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Particle Coating & Particle Surface Modification Services
Particle Coating & Particle Surface Modification
||AVEKA is pleased to offer particle coating and surface modification, including smoothing, coarsening, and color changes, for thicknesses ranging from 0.25 micron up to 2mm. We also feature binding, changing acid and base characteristics, attaching metal complexes to supports, and much more. To achieve our clients' required particle coating or surface modification, AVEKA uses a variety of state-of-the-art modification methods, such as magnetically assisted impact coating (MAIC), spray drying, impregnation, fluid bed coating, spherodization, and other unique techniques. Particle coating and surface modification yield numerous benefits, and can be used to:
For additional information regarding out surface modification and particle coating techniques and benefits, please see below or contact AVEKA directly.
- Mask flavors and odors;
- Change particle colors;
- Change adsorption properties;
- Change rheological properties of solids in liquids;
- Create catalytic sites; and
- Decrease release rates and more.
Particle Coating & Particle Surface Modification Specifications:
Research And Development
Innovation and IP Development
||ISO - 9001 - 2008
International Organization for Standardization
|Why do particle coating / surface modification:
- Mask flavors / odors
- Change color of particles
- Change adsorption properties
- Change rheological properties of solids in liquids
- Decrease release rates
- Change hydrophobicity / oleophilicity
- Create Catalytic sites
|Types of surface modifications:
- Change acid/base characteristics (Lewis acid or Bronsted acid)
- Change hydrophobic/hydrophilic
- React surface with organosilanes / titanates
- Bind other materials to the supports
- Attach metal complexes to supports
- Catalytic behavior
- Put metals onto supports
|Methods of particle coating / surface modification at AVEKA:
||1. MAIC [Magnetically Assisted Impact Coating] is a process in which small magnets move in an oscillating magnetic field to impact the coating material onto the larger particles.
2. Spray Drying is a process in which the particle to be coated is made into a slurry and then atomized into a warm chamber where the water is dried off; leaving a dry particle that has the second material coated onto it.
3. Impregnation uses a V-blending to apply smaller particles or small amounts of a liquid coating onto other particles. With heating to remove water this can also be used to add materials to surfaces to changing acid/base characteristics and to induce catalytic behavior.
4. Prilling can be used to embed and coat particles in a molten material which are spray cooled to form solid beads.
5. Fluid bed coating can be used to coat particles with dissolved polymers, sugars, inorganic salts, sol gels, or other materials inside a bed of moving air. As the solvent is removed in the fluidized air stream, the coating dries on the particles.
6. Ball Milling is similar to the MAIC but not quite as intensive. This process can be used to pound small materials onto larger particles.
7. Hot Blending is a basic method for coating non-melting particles with a small amount of a thermoplastic material.
8. Spheroidization can be used to coat particle by first putting small, meltable particles on larger particles. The particles are rapidly passed through an intensely heated area. The small meltable particles melt on the outside of the core particle and flow to provide a better coating.
9. Tablet Coating is similar to fluid bed coating; this is a process that tumbles particles in a rotating bed where air is used to dry solutions onto a particle.
|Magnetically Assisted Impact Coating
||(MAIC, pronounced "mace"), is a patented process used to coat smaller particles onto larger particles or to apply small amounts of liquids onto particles.
The system relies on a pounding process in which small magnets in an oscillating magnetic field are fluidized to rapidly force the coating material onto the larger particles. Likewise, the magnets will distribute a small amount of liquid, such as an organosilane, evenly onto core particles and robustly apply them to the surface.
The core and coating materials flow continuously through the magnet beds at rates of 8-600 pounds per hour. Materials that have been used in this process include glasses, pigments, metals, metal oxides, polymers, and organic and inorganic powders.
A unique aspect of the particle on particle product is that, in many cases, the dry coated composite particle will not dissociate in the dry state or when the composite is put into dispersion.
The MAIC process also has a large and permanent effect on flowability of the treated materials. When fumed silica is added to particle assemblies using traditional methods, the mixture flows better than the core material, but the fumed silica is not attached to the surface of the particles and will be removed from the surface with relatively minimal forces.
After a MAIC treatment, two effects are seen for silica flow agent addition. First, the amount of silica needed to improve the flow is reduced significantly, up to an order of magnitude as compared to the traditional mixing/application methods. The second, the resultant mixture is stable to shaking and transportation.
Essentially, the mixture of small and large particles does not separate, even with the vibration seen with handling.
|Impregnation via V-blending
||Impregnation via a v-blending can be used to apply smaller particles or a small amount of a liquid coating onto other particles.
The liquid is added to the mix via an intensifier bar or spray nozzles, and the mixture is rotated in the blender for some period of time. This is a workhorse in the industry for putting liquids onto or into solids. Frequently this is used to apply a silane or a titanate onto reactive or non-reactive particles. This can be used to introduce a metal salt or oil onto a particle. It can also be used to apply a flow aid or other coating particles to the material.
||Prilling also known as spray congealing, spray chilling, or melt atomization, is the process of atomizing molten liquids or mixtures and cooling the resultant droplets to form prills or beads that are the final product.
When particles are added to the molten material, they will become embedded and be encapsulated in the matrix of the final bead. In general, the matrix material must be a material that is solid at room temperature, has a discreet melting and freezing point and a low melt viscosity.
|Fluid bed coating
||Fluid bed coating or Wurster coating is a process that was developed at the University of Wisconsin in the 1950's. Particles to be coated are fluidized in a bed of moving air, and a solution of dissolved polymer, sugar, inorganic salts, sol gels, or other materials is sprayed onto the fluidized particles. As the fluidized particles dry, the coating dries on them creating a core/shell encapsulation. Due to the nature of fluidized beds, particle coating using this method is generally limited to particles larger than 100 microns, although AVEKA has been able to successfully coat 10 micron core material.
||Ball Milling is similar to the MAIC but not quite as intensive. This process can be used to pound small materials onto larger particles. Ceramic or steel balls are tumbled with the large particles and small particles to pound the small particles onto the large particles.
||Hot blending is a basic method for coating non-melting particles with a small amount of a thermoplastic material. Initially, the core particles are blended with the thermoplastic material at room temperature. Then the temperature is increased to the melting point of the thermoplastic. Blending continues as the temperature is returned to ambient. The resultant particles have a light coating of the material, such as a wax, that may improve the flow and reduce bridging of the powder.
||Spheroidization allows one to round the edges of a meltable particle. This is used to improve the flow characteristics of powders or to make an imperfect coating more continuous.
The particles are rapidly passed through an intensely heated area. The outside material melts, flows, and, as it cools, forms a smooth surface. If there are small meltable particles on the outside of the core material, these will melt and flow to provide a better coating. If the core is thermoplastic, it softens and allows the coating particles to become more strongly adhered.
||Tablet coating is a process that tumbles particles in a rotating bed where hot air or cool air is used to dry or freeze atomized coating solutions or melts onto particle surfaces. This is a process where thin coatings can be applied to the surface of particles or heavy coatings up to 100% of the core particle can be applied.
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