Rheological properties of filled polymers

The rheological properties of two model suspensions using a Newtonian polymeric matrix are presented and discussed in light of results presented in the literature. It is shown that particle-particle interactions in concentrated suspensions are responsible for a gel-type behavior at very small strain and strain hardening at a critical strain. Suspensions of concentrated colloidal particles in a Newtonian matrix behave like typical viscoelastic molten polymers, but the properties are strongly dependent on the solids dispersion, and strain at small strain. A simple rheological model is proposed to describe the shear viscosity of these suspensions.     

Rheology of highly filled polypropylene compounds: Measurement and applications

It is common knowledge among rheologists as well as polymer engineers that compounds of thermoplastics with a high volume content of mineral fillers show a viscoelastic behaviour which is significantly different from homogeneous systems. A strong nonlinearity is combined with the development of a second plateau region of the dynamic moduli at lower frequencies. This for one makes the rheological characterization of these materials more complicated, as could be shown in a round robin test, including a PP-compound with talc. The linearity criterion has to be handled carefully to achieve comparable and representative results. However, the viscoelasticity gives access to a quick characterization method regarding dispersion quality in compounds. This can be shown for the case of PP-talc-compounds, where correlations between relaxation spectrum and impact strength could be developed.     

Continuous flow synthesis of porous materials

Porous materials play an important role in chemical catalysis,separation and other industrial applications.High-efficiency preparation of porous materials has become an active research area.Conventional synthesis of porous materials has been dominated by one-pot solution processing conditions carried out by bulk mixing under conventional electric heating via hydrothermal,solvothermal or ionothermal reactions where high temperatures and pressures are the standard.Continuous flow synthesis has many key advantages in terms of efficient mass and heat transfer,precise control of residence times,improved opportunities for automation and feedback control of synthesis,scaling-up reactions and improved safety parameters compared to above mentioned conventional batch scale synthetic methods.In this review,continuous flow synthesis of various crystalline porous materials such as metal-organic frameworks(MOFs),covalent-organic frameworks(COFs),porous organic cages and zeolites is discussed.Combination of microfluidic methods with other techniques are also shown including various heating ways and various methods of substrate adding.     

Rheological properties of filled gels. Influence of filler matrix interaction

The dynamic moduli of gels filled with particles have been studied as a function of the volume fraction of dispersed particles _f (0–0.4) and of the way in which they interact with the gel matrix. Two gels of different nature were studied, viz. polyvinyl alcohol (PVA) — Congo red gels (a so-called rubber gel) and casein gels made by acidification of skimmed milk. Emulsion droplets stabilized by different macromolecules have been used as dispersed particles. If there was no interaction between the macromolecules adsorbed on the particles and the gel matrix, both the filled PVA and the filled casein gels showed a small decrease in the elastic moduli with _f , approaching the behaviour theoretically predicted for foams. In the case of interaction, the results for filled PVA gels roughly fitted the theoretical predictions, if the deformability of the emulsion droplets and the formation of an intermediate layer between the dispersed particles and the gel matrix was taken into account. The increase in the elastic moduli of the acid milk gels with _f was much greater than expected and was probably due to aggregation of the dispersed particles during gelation.     

Rapidly infrared-assisted cooperatively self-assembled highly ordered multiscale porous materials

In this paper, cooperative self-assembly (CSA) of colloidal spheres with different sizes was studied. It was found that a complicated jamming effect makes it difficult to achieve an optimal self-assembling condition for construction of a well-ordered stacking of colloidal spheres in a relatively short growth time by CSA. Through the use of a characteristic infrared (IR) technique to significantly accelerate local evaporation on the growing interface without changing the bulk growing environment, a concise three-parameter (temperature, pressure, and IR intensity) CSA method to effectively overcome the jamming effect has been developed. Mono- and multiscale inverse opals in a large range of lattice scales can be prepared within a growth time (15-30 min) that is remarkably shorter than the growth times of several hours for previous methods. Scanning electron microscopy images and transmittance spectra demonstrated the superior crystalline and optical qualities of the resulting materials. More importantly, the new method enables optimal conditions for CSA without limitations on sizes and materials of multiple colloids. This strategy not only makes a meaningful advance in the applicability and universality of colloidal crystals and ordered porous materials but also can be an inspiration to the self-assembly systems widely used in many other fields, such as nanotechnology and molecular bioengineering.     

Adsorption of dissolved organic compounds on porous polymeric materials

The structure and the adsorption characteristics of porous polymeric materials were studied by the methods of X-ray diffraction analysis and adsorption from solutions. The values of the adsorption capacity, the mean pore size, standard decrease in the molar free energy of adsorption, internal diffusion coefficients of nitrobenzene and p-nitroaniline in the primary and secondary porous structures were calculated.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 3, pp. 378–381, May–June, 1985.     

Rheological properties of polyacrylonitrile solutions containing highly dispersed carbon nanotubes

Rheological properties of dispersions of carbon nanotubes in dimethylsulfoxide solutions of polyacrylonitrile are studied at different concentrations of the components. The viscosity values of all the studied dispersions are substantially dependent on shear rate. For a number of systems, the energies of activation of viscous flow are determined. The relationship of viscosity and the energy of activation of flow to the compositions and possible structural features of dispersions is discussed. The concentration regime where a thermally reversible mixed network exists with crosslinks formed by physical contacts of the polymer with nano-tubes is characterized.     

Calculation of thermal conductivity of filled oligomeric compositions

Different models for the calculation of thermal conductivity of oligomeric compositions filled with a dispersed filler (silicon carbide) are studied. It is shown that the calculated values of thermal conductivity of oligomeric compositions with introduced dispersed filler provided by the van Krevelen model developed for the calculation of thermal conductivity of unfilled amorphous polymers with isolated regions of the crystalline phase are the closest to the experimental ones.     

Adsorption properties and porous structure of new carbon materials

The adsorption properties of the new carbon materials, sibunites, which are mesoporous samples with a developed surface of pores, were studied. The isotherms of the adsorption of benzene vapor were determined to estimate the porous structure of these materials. The principal methods for calculating the parameters of the porous structure of sibunites were analyzed. The application of the BET equation even in the presence of a small number of micropores can distort the results, therefore the most suitable method for estimating the surface of mesopores is one that is based on the Dubinin—Zaverina equation. The estimation of the surface of sibunites using water vapor adsorption is demonstrated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1377–1380, August, 1993.     

Rheological and transport properties of sulfonated polyacrylamide hydrogels for water shutoff in porous media

In this research, an optimal hydrogel, based on sulfonated polyacrylamide, was synthesized by statistical design of experiments using central composite method. This new hydrogel composed of sulfonated polyacrylamide (AN125VLM) and chromium triacetate as copolymer and crosslinker, respectively. The bottle and rheological tests were conducted to investigate the gelation time, thermal stability, gel strength and also ultimate elastic modulus, complex modulus, and yield stress. It was found that copolymer concentration had the main effect in both rheological and transport properties of hydrogels. The sample prepared at optimum condition, i.e. copolymer concentration of 26,340 ppm and crosslinker/copolymer ratio of 0.12, had an ultimate elastic modulus of 29.9 kPa, yield stress of 800 Pa, and complex modulus of 32 kPa. A coreflooding test through fracture was carried out to examine the optimum gel performance in a porous media. A value of 483 for the residual resistance factor ratio of water to oil confirmed the high ability of the hydrogel in reducing the relative permeability of water to oil in fractured media. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of the pore widths of highly porous materials with NMR microscopy

The quantitative characterization of macro-porous materials with regard to pore width and pore width distribution was accomplished for the first time by using ¹H-NMR microscopy in combination with suitable methods of digital image analysis. Here we present the newly developed algorithm and discuss the first experimental results. Large-pored glass filter systems filled with silicon oil as intrusion fluid were used as references. Silicates of unknown pore width were analyzed both with the new method and with Hg intrusion. NMR image data were recorded using a 3D spin echo sequence, which gave 128 slice images with a spatial resolution of 14.5 μm × 14.5 μm within each slice, with a slice-thickness of 37 μm or 48 μm. A quantitative evaluation of the 3D NMR data, with regard to pore width and pore width distribution, was done using the appropriate image processing function of the HORUS program. Individual slice evaluation was performed first, followed by an analysis of the binding elements between the slices. Pore widths of the glass filters determined using this analytical algorithm were in accordance with the manufacturer’s values, and silicate pore widths were in good agreement with the values determined by Hg intrusion. Received: 4 June 1996 / Revised: 12 August 1996 / Accepted: 15 August 1996     

Determination of the pore widths of highly porous materials with NMR microscopy

The quantitative characterization of macro-porous materials with regard to pore width and pore width distribution was accomplished for the first time by using ¹H-NMR microscopy in combination with suitable methods of digital image analysis. Here we present the newly developed algorithm and discuss the first experimental results. Large-pored glass filter systems filled with silicon oil as intrusion fluid were used as references. Silicates of unknown pore width were analyzed both with the new method and with Hg intrusion. NMR image data were recorded using a 3D spin echo sequence, which gave 128 slice images with a spatial resolution of 14.5 μm × 14.5 μm within each slice, with a slice-thickness of 37 μm or 48 μm. A quantitative evaluation of the 3D NMR data, with regard to pore width and pore width distribution, was done using the appropriate image processing function of the HORUS program. Individual slice evaluation was performed first, followed by an analysis of the binding elements between the slices. Pore widths of the glass filters determined using this analytical algorithm were in accordance with the manufacturer’s values, and silicate pore widths were in good agreement with the values determined by Hg intrusion. Received: 4 June 1996 / Revised: 12 August 1996 / Accepted: 15 August 1996     

Effect of MQ-copolymer and polymethylsilsesquioxane on thermal and mechanical properties of highly filled polyisoprene

Russian Chemical Bulletin - Highly filled vulcanizates based on polyisoprene, organosilicon fillers (polymethylsilsesquioxane and MQ-copolymers), and p-quinone dioxime derivative as a rubber...     

Synthesis of a highly porous carbon material with magnetic properties

Russian Journal of Applied Chemistry - Double modification of birch wood sawdust was performed with the aim to prepare porous carbon materials with magnetic properties.     

Using a quasi-heat-pulse method to determine heat and moisture transfer properties for porous orthotropic wood products or cellular solid materials

Understanding heat and moisture transfer in a wood specimen as used in the K-tester has led to an unconventional numerical solution and intriguing protocol to deriving the transfer properties. Laplace transform solutions of Luikov's differential equations are derived for one-dimensional heat and moisture transfer in porous hygroscopic orthotropic materials and for a gradual finite heat pulse applied to both surfaces of a flat slab. The K-tester 637 (Lasercomp) supplies a quasi-heat-pulse to both sides of a 2-ft-square specimen and records precise signals as function of time from surface thermocouples and heat flux thermopiles. We obtained transfer properties for moist and oven-dried redwood lumber flooring.     

Rheological behavior of fumed silica filled polyethylene oxide

Influence of molecular weight of polymer matrix on nanocomposites rheology is not yet well understood. Herein dynamic rheological responses of fumed silica (FS)/polyethylene oxide (PEO) nanocomposites are investigated as a function of viscosity‐averaged molecular weight (M_η) of PEO, volume fraction (?) and surface characteristics (hydrophilic or hydrophobic) of FS. In the nanocomposites, FS does not influence the glass transition and crystallinity of PEO in the mobile PEO phase while the interfacial interactions tend to immobilize a small fraction of PEO chains that could not undergo glass transition. In spite of the common observation that the reinforcement decreases with increasing M_η of PEO and improving hydrophobicity of FS, linear rheological responses are well reproduced by the two‐phase model, revealing the crucial contribution of the non‐Newtonian matrix undergoing microscopic strain amplified by the filler. Furthermore, nonlinear rheological responses of the nanocomposites are collapsed into master curves plotted against local strain of the matrix. Analyzing the nonlinear rheology by Fourier transform and stress waveform methods reveal the dominating contribution of the matrix and the role of strain amplification played by the filler. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 397–405     

Effective properties of suspensions/emulsions, porous and composite materials

A new method (a version of a mean field method) is suggested to calculate effective properties of suspensions/emulsions, porous and dispersed materials. The aim is to demonstrate a wide range of applicability of the new method. To show the idea of the new method the dependence of the effective diffusion coefficient in the porous medium on the porosity is deduced. Based on the same method the following dependences are deduced: the effective viscosity of suspensions and emulsions as functions of volume fraction of suspended particles or droplets, elastic modules of rubber/polymer sheets with cracks and elastic modules of composite materials on the volume fraction of inclusions in the case of an arbitrary number of different types of inclusions. In all cases the calculated dependences are compared with available experimental data and published theoretical models.     

Application of differential-scanning calorimetry for studying the properties of filled adhesive materials

The possibilities of increasing the thermal stability of polymer materials using fillers are considered. It is shown by the differential-scanning calorimetry that the introduction of schungite into the epoxy adhesive in the amount of 30–40 wt % allows one to increase the glass-transition point to 32°C.