Dry-coating Process Research Articles

Solvent-free battery electrodes

A new solvent-free manufacturing process could make batteries more sustainable and cut manufacturing costs by 15% and energy use by 47% ( Joule 2023, DOI: 10.1016/j.joule.2023.04.006 ). It could also be faster-charging than today’s electrodes. Manufacturers make electrodes by coating metal foils with a slurry of a solvent and battery materials. Then they recover the solvent and dry the electrodes. The energy-intensive process uses ovens the length of a football field. Alternatively, Yan Wang of Worcester Polytechnic Institute, Heng Pan of Texas A&M University, and their colleagues spray a dry, powdery mix of electrode materials onto metal foils. An electric field at the sprayer’s tip applies a charge to the powder so it forms a uniform coating on the grounded metal substrate. The researchers then use pressure rollers to compact the material and form a dense electrode. Other researchers have developed a dry-coating process that involves extruding electrode materials into

Sustainable Protein-Based Binder for Lithium-Sulfur Cathodes Processed by a Solvent-Free Dry-Coating Method.

In the market for next-generation energy storage, lithium-sulfur (Li-S) technology is one of the most promising candidates due to its high theoretical specific energy and cost-efficient ubiquitous active materials. In this study, this cell system was combined with a cost-efficient sustainable solvent-free electrode dry-coating process (DRYtraec®). So far, this process has been only feasible with polytetrafluoroethylene (PTFE)-based binders. To increase the sustainability of electrode processing and to decrease the undesired fluorine content of Li-S batteries, a renewable, biodegradable, and fluorine-free polypeptide was employed as a binder for solvent-free electrode manufacturing. The yielded sulfur/carbon dry-film cathodes were electrochemically evaluated under lean electrolyte conditions at coin and pouch cell level, using the state-of-the-art 1,2-dimethoxyethane/1,3-dioxolane electrolyte (DME/DOL) as well as the sparingly polysulfide-solvating electrolytes hexylmethylether (HME)/DOL and tetramethylene sulfone/1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TMS/TTE). These results demonstrated that the PTFE binder can be replaced by the biodegradable sericin as the cycle stability and performance of the cathodes was retained.

Affordable and reliable cationic-anionic magnetic adsorbent: Processing, characterization, and heavy metals removal

In this work, new and superb magnetic adsorbent has been tailored via one-step dry-coating process. The developed magnetic adsorbent was fabricated from Antigorite, Bentonite, and Iron oxide for the first time, showing excellent capability for adsorption of positively and negatively charged contaminants. The structural and surface characteristics of the adsorbent were analyzed by X-ray fluorescence, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, scanning electron microscopy-energy dispersive X-ray spectrometer, and Brunauer–Emmett–Teller analysis techniques. Zeta potential and particle size were sufficiently studied. Adsorption parameters for removal of both cations (Cd2+, Pb2+) and anions (AsO43− and CN−) were investigated. The maximum adsorption capacities were about 219.2 mg/g for Cd2+, 201.2 mg/g for Pb2+, 182.6 mg/g for AsO43−, and 157.7 mg/g for CN−. Freundlich isotherm was the best model to describe the chemisorption behavior of the studied heavy metals. The composite exhibited high regeneration efficiencies of about 92.8% and 91.3% for removal of Cd2+ and AsO43−, respectively after six reuse cycles. The composite could be efficiently implemented, easily separated and successfully recycled exhibiting 90% removal efficiency after treatment of real electroplating wastewater.

Coating Processes of Pharmaceutical Applicability: A Glimpse

Presentation of manuscript is aiming to furnish glimpse on coating processes. Coating is process of snugly covering substrate surface with coating materials (CoM). In due course coating process has gradually developed from sugar-coating to non-aqueous film-coating to aqueous film-coating to specialised-coating processes. In second half of past century sugar-coating was first choice for pharmaceutical industry. Lengthy and tedious processing along with issues of skilled-operator inherited to sugar-coating compelled them to spring-up and improve film-coating. From past five decades, volatile organic solvent (VOS) are preferred over water in film-coating. Momentum for using aqueous solvent in film-coating gets accelerated from past few decades. Nowadays these replacing the VOS based film-coating processes as later inherit issues relating toxicity; safety; worker hygiene & safety; environmental pollution; etc. During process of finding novelty of coating another exploited sphere is coating of particulate substrate surfaces with CoM is to confer them worthy functionalities and applications. In this area both wet- & dry-coating process finds applicability thru modifying and/or altering innate properties of substrate, physically and/or chemically. Dry-coating process basically comprises specialised and novel process & technologies. Nowadays there available numerous conventional, specialised, and novel coating processes. Amongst them state-of-art process are hot-melt coating (HMC) process, aqueous film-coating process, aerosolized coating process, Supercell® coating process, gas-/ vapour-phase process, photo curable coating process, electrical-electrostatic deposition process, Resonant acoustic coating process, thermal and mechanical process, thermo-mechanical process, fluidised-bed processes, etc. Herein conventional, specialised, and novel coating processes are briefed, to update professionals.
 Keywords: Coating, film-coating, novel, process, specialised.

Improving the Effectiveness of the Conical Screen Mill as a Dry-Coating Process at Lab and Manufacturing Scale.

The conical screen mill (comill) is investigated as a dry-coating process for flowability and bulk density enhancement of pharmaceutical powders. In this study, the effectiveness of the comill is improved by using modified screens with reduced open area. In comparison to the screens provided by the comill manufacturer, the modified screens increase mean residence time of the process and improve the extent of flowability and bulk density enhancement. The effectiveness of the comill as a dry-coating process is demonstrated using Avicel PH 105, a fine grade of microcrystalline cellulose, as a model cohesive powder. The process is evaluated thoroughly using a lab scale comill and scalability is demonstrated using a manufacturing scale model. The use of the modified screens is also compared against the so-called "multi-pass" approach in which material is passed through the comill, collected, and passed through once or several times. While the "multi-pass" approach is offered as a simple method to increase mean residence time and to improve process effectiveness, the use of the modified screens is shown to be the superior approach. Due to the ubiquitous use of the comill and the improvement in effectiveness attained in this study, dry-coating is shown to be a practical and readily implemented process for the pharmaceutical industry.

Inhibition of Gas-Evolved Electrolyte Decomposition in Cylindrical Li-Ion Battery Cells of Ni-Rich Layered Oxide with a Dry Coating Process Without Thermal Annealing

Inhibition of Gas-Evolved Electrolyte Decomposition in Cylindrical Li-Ion Battery Cells of Ni-Rich Layered Oxide with a Dry Coating Process Without Thermal Annealing

Design and preparation of nanocomposite acrylate coating agents for binder-free dry coating of 100 µm-sized drug-containing particles and their coating performance

For binder-free dry particulate coating to prepare controlled-release micron-sized particles, we designed nanocomposite coating agents with the intention to form a core-shell structure composed of two types of acrylic polymers with different glass transition temperatures (Tg) and evaluated their coating performance. A series of nanocomposite acrylic latexes synthesized by emulsion polymerization was freeze-dried after salting-out to create the powder form. An ion-exchange resin loaded with diclofenac sodium (DS, a model drug) (IER-DS) with a median diameter of approximately 100 µm was used as the core particle. Dry coating of the IER-DS with nanocomposite coating agents was carried out using a laboratory-made coating apparatus assisted with mild-intensity vibration and zirconia bead impaction. The coated particles were cured by heating at a temperature 20 °C higher than the Tg for 12 h to complete the film-forming process. It was found that the highest coating efficiency (more than 70%) and a remarkably prolonged release period of the drug (the time required for 50% release reached approximately 12 h) could be achieved when nanocomposite coating agents with a soft polymeric core (Tg = 30 °C) and a hard polymeric shell (Tg = 80 °C) were applied. In contrast, nanocomposite coating agents with a combination of a hard polymeric core and a soft polymeric shell resulted in lower coating efficiency. These results demonstrate that nanocomposite polymeric coating agents composed of a soft core and a hard shell are effective for the production of drug-loaded microparticles with a prolonged release function by a binder-free dry-coating process.

Feasibility of using organosilane dry-coated detoxified quartzes as raw material in different industrial sectors

Respirable crystalline silica (RCS), in the form of quartz and cristobalite from occupational sources, was classified by the International Agency for Research on Cancer (IARC) as carcinogenic to humans (category 1). In addition, RCS has recently been included in the Directive (EU) 2017/2398 about carcinogens and mutagens at work. Numerous studies suggest that the toxicity of quartz is conditioned by density and distribution of surface silanol groups, and it has been widely demonstrated at lab scale that masking these silanol groups significantly reduces silica toxicity. Based on these findings, a detoxifying, wet-coating method, using organosilanes as coating agent for reactive surface silanols, was previously developed and tested at industrial scale. In the present work, a new dry-coating process (patent pending) also using organosilanes was developed and applied to detoxify quartzes from different industrial branches. Dry-coating efficiency and stability were assessed and confirmed by both in-vitro tests (lactate dehydrogenase release and alkaline comet assay) and an intratracheal instillation study in rats. Finally, industrial trials were performed by different quartz end users (elastomers, foundry, adhesives, pigments and glazes) to evaluate the technical and economic feasibility of implementing this dry-coating process at industrial scale. From the obtained results, it can be drawn that the proposed methodology seems to represent a promising strategy to significantly reduce the risk associated with the handling of RCS-bearing materials. This RCS coating approach shows enough flexibility to be adapted to different industrial processes without significantly interfering with product quality.

Thermo-Mechanical Dry Coating as Dry Coating Process is for Pharmaceuticals

The manuscript aims to provide glimpse on updated information relating thermo-mechanical dry coating processes (TMDCP) suiting in modifying surface attributes of fine and ultra-fine particle (FiUlFiP). FiUlFiPs are the integral component of pharmaceutical processes. They exhibit complex and queer properties, are conferred mostly from their surface attributes colligated with their higher surface area. Particle engineering technocrats extensively working for modifying surface & surface attributes of FiUlFiPs. These efforts are to find their worthy applications & new functionalities. Among available diverse particle engineering technologies/ process, TMDCP, a dry coating process (DCP), advocated being worthy and efficient. The TMDCP finds multidisciplinary applications, mostly in drug development & drug delivery. Said DCP involves fixing and/or attaching coating material (CoM) as particles herein synonym guest particle (GP) onto core/substrate particle (CSP) herein synonym host particle (HP). Attaching/ fixing the GPs onto HPs, in TMDCP, involve their mechanical and/or thermal interactions. Scientific literatures are evidencing diverse techniques and/or process, basing on discussed interactions. Amongst them novel techniques/ processes are Hybridization, Magnetically assisted impaction coating process (MAICP), Mechanofusion, Theta-composer, and high shear compaction. In this area diverse devices/ equipments are prevailing in market. Important are Hybridizer, Magnetically assisted impaction coater (MAIC), Theta-composer, Mechanofusion, Quadro Comil®, Cyclomix®, and many others. Attempt of this article is to discuss and present their method of working, working principle, applicability, limitations, and benefits. Contained information might be beneficial for professionals of pharmaceutical and allied field.
 Keywords: dry coating, equipment, particles, processes, thermo-mechanical.

Slag erosion-resistant coating for periclase-magnesia-aluminum spinel brick

The magnesia-carbon bricks are used at the ladle slag line adds carbon to molten steel and thus has an adverse effect on the smelting process. Steel production enterprises hope to remove carbon from the ladle slag line. This study presents a Silica sol (SS)–magnesium aluminate spinel(MA) coating that can be applied to the surfaces of periclase–MA spinel brick (spinel brick) to improve their slag erosion resistance, facilitating the elimination of carbon from the ladle slag line. The slag corrosion resistance mechanism of a spinel brick covered with the SS–MA coating was analyzed through scanning electron microscopy and simulation using FactSage software. The results show that increasing the SS content (CSS) led to the formation of fine cracks during the coating-drying process and was detrimental to the slag erosion resistance of the coating. The optimum CSS was 20%. In the high-temperature slag erosion experiment, the MA in the coating was capable of forming solid solutions with Fe and Mn in the slag, and the nano-SiO2 in the coating interacted with the slag, increasing the viscosity of the slag and reducing its penetration. In addition, the presence of the coating extended the penetration path of the slag and reduced the contact area between the slag and the spinel brick and their chances to undergo chemical reactions, thereby protecting the spinel brick from slag erosion. The coated spinel bricks outperformed the magnesia-carbon brick in terms of slag erosion resistance, providing a basis for selecting carbon-free refractory materials for the ladle slag line.

Improving the effectiveness of the Comil as a dry-coating process: Enabling direct compaction for high drug loading formulations

This study investigated the Comil as a dry-coating process to enhance the flowability of pharmaceutical powders. As a major novelty, the mean residence time was measured and the effect of processing conditions on the extent of flowability enhancement was evaluated. As opposed to previous work which used a “multi-pass” approach to increase residence time and to improve the effectiveness of the Comil, this study reduces the open area of the screen. This simple modification to the screen increases residence time and allowed the Comil to improve flowability of a model cohesive powder, Avicel PH 105, as effectively as the LabRAM blender which was used as a benchmarking dry-coating device. The comilling process was applied to four fine and poorly flowing APIs which were subsequently used in high drug loading (50% w/w) formulations. In comparison to conventional blending, it was shown that comilling can significantly enhance the manufacturability of the formulations.

Dispersion state of TiO2 pigment particles studied by ultra-small-angle X-ray scattering revealing dependence on dispersant but limited change during drying of paint coating

The dispersion state of titania (TiO2) pigment particles in coatings is crucial to obtain optimal optical properties while minimizing the consumption of pigment, and thereby the cost and environmental impact of the product. By having the particles well-dispersed, with limited aggregation, the best opacity can be obtained with the smallest amount of pigment. The aggregation of titania particles is typically investigated using various microscopy techniques on the dry coating. In this work, Small-Angle X-ray Scattering was applied as a non-invasive tool to probe the distribution of titania during the coating drying process. The titania pigment particles were dispersed by using either a polymeric surfactant or nanosized silica particles as dispersant. The use of silica nanoparticles resulted in the highest degree of dispersion, both in dilute suspension, and in acrylic and alkyd-based coating formulations. Only minor changes in the aggregate structure was observed during drying of the coatings, indicating that the optical performance is to a large extent determined already before drying, in the wet paint. For the formulations containing nanosilica dispersant, the drying time was increased by diluting the paint or by adding less dryer catalyst. The former resulted in a reduced pigment dispersion, whereas the latter seems to increase the degree of dispersion. In both cases, however, the change of dispersion during the drying phase remained minor.

Particle electrification in an apparatus with a draft tube operating in a fast circulating dilute spout-fluid bed regime

The intensity of the electrostatic charge accumulated during the flow of Cellets® particles in a modified Wurster apparatus is investigated in terms of the bed mass, and the initial moisture and velocity of the spouting gas. Particle electrification is proportional to the increase in the velocity of the spouting gas, which is connected with a higher velocity of the cores and the strength of their impact on the walls of the device. The presence of moisture in the bed facilitates electrification, but does not affect circulation, since moisture simultaneously lowers the bed resistance and reduces the relaxation time of particles, leading to rapid discharging if brought into contact with the conducting elements of the apparatus. Therefore, with regard to classic dry-powder coating, the velocity of the spouting gas should be minimized to ensure good circulation, with the particle moisture held at the maximum level admissible for a given product. The investigations show that a unique construction of the apparatus, which brings about an intense natural electrification of the cores, makes it suitable for the electrostatic dry-coating process by means of a high-voltage feeder with the controlled charging of coating powder in the spray nozzle.

The influence of particle interfacial energies and mixing energy on the mixture quality of the dry-coating process

We investigate the effect of particle interface energies and mixing energy input on the macroscopic behavior of the dry-coating process by using the discrete element method (DEM). It is observed that the quality of the coating process is governed by two dimensionless numbers: the Stokes number St (mixing energy/strength of agglomerates) and the reduced intermixing coefficient Λ (cohesion /adhesion strength). Three unfavorable and one favorable process regimes were identified, and represented in a regime map as a function of St and Λ. For low St and Λ, carriers are lumped and random mixing is fairly poor. For low St and high Λ, the agglomerates are merged together and remain intact. At high St, the fine-carrier adhesion breaks and creates abundance of debris. Between these regions process conditions are favorable as is supported by experimental evidences. Results of this study can be used to establish guidelines for efficient operation of the dry-coating process in a high-shear mixer.

Development of Dry Coating Process for Micro-Particulate Pharmaceuticals Using Polymeric Nano-Powders

Development of Dry Coating Process for Micro-Particulate Pharmaceuticals Using Polymeric Nano-Powders

Dry-coated live viral vector vaccines delivered by nanopatch microprojections retain long-term thermostability and induce transgene-specific T cell responses in mice.

The disadvantages of needle-based immunisation motivate the development of simple, low cost, needle-free alternatives. Vaccine delivery to cutaneous environments rich in specialised antigen-presenting cells using microprojection patches has practical and immunological advantages over conventional needle delivery. Additionally, stable coating of vaccine onto microprojections removes logistical obstacles presented by the strict requirement for cold-chain storage and distribution of liquid vaccine, or lyophilised vaccine plus diluent. These attributes make these technologies particularly suitable for delivery of vaccines against diseases such as malaria, which exerts its worst effects in countries with poorly-resourced healthcare systems. Live viral vectors including adenoviruses and poxviruses encoding exogenous antigens have shown significant clinical promise as vaccines, due to their ability to generate high numbers of antigen-specific T cells. Here, the simian adenovirus serotype 63 and the poxvirus modified vaccinia Ankara – two vectors under evaluation for the delivery of malaria antigens to humans – were formulated for coating onto Nanopatch microprojections and applied to murine skin. Co-formulation with the stabilising disaccharides trehalose and sucrose protected virions during the dry-coating process. Transgene-specific CD8+ T cell responses following Nanopatch delivery of both vectors were similar to intradermal injection controls after a single immunisation (despite a much lower delivered dose), though MVA boosting of pre-primed responses with Nanopatch was found to be less effective than the ID route. Importantly, disaccharide-stabilised ChAd63 could be stored for 10 weeks at 37°C with less than 1 log10 loss of viability, and retained single-dose immunogenicity after storage. These data support the further development of microprojection patches for the deployment of live vaccines in hot climates.

Improved Electrochemical Performance of NH[sub 4]AlF[sub 4]-Coated LiCoO[sub 2] Cycled over 4.5 V

Cathode coatings are being developed to improve lithium-ion batteries. In this effort, particles were coated with by a simple dry-coating process to enhance capacity retention on a 4.5 V cutoff cycling. Compared with pristine , this coating greatly improved the electrode cyclability and rate capability. Electrochemical impedance spectroscopy and a cobalt dissolution test showed that the coating protected the particle surface from HF and, thus, suppressed the increase in interfacial impedance between the cathode and electrolyte that occurred with an uncoated cathode material.

Electroluminescence from monolayer ZnO nanoparticles using dry coating technique

We report ultraviolet electroluminescence from ZnO nanoparticle-based devices prepared by the dry-coating technique. With dry-coating process, the structure of the ZnO nanoparticle monolayer (90nm) in the device can be easily achieved. The method reduces the density of pinhole defects in the ZnO nanoparticles. The confirmation for dry coating is investigated using field-emission scanning electron microscopy. The devices show the ZnO band-gap emission peak at 380nm and the background emission from the interface between the host matrix and Aluminum tris-8-hydroxyquinoline. The origins of the ZnO band-gap emission and background emission are also discussed.

Processes and Principles of Self-Ordering of Nanoparticles in a Liquid Phase

A variety of functions of nanoparticle thin films are expected to be realized by two- or three-dimensional ordering of a large number of nanoparticles. The coating-drying process that induces a self-ordering of nanoparticles in a liquid phase is one of the most promising methods for industries. However, the structures of ordered nanoparticles are designed by empirical control of some process conditions in industries. We have modeled the dynamics of two-dimensional self-ordering of nanoparticles in a liquid phase, and have simulated the drying processes of nanoparticle suspensions. The relationships between the process conditions and the structures are derived from the simulation results as well as some experimental data. We have proposed three non-dimensional variables to represent principles of the two-dimensional self-ordering of nanoparticles: 1) Long-range inter-particle energy ratio, 2) Particle binding energy ratio, 3) Particle travel time ratio. These variables are functions of some process conditions, and the structures of ordered nanoparticles can be estimated by sets of these variables.

Application of dynamic speckle interferometry to the drying of coatings

In this work a new tool to study the drying of paints, based on an optical technique known as dynamic speckle interferometry is presented. The basic concepts of the technique are described and applied to the drying process of white solvent-borne and white water-borne paints (latex paint) following the time evolution of the activity of dynamic speckle patterns. For processing the data an alternative method based on the use of the second-order moment of the modified co-occurrence matrix of the time history of its intensity was used. The experimental results obtained were compared with the gravimetric technique and the resulting curves from the speckle-time evolution compared favorably with gravimetric drying curves. The results were also discussed on the basis of the knowledge of the coating drying process and factors related with the surface properties. Dynamic speckle interferometry seems to be a useful technique for assessing the time evolution of surfaces and, its sensitivity to refractive index changes helps to determine the start of different stages during the drying of latex paints. The dynamic speckle method tests mainly the activity on the surface and the measurements seem to confirm that the initial stage of drying is like a pure solvent. Finally, the study of different aspects of the drying process using this technique is proposed.