Increasing Polymer Concentration Research Articles

The differential depression of an oxidized starch on the flotation of chalcopyrite and graphite

It is difficult to achieve a clean separation during flotation when unwanted graphitic material exists in association with valuable copper sulphides such as chalcopyrite. Attempts to improve the separation has been driven by green and innocuous reagents such as starch or its derivatives to ensure environmental sustainability. In this study, the depressive action of an oxidized wheat starch in comparison to the normally used native counterpart during flotation of chalcopyrite and graphite was investigated. Starch oxidation, depending on the degree, yields an uncommon phenomenon of concurrent depolymerisation of the large supramolecular assembly of starch chains as well as generation of CO (carbonyl) and (COO) carboxyl moieties on the starch matrix. Adsorption and AFM imaging measurements were performed and correlated with flotation recovery to probe into the influence of the structural and functional changes due to starch oxidation. The base material (native wheat starch – NWS) exhibited a similar adsorption response on chalcopyrite and graphite with increasing polymer concentration, which corresponded to their similar depression during flotation. However, the oxidized starch (Ox 5/120) produced in the laboratory resulted in significant depression of graphite with a modest effect on chalcopyrite flotation. Ox 5/120 also showed marked differences in adsorption behaviour between graphite and chalcopyrite in consonance with the flotation results. It is clear that starch oxidation has an intriguing effect on the underlying binding mechanisms and conformations at mineral surface governing the separation efficiency.

The Influence of Polymer Concentration and Formation Technique on Gas Transport and Gas Sorption Properties of Copolyetherimide-Based Composite Membranes Containing MIL-101 Filler

Composite mixed-matrix membranes for gas separation containing copolyetherimide Siltem® as the polymer matrix and metal-organic framework MIL-101 (10 wt %) as the active filler, were obtained using dry and wet-dry formation techniques. It has been found that the polymer concentration in the initial solution does not significantly affect the CO2 and CH4 permeability of the film membranes obtained by dry molding. The addition of MIL-101 increases the CO2/CH4 selectivity of the dry-formed membranes approximately by 2 times compared to the selectivity of the filler-free polymer membranes. The materials synthesized by the wet-dry formation possess increased permeability and inverted CO2/CH4 selectivity, which indicates a change in the gas transport mechanism. With the increase of polymer concentration, the selectivity of the membranes obtained by the wet-dry technique, increases significantly due to the formation of the dense selective layer.

Cyclic Polymer of N-Vinylpyrrolidone via ATRP Protocol: Kinetic Study and Concentration Effect of Polymer on Click Chemistry in Solution

We hereby report the synthesis of a well-defined cyclic poly(N-vinylpyrrolidone) using propargyl-2-bromoisobutyrate as an ATRP initiator and NaN3 followed by the click reaction of alkynyl and azide groups. The decrease of polymer concentration is favorable for cyclization reaction, while the increase of polymer concentration leads to condensation reaction.

Microrheological study of physical gelation on poly (acrylic acid) polymer hydrophobically modified with C14 alkyl chains, comparison with C18 chain length

We present a diffusing-wave spectroscopy (DWS)-based microrheological study of hydrophobically modified poly(acrylic acid) physical hydrogels which are typically “living” networks. The modified polymer was synthetized with 3% randomly grafted C14 alkyl groups on PAA precursor chains (50 kg/mol), called HMPAA3C14. With increasing polymer concentration CP, intra-chain hydrophobic interactions are replaced by inter-chain hydrophobic ones at concentrations above a critical aggregation concentration, CAC. Then, non-relaxed aggregates percolate at a polymer concentration CP* (gel point) leading to a physical network connected, first, by unrelaxed strands (the Rubenstein and Semenov (R–S) regime), and then by relaxed ones. At observation times longer than the lifetime of the network connection or non-covalent reversible crosslink (hydrophobic groups belonging to neighboring chains form micelles) the system flows but exhibits elastic character at shorter time scales. We determined the gel point CP* at ~ 25 °C using viscoelastic loss tangent uniqueness method. We confirmed the gel point by performing time-cure superposition for the mean-squared displacement (MSD) curves for pregel and postgel regimes, and found that time and probe displacement shift factors increase when approaching CP14*. The viscosity plateau which characterizes the R–S regime around the gel point was larger than that of HMPAA3C18 with longer alkyl grafted chains (C18), in agreement with the fact that the lifetime of the physical crosslink for HMPAA3C14 is lower than that of HMPAA3C18. This behavior is confirmed even in the pregel zone where the size of the longest relaxing cluster for HMPAA3C14 (32 nm) is almost half that of HMPAA3C18, meaning that the latter lives longer. The variation of the plateau modulus (G0) in the low-frequency regime, compared to that of the relaxation modulus Gz determined in the high-frequency one, for the postgel regime suggests that the crosslinking micelles possibly change in size and shape as the polymer is added.

Optimization of polycaprolactone fibrous scaffold for heart valve tissue engineering

Pore size is generally small in nanofibrous scaffolds prepared by electrospinning polymeric solutions. Increase of scaffold thickness leads to decrease in pore size, causing impediment to cell infiltration into the scaffolds during tissue engineering. In contrast, comparatively larger pore size can be realized in microfibrous scaffolds prepared from polymeric solutions at higher concentrations. Further, microfibrous scaffolds are conducive to infiltration of reparative M2 phenotype macrophages during in vivo/in situ tissue engineering. However, rise of mechanical properties of a fibrous scaffold with the increase of polymer concentration may limit the functionality of a scaffold-based, tissue-engineered heart valve. In this study, we developed microfibrous scaffolds from 14%, 16% and 18% (wt/v) polycaprolactone (PCL) polymer solutions prepared with chloroform solvent. Porcine valvular interstitial cells were cultured in the scaffolds for 14 d to investigate the effect of microfibers prepared with different PCL concentrations on the seeded cells. Further, fresh microfibrous scaffolds were implanted subcutaneously in a rat model for two months to investigate the effect of microfibers on infiltrated cells. Cell proliferation, and its morphologies, gene expression and deposition of different extracellular matrix proteins in the in vitro study were characterized. During the in vivo study, we characterized cell infiltration, and myofibroblast and M1/M2 phenotypes expression of the infiltrated cells. Among different PCL concentrations, microfibrous scaffolds from 14% solution were suitable for heart valve tissue engineering for their sufficient pore size and low but adequate tensile properties, which promoted cell adhesion to and proliferation in the scaffolds, and effective gene expression and extracellular matrix deposition by the cells in vitro. They also encouraged the cells in vivo for their infiltration and effective gene expression, including M2 phenotype expression.

Two-Dimensional Decaying Elastoinertial Turbulence.

We numerically simulate two-dimensional, decaying elastoinertial turbulence using the finitely extensible, nonlinear, elastic spring model. We vary the polymer concentration over seven decades, and observe two turbulent elastoinertial regimes. In the weakly coupled regime only the small scale structures change, while in the strongly coupled regime all structures change. This regime is dominated by elastoinertial shock waves with drag reduction properties; i.e., the energy decay rate decreases when the polymer concentration increases.

In Ukrainian

The effect of the surface modification of fumed silica (SiO 2 ) with poly(dimethylsiloxane) (PDMS) on the rheological properties of its suspensions in vaseline oil has been studied in the current work. The composites with different polymer content (from 5 to 40 wt. %) were synthesized by using the method of liquid phase adsorption modification of silica with linear PDMS-1000 (molecular weight W m ≈ 7960, degree of polymerization d p = 105). It is shown that the structural and morphological characteristics of SiO 2 /PDMS composites are significantly different from those for the initial silica, and depend on the concentration of PDMS. In particular, the specific surface area of the composites, determined by the method of low-temperature desorption of argon, is inversely correlated with the content of polymer. The morphology of SiO 2 /PDMS composites and aggregation of primary particles of fumed silica strongly depends on the method of liquid phase adsorption modification: the initial fumed SiO 2 has a wider distribution of aggregates in size than that in polymer composites according to AFM data. Suspensions with a solid phase concentration (SiO 2 /PDMS) of 5 wt. % in a lyophilic dispersion medium (vaseline oil) demonstrate typical thixotropic behavior with a characteristic hysteresis loop on the rheogram, corresponding to increasing the destruction of the dispersion structure while stepwise shear rate increment and partial its restoration while subsequent stepwise shear rate decrement. Both the effective viscosity values corresponding to the maximum destruction of the suspension structure obtained at high shear rates and the effective viscosity values corresponding to partial restoration of the structure in the subsequent stepwise shear rate decrement mode decrease with increasing polymer content in the studied composites. However, it has been found that the initial values of the effective viscosity for the studied dispersions with a practically almost intact structure (at the lowest shear rates) are higher for dispersions of SiO 2 /PDMS composites with a low concentration of PDMS 10–20 wt. % compared with similar suspensions of the initial silica. A correlation between the effective viscosity and the specific surface area of composites is shown.

Surface Properties of Structure-Controlled Silica Films Prepared Using Organic-Inorganic Hybrid Solutions

Silica films with various microstructures were fabricated using organic-inorganic (O-I) hybrid solutions containing a mixture of silica sols, polymethylmethacrylate (PMMA), and urethane acrylate nonionomer (UAN) as an amphiphilic polymer, The O-I hybrid solutions were prepared with various UAN:PMMA and polymer/solvent ratios, then spin-coated on glass and calcinated at 450 °C to produce silica films with various microphase-separated structures. For higher UAN and PMMA concentrations, the silica films showed spherical inorganic domains dispersed over the surface, while many pores were formed in the films with lower polymer contents (observed using scanning electron microscopy). The surface hydrophobicity of the silica films was determined using water contact angle measurements. After surface modification using (1H, 1H, 2H, 2H-perfluorooctyl)trichlorosilane solution, the hydrophobicity of films with a highly microphase-separated structure increased significantly, and all surface-modified films showed increasing hydrophobicity with increasing polymer content. Furthermore, pencil scratch hardness tests showed that the silica films formed on glass substrates could withstand the 5H scratch, test even after surface modification.

Assaying How Phagocytic Success Depends on the Elasticity of a Large Target Structure

Biofilm infections can consist of bacterial aggregates that are an order of magnitude larger than neutrophils, phagocytic immune cells that densely surround aggregates but do not enter them. Because a neutrophil is too small to engulf the entire aggregate, it must be able to detach and engulf a few bacteria at a time if it is to use phagocytosis to clear the infection. Current research techniques do not provide a method for determining how the success of phagocytosis, here defined as the complete engulfment of a piece of foreign material, depends on the mechanical properties of a larger object from which the piece must be removed before being engulfed. This article presents a step toward such a method. By varying polymer concentration or cross-linking density, the elastic moduli of centimeter-sized gels are varied over the range that was previously measured for Pseudomonas aeruginosa biofilms grown from clinical bacterial isolates. Human neutrophils are isolated from blood freshly drawn from healthy adult volunteers, exposed to gel containing embedded beads for 1 h, and removed from the gel. The percentage of collected neutrophils that contain beads that had previously been within the gels is used to measure successful phagocytic engulfment. Both increased polymer concentration in agarose gels and increased cross-linking density in alginate gels are associated with a decreased success of phagocytic engulfment. Upon plotting the percentage of neutrophils showing successful engulfment as a function of the elastic modulus of the gel to which they were applied, it is found that data from both alginate and agarose gels collapse onto the same curve. This suggests that gel mechanics may be impacting the success of phagocytosis and demonstrates that this experiment is a step toward realizing methods for measuring how the mechanics of a large target, or a large structure in which smaller targets are embedded, impact the success of phagocytic engulfment.

Effect of Emulsification on Surfactant Partitioning in Surfactant‐Polymer Flooding

AbstractA laboratory surfactant‐polymer flooding experiment was performed to study the effect of emulsification on surfactant partitioning. The partition coefficient of petroleum sulfonates (KPS) after emulsification was significantly higher than that under static conditions. The partition coefficient of KPS gradually decreases with the increase of polymer concentration from 1000–3000 mg L−1, indicating that the increase of polymer concentration could protect KPS from the partition loss of emulsification. The lower the oil–water ratio, the higher the partition coefficient. The partition coefficient of KPS of resin and asphaltene was higher than that of crude oil. Alkanes, aromatics, and other polar components in crude oil have a significant influence on the partition of KPS.

Effect of Mixed Solvents on the Structure of Polyvinylidene Fluoride Flat Membrane in Thermally Induced Phase Separation Method.

Polyvinylidene fluoride (PVDF) flat membrane was prepared by thermally induced phase separation (TIPS) method using a mixture of dimethyl phthalate (DMP) and dioctyl phthalate (DOP) as a diluent. The PVDF/DMP/DOP system phase separation was test by DSC, cross section structure of membrane was observed by SEM. The effect of polymer concentrations, cooling rate and coagulation bath temperature on the cross section structure of membrane and surface micro-structure were studied. Results showed that membrane pore size porosity and water flux decreased with the increase in polymer concentration. The membrane section by the dendritic structure transition of nodular structure eventually turned into a compact structure. Pore size and water flux increased with the increase in coagulation bath temperature. The spherulite structures of the cross section of the membrane reduced while the lacy structure increased cross section smoothing.

Tertiary Amine Methacrylate based Polymers as Corrosion Inhibitors in HCl Solution. Part II

In this study, the inhibitive performance of novel synthesised water-soluble of different molecular weight diblock copolymers of derivative methyl methacrylate (VB84, VB206, VB207, VB361, VB371,VB406) on the corrosion behavior of AISI 304 stainless steel in 10–3 M HCl containing various concentrations of polymers was investigated using potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), scanning electron microscopy(SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and inductively coupled plasma optical emmision spectrometry (ICP-OES) methods. Polarisation curves indicated that all studied polymers were acting as mixed type inhibitors. All electrochemical measurements showed that inhibition efficiencies increased with increasing polymer concentration. It was determined that the increase of inhibitor efficiency by concentration resulted from the adsorption of polymers to metal surface, and the adsorption fitted to the Langmuir adsorption equation. The variation in inhibitive efficiency mainly depends on the type and the nature of the substituents present in the polymer molecule and also depends on the molecular weight of the polymer. The best inhibition in 10-3 M HCl shows VB84 homopolymer. Surface images obtained with SEM, EDX, and AFM methods determined by verifying these results that inhibitors decrease the dissolution of metal, prevented the corrosion.

Broadband Dielectric Spectroscopy Study of the Ion Dynamics in Blends of Polymerized and Molecular Ionic Liquids

The primary focus in describing the decoupling of ion dynamics from the structural relaxation and dynamic glass transition (Tg) in polymerized ionic liquids (PILs) has been the effect of polymer molecular weight and chemistry of the ionic repeat unit. A particular aspect that has not been studied in attempt to understand the physicochemical properties of these fascinating materials is the concentration dependence of PILs with their low molecular weight or monomeric derivatives. Here we present studies of mixtures containing the low molecular weight monomer and the corresponding polymer of [(methacryloyloxy)ethyl]dimethylammonium (DMAEMA+), the quaternized ammonium cation of dimethylaminoethyl methacrylate, with the bis[(trifluoromethyl)sulfonyl]imide (NTf2) counter anion. The temperature dependent ion dynamics were measured using broadband dielectric spectroscopy. Our results show that there is an exponential relationship between the dc conductivity and concentration which decreases with temperature. At ~80mol% PIL this this inverse relationship between log σ0 and concentration “saturates” then reverses approaching 100% PIL. Only a single calorimetric glass transition temperature was observed for each of the concentrations measured. The Tg is concentration independent from 0-75% (~-60°C) then rapidly increases to that of the polymer (~55°C). The S-N-S bending modes, as observed in the Raman spectrum of the blends, blueshifts with increasing concentration, but exhibits a slight redshift from 85-100% polymer. This suggests the anion becomes more coordinated to the cation with increasing polymer concentration, but then reverses approaching pure polymer. In concert with results from a recent simulation study, we suggest that the ion hopping mechanism changes drastically from dilute to concentrated PIL/IL blends at a characteristic concentration (~85% for DMAEMA+ NTf2), but then this mechanism reverses as the ion dynamics and structural relaxation become decoupled in the pure polymer. A continuation of these concentration dependent studies of PIL and low molecular weight ionic liquid blends is a promising direction toward fully understanding the dynamics in these systems for rational design of PILs. Figure 1

Structure of poly(acrylic acid), poly(methacrylic acid) and gelatin solutions

The structure of poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), and gelatin solutions are studied using the turbidity spectrum and dynamic light scattering methods. The effect of the polymer concentration and pH value of the solutions on the structure and optical properties of polyelectrolyte solutions are investigated. The size of light scattering particles in different systems is calculated. An increase in size was observed with increasing polymer concentration for the PAA solution. The dependence of the particle sizes on concentration is described by a curve with maxima for the PMAA solution. The sizes of the light scattering particles in solutions are compared with data on quality of solvents. The gelation mechanism of gelatin in water solutions was investigated in the wide range of concentration and at different рН values.

Isotactic polypropylene–1,2,4,5-tetrachlorobenzene: porous bodies via thermally induced phase separation

Using recently constructed experimental phase diagram isotactic polypropylene–1,2,4,5-tetrachlorobenzene (TeCB), we formulate a physically consistent scenario of the mixture evolution under thermally induced phase separation and predict the morphology of capillary-porous bodies that are formed after cooling down the binary system and removal of the low molecular mass component. This approach allows us to interpret the experimental data obtained by optical microscopy, scanning electron microscopy, and differential scanning calorimetry on the system with two crystallizable components. At any composition, TeCB forms needle-like crystals of nearly square section. Increasing polymer content affects crystal growth by limiting their length and by generating another population of small TeCB crystals of irregular shape and close to log-normal size distribution, located in the amorphous polymer regions. Finite rate of cooling the system leads to a hysteresis, when the values of characteristic temperatures and compositions in the phase diagram appear to be considerably shifted to lower temperatures and higher polymer contents. Combination of structural and calorimetric data provides an opportunity to characterize polymer–solvent systems from both thermodynamic and technological standpoints.

Experimental study on treatment of tertiary oil recovery wastewater by electrocoagulation

The mechanisms of the treatment of tertiary oil recovery wastewater by electrocoagulation are still unclear. Here, an electrocoagulation device for oilfield application was designed and used for a study of this system. Single factor analysis was used to investigate the effects of current density, initial pH value, polymer concentration (HPAM) and electrode type on the electro-coagulation treatment performance of oilfield sewage. Treatment effectiveness was quantified by measuring the oil fraction and turbidity as a function of time. The results show that the treatment is more effective at higher current density. Regarding pH, neutral conditions led to the most effective treatment, followed by acidic, then alkaline conditions. The polymer concentration had a significant influence on the final treated water quality, with treatment effectiveness decreasing gradually with increasing polymer concentration. These effects could all be explained by factors related to the stability of oil droplets against collision and coalescence. Compared to the Al electrode, the floc generated by Fe electrode in the treatment experiment is smaller, and therefore not as easy to coagulate and settle in a short time. Thus, Fe electrodes are not conducive to the rapid treatment of wastewater by electrocoagulation.

Investigation of PEG4000/Natural clay-based hybrids: Elaboration, characterization and theory

In this work, we first examine in depth the chemical composition, the structure and the mineralogy of a local clay mineral as well as its peculiar physicochemical properties. Second, we elaborate new hybrid material models based on natural clay with a polymeric supporting matrix. To this end, the standard procedures combined with analyses by Transmission Electron Microscopy (TEM), X-ray Fluorescence (XRF), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR), are used to analyze both the raw material and the elaborated hybrids. It is found that the clay sample contains essentially kaolinite, illite, chlorite and some typically associated minerals such as calcite and quartz. The study reveals that the clay mineral has a low capacity to adsorb water; thereby, a low porosity is expected. On the other hand, FTIR-analysis shows the presence of new interactions between the polymer-chains and the clay-layers surfaces, which favor its adsorption and contribute to form an intercalated structure. Chromatic features of the considered clay-polymer-samples are also investigated experimentally. Finally, using a scaling theory of adsorption, we explain the inter-plate separation profile as the polymer concentration increases, and it is found that the theoretical predictions agree well with the experimental results.

Effect of Inorganic Polymer Gel Systems on Residual Resistance Factor in Fractured Core Model

Excessive water production through fractures become an important problem in oil exploration of fractured reservoirs. For this purpose, polymer gels were prepared by crosslinking of aqueous solutions of polymer and crosslinker for the purpose of water management in high water cut fractured reservoirs. A copolymer of sulfonated polyacrylamide was used as polymer and chromium triacetate (Cr(OAc)3) and aluminum nitrate nonahydrate (Al(NO3)3.9H2O) were used as inorganic crosslinkers at 90oC. Two quadratic models were presented for the two inorganic polymer gel systems to predict the gelation time by using a central composite design which showed highly significant results. The results also showed that polymer concentration was the main effect on gelation time. Increasing polymer concentration leads to accelerate the gelation process and then decrease of gelation time. Based on the gelation time and strength of three dimensional structure of polymer gel, the selected polymer gels of Cr(OAc)3 and Al(NO3)3.9H2O were applied to study the performance of polymer gel system in fractured core with the same polymer concentration of 37071 ppm and the crosslinker concentration of 13096 ppm and 2707 ppm, respectively. Also, the gelation time of these polymer gels was determined 12 h and 34 h, respectively. For this purpose, the coreflooding test was carried out to measure the output flow rate before and after polymer gel treatment in order to calculate the Residual Resistance Factor (RRF). As a result, after polymer gel treatment, the output flow rate decreased intensively and by increasing injection pressure, the RRF decreased gradually. The polymer gels of Cr(OAc)3 and Al(NO3)3.9H2O in the fracture were renitent up to 70 and 60 bar against the water pressure drop, while these polymer gels were renitent up to 60 and 40 bar against the oil pressure drop, respectively. The polymer gel of Cr(OAc)3 demonstrated higher residual resistance factor than the polymer gel of Al(NO3)3.9H2O.

Flocculation monitoring of wastewater by using impedance spectroscopy.

The aim of the present work is to monitor the flocculation process using the analysis of the electric and dielectric properties. Therefore the dielectric and electrical characteristics of wastewater with different cationic polymer concentrations were investigated via the impedance spectroscopy (IS) method. Impedance measurements were carried at different concentration of cationic polymer in the frequency range from 0.1 Hz to 100 kHz. The analysis of complex permittivity spectra was described by the superposition of a power law at a low frequency related to the diffusion process and Cole-Cole relaxation behavior at high frequency. Moreover, an equivalent circuit model was developed in order to analyze the experimental data and to further investigate both processes. The variation of the parameters extracted from the equivalent circuit with the increase of cationic polymer concentrations has shown a net transition at 10 mg/l. This behavior could reflect the flocculation of dispersed particles at 10 mg/l. The findings in this work could draw new attention toward the monitoring of the coagulation-flocculation process using impedance spectroscopy and could be extended to other kinds.

Sprayable and injectable visible-light Kappa-carrageenan hydrogel for in-situ soft tissue engineering

The aim of this study was to develop injectable and sprayable visible-light crosslinked Kappa-carrageenan (κCA) hydrogel and to investigate the role of polymer concentration (2, 4 and 6 wt%) and degree of methacrylation (6 and 12%) on its properties. It was found that, the average pore sizes, water content and swelling ratio of hydrogel were tunable by changing the methacrylate κCA (KaMA) concentration and methacrylation degree. Furthermore, the mechanical properties of KaMA could be noticeably modulated, depending on the formulation of hydrogel. Tensile and comprehensive modules were enhanced from 68 to 357 kPa and from 213 to 357 kPa, respectively, by increasing KaMA concentration from 2 to 6 wt% and methacrylation degree from 6 to 12%. Furthermore, with increasing methacrylation degree and polymer content, the absorbed energy and energy loss were increased. Moreover, recovery significantly enhanced from 27.3% to 74.4% with increasing polymer content from 2 to 6 wt%. Finally, visible-light crosslinked KaMA hydrogels not only was biocompatible, but also could promote HaLa cell and fibloblasts function. The visible-light crosslinked KaMA is thought to be an exclusive biomaterial as a sprayable hydrogel being able to cover skin injuries or to inject as a bio-printing material to in situ heal soft tissue damages.