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Levasil Colloidal Silica aqueous dispersions are available in a variety of grades

These are determined by particle size, structure, concentration, pH, surface charge and surface modification. It is a versatile, inorganic material, also known as silica sol, that can be used for many different industrial functions.

  • Concentrations: 7– 50% SiO2
  • Particle size distributions: narrow, medium or wide
  • Structures: Discrete particles or chains
  • Particle diameters: 2–150 nm (nanometer)
  • Surface areas: 30-1100 m2/g
  • pH: 2–12
  • Modifications: ammonium, aluminate, chloride, potassium, silane, deionized
  • Morphology
Anionic particles silane modified pH 7-9
Anionic particles silane modified pH 7-9

Abrasion and scratch-resistance - tougher surfaces last longer

Abrasion and scratch-resistance is key in the waterborne coatings industry. The reason is that abrasion and scratch-resistant coatings last longer and require less frequent recoating. And, in some applications, help protect substrates from corrosion.

Benefits

How it works

  • Improved abrasion, scratch and corrosion resistance
  • Safe handling and easy to use

Coating formulations made with colloidal silica help surfaces resist abrasions and scratches in two principal ways:

  1. Colloidal silica increases the cross-linking density of reactive groups in organic resins thanks to its high number of hydroxyl surface groups.
  2. Colloidal silica particles are very hard (5.5 on the Mohs scale of mineral hardness) and significantly improve coating hardness.

Adhesion - improving the surface attraction

Levasil Colloidal Silica can be added to waterborne adhesive formulation to improve heat resistance and shear strength and to reduce drying time. In addition, colloidal silica can be used to adjust the viscosity without needing additional thickeners.

Benefits

How it works

  • Reduced drying time
  • Good formulation stability
  • Adjustment of rheological properties
  • Improved heat and creep resistance
  • Improved initial wet bonding strength
  • Safe handling and easy to use

Adhesion describes the tendency for dissimilar surfaces to stick to one another. Colloidal silica dispersions can improve the molecular interaction of waterborne coatings and adhesives with substrates, resulting in better adhesion, in several ways:

  1. The high number of hydroxyl surface groups interacts with other chemical groups (i.e., oxide, hydroxyl or carboxylic groups) on multiple substrates.
  2. By forming strong calcium silicate bonds, enhancing resin-based-coating adhesion on glass and mineral substrates.
  3. By reducing shrinkage of polymer matrices in lacquers during drying.

 

 

 

Anti-blocking - keeping surfaces separated

Coated surfaces or layers, especially tacky or those recently coated, have a tendency to stick together. When this happens, they are often ruined. Preventing this from happening is called anti-blocking.

Benefits

How it works

  • Increased heat resistance
  • Controllable drying times
  • Reduced shrinkage during drying
  • Excellent water retention
  • Safe handling and easy to use

When added to coating formulations, colloidal silica gives surfaces an anti-blocking capacity for two main reasons:

  1. Colloidal silica makes surfaces more hydrophilic, causing more moisture to be retained by surfaces during drying, which reduces their tackiness.
  2. Considered small “glass particles,” colloidal silica resists high temperatures (SiO2 has a melting point of about 1650ºC) and even under high temperature particles stay discrete and do not fuse.

Anti-soiling - keeping surfaces cleaner

Anti-soiling is very important in exterior coatings. The better these coatings resist soiling, the fresher and cleaner they look. And when cleaning is required, dirt is easily removed by rinsing.

Benefits

How it works

  • Increases hydrophilicity/wetting
  • Safe handling and easy to use

 

Dirt is attracted to surfaces that are hydrophobic, in other words, afraid of water. When surfaces are more hydrophilic, or water loving, dirt is repelled. This is called anti-soiling.

Silica particles in colloidal silica dispersions have many surface hydroxyl-silanol groups, which are very hydrophilic. Thanks to the enrichment of colloidal silica particles in the coating surface you get a less tacky and more hydrophilic surface. This means that water forms a film on the surface, allowing dirt to run off with the water.

Binding - making a good connection

Binding is the process of drawing and holding together materials to form a cohesive whole. Levasil Colloidal Silica is the perfect binder in a number of different binding applications.

Benefits

How it works

  • Increased temperature tolerance
  • Amorphous and non-crystalline 
  • Safe handling and easy to use

 

  1. At high temperatures, colloidal silica particles sinter and bind components together (investment casting, ceramics, and catalyst applications) or form a hard glassy surface coating (electric steel).
  2. At lower temperatures, colloidal silica can form an inorganic matrix based on chemical bonds (zinc-rich primers and cementitious systems).
  3. In a polymer resin based matrix, the surface groups of silane-modified silica particles can react and cross-link with resin groups providing additional binding for the coating system.

Dispersing - preventing re-agglomeration

The small size of Levasil Colloidal Silica particles allows them to be used as a dispersant in some applications. This is particularly useful to formulate highly concentrated, long-term stable, surfactant-free dispersions of pigments.

Benefits

How it works

  • Surfactant-free pigment paste
  • Easy to use and safe to hande
  • Not shear-sensitive
  • Stable suspension
  • Foam-free
  • Improved wettability

Dispersing is the creation of a uniform and consistent liquid formulation that resists settling or clumping through improved separation of particles. By improving the separation of particles, a uniform and consistent liquid dispersion that resists settling or clumping is created.
Thanks to consistent particle size and charge, colloidal silica is an ideal dispersing agent in a number of applications.

The particles act as a physical spacer, preventing re-agglomeration, and help keep the dispersed material separated by adsorbing on the surface.

Flocculation - removing unwanted particles

Flocculation is the process of removing unwanted particulates (solids) from liquid, which are otherwise difficult to filter or settle out. Flocculation is common in refractory fiber bonding, the food and beverage, and water treatment industries.

Benefits

How it works

  • Safe handling and easy to use
  • Non-hazardous

When colloidal silica is introduced to a liquid, the liquid becomes destabilized electrically. Solids with opposite surface charges are attracted to the colloidal silica particles, forming clusters or clumps called flocs. These flocs then float to the top (creaming), settle to the bottom (sedimentation), or are readily filtered from the liquid.

Frictionizing - increasing surface roughness

Abrasion and scratch-resistance is key in the waterborne coatings industry. The reason is that abrasion and scratch-resistant coatings last longer and require less frequent recoating. And, in some applications, help protect substrates from corrosion.

Benefits

How it works

  • Increased frictional coefficient
  • Easy to use and safe handling

This higher coefficient of friction is produced in two primary ways:

  1. When introduced into an aqueous coating formulation, colloidal silica is transported to the coating film through capillary action during drying of these coatings.

  2. When sprayed onto a surface, for example to create anti-slip surfaces on paper, colloidal silica stays on the substrate surface without penetrating deep into the substrate.

After drying, the surfaces in both cases are populated by the small silica particles, increasing their surface roughness and thereby the coefficient of friction.

Gelling - making a liquid solid

Gelling is the process by which a liquid become viscous and eventually a solid. With this functionality Levasil Colloidal Silica is a valuable tool in ground consolidation and when producing gel and AGM batteries.

Benefits

How it works

  • Improved gel stability and strength
  • Controllable and adjustable gel times
  • Safe handling and easy to use

Colloidal silica particles form gels by linking together along siloxane bridges in branched chains, resulting in a contiguous gel network. The formed network prohibits liquid transport within the gel volume, but can still retain a liquid component through capillary action. In battery applications, sulfuric acid is retained in the gel; while in ground consolidation, it is water that is retained.

Printability - improving the output

The efficiency with which images and type can be printed onto a surface is referred to as a medium’s printability. Improved printability means that ink colors and images hold to surfaces better and are less likely to penetrate the material below.

Benefits

How it works

  • Improved wettability
  • Increased ink adsorption
  • No ink bleeding

In the simplest of terms, when Levasil Colloidal Silica is used in coatings applied to both paper and plastic films, it enhances printability by improving surface hydrophilicity, resulting in better retention of waterborne inks.

For inkjet paper, positively charged (cationic) colloidal silica is used in coating formulations. When allowed to dry, the silica agglomerates with a small amount of binder to create a porous coating with excellent dye fixing properties.

Polishing and planarization - for the perfect substrate

Levasil Colloidal Silica can be used to physically and chemically polish various substrates to create nearly defect-free, flat surfaces. Our aqueous dispersions of colloidal silica is commonly used with polishing pads to smooth and polish uneven surfaces. This is the preferred process in the manufacture of integrated circuits and high performance substrates.

Benefits

How it works

  • Predictable and repeatable polishing performance
  • Consistent particle size and pH with low level of impurities
  • High removal rate to desired surface finish
  • High cost efficiency
  • Often eliminates intermediate polishing steps
  • Safe to handle and easy to use

The ideal balance between the surface removal rate and surface roughness, or waviness, is achieved by selecting the proper silica particle with respect to: size, morphology, size distribution, concentration, pH and impurity level.

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For more information about our Levasil Colloidal Silica products, please contact our experts. We look forward to hearing from you.

 

 

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