混合条件对环氧有机土纳米复合材料插层剥离行为及性能的影响

采用X 射线衍射仪、透射电镜 (TEM )研究了混合条件 ,即混合温度和时间 ,对环氧 /16 烷基胺有机蒙脱土体系在固化前的混合物以及加入固化剂、促进剂固化后有机土的插层与剥离行为的影响 .同时采用拉伸试验机、冲击试验机和热机械分析仪测定了插层与剥离型纳米复合材料的物理力学性能 .从X 射线衍射看出 ,有机土很容易在混合过程被环氧所插层 .混合物经固化后可以形成插层型或剥离型纳米复合材料 .存在一个混合温度 时间 插层剥离转变的 3 T图 .只有在一定的混合条件的区域内才能形成剥离型纳米复合材料 .剥离型比插层型纳米复合材料具有较高的力学性能     

Mixing Properties of Two-Dimensional Lattice Solutions of Amphiphiles

Lattice Monte Carlo simulations of two-dimensional amphiphile solutions are used to examine the accuracy of the mixing properties predicted by lattice theories such as the Flory-Huggins theory, random-solution approximation, and quasichemical approximation. The internal energy, Helmholtz free energy, and entropy of mixing have been calculated from the configurational energy data obtained from the simulations, and the effect of nonrandom mixing on these properties has been determined. The quasichemical approximation predicts the entropy and Helmholtz free energy of mixing accurately for the amphiphile solution, but fails to predict the energy of mixing, due to the presence of microphase (self-aggregation) separation, which is beyond the reach of the quasichemical approximation, a mean-field theory. Helmholtz free energy of mixing is predicted accurately, and the shielding of the solvophobic segments in the microphase leads to small energies of mixing compared to the entropy of mixing. Copyright 2000 Academic Press.     

Monolayer properties of fatty acids : III. Thermodynamics of mixing

The thermodynamic properties of mixed fatty acids have been studied in the region of the surface vapor pressure. Using myristic acid as a common component various saturated and unsaturated fatty acid mixtures have been compared with regard to their tendency to be miscible or immiscible. Deviations from expected ideal behavior have allowed estimation of activity coefficients. Measurement of surface heats of vaporization has led to the determination of solubility parameters for each fatty acid. Applying regular solution theory or using activity coefficients allows independent estimation of , the partial molar enthalpy of mixing, and the two approaches are in good agreement. Therefore, it is possible to predict mixing tendencies for any combination of fatty acids used in this study.     

Nonequilibrium features of the association between poly(vinylamine) and sodium dodecyl sulfate: the validity of the colloid dispersion concept

The effect of different mixing protocols on the bulk and surface properties of the aqueous mixtures of linear poly(vinylamine) (PVAm) and sodium dodecyl sulfate (SDS) has been investigated using pH, electrophoretic mobility, dynamic light scattering, coagulation kinetics, and surface tension measurements. For the preparation of the solutions, two kinds of mixing protocols were applied. The so-called "stop flow mixing" enables a very rapid mixing whereas in the case of "gentle mixing" the mixing of the components is less efficient. At high surfactant concentrations a kinetically stable colloid dispersion of the PVAm/SDS particles is formed via the application of the stop flow mixing method. The mixing protocols have a significant effect on the bulk properties of the PVAm/SDS system, in particular, at the low pH range and at large PVAm concentrations. The effect of mixing can be qualitatively understood in terms of the enhanced local rate of coagulation of the PVAm/SDS complexes as well as of the appearance of polyelectrolyte/surfactant aggregates via the application of a less efficient mixing. The study also reveals that the applied methods of solution preparation do not have a major impact on the bound amount of the surfactant as well as on the surface tension isotherms of the system. This latter finding is attributed to the hindered adsorption of the large polyelectrolyte/surfactant aggregates at the air/water interface.     

Dispersive mixing in immiscible polymer blends

Dispersive mixing of immiscible polymer blends as well as polymer systems containing solids is achieved in compounding equipment at two stages of the system's processing experience: first, while one or more of the polymer components are melting, and second, after all polymer components have melted. That is, the first mode of dispersive mixing occurs during the melting mechanism of “dissipative mix melting” (Ref. 1), while the second is melt-melt mixing. During the compounding of a given blend system, there are a number of processing parameters that can be changed in order to improve mixing. These range from machine operating variables to the addition of processing aids. If such processing changes fail to produce the desired morphology, the most common change to consider is the screw geometry. This, in practice involves a trial and error procedure, or the use of an existing database built from prior experience. The role which the thermomechanical and rheological properties of the blend component play in dissipative mix melting and melt-melt mixing has not yet been well understood. The reason for this is that although most blend systems have components which are strongly non-Newtonian and strongly viscoelastic, the thinking and rules of thumb for mixing such materials has been heavily influenced by the analysis of G. I. Taylor (Ref. 2), who in 1932 addressed the phenomenon of the dispersion of a single Newtonian droplet by a Newtonian matrix flowing in laminar shear flow. This paper addresses the strong role that the rheology of blend components, under processing conditions, play in laminar dispersive mixing of polymer blends. From a practical point of view, if the dispersion mechanisms and rates of dispersion depend on the component rheology, then such knowledge can lead us to the selection of advantageous mixing element designs and processing conditions. The experimental results were obtained in dispersive mixing carried out in devices developed in the Polymer Mixing Study (Ref. 3). Such model devices include the Couette Flow Intensive Mixer (CIM) (Ref. 4), where a constant shear stress is applied on the blend components and the Twin Screw Mixing Element Evaluator (TSMEE) (Ref. 5), where the mixing flows are those encountered in actual mixing/compounding operations. The TSMEE will be described in the body of this paper together with its on- and off-line morphology determination capabilities and its in-line rheology sensor. The low-density polyethylene (LDPE) and polystyrene (PS) polymers studied were selected because they cover a wide spectrum of rheological properties.     

Characterization and preferential solvation of the hexane/hexan-1-ol/methylbenzoate ternary solvent

The thermophysical properties of the hexane/hexan-1-ol/methylbenzoate ternary system and its binary constituents were studied at 298.15 K over the whole composition range. The excess and mixing properties calculated from the experimental values combined with the mixture activity coefficients deduced from the UNIFAC group contribution method were used to calculate the integrals of the Kirkwood-Buff fluctuation theory for the ternary system and the binary constituents. Also the local composition and the excess or deficit number of molecules around a central molecule have been determined. The volumetric properties for the ternary system and its binary constituents were correlated and predicted successfully with several cubic equations of state combined with two simple mixing rules. The structural and intermolecular interactions of the mixtures were analyzed on the basis of the measured and derived properties.     

Adsorption,wetting, foaming,and emulsification properties of mixtures of nonylphenol dodecyl sulfonate based on linear alpha-olefin and heavy alkyl benzene sulfonate

Nonylphenol dodecyl sulfonate (C₁₂NPAS) has been synthesized, and mixed with heavy alkyl benzene sulfonates (HABS) in different proportions. The effects of different mixing ratios on properties such as adsorption, wetting, foaming, and emulsification, of the C₁₂NPAS/HABS surfactant mixtures have been systematically investigated. Experimental results have shown that, after mixing, the wetting and foaming properties of C₁₂NPAS/HABS are improved remarkably. Compared with C₁₂NPAS and HABS alone, the adsorption and emulsifying properties of C₁₂NPAS/HABS are far superior, which we attribute to a synergistic effect between these surfactants.     

Thermal properties and mixing state of ethylene glycol-water binary solutions by calorimetry, large-angle X-ray scattering, and small-angle neutron scattering

Thermal properties and mixing states of ethylene glycol (EG)-water binary solutions in the entire mole fraction range of EG, 0 < or = x(EG) < or = 1, have been clarified by using differential scanning calorimetry (DSC), large-angle X-ray scattering (LAXS), and small-angle neutron scattering (SANS) techniques. The DSC curves obtained have shown that the EG-water solutions over the range of EG mole fraction 0.3 < or = x(EG) < or = 0.5 are kept in the supercooling state until approximately 100 K, and those in the range of 0.6 < or = x(EG) < or = 0.8 are vitrified, and those in the ranges of 0 < x(EG) < or = 0.2 and 0.9 < or = x(EG) < 1 are crystallized. The radial distribution function (RDF) for pure EG obtained from the LAXS measurements has suggested that a gauche conformation of an EG molecule is favorable in the liquid. The RDFs for the EG-water solutions have shown that the structure of the binary solutions moderately changes from the inherent structure of EG to the tetrahedral-like structure of water when the water content increases. The SANS intensities for deuterated ethylene glycol (HOCD2CD2OH) (EGd4)-water solutions at x(EG) = 0.4 and 0.6 have not been significantly observed in the temperature range from 298 to 173 K, showing that EG and water molecules are homogeneously mixed. On the other hand, the SANS intensities at x(EG) = 0.2 and 0.9 have been strengthened when the temperature decreases due to crystallization of the solutions. On the basis of all the present results, a relation between thermal properties of EG-water binary solutions and their mixing states clarified by the LAXS and SANS measurements has been discussed at the molecular level.     

Synthesis and physical properties of new surfactants based on ionic liquids: Improvement of thermal stability and mechanical behaviour of high density polyethylene nanocomposites

Ionic liquids based on alkyltriphenyl phosphonium and dialkyl imidazolium cations with long alkyl chains have been synthesized and used as new surfactants for cationic exchange of layered silicates. The influence of the alkyl chain length and the chemical nature of the conteranion or of the cation on the thermal stability of these new intercalating agents and on imidazolium- (MMT-I) or phosphonium- (MMT-P) modified montmorillonites have been analyzed by thermogravimetric analysis (TGA). Thermoplastic nanocomposites based on these modified montmorillonites with a very low amount of nanofillers (1wt.%) have been processed by melt mixing using a twin screw extruder. The distribution of the clay layers in a high density polyethylene (HDPE) matrix was characterized and finally the mechanical and thermal properties of the corresponding nanocomposites were determined.     

Ion beam modification of metals: Compositional and microstructural changes

Ion implantation has become a highly developed tool for modifying the structure and properties of metals and alloys. In addition to direct implantation, a variety of other ion beam techniques such as ion beam mixing, ion beam assisted deposition and plasma source ion implantation have been used increasingly in recent years. The modifications constitute compositional and microstructural changes in the surface of the metal. This leads to alterations in physical properties (transport, optical, corrosion, oxidation), as well as mechanical properties (strength, hardness, wear resistance, fatigue resistance). The compositional changes brought about by ion bombardment are classified into recoil implantation, cascade mixing, radiation-enhanced diffusion, radiation-induced segregation, Gibbsian adsorption and sputtering which combine to produce an often complicated compositional variation within the implanted layer and often, well beyond. Microstructurally, the phases present are often altered from what is expected from equilibrium thermodynamics giving rise to order-disorder transformations, metastable (crystalline, amorphous or quasicrystalline) phase formation and growth, as well as densification, grain growth, formation of a preferred texture and the formation of a high density dislocation network. All these effects need to be understood before one can determine the effect of ion bombardment on the physical and mechanical properties of metals. This paper reviews the literature in terms of the compositional and microstructural changes induced by ion bombardment, whether by direct implantation, ion beam mixing or other forms of ion irradiation. The topics are introduced as well as reviewed, making this a more pedogogical approach as opposed to one which treats only recent developments. The aim is to provide the tools needed to understand the consequent changes in physical and mechanical properties.     

The semi-ideal solution theory for mixed ionic solutions at solid-liquid-vapor equilibrium

The semi-ideal solution theory has been presented to describe the changes in thermodynamic properties accompanying the process of mixing the nonideal electrolyte solutions M(i)X(i)-(NY)sat-H2O (i = 1 and 2) at constant activities of NY and H2O, including concentration, chemical potential, activities of all M(i)X(i), Gibbs free energy, enthalpy, entropy, thermal properties, and volumetric properties. The theory states that, under the conditions of equal activities of NY and H2O, the average hydration numbers characterizing the ion-solvent interactions have the same values in the mixture as in the subsystems and the process of mixing these nonideal electrolyte solutions is as simple as that of mixing the ideal solutions if the contributions from the ion-ion interactions to the solvent activity are assumed to be the same in the mixture as in its subsystems, which has been justified by the calculations of the Pitzer equation. Therefore, a series of novel linear equations are established for the thermodynamic properties accompanying the process of mixing these nonideal solutions as well as mixing the ideal solutions M(i)X(i)-(NY)sat-H2O (i = 1 and 2) of equal mole fractions of NY and H2O. From these equations, the widely applied empirical Zdanovskii's rule is derived theoretically, and the important constant in the McKay-Perring equation under isopiestic equilibrium is determined theoretically, which has been substantiated by comparisons with the experimental results for 18 mixtures reported in the literature. Isopiestic measurements have been made for the systems BaCl2-LaCl3-H2O, NaCl-BaCl2-LaCl3-H2O, and NaCl-LaCl3-BaCl2.2H2O(sat)-H2O at 298.15 K. The results are used to test the novel linear concentration relations, and the agreement is excellent. The novel predictive equation for the activity coefficient of M(i)X(i) in M1X1-M2X2-(NY)sat-H2O has been compared with the calculations of the Pitzer equation, and the agreement is good.     

Propriétés thermodynamiques des mélanges binaires. Volume et énergie interne de formation des solutions de l'hexadécane dans les isomères de l'hexane

The volumes of mixing of hexadecane and each of the isomers of hexane have been measured for the equimolar mixtures at 20°C. The results have been used together with previously measured values of ΔH to obtain ΔU_v. A very good correlation is found between the energy of mixing and the properties of the pure alkanes.     

Biodegradable systems: Thermodynamics, rheological properties, and biocorrosion

Systems based on starch and chitosan blends with synthetic polymers and cellulose derivatives (poly(ethylene oxide) and methyl cellulose of various molecular masses, PA, and ethylene-vinyl acetate copolymers containing different amounts of vinyl acetate groups) have been studied. The thermodynamic characteristics of the formation of blends have been determined. The rheological properties characterizing formation of blends from melts have been investigated. The biocorrosion ability of the blends after their use has been estimated by various methods. The concentration dependences of the thermodynamic functions of mixing of components (change in the Gibbs energy, enthalpy, and entropy) change sign in a wide composition range, indicating the complexity of mixing of rigid-chain natural polysaccharides with synthetic polymers. The rheological study of blends in which starch or chitosan plays the role of a biodegradation modifier shows that they are non-Newtonian fluids. The absolute values of viscosity and the activation parameters of melts increase with the content of polysaccharide in the system. The values of viscosity correspond to those typical for commercially processable polymers. The blends under study are biodegradable in a wet and water-soil medium with the content of the natural component being in the range 15–30 wt %.     

Thermodynamic and structural investigations of liquid magnesium-thallium alloys

The thermodynamic and microscopic structure of MgTl liquid alloy at 923 K has been studied by using regular associated solution model. The free energy of mixing, heat of mixing, entropy of mixing, activity, concentration fluctuations in long-wavelength limit S_CC(0) and the Warren-Cowley short-range parameter α₁ have been determined. The analysis suggests that this alloy is of a moderately interacting nature. The theoretical analysis reveals that the pairwise interaction energies between the species depend on temperature and there is a tendency of unlike atoms pairing (Mg-Tl) in liquid MgTl alloys at all concentration. The observed asymmetry in the properties of mixing of MgTl alloy in molten state is successfully explained by assuming MgTl complex on the basis of regular associated solution model.     

Joint Conversion of Methane with Pentane on Alumina–Platinum Catalysts Modified with Zirconium Oxide under Nonoxidizing Conditions

Kinetics and Catalysis - The physicochemical properties of alumina–platinum catalysts with supports prepared by mixing aluminum and zirconium hydroxides have been studied. The chemisorption...     

全氟壬烯氧基苯磺酸钠/辛基酚聚氧乙烯醚-10复配体系的铺展性能

分析全氟壬烯氧基苯磺酸钠(OBS)与辛基酚聚氧乙烯醚-10(OP-10)复配比例对溶液的表面张力、油/水界面张力及铺展性能的影响,寻求最佳复配比例和最佳铺展浓度.研究结果表明,OBS/OP-10混合水溶液与OBS单一组分水溶液相比,表面张力略有增加,界面张力显著降低,因此混合水溶液的铺展性能显著改善,原来在环己烷上不铺展,复配后变得铺展.尤其以质量比为1∶3,浓度为3.12 mmol/L体系水溶液的铺展性能最好,可以在环己烷上快速铺展,而且显著降低了OBS的用量,约降低了67％ OBS用量,提高了经济效益.同时对OBS/OP-10不同复配比例的水溶液最佳铺展浓度进行了研究,发现由表面张力确定的临界胶束浓度、界面张力确定的临界胶束浓度并非最佳铺展浓度,三者之间有一定偏差,其中,最佳铺展浓度介于表面临界胶束浓度、界面临界胶束浓度之间,差额取决于氟碳表面活性剂和碳氢表面活性剂的性质及配比.     

Preliminary communication - The effects of bending sites on unconventionally shaped hydrogen-bonded liquid crystals

Angular mesogenic structures of hydrogen-bonded supramolecules have been constructed from a 1:1 molar ratio of 3(or 4)-decyloxybenzoic acid, MA (or PA), mixing either with trans-4-alkoxy-3'(or 4')-stilbazoles, CnM (or CnP), or with their analogous N -oxides (CnMO and CnPO) to form the hydrogen-bonded (H-bonded) complexes CnPPA, CnPMA, CnMPA, CnPOPA, CnPOMA and CnMOPA. By controlling the relative bending position of the H-bonded complexes, the variety of supramolecules offer new molecular structures of different linearities. By means of these bending effects we are able to tune the shape of the molecular architecture and thus to modify molecular packing as well as mesogenic properties. New liquid crystalline properties are introduced by the nonlinear effects of molecular geometry, and powder X-ray diffraction (XRD) patterns have confirmed their novel molecular architectures.     

Mixing properties of tris(2-hydroxyethyl)methylamonium methylsulfate,water, and methanol at 298.15 K. Data treatment using several correlation equations

Densities, viscosities, and refractive indices at 298.15 K and atmospheric pressure are reported for the binary and ternary mixtures formed by tris(2-hydroxyethyl) methylamonium methylsulfate, water, and methanol. Excess molar volumes and viscosity logarithm variations have been calculated from the physical properties of the pure compounds and their mixtures. The UNIQUAC volume and area parameters have been determined for the tris(2-hydroxyethyl) methylamonium methylsulfate ionic liquid. All properties changes of mixing have been fitted using two polynomial models and the UNIQUAC equation. An evaluation of the correlation capacity has been analyzed for the three models.     

Modification of Particle Filled Polymers with High Energy Electrons Under In-Stationary Conditions of Melt Mixing

Summary: Polymer modification with high energy electrons is well-established in polymer industry and used for degradation, cross-linking, grafting, curing, and polymerization. These applications use local and temporal precise input of energy in order to generate excited atoms or molecules and ions for subsequent molecule changes via radical induced chemical reactions. In the present study, high energy electrons have been used to modify polyolefine (polyethylene and polypropylene) systems in presence of a grafting agent under stationary and in-stationary conditions. Polymer modification with high energy electrons under stationary conditions characterizes a process where required absorbed dose is applied to polymers in solid state and at room temperature. Polymer modification with high energy electrons under in-stationary conditions is a novel process where required absorbed dose is applied in molten state during melt mixing process. In this novel process, the penetration depth of electrons is limited to a part of mixing volume. The total mixing volume is modified due to the change of polymer mass within the penetration depth of electrons during mixing process. A 1.5 MeV electron accelerator has been directly coupled to a banbury mixing chamber in order to study this novel process. In comparison to the stationary process, the main differences are working at higher temperature, absence of any crystallinity, intensive macromolecular mobility as well as intensive mixing during dose application. The influence of both processes on mechanical properties and flame resistance of polymer composites is discussed.