The average value of interaction energy densities between PC and PMMA obtained from the phase boundaries and the equation of a state theory based on the lattice fluid model was 0.04 cal/cm3. This result confirmed that miscibility of PC and PMMA blends at equilibrium depends upon the molecular weights of components. Gas transport properties of miscible blends and immiscible blends having the same chemical components and composition but a difference in morphology were examined at 35°C and 1 atm for the gases N2 and O2. Permeability and apparent diffusion coefficients were ranked in the order of the immiscible blend having a domain–matrix structure > the immiscible blend having an interconnected structure > the miscible blend. These results might be related to the differences in the local chain motions that depend on the intermolecular mixing level. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2950–2959, 1999

Miscibility of Polyolefin Blends

Abstract: Phase separation in polymers is important for many technical applications but is difficult to predict theoretically. Recently, extensive experimental studies on the miscibility of polyolefins revealed that these systems display a wider variety of mixing behavior than their chemical similarity suggests. In order to predict phase diagrams of polyolefin blends from pure component properties, we have developed a method in which small scale simulations of local interactions are combined with an analytical model for the thermodynamics, the Born-Green-Yvon lattice model. In this work, we present results for a variety of polyolefin blends and show that the new approach yields qualitatively correct results for phase separation in these blends, including the effects of varying pressure and molar mass of the components on phase separation temperatures.

Influence of Stereoregularity of Polypropylene on Miscibility with Ethylene−1-Hexene Copolymer

Abstract: The influence of stereoregularity of polypropylene on the miscibility with the ethylene−1-hexene copolymer (EHR) whose 1-hexene content is 57 mol % was studied by means of viscoelastic measurements...

Hydrogen bonding in polyamide toughened novolac type phenolic resin

Abstract: The hydrogen bonding, miscibility, and thermal stability of polyamide toughened novolac type phenolic resin were investigated The intermolecular force of the resin increased with the content of the soft segments of polyamides (nylon 6, nylon 66) that absorb the loads in the network of brittle phenolic resin IR (IR region) spectra and differential scanning calorimetry results confirmed that the phenolic/polyamide blend was completely miscible Its thermal degradation temperature was higher than 400°C and increased with the increasing of polyamide content © 1999 John Wiley & Sons, Inc J Appl Polym Sci 74: 2283–2289, 1999

Pressure–Volume–Temperature properties of polyolefin liquids and their melt miscibility

Abstract: The pressure–volume–temperature (P–V–T) properties of a number of metallocene-produced polyolefins were measured experimentally at 10 MPa ≤ P ≤ 200 MPa and 30°C ≤ T ≤ 220°C in a dilatometer-type P–V–T apparatus. These included ethylene copolymers typical of linear low density polyethylene, with several α-olefins as comonomers and a wide range of comonomer content. The experimental P–V–T data were correlated with the equations of state from the Sanchez–Lacombe and Flory–Orwoll–Vrij theories. The solubility parameter map of the polyolefins, at atmospheric pressure, was established on the basis of the thermodynamic data. As the temperature increases, the solubility parameter of the polyolefin decreases. The solubility parameters of copolymers of ethylene with propylene, butene, hexene, and octene under constant temperature are all more or less the same at equal weight percent of comonomer. As the incorporation of branches increases, the solubility parameter decreases. The melt miscibility of the polyolefin blends can be predicted to design various blend products for specific applications from this solubility parameter map. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2835–2844, 1999

Interrelation Between Phase State and Gas Permeation in Polysulfone/Polyimide Blend Membranes

Abstract: The phase state of polysulfone/polyimide (PSF/PI) blends has been studied by differential scanning calorimetry, rheology, and X-ray scattering The blends rich in PSF form miscible blends when prepared by solution casting from a common solvent In these PSF-rich blends, the single dynamic process in rheology shifts and broadens, with composition reflecting the change in local friction and the enhancement of concentra- tion fluctuations, respectively Heating to temperatures above the glass transition temperature results in phase separation into PSF- and PI-rich domains An apparent phase diagram has been constructed, and helium permeability has been measured in different regimes corresponding to miscible, partially miscible, and completely phase- separated states We find that one component (PI) controls the permeability values and activation energies for helium permeation in the blends Gas permeation is found to be very sensitive to local concentration fluctuations and thus can be used as a probe of the phase state in polymer blends © 1999 John Wiley & Sons, Inc J Polym Sci B: Polym Phys 37: 2788 -2798, 1999

Miscibility of isotactic polypropylene/ethylene-propylene random copolymer binary blends

Abstract: Miscibility for blends of isotactic polypropylene (PP) and ethylene-d4−propylene random copolymer (EPR)s prepared by copolymerization of propylene and perdeuterated ethylene with metallocene catalyst has been investigated by small-angle neutron scattering (SANS). SANS experiments were conducted for the blends of PP with EPRs containing 19 mol % (D-EPR19) and 47 mol % (D-EPR47) of deuterated ethylene unit at various temperatures. SANS results indicated that most of the blends are in the homogeneous one-phase mixture, and the Flory−Huggins interaction parameter χ analyzed by the random phase approximation is approximately 5.0 × 10-3 for the PP/D-EPR47 blend while it is very small and within the range −1.0 × 10-3 ≤ χ ≤ 1.0 × 10-3 for the PP/D-EPR19 blend. It was also revealed that χ does not change with temperature meaningfully within the temperature range 440 ≤ T ≤ 482 K, while phase separation due to crystallization of PP was observed at 373 K. No domain structure of EPR whose size is in the range of an op...

Impact modification of polypropylene by ethylene propylene copolymer-grafted maleic anhydride

Abstract: Blends of polypropylene (PP) and ethylene propylene rubber (EPR) were studied. The effect of the level of rubber addition and the ethylene content is described. The results show that the viscosity of the PP, rubber content, ethylene content, and grafted EPR by maleic anhydride (MA) are important factors in controlling the blend properties. The miscibility and dynamic properties of the blends were studied by DMTA. Impact and tensile properties were also studied. SEM was used for the investigation of the phase morphology and rubber particle size and particle-size distribution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1257–1265, 1999

Miscibility and pressure‐sensitive adhesive performances of acrylic copolymer and hydrogenated rosin systems

Abstract: Relationship between the miscibility of pressure-sensitive adhesives (PSAs) acrylic copolymer/hydrogenated rosin systems and their performance (180° peel strength, probe tack, and holding power), which was measured over a wide range of time and temperature, were investigated. The miscible range of the blend system tended to become smaller as the molecular weight of the tackifier increased. In the case of miscible blend systems, the viscoelastic properties (such as the storage modulus and the loss modulus) shifted toward higher temperature or toward lower frequency and, at the same time, the pressure-sensitive adhesive performance shifted toward the lower rate side as the Tg of the blend increased. In the case of acrylic copolymer/hydrogenated rosin acid systems, a somewhat unusual trend was observed in the relationship among the phase diagram, Tg, and the pressure-sensitive adhesive performance. Tg of the blend was higher than that expected from Tgs of the pure components. This trend can be due to the presence of free carboxyl group in the tackifier resin. However, the phase diagram depended on the molecular weight of the tackifier. The pressure-sensitive adhesive performance depended on the viscoelastic properties of the bulk phase. A few systems where a single Tg could be measured, despite the fact that two phases were observed microscopically, were found. The curve of the probe tack of this system shifted toward a lower rate side as the Tg increases. However, both the curve of the peel strength and the holding power of such system did not shift along the rate axis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 651–663, 1999