Showing papers on "Miscibility published in 1978"

Polyester–polycarbonate blends. I. Poly(butylene terephthalate)

Abstract: Melt blends of bisphenol A polycarbonate with poly(butylene terephthalate) were studied by DTA and dynamic mechanical behavior to determine their state of miscibility. Both techniques showed multiple glass transitions indicative of incomplete miscibility in the amorphous phase. However, these transitions in some cases did not correspond to those in the pure components and varied with overall blend composition in some instances. This indicates that there are amorphous phases containing both components, i.e., partial miscibility. This view was supported by the crystallization behavior of the polyester. Two crystallization exotherms were observed for quenched samples, which is interpreted as polyester crystallization from two separate phases, one richer in this component than the other. Other interpretations of these results are discussed.

Polyester/polycarbonate blends. I. Poly(butylene terephthalate)

Abstract: Melt blends of bisphenol A polycarbonate with poly(butylene terephthalate) were studied by DTA and dynamic mechanical behavior to determine their state of miscibility. Both techniques showed multiple glass transitions indicative of incomplete miscibility in the amorphous phase. However, these transitions in some cases did not correspond to those in the pure components and varied with overall blend composition in some instances. This indicates that there are amorphous phases containing both components, i.e., partial miscibility. This view was supported by the crystallization behavior of the polyester. Two crystallization exotherms were observed for quenched samples, which is interpreted as polyester crystallization from two separate phases, one richer in this component than the other. Other interpretations of these results are discussed.

Polymer blends containing poly(vinylidene fluoride). Part I: Poly(alkyl acrylates)

Abstract: The transitional behavior of poly(vinylidene fluoride) (PVF2) blends with poly(methyl acrylate) and with poly(ethyl acrylate) was examined by differential thermal analysis and dynamic mechanical testing. Both blend systems were judged to be miscible on the bases of the presence of single, composition dependent glass transitions and of the strong melting point depression of the PVF2 component, Blends of poly(isopropyl acrylate) with poly(vinylidene fluoride) were found to be immiscible. These results suggest that miscibility of the acrylate series depends on a specific attractive interaction between the PVF2 and oxygen within the acrylate and the effect of this interaction is diminished as the hydrocarbon content of the ester is increased.

Polymer blends containing poly(vinylidene fluoride). Part III: Polymers containing ester, ketone, or ether groups

Abstract: To further investigate the nature of the specific interaction leading to the miscibility of poly(vinylidene fluoride), PVF2, with certain oxygen containing polymers, blends of PVF2 with poly(e-caprolactone), PCL, with poly(vinyl methyl ether), PVME, and with poly(vinyl methyl ketone), PVMK, were prepared. PVMK/PVF2 blends were found to be miscible while blends of PVME/PVF2 and PCL/PVF2 were found not to be miscible. These results show that the specific interaction with PVF2 involves mainly the carbonyl group rather than the entire ester group. The relative effectiveness of having this group in the chain or pendant to it is not yet resolved.

Phase separation behaviour of a metal-organic derived sodium silicate glass

Abstract: The phase separation behaviour of an 18.56 mol % Na2O-SiO2 glass prepared via the standard glass preparation technique and the metallic-organic derived (MOD) method have been studied and contrasted. Our results suggest that at this composition the miscibility temperature is significantly elevated when a MOD preparation procedure is used. The origin of this effect appears to be related to the enhanced water content in the glass prepared by the MOD procedure.

Polypropylene membranes with porous surface - are used for filters, microfilters, membrane supports and as oxygenation agents

Abstract: Mfr. of membranes of a thermoplastic polymer contg. 10-90 vol. % pores in connection with each other comprises (A) extruding a homogeneous liq. mixt. consisting of at least 10-90 wt.% of a fusible polymer (I) and 90-10 wt.% of a pore-forming liq. (II) which is inert w.r.t. (I); (B) choosing the type and amt. of the inert liq. (II) such that (II) forms a binary system with (I) which in the liq. state has a region of complete miscibility and a region of incomplete miscibility of the components and which demixes into two phases at a temp. (the demixing temp.) below the extrusion temp.; (C) leading the extruded mass into a bath in which the bath liquor is below the demixing temp. and cooling such that the (II) and (I) demix into two co-existing liq. phases before the polymer (I) solidifies and (D) opt. washing (II) out of the solidified membrane with a solvent, such that the bath contains the same inert solvent, e.g. N,N-bis-(2-hydroxyethyl)hexadecylamine, as the extruded mixt. and the membrane, esp. formed from polypropylene and extruded in the form of flat film, tubular film or a hollow fibre, has a smooth surface with open pores occupying 10-90 % of the surface area.

Solvation and phase separation in ABA block copolymers

Abstract: A conceptual scheme is presented for classifying the phase behavior of ABA block copolymers and solvents. The effect of solvent fraction ϕS on microphase separation is described for macroscopically homogeneous systems, but more attention is focused on the limits of solubility. A “miscibility map” is developed in terms of solubility parameters δA, δB, and δS and used to define regions of macrophase separation, complete miscibility, and partial miscibility. Combined with known triblock molecular structure, the miscibility map can be used to predict the character of solvated systems and guide the selection of solvents for special purposes. A survey of reports in the literature shows qualitative consistency with this treatment. New observations are reported on solvation of a polystyrene–polybutadiene–polystyrene polymer in numerous solvents; these are used to infer microstructural information and define the miscibility map more realistically.

Solubility criteria for a thermally stable polymer determined by gas–solid chromatography

Abstract: The Gibbs energy of adsorption, the Flory-Huggins interaction parameter χ, and a specific interaction parameter A, based on hydrogen-bonding and charge-transfer complexing properties of solvents, are obtained by gas—solid chromatography for a type of polyquinoxaline denoted as PQF. Interactions between 40 organic solvents and PQF have been determined at 176.35° and 200.85°C. PQF is an aromatic, heterocyclic polymer which is at least partially soluble in several organic solvents. The parameters χ and Λ and the solubility parameters of solvents are proposed to be the determining factors for miscibility of a PQF—solvent pair.

The effects of various factors on the thermodynamics of the polymer reactions in system solvent-polymer-polymer☆

Abstract: This investigation deals with the effects of the mol.wt. of the polymer, the solvent type and the nature of the polymers in contact with each other on the thermodynamics of the reaction between the polymers, α 23 , present in the ternary system: (1) solvent-(2) polymer-(3) polymer. The α 23 was evaluated by the method of Scott by determining α 23cr at the critical point, and by that of Allen in stratifying systems. The thermodynamic parameters of the PS-MMA reaction increased at the critical point and at higher concentration as the mol.wt. of the mixture of polymers decreased, but also with solvent quality. A new method permitting the estimation of how the type of polymers affects their miscibility (compatibility) in solution is proposed on the basis of our results. The sequence in which the polymers can be placed in order of decreasing solubility disagreed with the miscibility given by Hildebrand who calculated the reaction between the polymers from their solubilities. The experimentally determined parameter α 23 c contains a considerable entropic factor.

Preparation of aqueous polymer dispersion

Abstract: PURPOSE:Two or more specific monomers are radically copolymerized using a specific oligomer as an emulsifier to provide an aqueous polymer dispersion having reduced frothing, good pigment miscibility, and giving coating films having good water resistance.

A computer study of the miscibility limits of PdCz.sbnd;uSi

Abstract: Metallic glasses are of interest because of their mechanical properties. They are ductile as well as brittle. This is true of Pd 77.5 Cu 6 Si 16.5 , a ternary glassy alloy. Actually, the most stable metallic glasses are those which are alloys of noble or transition metals A general formula is postulated as T 70–80 G 30-20 where T stands for one or several 3d transition elements, and includes the metalloid glass formers. Another general formula is A 3 B to A 5 B where B is a metalloid. A computer method utilising the MIGAP computer program of Kaufman is used to calculate the miscibility gap over a range of temperatures. The precipitation of a secondary crystalline phase is postulated around 1500K. This could produce a dispersed phase composite with interesting high temperature-strength properties.