Water-based Dispersions Research Articles

Electrophoretic deposition of plasma activated sub-micron alumina powder

The positive effect of plasma mediated treatment of powder fraction in water-based dispersion is a rather well documented fact. Despite its importance for ceramic processing, the applicability of plasma treatment of ceramic particles in a non-aqueous dispersions remains unexplored. In the presented article, a specific planar type of dielectric barrier discharge - Diffuse Coplanar Surface Barrier Discharge (DCSBD), operated in atmospheric pressure air was used for the surface activation of sub-micron alumina particles. These were consequently dispersed in organic solvent of 2-propanol and evaluated for the performance during the process of electrophoretic deposition (EPD). The surface of ceramic particles and the dispersion behaviour were investigated using thermogravimetric analysis, XPS, measurement of zeta potential and particle size distribution. Plasma treatment of ceramic particles had a substantial effect on the deposition rate, which caused a significant reduction of surface roughness and slight improvement of the density and mean grain size of the fabricated coatings. Moreover, the plasma treatment resulted in a simultaneous anodic and cathodic EPD.

Thermal insulation coating based on water-based polymer dispersion

For Russia, due to its long winter period, improvement of thermal insulation properties of envelope structures by applying thermal insulation paint and varnish coating to its inner surface is considered perspective. Thermal insulation properties of such coatings are provided by adding aluminosilicate microspheres and aluminum pigment to their composition. This study was focused on defining the effect of hollow aluminosilicate microspheres and aluminum pigment on the paint thermal insulation coating based on water-based polymer dispersion and on its optimum filling ratio. The optimum filling ratio was determined using the method of critical pigment volume concentration (CPVC). The optimum filling ratio was found equal to 55%.

Thermal insulation coating based on water-based polymer dispersion

For Russia, due to its long winter period, improvement of thermal insulation properties of envelope structures by applying thermal insulation paint and varnish coating to its inner surface is considered perspective. Thermal insulation properties of such coatings are provided by adding aluminosilicate microspheres and aluminum pigment to their composition. This study was focused on defining the effect of hollow aluminosilicate microspheres and aluminum pigment on the paint thermal insulation coating based on water-based polymer dispersion and on its optimum filling ratio. The optimum filling ratio was determined using the method of critical pigment volume concentration (CPVC). The optimum filling ratio was found equal to 55%.

Distinct dispersion stability of various TiO2 nanopowders using ammonium polyacrylate as dispersant

The dispersion stabilities of three titania (TiO2) nanopowders with different particle sizes and surface chemistries in aqueous suspensions containing a common water-based dispersant, ammonium polyacrylate (PAA-NH4), have been investigated and compared. According to adsorption isotherm and Fourier transform infrared spectroscopy analyses, the adsorption conformations of PAA-NH4 are distinct for the different TiO2 nanopowders. In addition, PAA-NH4 exhibited the greatest adsorption affinity to the larger, hydrophilic TiO2 nanopowder and the least affinity to smaller, hydrophobic nanopowder. From sedimentation and rheological results, the dispersion stability of the larger, hydrophilic TiO2 nanopowder was demonstrated to be the greatest. Based on thermodynamic and kinetic calculations for the stabilization energies, the larger, hydrophilic TiO2 nanopowder was also shown to be the best-stabilized powder, although it settles faster than the smaller, hydrophilic TiO2 nanopowder; this is due to the greater affection of sedimentation flux on the larger nanopowder. In contrast, the hydrophobic TiO2 nanopowder formed a gel-like structure in the aqueous suspension when the solid content was greater than 10wt%, which is attributed to polymer bridging between PAA-NH4-adsorbed TiO2 nanoparticles.

Electromechanical properties of polyamide/lycra fabric treated with PEDOT:PSS

One of the challenges in smart textiles is to develop suitable multifunctional materials that can address simultaneously several characteristics such as durability, stretchability, lightweight, and conductivity. Conductive polymers which showed success in different technological fields like polymer solar cells and light emitting diodes are promising in many smart textile applications. In this work, we treated a common polyamide/lycra knitted fabric with PEDOT:PSS for stretchable e-textiles. PEDOT:PSS, with DMSO as a conductivity enhancer and different ratios of water-based polyurethane dispersions as a binder, was applied to the fabric with simple immersion and coating applications. The effect of different application methods and binder ratio on the surface resistance of the fabric was monitored with four point probe electrical surface resistance measurement systems. Samples prepared by immersion technique are more uniform and have higher conductivity than those prepared by a coating technique. SEM images showed that PEDOT:PSS is incorporated into the structure in the immersion method while in the coating it is majorly present on the surface of the fabric. The tensile measurement showed that the acidic PEDOT:PSS and polyurethane dispersion coating has no adverse effect on the tensile strength of the fabric. The coated samples can be stretched up to 700% while still reasonably conductive. The resistance increases only by a small amount when samples were stretched cyclically by stretching 100%. Generally, samples prepared by the immersion method maintained better conductivity while stretching than those by a coating method. The washing fastness of the samples was also assessed.

Mechanochemical Synthesis of PEDOT:PSS Hydrogels for Aqueous Formulation of Li-Ion Battery Electrodes.

Water-soluble binders can enable greener and cost-effective Li-ion battery manufacturing by eliminating the standard fluorine-based formulations and associated organic solvents. The issue with water-based dispersions, however, remains the difficulty in stabilizing them, requiring additional processing complexity. Herein, we show that mechanochemical conversion of a regular poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) water-based dispersion produces a hydrogel that meets all the requirements as binder for lithium-ion battery electrode manufacture. We particularly highlight the suitable slurry rheology, improved adhesion, intrinsic electrical conductivity, large potential stability window and limited corrosion of metal current collectors and active electrode materials, compared to standard binder or regular PEDOT:PSS solution-based processing. When incorporating the active materials, conductive carbon and additives with PEDOT:PSS, the mechanochemical processing induces simultaneous binder gelation and fine mixing of the components. The formed slurries are stable, show no phase segregation when stored for months, and produce highly uniform thin (25 μm) to very thick (500 μm) films in a single coating step, with no material segregation even upon slow drying. In conjunction with PEDOT:PSS hydrogels, technologically relevant materials including silicon, tin, and graphite negative electrodes as well as LiCoO2, LiMn2O4, LiFePO4, and carbon-sulfur positive electrodes show superior cycling stability and power-rate performances compared to standard binder formulation, while significantly simplifying the aqueous-based electrode assembly.

Technical and economic analysis of solvent-based lithium-ion electrode drying with water and NMP

ABSTRACTProcessing lithium-ion battery (LIB) electrode dispersions with water as the solvent during primary drying offers many advantages over N-methylpyrrolidone (NMP). An in-depth analysis of the comparative drying costs of LIB electrodes is discussed for both NMP- and water-based dispersion processing in terms of battery pack $/kWh. Electrode coating manufacturing and capital equipment cost savings are compared for water vs. conventional NMP organic solvent processing. A major finding of this work is that the total electrode manufacturing costs, whether water- or NMP-based, contribute about 8–9% of the total pack cost. However, it was found that up to a 2 × reduction in electrode processing (drying and solvent recovery) cost can be expected along with a $3–6 M savings in associated plant capital equipment (for a plant producing 100,000 10-kWh Plug-in Hybrid Electric Vehicle (PHEV) batteries) using water as the electrode solvent. This paper shows a different perspective in that the most important benefits of aqueous electrode processing actually revolve around capital equipment savings and environmental stewardship and not processing cost savings.

Development Strategies and Prospects of Nano-based Smart Pesticide Formulation.

Pesticides are important inputs for enhancing crop productivity and preventing major biological disasters. However, more than 90% of pesticides run off into the environment and reside in agricultural products in the process of application as a result of the disadvantages of conventional pesticide formulation, such as the use of a harmful solvent, poor dispersion, dust drift, etc. In recent years, using nanotechnology to create novel formulations has shown great potential in improving the efficacy and safety of pesticides. The development of nano-based pesticide formulation aims at precise release of necessary and sufficient amounts of their active ingredients in responding to environmental triggers and biological demands through controlled release mechanisms. This paper discusses several scientific issues and strategies regarding the development of nano-based pesticide formulations: (i) construction of water-based dispersion pesticide nanoformulation, (ii) mechanism on leaf-targeted deposition and dose transfer of pesticide nanodelivery system, (iii) mechanism on increased bioavailability of nano-based pesticide formulation, and (iv) impacts of nanoformulation on natural degradation and biosafety of pesticide residues.

Anionic water-based polyurethane dispersions for antimicrobial coating application

A new halo-ester diol has been synthesized by esterification reaction of trichloroacetic acid and pentaerythritol by using p-Toluenesulfonic acid as a catalyst. The synthesized diol was reacted with isophorone diisocyanates, polyester polyol, di-methylol propionic acid to form polyurethane dispersion. The antimicrobial properties of polyurethane dispersions were evaluated against Gram-negative E. coli and Gram-positive bacteria L. plantarum by Kirby–Bauer test. The structure of the diol was examined using Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance and mass spectroscopy. The physical, chemical and thermal properties such as viscosity, particle size, chemical resistance and DSC, XRD, SEM and GPC of polyurethane dispersion were evaluated. The significant effect of diol and its chain length, particle size and zeta potential properties of resulting polyurethane dispersion were investigated.

Nanocellulose in Thin Films, Coatings, and Plies for Packaging Applications: A Review

This review article was prompted by a remarkable growth in the number of scientific publications dealing with the use of nanocellulose (especially nanofibrillated cellulose (NFC), cellulose nanocrystals (CNC), and bacterial cellulose (BC)) to enhance the barrier properties and other performance attributes of new generations of packaging products. Recent research has confirmed and extended what is known about oxygen barrier and water vapor transmission performance, strength properties, and the susceptibility of nanocellulose-based films and coatings to the presence of humidity or moisture. Recent research also points to various promising strategies to prepare ecologically-friendly packaging materials, taking advantage of nanocellulose-based layers, to compete in an arena that has long been dominated by synthetic plastics. Some promising approaches entail usage of multiple layers of different materials or additives such as waxes, high-aspect ratio nano-clays, and surface-active compounds in addition to the nanocellulose material. While various high-end applications may be achieved by chemical derivatization or grafting of the nanocellulose, the current trends in research suggest that high-volume implementation will likely incorporate water-based formulations, which may include water-based dispersions or emulsions, depending on the end-uses.

Nanocellulose in Thin Films, Coatings, and Plies for Packaging Applications: A Review

This review article was prompted by a remarkable growth in the number of scientific publications dealing with the use of nanocellulose (especially nanofibrillated cellulose (NFC), cellulose nanocrystals (CNC), and bacterial cellulose (BC)) to enhance the barrier properties and other performance attributes of new generations of packaging products. Recent research has confirmed and extended what is known about oxygen barrier and water vapor transmission performance, strength properties, and the susceptibility of nanocellulose-based films and coatings to the presence of humidity or moisture. Recent research also points to various promising strategies to prepare ecologically-friendly packaging materials, taking advantage of nanocellulose-based layers, to compete in an arena that has long been dominated by synthetic plastics. Some promising approaches entail usage of multiple layers of different materials or additives such as waxes, high-aspect ratio nano-clays, and surface-active compounds in addition to the nanocellulose material. While various high-end applications may be achieved by chemical derivatization or grafting of the nanocellulose, the current trends in research suggest that high-volume implementation will likely incorporate water-based formulations, which may include water-based dispersions or emulsions, depending on the end-uses.

環境調和型水性ポリウレタン樹脂

環境調和型水性ポリウレタン樹脂

Eco-friendly fabrication of PBDTTPD:PC71BM solar cells reaching a PCE of 3.8% using water-based nanoparticle dispersions

In this work we report on the eco-friendly processing of PBDTTPD:PC71BM organic solar cells using water-based nanoparticle (NP) dispersions. The polymer:fullerene NPs are prepared using the miniemulsion-solvent evaporation method, despite employing high-boiling solvents. Polymer solar cells are fabricated from these blend NPs and the device characteristics are studied in function of annealing time and temperature. The photoactive layer formation is carefully analyzed using atomic force microscopy (AFM). Annealing for longer times significantly increases the power conversion efficiency (PCE), up to 3.8%, the highest value reported for surfactant based NP solar cells. Our work shows that the low bandgap polymer PBDTTPD has the ability to afford reasonable efficiencies in NP solar cells in combination with PC71BM and paves the way to a truly eco-friendly processing of organic photovoltaics (OPVs).

Kao buys Collins (US) & Chimigraf (Spain) to refine inkjet water-based pigment dispersion technology

Kao buys Collins (US) & Chimigraf (Spain) to refine inkjet water-based pigment dispersion technology

Surface modification of multiwall carbon nanotubes by sulfonitric treatment

Carbon nanotubes are widely used for electronic, mechanical, and optical devices due to their unique structural and quantum characteristics. The species generated by oxidation on the surface of these materials permit binding new reaction chains, which improves the dispersibility, processing and compatibility with other materials.Even though different acid treatments and applications of these CNT have been reported, relatively few research studies have focused on the relationship between the acid treatment and the formation of nanodefects, specific oxidized species or CNT surface defects.In this work, multiwall carbon nanotube (MWCNT) oxidation at 90°C was characterized in order to determine the acid treatment effect on the surface.It was found that oxidized species are already present in MWCNT without an acid treatment, but there are not enough to cause water-based dispersion. The species were identified and quantified by infrared spectroscopy and X-ray photoelectron spectroscopy. Also, transmission electron microscopy observations showed not only modifications of the oxidized species, but also morphological damage on the surfaces of MWCNT after being subjected to the acid treatment. This effect was also confirmed by Raman spectroscopy. The acid treatment generates higher oxidized species, decreasing the zeta potential in the whole pH range.

Anionic waterborne polyurethane dispersions from maleated cotton seed oil polyol carrying ionisable groups

A novel class of bio-based, DMPA free, catalyst free, anionic waterborne polyurethane dispersions (PUD) have been successfully synthesized. Hydroxylated cottonseed oil has been maleated using maleic anhydride to introduce hydroxyl groups and ionisable carboxyl groups. This maleated polyol (MAHCSO) has been employed to develop water-based polyurethane dispersions through a prepolymer method and chain extension with dihydrazides at the dispersion stage. The –OH groups of the MAHCSO formed urethane bonds, and the carboxylate groups acted as an internal ionizer to stabilize the polymer dispersion in water. The significant effect of the ionic content in the polyol (MAHCSO) and chain length of dihydrazide on particle size, physico-chemical, thermal and mechanical properties of the resulting PUD films were investigated.

Fabrication of Tunable, High‐Refractive‐Index Titanate–Silk Nanocomposites on the Micro‐ and Nanoscale

The combination of water-based titanate nanosheets dispersion and silk fibroin solution allows the realization of a versatile nanocomposite. Different fabrication techniques can be easily applied on these nanocomposites to manipulate the end form of these materials on the micro- and nanoscale. Easy tunability of the refractive index from n = 1.55 up to n = 1.97 is achieved, making it attractive for flexible, biopolymer-based optical devices.

Synthesis of Water-Based Dispersions of Polymer/TiO₂ Hybrid Nanospheres.

We develop a strategy for preparing water-based dispersions of polymer/TiO2 nanospheres that can be used to form composite materials applicable in various fields. The formed hybrid nanospheres are monodisperse and possess a hierarchical structure. It starts with the primary TiO2 nanoparticles of about 5 nm, which first assemble to nanoclusters of about 30 nm and then are integrated into monomer droplets. After emulsion polymerization, one obtains the water-based dispersions of polymer/TiO2 nanospheres. To achieve universal size, it is necessary to have treatments with intense turbulent shear generated in a microchannel device at different stages. In addition, a procedure combining synergistic actions of steric and anionic surfactants has been designed to warrant the colloidal stability of the process. Since the formed polymer/TiO2 nanospheres are stable aqueous dispersions, they can be easily mixed with TiO2-free polymeric nanoparticle dispersions to form new dispersions, where TiO2-containing nanospheres are homogeneously distributed in the dispersions at the nanoscale, thus leading to various applications. As an example, the proposed strategy has been applied to generate polystyrene/TiO2 nanospheres of about 100 nm in diameter.

3D bioprinting of neural stem cell-laden thermoresponsive biodegradable polyurethane hydrogel and potential in central nervous system repair

The 3D bioprinting technology serves as a powerful tool for building tissue in the field of tissue engineering. Traditional 3D printing methods involve the use of heat, toxic organic solvents, or toxic photoinitiators for fabrication of synthetic scaffolds. In this study, two thermoresponsive water-based biodegradable polyurethane dispersions (PU1 and PU2) were synthesized which may form gel near 37 °C without any crosslinker. The stiffness of the hydrogel could be easily fine-tuned by the solid content of the dispersion. Neural stem cells (NSCs) were embedded into the polyurethane dispersions before gelation. The dispersions containing NSCs were subsequently printed and maintained at 37 °C. The NSCs in 25–30% PU2 hydrogels (∼680–2400 Pa) had excellent proliferation and differentiation but not in 25–30% PU1 hydrogels. Moreover, NSC-laden 25–30% PU2 hydrogels injected into the zebrafish embryo neural injury model could rescue the function of impaired nervous system. However, NSC-laden 25–30% PU1 hydrogels only showed a minor repair effect in the zebrafish model. In addition, the function of adult zebrafish with traumatic brain injury was rescued after implantation of the 3D-printed NSC-laden 25% PU2 constructs. Therefore, the newly developed 3D bioprinting technique involving NSCs embedded in the thermoresponsive biodegradable polyurethane ink offers new possibilities for future applications of 3D bioprinting in neural tissue engineering.

Inkjet Fabrication of Copper Patterns for Flexible Electronics: Using Paper with Active Precoatings.

Low-cost solution-processing of highly conductive films is important for the expanding market of printed electronics. For roll-to-roll manufacturing, suitable flexible substrates and compatible postprocessing are essential. Here, custom-developed coated papers are demonstrated to facilitate the inkjet fabrication of high performance copper patterns. The patterns are fabricated in ambient conditions using water-based CuO dispersion and intense pulsed light (IPL) processing. Papers using a porous CaCO3 precoating, combined with an acidic mesoporous absorption coating, improve the effectiveness and reliability of the IPL process. The processing is realizable within 5 ms, using a single pulse of light. A resistivity of 3.1 ± 0.12 μΩ·cm is achieved with 400 μm wide conductors, corresponding to more than 50% of the conductivity of bulk copper. This is higher than previously reported results for IPL-processed copper.