Redispersible Powder Research Articles

Derivative spectrophotometry allows quantitative determination of essential oils in dispersible powders of spray-dried nanocapsules

This study aimed to develop and validate an analytical methodology based on derivative spectrophotometry to determine the true concentration of ginger (ZEO) and rosemary (REO) essential oils in nanocapsule redispersible powder formulations. Second-order derivative spectrophotometry made it possible to nullify the interference of nanocapsule components at 240 and 245 nm wavelengths for ZEO and REO, respectively. The validated method was linear in the range 0.01-0.04 mg mL−1 for ZEO and 0.6-0.96 mg mL−1 for REO. It is also accurate with RSD of 1.82 and 1.44 for ZEO and REO respectively, and shows recovery rates close to 100% in both essential oils when assessing accuracy. The methodology used allowed the determination of the essential oils in the presence of the formulation components, simply and quickly, showing to be an option to be used for quantification of OEs in these nanometric systems.

Spray drying of polymer dispersions for redispersible powder coatings: Effects of stabilization mechanisms and process conditions

Spray drying of polymer dispersions for redispersible powder coatings: Effects of stabilization mechanisms and process conditions

Innovative synthesis of multicomponent acrylate based redispersible powder and approaches for application in interior paints

The present work discloses the synthesis of multicomponent acrylate based waterborne latex for especially interior coatings. Redispersible powder (RDP) can be utilized in the paint and coatings industry due to its simplicity of use in variety of applications. In this paper, acrylate based latex was prepared by emulsion polymerization method. Three components were mixed for the preparation of the emulsion of RDP. The prepared acrylic latex was later spray dried and converted into RDP. The obtained dried RDP has very good redispersibility. The characterization of RDP was carried out using a Fourier transform infrared spectrometer (FTIR), Particle size analyzer, Differential scanning calorimeter (DSC), and Field emission scanning electron microscope (FE-SEM). The viscosity, freeze thaw stability, redispersibility and storage stability were also studied for RDP. Results show that the Total solid content (TSC) of synthesized RDP is 89%. Freeze thawing stability shows good quality with a milky white appearance of latex. There is no gelation, setting and coagulation of emulsion. The prepared RDP shows good storage stability with no aggregation of particles after 48 to 96 h of storage. In this study, it is seen that as the inlet temperature of the dryer increases, the percentage of moisture in the final product decreases which leads to a free – flowing powder. It can be seen that RDP was free-flowing in nature having angle of response≈ 38.7° with a bulk density of 270 to 350 kg/m3. In the context of acrylate, FTIR peaks indicate the presence of carbonyl group, which is characteristic of the acrylate functional group. The Particle size of RDP is 133.6 μm. The optimum temperature to melt the powder was found to be 200 °C. SEM micrograph of RDP is recorded at magnification 1.00, 5.00, 5.00, 10.00 KX, and applied voltage 20 kV and scale range of images are 20 μm, 2 μm, 2 μm and 1 μm, respectively. Results showed a dented surface with a shrunken spherical form. In this paper, RDP based paint formulations were synthesized by mixing RDP with water, calcium carbonate, and titanium dioxide. Here, RDP acts as a binder. Paint formulations were applied to the specimen and dried. The resultant paints were characterized by pendulum hardness, cross cut, pencil hardness, methyl ethyl ketone (MEK) rubbing test and gloss test to understand the physical properties of the paint coating.Graphical

Nanocellulose-Based Materials for Water Pollutant Removal: A Review.

Cellulose in the nano regime, defined as nanocellulose, has been intensively used for water treatment. Nanocellulose can be produced in various forms, including colloidal, water redispersible powders, films, membranes, papers, hydrogels/aerogels, and three-dimensional (3D) objects. They were reported for the removal of water contaminants, e.g., heavy metals, dyes, drugs, pesticides, pharmaceuticals, microbial cells, and other pollutants from water systems. This review summarized the recent technologies for water treatment using nanocellulose-based materials. A scientometric analysis of the topic was also included. Cellulose-based materials enable the removal of water contaminants, and salts offer advanced technologies for water desalination. They are widely used as substrates, adsorbents, and catalysts. They were applied for pollutant removal via several methods such as adsorption, filtration, disinfection, coagulation/flocculation, chemical precipitation, sedimentation, filtration (e.g., ultrafiltration (UF), nanofiltration (NF)), electrofiltration (electrodialysis), ion-exchange, chelation, catalysis, and photocatalysis. Processing cellulose into commercial products enables the wide use of nanocellulose-based materials as adsorbents and catalysts.

Mechanical Performance Evaluation of Repair Materials Suitable for Mechanical Pressurizing Equipment for Cross-Sectional Repair of Concrete Box Structures

This study entailed performance tests to confirm the bond performance of the proposed new repair material and the pressurization effect of the developed mechanical pressurizing equipment. The physical property changes of the new repair material were reviewed by varying the mixing ratio of high aluminate cement (HAC)-mixed mortar. Strength tests were performed according to the mixing ratios of polymer and silica fume to improve the bond performance. To improve water retention, the mixing ratios of the cellulose and nylon fibers were adjusted, and the change in water retention was measured. The proposed repair material mixing ratio yielded the best performance when pressure was applied to the repair surface. Comparing the existing repair materials and the new repair material prepared by adjusting the ratios of HAC-mixed mortar, cellulose fiber, redispersible powder resin, and other factors confirmed that the new repair material has a high bond strength.

Concrete Strengthening by Introducing Polymer-Based Additives into the Cement Matrix-A Mini Review.

The modern types of concrete are a mixture of aggregates, cement, water and optional additives and admixtures. In particular, polymer additives seem to be a promising type of component that can significantly change concrete and mortar properties. Currently, the most popular polymer additives include superplasticizers, latexes and redispersible powders. Moreover, in order to improve the properties of concrete-based composite admixtures, which enhance the resistance to cracking, polymer fibres and recycled polymers have been researched. All the types of polymeric materials mentioned above are broadly used in the construction industry. This work summarizes the current knowledge on the different types of popular polymeric additives. Moreover, it describes the correlation between the chemical structure of additives and the macro-behaviour of the obtained concrete.

Recent trends and applications in the research and development activities of redispersible powder: a vision of twenty-first century

Recent trends and applications in the research and development activities of redispersible powder: a vision of twenty-first century

An Evaluation of <i>Dictyophora indusiata</i> Mucilage as a Binder in Tablet Formulations

Dictyophora indusiata known as bamboo mushroom is an edible mushroom in Genus Dictyophora, Family Phallaceae that could produce highly viscous mucilage encased in the peridium. The viscous mucilage is clear-colorless hydrocolloid with high viscosity and high adhesive nature which made it possible to be developed into pharmaceutical excipients. This research work aimed at the application of the mucilage as a tablet binder. The mucilage was prepared as redispersible powder by lyphilization before used. The dried mucilage could be effectively used as a binder in paracetamol tablet formulations both as dry and wet binder. Increasing of the dried mucilage amount caused the stronger tablet with higher disintegration time. The optimum concentrations of the dried mucilage in tablet formulations were 2.0% w/w as dry binder and 1.0% w/w as wet binder. The obtained tablets revealed low friability and fast disintegration time. The drug dissolution was conformable to USP37 standard and comparable to that of commercial product. Accordingly, the Dictyophora indusiata mucilage could be functionally used as a tablet binder

The Rheometric Analysis of the Polymer Modifier's Properties in the Environment of Hydrated Cement.

This paper investigates the effect of polymer modifiers (re-dispersible powder, multifunctional additives, methylhydroxyethylcellulose) on the rheological behavior of emulsions, saturated of calcium hydrosilicates to simulate a hydrating cement structure. The subjects of the study were modified emulsions which had varied concentrations of each additive and they were examined comparatively to a base emulsion. Tests were performed with a CR-rheometer (“Himpribor-1”, Tula, Russia) applying the Searle measuring principle at various shear rates to characterize viscosity properties. The performance of modified mixtures within the operating period was analyzed by using two parameters—effective viscosity (η) and the proportion of structural failure (|m|). The test results showed that the most important factor influencing rheological characteristics is the addition of methylhydroxyethylcellulose additive—the higher additive amount in the emulsion, the higher the viscosity. Furthermore it was noted in the work that adding olefin sulfonate sodium salt causes reduced viscosities as well as lower shear moduli. If ethylhydroxyethylcellulose and ethylene vinyl acetate additives are used in the same mixture together, the rate of structural failure |m| can be relatively similar and low regardless of whether the mixture has large or small viscosity values.

Influence of Redispersible Powder on Properties of Self-Leveling Mortar of Ternary Cementitious System.

The self-leveling mortar (SLM) of a ternary cementitious system with different dosages of redispersible powder (RP) with ordinary Portland cement (OPC), sulfoaluminate cement (SAC), and calcium sulfate (CS) as cementitious materials was investigated with regard to fluidity, bond strength, shrinkage rate, abrasion resistance, flexural strength, and compressive strength. The performance parameters obtained from the experimental test for SLM were weighted values calculated with an analytic hierarchy process (AHP). The comprehensive index of performance was evaluated on the basis of a weighted-sum method, and the optimal dosage of RP was determined according to the comprehensive index. The experimental results demonstrated that the fluidity of SLM decreased with the increase in RP dosage at the beginning but then increased thereafter and decreased rapidly as the dosage went beyond 3.0%. The addition of RP resulted in a significant improvement in bond strength (of SLM), reduction in the shrinkage rate, abrasion loss, early flexural strength and compressive strength, and resistance to cracking. The properties of SLM with 3.0% RP can meet the requirements of the industrial standard for cementitious self-leveling floor mortar. Compared with the SLM without RP, the bond strength of SLM with 3.0% RP was increased by 46.7%, while the shrinkage rate and abrasion loss were reduced by 50% and 71.9% respectively. The weighted values of fluidity, compressive strength, flexural strength, stability, cohesiveness, and abrasion resistance were 0.422, 0.196, 0.196, 0.089, 0.058, and 0.039, respectively. A higher value of the comprehensive index generally denotes a better performance. The comprehensive index of SLM with 3.0% RP was the highest.

Encapsulation of octenidine hydrochloride into bioresorbable polyesters for extended antimicrobial activity

Nosocomial infections remain a serious threat even for patients of highly industrialized countries. These infections occur on surgical sites and wounds, on catheter entry sites, tubes and other indwelling devices. Medical devices providing local antiseptic action over an extended time period represent an opportunity to prevent such infections. One way to achieve this goal is the encapsulation of active molecules into bioresorbable polymer microparticles, which can locally release the compound of interest along a tunable time span depending on the polymer characteristic. In this work, spray drying is used to encapsulate the broad band antiseptic octenidine hydrochloride into a set of poly(d,l-lactide) (PDLLA) and poly(d,l-lactide-co-glycolide) (PLGA) carrier materials with different molecular weights and chain end-groups, forming redispersable powders. It is demonstrated that the carrier materials bearing acid end-groups provide a significantly larger entrapment efficacy comparing with their ester counterparts independently of carrier composition and molecular weight. The quantitative understanding of the release mechanism allows guiding the selection of suitable encapsulating polyesters to tune initial burst and long time release of a given drug. Finally, it is demonstrated on cultures of Staphylococcus epidermidis that the encapsulated and subsequently released OHC has conserved its antiseptic activity, which supports the potential applicability of the approach.

Improvements in setting behavior and strengths of cement paste/mortar with EVA redispersible powder using C-S-Hs-PCE

This work aimed to improve the setting behavior and strengths of cement paste/mortar with ethylene and vinyl acetate copolymer redispersible powder (EVA-DP) using C-S-H seeds and polycarboxylate superplasticizer (C-S-Hs-PCE) and meanwhile explore the reasons for these two improvements by means of the heat flow, water requirement, air content, apparent density and pore size distribution. The experimental results show that C-S-Hs-PCE used in this work notably cuts down the setting behavior and increases the strengths at 3d of mortars with EVA-DP; however, less than 2% C-S-Hs-PCE hardly increases their strengths at 28d. C-S-Hs-PCE promotes the hydration of paste with EVA-DP in several manners; it enhances heat flow in the first deceleration period, the initial several hours in the acceleration period and at the main exothermic peaks/merged peak, or advances the onset of the acceleration period, or shifts the maximum of the hydration rate to earlier time. This promotion in the hydration at different levels is the reason for the shortened setting behavior of paste with EVA-DP in the presence of C-S-Hs-PCE. Except for the promoted hydration, the increased apparent density resulted from lowered water requirement, as well as the less pores, especially the middle and large capillary pores, are the other main contributors to the increment in the strengths of mortar with EVA-DP and C-S-Hs-PCE, especially the strengths at 28d of the mortars with 6% and 10% EVA-DP and 2% C-S-Hs-PCE.

A study of the transport properties of emulsified asphalt powder-modified cement mortar

Emulsified asphalt powder (EAP) is a redispersible powder material prepared by spray drying process using emulsified asphalt as raw material that has been developed following the successful utilization of emulsified asphalt in the ballastless track structures of high-speed railways and in road and bridge engineering. In this study, the influence of EAP on the surface properties, transport properties and pore structure of cement mortar was investigated. The results revealed that EAP can improve the surface properties and reduce the transport properties of cement mortar. Furthermore, it was observed that there are intrinsic links between different transport property parameters of cement mortar incorporating EAP, and that the reduction of transport properties is essentially related to the increase of hydrophobicity and the improvement of pore structure afforded by EAP. The capillary water absorption and the drying mass loss of EAP-modified cement mortar decreased with the reduction of critical pore diameter, indicating that the addition of EAP beneficially reduced the transport properties of cement-based materials, thereby improving their durability.

INFLUENCE OF REDISPERSIBLE POWDERS AND LOW-MODULAR INCLUSIONS ON THE FROST RESISTANCE OF THE FINE-GRAINED CONCRETE CONTACT ZONE

Objectives. The aim of this study was to identify variation patterns of the in-series variation coefficient of adhesive strength to base and the dependency of the frost resistance coefficient on the criterion of adhesion on prescription factors of fine-grained concrete obtained from dry building mixtures based on various Portland cements containing various low-modulus inclusions and redispersible polymer powders from 0 to 3%. According to GOST 31357, the main quality indicators of the hardened mixture or fine-grained concrete, in addition to frost resistance, include the indicator of “frost resistance of the contact zone”, which characterises the ability of the hardened concrete to maintain adhesion to the base during normal separation following a certain number of freeze-thaw cycles.Method. The tests of the main samples were carried out after 75 freeze-thaw cycles in accordance with GOST 31356. The marks of the frost resistance of the contact zone are set from FKZ25 to FKZ100. The number of freeze-thaw cycles is taken as a mark, after which the adhesion strength to the base, determined according to GOST 31356, is at least 80% of the strength of the control samples. The arithmetical average is taken at between at least 5 values, while the variation coefficient measured across a series of adhesion strength values is not considered.Results. The average values of the variation coefficient of adhesion strength were: following 75 cycles of freezing-thawing – 0.224 (in a range from 0.058 to 0.616); following 25 cycles of freezing-thawing – an average of 0.129 (in a range from 0.016 to 0.352). The variation coefficient of adhesion strength can exceed the variation coefficient of compression strength by approximately 2.5 to 3 times. When introducing the redispersible powders into the structure of fine-grained concrete, there is no unambiguous pattern of change in the values of the variation coefficient of adhesion to base and it is possible to increase or decrease this value, while the values of the variation coefficient of adhesion can vary by an order of magnitude.Conclusion. For all concretes, there is a tendency of increase of the coefficient of frost resistance with a decrease in the adhesion variation coefficient both after hardening under normal conditions as well as during cyclic freezing and thawing. When conditions VF/V28A<1 are met, the coefficient of frost resistance of adhesion, determined when considering the variation coefficient, will satisfy the requirements of GOST 31356.

Effect of Dosage of Redispersible Powders on the Properties of Fine Concrete

The RPP introduction has been established up to 3% by weight of the dry concrete mix is ​​accompanied by a decrease in the fine-grained concrete tensile strength in compression to 40% and in tension during bending to 15%. The relationship between the tensile strength limit in bending and compression for the studied materials is invariant to the cement and RPP type. With the concrete tensile strength in tensile bending increase, there is a weak tendency to a decrease in the adhesion ratio value to the concrete base and tensile strength. The adhesion amount to the concrete base with RPP increasing dosage can either increase or decrease after a certain limit, depending on the cement properties. The maximum increase in adhesion to the concrete base was 37%, while the decrease in the concrete elasticity initial modulus was 26%.

HYDRO-ISOLATING DECORATIVE PLASTER FOR CONCRETE RESERVOIRS

Development of Ukrainian build materials production takes place in the direction of new competitive dry build mixtures creation with polyfunctional and decorative setting, including for implementation of hard hydro-isolating plaster of concrete reservoirs, assuming introduction of dyes-pigments either directly in the complement of mixture or in the special composition for implementation of decorative integumentary layer. The competitiveness of such dry build mixture is provided by the innovative decision on plasticiting, compacting and hydro-phobization at hydrative hardening of Portland-cement composition due to introduction to its composition in small concentrations of inexpensive and unscarce additions, in particular, of calcium nitrate. For expansion of application domain of such hydro-isolating compositions introduction of pigments-dyes with the simultaneous presence of modifying additions is possible, in particular, of ammonium sulfate, sulfite yeast brew or technical lignosulfonate (in the amount of to 0,2 mass. %) or redispersible powders of a vinyl-acetate type (to 0,005 – 0,1 mass. % from mass of cement). Scenery of the hard hydro-isolating plaster executed on the basis of base dry build mixture assumes application of the prepared compositions present at the market of build materials of Ukraine (for example, Ceresit CT-64).

Sonochemical Synthesis and Properties of YVO4:Eu3+ Nanocrystals for Luminescent Security Ink Applications

Solutions and redispersible powders of nanocrystalline, europium-doped YVO4, are prepared via a wet chemical method using the ultrasonic processor (sonochemical) and microwave and thermal stirring. From X-ray diffraction (XRD) results, YVO4:Eu3+ nanoparticles synthesized using sonochemical method have better crystallinity than those prepared using thermal stirring and microwave methods exhibiting the tetragonal structure known for bulk material. From field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) results, it is found that the size of nanoparticles is around 25 nm and increasing after annealing at 900°C. From UV-Vis result, there is a peak at 270 nm corresponding to the absorption of VO43− groups. The photoluminescence (PL) results clearly show the strongest red emission peak at the wavelength around 618 nm. The highest luminescent intensity is obtained for the sample prepared by the sonochemical method at pH = 12 and annealing temperature at 900°C for 4 h. The average lifetimes of the Eu3+ ions in the samples annealed at 300, 600, and 900°C for 1 h at 618 nm emission under 275 nm excitation are 0.36, 0.62, and 0.64 ms, whereas sample annealed at 900°C for 4 h has lifetime of 0.70 ms. The security ink, containing synthesized YVO4:Eu3+ nanoparticles, is dispersed in glycerol and other necessary solvents. The experimental security labels are printed by inkjet using the electrohydrodynamic printing technique. The resulting lines represented to the security labels are analyzed by the 3D microscope equipment and UV 20 W mercury lamp with a wavelength of ∼254 nm. The seamless line of the printed security label has the value of the width at ∼230 μm, thickness at ∼0.68 μm, and distance between two adjacent lines at 800 μm. This result is compatible for producing security labels in small size (millimeter) in order to increase security property.

Can spray freeze-drying improve the re-dispersion of crystalline nanoparticles of pure naproxen?

Spray freeze drying (SFD) was used to prepare re-dispersible powders of crystalline, pure-drug nanodispersions of naproxen in lactose and stabilized with hydroxypropyl cellulose. The particle size of the rehydrated powders was determined using static light scattering/Mie analysis. The nanoparticles present in the SFD powders were aggregated but could be dispersed on re-dispersion with water and stirring either with or without additional ultrasonic treatment. The disaggregation of the SFD nanoparticles was superior to that reported in the literature for spray dried nanoparticles of the same composition. It appears that the moderately-rapid freezing of the large spray droplets in LN2 during SFD produces less aggregation than does evaporative drying of the much smaller droplets during spray drying. Re-dispersion was also found to depend strongly on the pH of the original nanodispersion. The solubility of this weak acid is greater at higher pH which resulted in formation of a dissolved fraction of drug in the nanodispersions during media milling. After SFD, the dissolved naproxen fraction formed an amorphous solid which re-dissolves on re-hydration whereas the crystalline nanoparticles disaggregate.

Core-Shell Morphology of Redispersible Powders in Polymer-Cement Waterproof Mortars.

Redispersible powders based on soft core-hard shell polymer particles can be used as additives in polymer-cement mortars. The role of this morphology on the spray-drying production of these powders and on the crack-bridging properties of the corresponding cement-based membranes is investigated. Different polymer latexes at high solid content with varied core-shell ratio, shell thickness and chemical composition (hardness) were prepared from styrene and 2-ethylhexyl acrylate monomers via semi-batch emulsion polymerization. The latexes were characterized in terms of size, composition, and glass transition temperature (T), and spray-dried to obtain redispersible polymer powders (RPPs) using poly (vinyl alcohol) and limestone powder as anti-caking agents. The polymer powders were mixed with a mortar mixture and redispersed in water to produce cement-based membranes, which were tested for crack-bridging properties at different temperatures. The results showed that it was not possible to spray-dry a dispersion of homogeneous polymer particles with T of −25 C, unless these particles are protected by much harder (high T) shell. In particular, it was observed that a thicker shell improved the spray-ability, but lowered the crack-bridging properties of the produced membrane. A trade-off between these two was revealed to be the key for the optimal design of the polymer nanoparticles, as proven by the systematic study of the core-shell morphology reported in this work. The best compromise was shown to consist of particles larger than 300 nm, shell thickness of about 5 nm, and core-shell ratio of 97%, with styrene content in the shell not larger than 80% to avoid excessive hydrophobicity.

Freeze drying of polyelectrolyte complex nanoparticles: Effect of nanoparticle composition and cryoprotectant selection

This work investigates the impact of nanoparticle (NP) composition and effectiveness of cryo-/lyo-protectants in a freeze drying process, which was employed to convert liquid dispersions of polyelectrolyte complex (PEC) NPs into completely redispersible powders. PEC NPs, with and without peptide, were produced by complex coacervation. The cryo-/lyo-protectants investigated were mannitol, trehalose (TRE) and poly(ethylene glycol) (PEG). The solid state of lyophilised powders was studied by thermal analysis and X-ray diffraction. Cytotoxicity studies were done by MTS assay and flow cytometry. The presence of a cryoprotectant was essential to achieve a successful powder reconstitution. The concentration of TRE was optimised for each type of PEC NPs. Protamine- and hyaluronate-based NPs reconstituted better than chitosan- and chondroitin sulphate-based NPs, respectively. PEG polymers were found to be more effective cryoprotectants than TRE and best results were achieved using co-freeze drying of NPs with TRE and PEG. These ternary NPs/TRE/PEG samples were crystalline, with expected better storage stability. PEG polymers were well tolerated by Caco-2 cells, with the exception of linear PEG 10 kDa. This work shows that, as regards the formulation design and maximising NP loading in the dried product, optimisation of the cryoprotectant type and content is needed as it is highly dependent not only on the type of polyelectrolyte pair in the PEC, but also the polyions ratio.