Latex Emulsion Research Articles

Influence of sisal fibres and rubber latex on the engineering properties of sand concrete

This experimental study aims to investigate the properties of sand concrete (SC) by using sisal fibres and latex in various fields in construction. Sisal fibres were applied at four ratios of 0.05%, 0.10%, 0.15% and 0.20%, while liquid latex was replaced with three ratios of 15%, 25% and 35%. In this context, ideal percentages of sisal fibre (0.1% F) and latex (35% L) were combined in a single cement matrix. For each percentage, tests on flow, density, compressive strength, flexural strength, ultrasonic pulse velocity, modulus of elasticity, water accessible porosity, water absorption and shrinkage were performed on fresh and hardened SC. Scanning electron microscopy (SEM) was also conducted for microstructure analysis. Results indicate that adding latex emulsion to SC containing sisal fibres increased the adhesion of the fibres to the cement matrix, which contributed to the increase in flexural strength and the decrease in shrinkage. This condition also helped reduce the porosity and water absorption of latex-modified SC with sisal fibres compared with SC that contained fibres. The improvement occurred in the properties that constitute an obstacle to the widespread use of SC. Thus this improvement has practical implications.

Modelling study of emulsion latex coagulation processes in coagulators

AbstractThis paper presents a numerical study of emulsion latex coagulation processes in continuous coagulators based on the full computational fluid dynamics approach. The RANS approach together with the k‐ε turbulence model was used to describe the detailed flow field in the coagulators. The coagulant mixing process was modelled by the convection‐diffusion equation and the emulsion latex coagulation process was formulated by the population balance equation of the particle size with a coagulation kernel including a perikinetic and orthokinetic combined mechanism. The flow and coagulation models were independently validated by means of comparing simulated results to the relevant experimental data from the literature. A series of simulations were carried out to study the effects of coagulator bottom shape, salt solution feeding location, residence time and agitation speed, as well as the influence of four typical scale‐up criteria on the latex particle coagulation process. The presented results would be helpful for the relevant process design, development, and scale‐up of continuous latex coagulators.

High-Density Carbon Adsorbents for Natural Gas Storage

Physicochemical regularities are studied for the synthesis of molded active carbons based on coconut shells and peat, with a latex emulsion and a carboxymethyl cellulose (CMC) sodium salt solution being used as binding agents. The materials are obtained at compacting pressures of 25, 50, and 100 MPa. The specific surface areas of the composite samples obtained from peat and coconut shells are SBET ≈ 1320 and ≈1290 m2/g, respectively. The specific micropore volumes of the composites based on peat and coconut shells are W0 = 0.50 and 0.45 cm3/g, respectively. Latex-modified carbon samples have a higher bulk density than those molded with CMC. The molding of the active carbons is accompanied by partial degradation of their porous structure. The Dubinin theory of volume filling of micropores (TVFM) has been employed to calculate the values of adsorption and active specific capacity of the molded adsorbents with respect to methane at a temperature of 273 K and a pressure of up to 100 bar. The experimental and calculated data have shown that the active capacity of the new microporous carbon composite materials may be as large as 180 m3 (NTP)/m3, when the pressure drops from 100 to 1 bar. It has been concluded that it is reasonable to employ the TVFM for preliminary calculations of the parameters of adsorption systems used for natural gas storage.

FEATURES OF BEHAVIOR OF ORGANIC AMMONIUM SALTS WHEN ISOLATING RUBBER FROM LATEX

The influence of low-and high-molecular substances on the stability of various lyophobic colloidal systems is among the earliest empirical and intuitively used phenomena. The water-soluble organic salts are applied in different industries including latex technology. This is related to a complex of various colloid-chemical phenomena and their interaction with latex dispersed phase and its components. Nowadays some high-molecular and low-molecular organic reagents are used to reduce the aggregate stability of latex system on an industrial scale. In the article, the coagulating ability of ammonium acetate, ammonium oxalate and ammonium citrate were estimated for the latex coagulation in the comparison with an inorganic ammonium salt and sodium chloride. The influence of the nature of salt component, as well as its consumption, on the technological features of the coagulation process in the emulsion latex was established. The relationship between the consumption of organic ammonium salt and acidifying component on the complete coagulation was shown. It’s worth noting that the strength of the acid, which forms the ammonium salt, has an effect on the technological extraction process of rubber from latex. The stronger the organic acid, the lower the consumption of the acidifying agent, and complete coagulation is achieved at lower consumption of coagulants. Peculiar behavior of ammonium citrate has been noted: complete coagulation wasn’t achieved with the consumption of this salt over 200 kg/t of rubber and increased consumption of the acidifying agent. It can be due to the fact that citric acid is an oxyacid and shows properties characteristic for surfactants and increases the aggregate stability of the system. These rubbers, rubber compounds and vulcanizates obtained correspond to standard parameters.

Application of Acrylate Latex Emulsion as the Binder for Coating Aluminum Substrate by Silica-Gel Powder

The adsorbent coated exchangers are the main part of adsorption refrigeration systems. Although coated exchangers are commercially available, the coating technique and the binder used are seldom revealed and left as a challenge for researchers. Dip-coating is the most commonly used coating technique. However, the variety of binders used indicates that choosing the appropriate binder is still a matter of trial-and-error. A series of experiments were performed to introduce acrylic latex emulsion (ALE) and bitumen emulsion as the new binder for coating silica-gel powder on aluminum. The results indicate coats created by both emulsion binders are stable but the bitumen emulsion keeps its stability for about 10[Formula: see text]min after mixing with water and silica-gel powder. The effect of ALE binder and water concentrations on water vapor equilibrium and desorption kinetics was investigated. The outcomes indicated that the sample containing 0.8[Formula: see text]g water/g silica-gel, 0.08[Formula: see text]g ALE binder/g silica-gel shows the fastest desorption kinetic and the minimum capacity loss. The mechanical stability of this sample was evaluated by the shear test and the pull-off test. The measured values show that the prepared laminate withstands up to 27[Formula: see text]N/cm2 shear stress and 18[Formula: see text]N/cm2 tensile stress.

Accelerated CO2 capture on adsorbent coated finned tube: An experimental study

In this study, the external surface of a finned tube was coated by 13X zeolite powder, and the CO2 adsorption equilibrium and dynamics were investigated experimentally. A slurry consisting of dionized water, 13X zeolite powder, and Acrylic latex emulsion (ALE) was used to coat the finned tube. The finned tube was coated by deep coating method. The equilibrium isotherms were measured at the range of 20–90 °C and fitted well by the dual-site Langmuir model. The average difference between the model and the results obtained from the experiments is about 2.5%. The nitrogen adsorption/desorption at 77 K was used for characterization of adsorbents. A 11% reduction was observed in pore volume and surface area. The dynamic test showed that the desorption of adsorbed CO2 takes place in about 14 s which is an order of magnitude faster than the fastest developed method. A conservative criterion was developed for estimating adsorbent working capacity. This criterion showed that the working capacities of the adsorbent are about 80% of its ideal values.

The strength of sawdust concrete, produced without mineral aggregates

The construction industry widely uses concrete for various purposes. The addition of lightweight fillers to the compounding of concrete allows to obtain lightweight concrete with high heat-insulating indicators and a smaller mass. Various materials can be used as fillers, including industrial waste. The paper is devoted to the study of the properties of lightweight concrete with the addition of sawdust. As a result of experimental studies, the strength properties of sawdust concrete produced without the use of mineral fillers (sand) were determined. The positive effect of tempering the mixture with latex emulsion on the strength properties of sawdust concrete has been established. The strength characteristics of samples made with the addition of a latex emulsion were 3.65 MPa at a density of 1080 kg/m3. Such indicators allow using the material as a structural thermal insulation during construction.

Facile Fabrication of Superhydrophobic Nanocomposite Coatings Based on Water‐Based Emulsion Latex

AbstractTo prepare water‐based superhydrophobic coatings with excellent properties would be of great significance, but it remains difficult to solve the problems of uneven dispersion of hydrophobic modified inorganic nanofillers in water and poor interfacial compatibility between hydrophilic inorganic nanofillers and polymer matrix in the film. Herein a novel and green technology is reported to disperse dodecyltriethoxysilane in water‐based polymer system uniformly by adsorbing it on the surface of emulsion latex particles first. Then after silica nanoparticles being introduced into the system, the hydrophobic modification is realized by the coupling reaction between silica nanoparticles and the alkylsilane in the film‐forming process. Furthermore, various common water‐based emulsion latexes are able to be applied as the binder between the modified nanoparticles and substrates. The resulting coatings exhibit excellent superhydrophobicity and show remarkable mechanical durability as well as chemical stability. In addition, these nanocomposite coatings are demonstrated of high performance for oil/water separation. The findings provide a valuable way to fabricate water‐based and fluorine‐free superhydrophobic coatings with excellent properties for potential industrial applications.

Latex Based Emulsion Functional Conductive Polymer Binder for Si Composite Electrode

Functional conducting polymer binders are a class of stable, elastic, electrically conductive adhesive that makes possible the fabrication of silicon composite electrodes for a new generation of low-cost, high-capacity lithium-ion batteries. The vastly higher storage capacity of Si has not been fully realized because silicon swells up to nearly four-times its volume when the Si electrode draws in lithium ions during the charging process. This mechanical expansion and contraction quickly damage the electrode, rendering Si material useless. Functional conductive polymer binder directly addresses the volume-expansion problem by connecting the volume changing Si particles with an elastic polymer to form the anode electrode of a rechargeable lithium battery. This elastic adhesive polymer not only holds the silicon particles in place, but also stretches as those particles expand and contracts when they shrink back to their original volume. We have advanced the functional conductive polymer binder technology into its 4th generation, which is now a water based latex emulsion similar to industry standard styrene-butadiene rubber (SBR) binder, but electronically conductive. The latex based emulsion system of the 4th generation of functional conductive polymer binder ensures that the binder is low cost, and the battery manufacturing process is compatible with the current industry standard.

English

The presence of water in the pavement structure causes early deterioration and leads to less pavement durability as a result of loss of bond between aggregate and binder and may causes loss of strength and stability in mixture, The main goal of this study was to investigate the effect of various polymer additives on permeability of asphalt concrete mixture. The surface wearing coarse type IIIA was chosen in this study. Three types of polymer additives were used in this study; (7% Latex Emulsion (LE), 7% Poly Vinyl Acetate with 4% Styrene Butadiene Styrene (PVA + SBS) and 8% Ethylene Diamine (ED)). The results appeared that the permeability average of all mixtures were (27.745, 17.18, 7.773 and 11.409 * 10 -5 cm/s) for (control blend, LE, PVA+SBS and ED) and the percent of decreasing in permeability were (48.52%, 74.547% and 58.312%) for (LE, (PVA + SBS) and ED) respectively.

Role of emulsifier on the particle size and polymer particle size distribution using multiwavelength spectroscopy measurements

ABSTRACTLatex emulsions depend strongly on the polymer composition, and particle size distribution, which in turn, is a function of the preparation of the latex and on the formulation and composition variables. This study reports measurements of particle size and particle size distribution of latex emulsions as function of the reaction time and the type and concentration of emulsifier by using the multiwavelength spectroscopy technique. Results show changes in the particle size of latex emulsions with the reaction time, obtaining larger particles and broader distributions with increasing of Tween 80 ratio. The steric stabilization provides the sole nonionic emulsifier is not enough to protect the polymer particle, causing the flocculation among the interactive particles, resulting in unstable latex. However, latex emulsions prepared with Tween 80 ratio <70 wt.% can stabilize efficiently the nucleated particles, probably due to the effects provided by both, the electrostatic and steric stabilization mechanisms. The same effect is shown in the curves of conversion (%) as a function of reaction time, resulting in slower polymerization rate for Tween 80 ratio >70 wt.%. On the other hand, smaller polymer particles, in all range of emulsifier mixture, have been obtained to higher emulsifier concentration.

Processing of Aqueous Tape Casting of Glass-Ceramic in the SiO&lt;sub&gt;2&lt;/sub&gt;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-MgO-Li&lt;sub&gt;2&lt;/sub&gt;O System with ZrO&lt;sub&gt;2 &lt;/sub&gt;and B&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Addition

The aim of this work was to fabricate glass-ceramic substrates using aqueous tape casting technique of the parent glass powder in the SiO2-Al2O3-MgO-Li2O system with addition of ZrO2 and B2O3. The powder mixture was melted at 1650°C/1h and the obtained glass (frit) was milled and processed by tape casting in thin substrates with 700 μm thickness. Suspensions were prepared by aqueous medium and latex emulsion binder. Flexible green tapes with few defects were obtained using suspensions prepared with 7 and 10 wt% of binder in relation to glass powder. Substrates were submitted to burn out at 700 °C and thermal treatment at 950 oC/30min, 950 oC/4h and 1000 °C/1h. The green density of the substrates was around 1.55 g/cm3 and 2.10 g/cm3 after sintering/crystallization. Microstructure in all treatments showed high porosity. The major crystalline phases identified by XRD were Li0,6Al0,6Si2,4O6, ZrO2 and ZrSiO4.

Synthesis and characterization of polymer-silica hybrid latexes and sol-gel-derived films

Sol-gel derived organic-inorganic hybrid systems were obtained by applying alkaline-catalyzed co-hydrolysis and copolycondensation reactions of tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), isobutyltriethoxysilane (IBTES), diethoxydimethylsilane (DMDES), and vinyltriethoxysilane (VTES), respectively, into a polymer latex functionalized with vinyltriethoxysilane (VTES). The properties of the latex hybrid materials were analyzed by FTIR, water contact angle, environmental scanning electron microscopy (ESEM), TEM and AFM analysis, respectively. FT-IR spectra confirmed that the chemical structures of the sol-gel derived organic-inorganic materials are changed as function of inorganic precursor and SiOSi networks are formed during the co-hydrolysis and copolycondensation reactions. The water contact angle on the sol-gel latex film containing TEOS+VTES increased to 135°±2 compared to 65°±5 for the blank latex, due VTES incorporation into latex material. TGA curves of hybrid sample modifies against neat polymer, the thermal stability being influenced by the presence of the inorganic partner. ESEM analysis showed that the latex hybrid films prepared with different inorganic precursors were formed and the Si-based polymers were distributed on the surface of the dried sol-gel hybrid films. TEM and AFM photos revealed that the latex emulsion morphology was modified due to the VTES incorporation into system.

Morphology and Mechanical Properties of Polyacrylic-Silica Nanocomposites

ABSTRACTOrganic-inorganic hybrid nanocomposites are considered a new generation of high performance materials because they combine both the advantages of inorganic materials (stiffness, high thermal stability, barrier properties, optical, catalytic, electrical and thermal conductivity among others) and organic polymers (flexibility, dielectric, toughness, lightweight, processing). Each part of a nanocomposite has a synergistic function in its performance and has much better combination properties than a single material. We report on the thermo-mechanical properties and morphology of polyacrylic-nanosilica (SiO2) composites prepared in-situ via emulsion polymerization, using a semi-continuous mode. The latex emulsion thus obtained was stable for at least six months. Moreover, this process produced controlled molecular weight in the final latex and low formation of agglomerates. Films drawn from the latex exhibited excellent optical transparency, suggesting good dispersion of the nanosilica, and confirmed by scanning electron microscopy (SEM). There was an increase in glass transition temperature, Tg, suggesting a modification of molecular dynamics; hydrophobic behavior, as probed by water contact angle, was also promoted. Moreover, the Young’s modulus of the nanostructured latex films increased up to 57% with only 3 wt% nanosilica, therefore denoting a reinforcing effect of the nanoparticles.

Preparation and properties of paper–plastic laminating adhesive used for medical packaging materials

Paper–plastic packaging materials have become important materials in the printing industry. Water‐based paper–plastic laminating adhesive is a new type of adhesive that has been widely applied in the modern packaging and printing industry. The adhesive used for medical packaging materials asked for higher performance, such as stability, peel strength, and aging resistance, so there is a large necessity in developing an environment‐friendly paper–plastic laminating adhesive with excellent performance. Wax emulsion, natural latex and waterborne polyurethane emulsion are mixed in the experiment, while epoxy resin emulsion was added to blending modification. The paper discusses the influence of the dosage of epoxy resin emulsion, wax emulsion, and waterborne polyurethane emulsion for T‐peel strength and paper breakage rate; also, the storage stability of the emulsion, partical size, and partical size distribution and differential scanning calorimeter are tested to determine the best prescription of the paper–plastic adhesive. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Comparison of Different Alumina Powders for Aqueous Tape Casting Process

Tape casting process was used to produce Al2O3 substrates in an aqueous system with acrylic latex emulsion as binder. The present work studied the slurry formulations in aqueous medium of Al2O3 powders with different particle size distribution and made correlation to the green and sintered tapes. Two commercial alumina powders, one sub-micrometric and other micrometric were used. Compositions of Al2O3 slurries with 80 and 83 wt% of solids were prepared by dispersing the powders in water with a dispersant with subsequently additions of 7 and 10 wt% of binder. Sub-micrometric Al2O3 resulted in a high densification tapes regardless solid concentration and binder amount in the slurry, though green density was affected. For micrometric alumina, increasing the solid concentration resulted in a little higher final density.

Use of Natural Rubber Membranes as Support for Powder TiO2and Ag/TiO2Photocatalysts

The purpose of this study was to synthesize TiO2-polymer composites able to act as photocatalyst membranes. TiO2 catalysts were prepared using the sol-gel method to contain 0.0, 0.5, 1.0, and 2.0 wt.% of embedded Ag particles, subsequently incorporated into natural rubber latex at a weight fraction of 15%. Samples of these ceramic powders were suspended in a latex emulsion (natural rubber), cast in Petri dishes and slowly dried in an oven. The resulting materials were evaluated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, diffuse reflectance spectroscopy, differential scanning calorimetry, thermogravimetry, and photocatalytic assaying using methylene blue as an organic pollutant reference. All composite membranes exhibited good photoactivity conferred by TiO2 powder, with 98% dye fading after 300 min of ultraviolet irradiation.

Microstructure of Cured Urea-Formaldehyde Resins Modified by Rubber Latex Emulsion after Hydrolytic Degradation

ABSTRACT This study investigated microstructural changes of cured urea-formaldehyde (UF) resins mixed with aqueous rubber latex emulsion after intentional acid etching. Transmission electron microscopy (TEM) was used in order to better un-derstand a hydrolytic degradation process of cured UF resins responsible for the formaldehyde emission from wood-based composite panels. A liquid UF resin with a formaldehyde to urea (F/U) molar ratio 1.0 was mixed with a rubber latex emulsion at three different mixing mass ratios (UF resin to latex = 30:70, 50:50, and 70:30). The rate of curing of the liquid modified UF resins decreased with an increase of the rubber latex proportion as determined by differential scanning calorimetry (DSC) measurement. Ultrathin sections of modified and cured UF resin films were exposed to hydrochloric acid etching in order to mimic a certain hydrolytic degradation. TEM observation showed spherical particles and various cavities in the cured UF resins after the acid etching, indicating that the acid etching had hydrolytically degraded some part of the cured UF resin by acid hydrolysis, also showing spherical particles of cured UF resin dispersed in the latex matrix. These results suggested that spherical structures of cured UF resin might play an important role in hindering the hydrolysis degradation of cured UF resin.

The synthesis of styrene acrylate emulsion and its application in xerographic paper

Abstract During xerographic printing processes, the electric charge properties of the paper surface are essential to obtain effective toner transfer and high image quality. Surface and volume resistance are indispensable to the accumulation of the surface charge and different resistance values generate different electrical fields with optical drum, and have a significant effect on toner transfer efficiency. In this paper, surface sizing was investigated to improve the surface properties for better toner transfer and image quality. Styrene acrylate emulsion (SAE) latex was successfully synthesized and fully characterized with a Fourier transform infrared (FT-IR) spectrometer, a laser particle analyzer and a scanning electron microscope (SEM). The results showed that under the conditions of emulsifier dosage at 3 wt%, initiator concentration at 0.5 wt% and the reaction temperature at 80°C, the monomer conversion can reach 80%. The effects of various factors including initiator dosage, emulsifier dosage and monomer ratio on the sizing performance were studied. The effects of different ratios of SAE to starch on surface and volume resistance of paper were also systematically investigated. The differences in electric properties of various paper samples were quantified and their influence on paper-toner adhesion and print quality was clarified. Relationships between electrical properties of paper and paper-toner adhesion force, and thus print quality were established. Strategies to improve printing performance through effective control of paper electrical properties were also developed. It is concluded that the best printing quality and toner adhesion were achieved when the ratio of SAE to starch is between 1:10 and 2:10.

Stabilization Mechanism of the Reconstituted Emulsion of Polyacrylate Redispersible Powder

Polyacrylate redispersible powder was prepared from polyacrylate emulsion with a soft-core and hard-shell configuration by spray drying. The effect of polyvinyl alcohol (PVA) solution as a protective colloid on the redispersibility of the polyacrylate powder was investigated, along with the stabilization of the reconstituted emulsion. The results show that bulk carboxylic ions were formed on the particle surface when the pH value was between 9.0 and 10.0, leading to a high zeta potential and strong electrostatic repulsion force among the latex particles of the reconstituted emulsion. The hydrophilic group –OH of the protective colloid PVA combined with water molecules and the hydrophobic polyethylene long-chain groups were adhered onto the particle surface of the reconstituted emulsion latex, which induced steric hindrance between latex particles and prevented particle aggregation. The synergistic effect of the strong electrostatic repulsion force produced by carboxylic ions and the space steric hindrance generated by the PVA solution provided excellent redispersibility and stability to the reconstituted emulsion.