Showing papers on "Miscibility published in 1986"

Polymer-polymer miscibility

Abstract: The theoretical and practical aspects of polymer-polymer miscibility in the solid amorphous state are reviewed. The polymers include homopolymers and both random and block copolymers. Although present theoretical treatments of polymer-polymer miscibility all contain the random mixing hypothesis and are thus not applicable to mixtures that involve specific interactions between the components, most of the observed singlephase polymer-polymer mixtures involve hydrogen-bonding or other specific interactions between the components. Even in the absence of specific interactions, the composition of a random copolymer can often be tailored to provide miscibility with a particular homopolyner. Many polymer-polymer mixtures have lower critical solution temperatures, and a small number of such mixtures have given indications of upper critical solution temperatures. The special phenomena that may be observed when other polymers are mixed with block copolymers are discussed.

Polysiloxane-polylactone block copolymers

Abstract: Novel linear polysiloxane-polylactone block copolymers are useful as surface modifying additives due in part to their miscibility with a wide variety of base polymers. A particularly preferred polysiloxane-polycaprolactone linear blocked copolymer is miscible with nylon and is useful for forming surface modified nylon products.

Interchain electron donor-acceptor complexes: a model to study polymer-polymer miscibility?

Abstract: Preparation d'une serie de polymeres en peigne contenant le fragment carbazole donneur dans la chaine laterale, les poly [(N-alkylcarbazolyl-3) methyl methacrylates] avec alkyl n=1-16 et leurs complexes interpolymeriques EDA avec un polymere accepteur, le poly [(dinitro-3,5 benzoyl)-2 oxy ethyl methacrylate] sont etudies par DSC

Deuteration effects on the miscibility and phase separation kinetics of polymer blends

Abstract: Influence de la deuteriation du polystyrene dans le melange polystyrene hydrogene/poly(methyl vinyl ether)

Analysis and correlation of nitrogen and lean-gas miscibility pressure

Abstract: The vaporizing gas drive (VGD) process was modeled with the Peng-Robinson equation of state (PR-EOS) and a compositional simulator. The comparison of numerical results with available experimental data has shown that the PR-EOS overestimates the minimum miscibility pressure (MMP), but it correctly shows that the length required to achieve miscibility is different for N/sub 2/ and methane. Experimental data and some simulation runs have been used to develop a simple and reliable correlation for the prediction of MMP.

Miscible blends of aromatic polybenzimidazoles and aromatic polyimides

Abstract: A new family of high performance, miscible polymer blends based on aromatic polybenzimidazoles and aromatic polyimides has been discovered. Preliminary evidence, obtained with commercially available, soluble polymers suggests that polymers of these generic types may be miscible over a wide range of compositions and structural variations. Blend miscibility was evidenced in the form of single Tg1s and well-defined single tan δ relaxations intermediate to those of the component polymers, the formation of clear films and, in one case, enhanced solvent resistance.

Phase behavior of blends of aliphatic polyesters with a vinylidene chloride/vinyl chloride copolymer

Abstract: A series of aliphatic polyesters having CH2/COO ratios from 2 to 14 in their repeat units were blended with a copolymer of vinylidene chloride containing 13.5% by weight of vinyl chloride. Blends of polyesters having CH2/COO < 4 did not form completely miscible amorphous phases, whereas polyesters having CH2/COO ≥ 4 did form completely homogeneous amorphous phases for all temperatures below the decomposition point except for the polyester with CH2/COO = 14 which showed reversible phase separation on heating, i.e., lower critical solution temperature behavior. Interaction parameters were estimated by melting point depression and by analog calorimetry. The behavior reported here is qualitatively similar to that reported earlier for blends of aliphatic polyesters with poly(vinyl chloride), polyepichlorohydrin, polycarbonate, styrene–allyl alcohol copolymers, and the hydroxy ether of bisphenol A.

Blends containing polymers of epichlorohydrin and ethylene oxide. II. Polyacrylates

Abstract: The phase behavior of blends of various polymethacrylates with poly(epichlorohydrin) (PECH); poly(ethylene oxide) (PEO); and a copolymer of epichlorohydrin and ethylene oxide [P(ECH/EO)], was examined using differential scanning calorimetery (DSC), dynamic mechanical properties, and optical indications of phase separation on heating, namely lower critical solution temperature (LCST) behavior. Poly(methyl methacrylate) (PMMA), was shown to be miscible with PECH, PEO, and P(ECH/EO), while only PECH was found miscible with the higher polymethacrylates: poly(ethyl methacrylate), poly(n-propyl methacrylate), poly(n-butyl methacrylate), and poly(cyclohexyl methacrylate). However, even PECH was found to be only partially miscible with poly(isopropyl methacrylate). In many cases, unusually broad glass transitions were observed by DSC for blends which are believed to be the result of equilibrium composition fluctuations. All mixtures showed LCST behavior and based on this and excess volume measurements, to the extent possible, qualitative conclusions were made concerning the relative strength of the interactions among the various blend pairs. For PECH, it appears that the interaction with polymethacrylates decreases with increasing size of the alkyl pendant group, with poly(cyclohexyl methacrylate) being a possible exception. The interaction with PMMA is apparently about the same for PECH and PEO, but somewhat less for P(ECH/EO). The latter is consistent with an intrachain attraction of ECH and EO believed to exist. The reasons for similar interactions of PEO and PECH with PMMA are not understood; however, it is clear that the chlorine moiety of PECH is needed for miscibility with higher polymethacrylates.

UCST and LCST Behavior in Polymer Blends and Its Thermodynamic Interpretation

Abstract: A pair of dissimilar polymers with high molecular weights, poly(acrylonitrile-co-styrene) poly(acrylonitrile-co-butadiene), was found to exhibit both UCST (upper critical solution temperature) and LCST (lower critical solution temperature) behavior. This phase behavior is interpreted by combining the solubility parameter theory involving the free volume term and the recent idea of “miscibility window” for the polymer blends including random copolymers.

Phase behavior of poly(methylmethacrylate) and poly(styrene-co-acrylonitrile) blends

Abstract: Laser light scattering was used to study the miscibility behavior of PMMA/SAN blends. These systems tend to phase separation at elevated temperatures, Above the lower critical solution temperature (LCST) a regular highly interconnected two-phase morphology is displayed. The region of stability of this structure is determined. Finally, the binary interactional parameter is estimated. It is negative due to the sufficiently repulsive intramolecular interactions relative to the repulsive intermolecular interactions.

Patterns of phase behavior in ternary ethoxylated alcohol-n-alkane-water mixtures

Abstract: Certain ternary mixtures of ethoxylated alcohols, n-alkanes, and water at 25/sup 0/C separate at equilibrium into three liquid phases. The development of an amphiphile-rich middle phase is sensitive to alcohol molecular weight, alkane carbon number (ACN), and temperature. A middle phase arises when all three variables are adjusted such that the alcohol has no preference to partition into either an oleic or aqueous phase. A change in one of these variables yields a sequence of ternary phase diagrams in which the range of the three phases is from one critical tie line to a second. There are two distinct patterns, however, in which the critical tie lines arise. With a low molecular weight ethoxylated alcohol, both critical tie lines lie in the miscibility gap between water-rich and alkane-rich phases. With larger ethoxylated alcohols, however, one of the critical tie lines arises from the fusion of that miscibility gap with the critical point on a second one between water-rich and alcohol-rich phases. Both patterns are modeled well by modifying the Flory-Huggins equation of state to account for the tendency of amphiphile to concentrate between water-rich and alkane-rich domains, thereby attenuating or screening the enthalpic repulsion between water and alkane. The screeningmore » is expressed by a factor which is exponential in amphiphile concentration. The type of three-phase equilibria which arises from fusion of two miscibility gaps requires a pair of screening factors. Other available thermodynamic models appear incapable of approximating this second pattern of three-phase equilibria.« less

Extensional Flow Induced Miscibility in a Polymer Blend

Abstract: Extensional flows can induce miscibility in a polymer blend of polystyrene with poly(vinyl methyl ether). Miscibility is observed as a change from turbidity to optical clarity when a phase separated blend flows isothermally in planar extension. In a start-up experiment at temperatures above the LCST, optical clarity does not appear instantaneously but after a time which depends on the rate of extension and the temperature, and it appears first near the region of highest extension. This effect is opposite to the observation for polymer solutions which exhibit shear-induced demixing. We attribute this to the fact that enthalpic effects largely determine blend miscibility, while the phase behavior of solutions is essentially controlled by entropic contributions. Since a deformation field decreases the configurational degrees of freedom of a polymer molecule, demixing is favored in solutions. However, the alteration of specific interactions rather than this entropic effect appears to be much more important in blends.

Influence of hydrogen bonding on the properties of elastomers and elastomeric blends

Abstract: Polybutadienes and polyisoprene are modified using 4-phenyl-1,2,4-triazoline-3,5-dione. The resulting urazole moieties give rise to the formation of hydrogen bonds. From the temperature dependence of the dilute solution viscosity as well as from GPC it can be deduced that intra- and intermolecular hydrogen bonds are formed. The intermolecular hydrogen bonds can be used to overcome the demixing tendency in blends of polybutadiene and polyisoprene. DSC measurements indicate enhanced miscibility depending on the degree of modification.

A dielectric study of poly(ethylene‐co‐vinylacetate)–poly(vinyl chloride) blends. I. Miscibility and phase behavior

Abstract: Measurements of the complex permittivity were used to study miscibility and phase behavior in blends of poly(vinyl chloride) (PVC) with two random ethylene—vinyl acetate (EVA) copolymers containing 45 and 70 wt % of vinyl acetate. The dielectric β relaxation of the pure polymers and blends was followed as a function of temperature and frequency for different blend compositions and thermal treatments. Blends of EVA 70/PVC were found to be miscible for compositions of about 25% EVA 70 and higher. Blends of lower EVA 70 content showed evidence of two-phase behavior. EVA 45/PVC blends were found to be miscible only at the composition extremes; at intermediate compositions these blends were two-phase, partially miscible. Both blend systems showed lower critical solution temperature behavior. Phase separation studies revealed that in the EVA 45/PVC blends, PVC was capable of diffusing into the higher Tg phase at temperatures below the Tg of the upper phase. In the blends, ion transport losses were significant above the loss peak temperatures, and in the two-phase systems, often obscured the upper temperature loss process. It was shown possible, however, to correct the loss curves for this transport contribution.

Miscibility of polyethyloxazoline with thermoplastic polymers

Abstract: Polyethyloxazoline (PEOx) blends with several other thermoplastic polymers were examined by differential scanning calorimetry (DSC) for miscibility. Styrene/acrylonitrile (SAN) copolymers having compositions in the range of about 20–40% acrylonitrile (AN) by weight were found to be miscible with PEOx whereas SANs outside this range were not. The polyhydroxyl ether of bisphenol A (Phenoxy) was also found to be miscible with PEOx. A vinylidene chloride copolymer (Saran) was found to be partially miscible with PEOx, whereas poly(methyl methacrylate) and polycarbonate were not miscible at all.

Single phase blends of polycarbonate and polymethyl methacrylate

Abstract: Clear, transparent, single phase blends of polycarbonate and a polyalkyl methacrylate in which the alkyl radical contains from 1 to about 10 carbon atoms, and in which the polycarbonate and the polyalkyl methacrylate are miscible in all proportions are obtained. Polymethyl methacrylate (PMMA) is the preferred polyalkyl methacrylate. These blends may be prepared by dissolving the two polymers in a mutual solvent having a boiling point of at least about 30° C. and evaporating the solvent at a temperature of from about 30° C. to the boiling point of the solvent. The preferred evaporation temperatures are from about 45° C. to the boiling point of the solvent. This is in contrast to presently known PC/PMMA blends, which are miscible only when the content is nearly all PC or nearly all PMMA. Preferred blends according to this invention contain from 10 to 80 percent by weight of PC and conversely 90 to 20 percent by weight of PMMA. The single phase blends are moldable and transparent.

Homogeneous nucleation of binary vapors partially miscible in liquid state

Abstract: A general analysis of nucleation in a vapor phase containing two components that are partially miscible in the liquid state is presented. The analysis has been applied to three systems: diethylene glycol+n‐heptane, methanol+cyclohexane and diethylene glycol+benzene. On the basis of the classical nucleation theory, the results indicate that a range of saturation ratios, depending on the degree of miscibility, leads to the formation of two types of critical nuclei differing in size and composition. The likelihood of formation of two types of critical nuclei increases as the miscibility gap of the system increases. In some situations, both kinds of nuclei can have the same free energy of formation, and can nucleate at the same rate.

Molecular demixing in poly[cross-(ethyl acrylete)]-inter-poly[cross-(methyl methacrylate)] interpenetrating polymer networks brought about by selective decrosslinking and annealing

Abstract: The extent of molecular demixing of poly[cross-(ethyl acrylate)]-inter-poly[cross-(methyl methacrylate)] interpenetrating polymer networks (PEA/PMMA IPNs), of mid-range composition was investigated by decrosslinking and/or annealing using dynamic mechanical spectroscopy. A single broad transition characteristic of extensive but incomplete molecular mixing was observed for the PEA/PMMA IPN. The presence of crosslinking in both phases of an IPN enhances the mutual miscibility of the polymers. Through the use of a labile crosslinker, acrylic acid anhydride (AAA), polymer networks may be decross-linked, allowing the chains to separate and form two distinct phases. Annealing further sharpens the transitions, and phase separation becomes most pronounced when decrosslinking is followed by annealing.

The miscibility of polyethersulfone with phenoxy resin

Abstract: Polyethersulfone has been shown to be miscible with phenoxy resin. Cast films were found to be clear and show a single, composition-dependent glass transition-Blends were found to phase separate on heating with a lower critical solution temperature around 185°C. The heat of mixing of low molecular weight analogs was small and negative, suggesting a favorable interaction between the polymers. Phase diagrams were simulated using the equation-of-state theory of Flory and co-workers and were found to agree closely with the observed behavior. The water vapor sorption of the blends was investigated, and this also suggested a weak favorable interaction between the polymers.

Polymer blends based on mesomorphic components, 1. Properties of poly(tetramethylene terephthalate)/poly(decamethylene 4,4′-terephthaloyldioxydibenzoate) blends

Abstract: Blends of poly(tetramethylene terephthalate) [poly(butylene terephthalate) (PBT)] with a liquid crystalline polyester, poly(decamethylene 4,4′-terephthaloyldioxydibenzoate) (HTH 10), obtained by solution precipitation, were characterized by optical microscopy, X-ray diffraction and differential calorimetry. The morphology and phase behaviour of the blends are sensibly influenced by the composition. X-ray data support the existence of separated crystal phase of the two polymers only for HTH10 contents higher than 30 wt.-%. An increase of the clearing temperature of the original blends is found with decreasing concentration of the mesomorphic polymer in the range 100 to 30 wt.-%. On cooling from the isotropic melt, a single crystallization process is observed, whose temperature decreases with increasing amount of HTH10. A large depression of the melting temperature of PBT is found in the composition range 0 to 50 wt.-% of HTH10. Blends quenched from the isotropic state exhibit one single glass transition temperature, intermediate between those of the starting polymers. The results suggest the occurrence of miscibility phenomena of PBT and HTH10 in the amorphouse phase.

Vibrational analysis of functionalized polyolefins/poly(vinylchloride) blends

Abstract: Polyolefins functionalized with diethylmaleate were mixed with poly(vinylchloride) (PVC) in different compositions. Intermolecular interactions involving the carbonyl groups of the side chains of the functionalized polyolefins and methine hydrogens of PVC were investigated by means of infrared spectroscopy. The major flexibility of the ester groups attached to the backbone chains, with respect to polyesters, seems to increase the capability of such groups to interact with groups of more polar polymers, thus allowing prediction of easier miscibility, which however also depends on the starting polyolefin structure and function-alization degree.

Upper and lower critical solution temperature behavior in thermoplastic polymer blends

Abstract: Comportement de phase de melanges de polystyrene avec un copolymere statistique de poly(dimethyl-2,6 phenylene-1,4 oxyde) carboxyle, par calorimetrie differentielle et diffusion de la lumiere

Effect of chemical and configurational sequence distribution on the miscibility of polymer blends: 1. Blends of monotactic homopolymers

Abstract: Melange d'homopolymeres identiques ou non quant a leur chimie. Prise en compte des interactions inter- et intramoleculaires