涂料填料性能介绍

Mineral properties that must be considered:
pH is a function of the metallic ions in the structure. Aluminum in the structure makes the mineral acidic. Calcium, potassium, barium or sodium make the mineral alkaline. Some minerals, such as calcite or serpentine, are soluble in acids and can’t be used in coatings that have pH <7.
Mineralogy
A mineral can’t be defined simply by its chemical formula. The crystal structure must also be considered. For example, there are many aluminum silicates. Hydrous kaolin [Al2Si2O5(OH)4], mullite [Al2SiO5], pyrophyllite [Al2Si4O10(OH)2], kyanite [Al2OSiO4] and sillimanite [Al2SiO5] are all aluminum silicates but are unique minerals. They have different crystal structures and different properties.
Mineral Fillers = something cheap to take up space—not so!
Filler
Minerals and o来自百度文库her chemical additives in paints and coatings are used to improve properties
Mineral properties that must be considered:
The oil absorption of a mineral is a characteristic of the mineral itself and how finely it is ground. The denser the mineral, the lower the oil absorption. The oil absorption indicates the amount of the resin the mineral will absorb and affects the viscosity of the paint and the gloss.
Mineral properties that must be considered:
The refractive index is a measure of how light is bent when it passes from one medium to another. The higher the refractive index, the more the light is bent which results in greater opacity. Rutile TiO2 has a high refractive index and gives good opacity to coatings.
Effects of addition of minerals to paints and coatings depend on:
Mineralogy (chemistry, crystal structure, Mohs hardness, etc.) Oil absorption, brightness, pH, chemical inertness, refractive index, purity, soluble salts, etc. Particle size and particle size distribution Particle shape and aspect ratio Volume fraction in the matrix (PVC and CPVC)
Particle size by Hegman Fineness
Hegman fineness measurements indicate only size of the coarsest particles. This is a good first approximation of the fineness of grind and the dispersion of the mineral pigments in the paint. Hegman fineness does not tell anything about the overall distribution of the minerals.
Particle size distribution and particle size distribution
The particle size of a mineral can be expressed in several ways, depending on the method by which it is measured. Common methods of measuring particle size are Hegman fineness, screening, sedimentation and laser light scattering methods. Each method will yield a distinct result. When comparing data of different minerals, be sure that the particle size distributions are measured the same way.
Mohs Hardness Scale
Mohs scale 1 Talc 2 Gypsum 3 Calcite 4 Fluorite 5 Apatite 6 Feldspar 7 Quartz 8 Topaz 9 Corundum 10 Diamond
Relative Hardness
1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0
Particle size by screening
The screen residue measures the quantity of particles retained, it does not tell anything about the size of those retained particles except that they are larger than the screen openings.
Mineral properties that must be considered:
Water-soluble salts in certain minerals can adversely affect corrosion resistance and exacerbate blistering. Exterior paint frosting and chalking also are caused by the presence of soluble salts in the minerals. The dry brightness and color-in-oil of a mineral will affect how the mineral appears in a coating. A mineral can have excellent dry brightness but change color when put into a resin. Color-in-oil can vary from cream to gray or even green, depending on the mineral. The color is usually an effect of minor impurities.
Most mineral fillers have a significantly lower refractive index than TiO2 and don’t contribute to the opacity, but they can be used in conjunction with TiO2 to achieve opacity at reduced cost. Some minerals, such as amorphous silica, have refractive index the same or lower than the resin and will be invisible in the dry film. They can be used to reduce the gloss of a clear coating without creating haze.
Mineral properties that must be considered:
Mohs hardness is a relative measure of abrasivity or abrasion resistance of a mineral. Talc is the softest mineral and diamond the hardest. Harder minerals will have better scrub resistance and better burnish resistance. Because of their abrasivity, harder minerals are also more likely to damage process equipment than softer minerals.
Particle size by screening
Screen residues only indicate the % coarser than some given mesh size. Typical mesh sizes are 100, 200, 325 and 450 mesh. These are equal to 150 μm, 75 μm, 44 μm and 32 μm respectively. Screenings can be done dry or wet. Wet screenings usually yield a smaller quantity retained than dry screenings.
An Introduction to Mineral Fillers for Paints & Coatings
Overview
Introduction General discussion about the function of mineral fillers Mineral fillers from R.T. Vanderbilt Company, Inc. Other mineral fillers, not sold by R.T. Vanderbilt Company, Inc. An example of the effect of different mineral fillers in a low VOC interior latex flat paint Summary