Kaolin, also known as kaolinite, is a soft, white, naturally occurring clay mineral that primarily consists of the mineral kaolinite, along with varying amounts of other minerals like muscovite, quartz, feldspar, and anatase. It is extensively used in various industrial applications such as ceramics, paints, cosmetics, pharmaceuticals, and agriculture due to its desirable properties including chemical inertness, adsorbency, and non-swelling capabilities.
Kaolin deposits appear in the soil and rock across vast regions worldwide, including in Southeast Asia, Western and Eastern Europe, South America, Australia and Sub-Saharan Africa.
In the United States, kaolin is most abundant in Georgia, including in the city of Sandersville, which is the world’s kaolin capital. Extracting kaolin clay from the earth requires mining. Then, manufacturers process extracted kaolin minerals and prepare them into powder forms for commercial use.
What Is Kaolin Clay and Its Properties?
The mineral kaolinite primarily makes up kaolin. Depending on its source, kaolin also contains various other minerals, including muscovite, quartz, feldspar and anatase. When kaolin comes out of the earth, it’s naturally bright white, but may have a yellow or rust-colored stain due to its exposure to iron oxide. Kaolin’s natural state is as a powder, and its texture is soft.
Below are other kaolin clay properties.
- Chemistry: In its natural mineral state, kaolin’s chemical formula is Al2Si2O5(OH)4. Kaolinite is an aluminum silicate mineral that develops through chemical weather of aluminum rich feldspars contained in granites and pegmatites.
- Structure: Kaolin composition consists of hexagonal crystals ranging in size from 0.1 to 10 micrometers. These crystals form in stacked layers, and this kaolinite structure partially gives the clay its desirable properties.
Due to kaolin’s chemical and structural composition, its natural properties are highly desirable for industrial uses.
- Chemically inert: Kaolin has a neutral pH level, making it ideal for use in pharmaceuticals, cosmetics, and industrial mixtures because it doesn’t alter the product’s chemical composition, or promote bacterial growth.
- Adsorbent: One of kaolin clay’s primary uses is to aid in the adsorption of other substances. Kaolin clay is naturally highly adsorbent, so it can help extract and remove undesirable impurities, pathogens or other substances in any given mixture or application.
- Non-swelling: Between each layer of kaolinite crystals are hydrogen bonds that prevent water molecules from infiltrating the layers. This ability to prevent water from penetrating kaolin’s crystal structure gives it non-swelling properties. Non-swelling is a valuable property of additives like kaolin, so they don’t alter the physical properties of the mixture or product in question.
Learn more about the properties of kaolin clay and the benefits of kaolin products by contacting us today.
Mining companies extract kaolin clay from the earth through open-pit mining methods, through draglines or more commonly excavators to strip, mine, and load haul trucks. Depending on the mining operation, workers may also extract kaolin via a hydraulic or dredging method. As the mining buckets bring the clay to the surface, loaders transport the extracted clay to trucks, which take the minerals away for further processing into industrial uses.
There are various kaolin processing methods, ranging from crushing to grinding to screening. These techniques do not alter the clay’s chemical or physical properties, but merely convert them into a form that’s easier to manage for the desired use. In some cases, processed kaolin clay may undergo other preparations like drying, calcining, bleaching, blunging and extruding.
Kaolin preparation processes include wet and dry processing. Dry-processed kaolin gets crushed and pulverized until it achieves the desired grit or coarseness. This kaolin typically gets used in applications such as rubber manufacturing, paper-filling or producing Fiberglass and sanitary ceramic ware.
Processing wet kaolin involves blunging to convert it into a slurry. Then, it passes through centrifuges or other separators. Kaolin clay might undergo numerous additional processes, including bleaching, filtering and dewatering. It may also require chemical processing, including leaching with sulfuric acid or reduction with hydrosulfite or a similar reducing agent. Depending on its eventual use, the filtered and dewatered kaolin may also go through drying and calcination processes. Calcining kaolin happens in hearth furnaces, as well as through rotary or flash calcining. Calcined kaolin is a filler or refractory material. The paper manufacturing industry primarily uses wet-processed kaolin.
Uses of Kaolin Clay
Kaolin Clay in Ceramics
What is kaolin used for? One of the most prevalent industrial uses of kaolin is in manufacturing ceramics, porcelain ware and floor or wall tiles. Because of its ideal properties for ceramic manufacturing, some people call kaolin clay china clay for its role in producing whiteware. Kaolin clay has a high fusion temperature, and its naturally bright white color makes it useful for manufacturing pure white ceramics, porcelain, china, sanitary ware and kaolin pottery.
Because kaolin contains low concentrations of iron or alkalis, it is ideal for use in various forms of ceramics. When producing ceramics and whiteware, manufacturers usually combine kaolin with additional silica and feldspar, along with a small amount of another type of clay called ball clay, which is a plastic light-burning clay. The combination of kaolin and other ingredients allows ceramic manufacturers to achieve the ideal plasticity, shrinkage, vitrification and other processes to properly shape and heat the ware. Kaolin offers high dry strength, meaning that as an additive, it helps reinforce and strengthen the final product, which is crucial in manufacturing ceramic ware.
Learn more about how AMI’s kaolin products play a role in manufacturing ceramic bodies and tile.
Kaolin in Concrete and Cement
Traditionally, concrete products consist of a mixture of Portland cement, water and aggregates, like gravel, sand or silica. Depending on their proprietary blends, concrete producers may use other aggregates or fillers to give their mixture additional properties that make it useful for other products, including building supplies.
Kaolin is a popular additive product to use in concrete mixtures because it is a silicate mineral, which is necessary for giving concrete its required properties. Kaolin clay is becoming more desirable in the construction industry because of its ability to provide bright white coloring to cement mixtures. As a concrete mix additive, kaolin is also ideal because it is chemically inert and will have minimal effect on the formula’s chemical or physical properties. It also helps increase the strength and durability of concrete or cement materials.
Kaolin is also desirable in cement systems because of its high pozzolanic activity, which is its ability to react with Portland cement. In other words, it can accelerate the hydration of the Portland cement in the concrete mix. Kaolin behaves as a superfiller, packing its fine particles into the cement matrix and improving its density. Studies have found that compared to other silica minerals, using kaolin clay in cement enhances the concrete products’ mechanical properties, including increasing their compressive strength.
Kaolin in Paper and Board Production
The paper and board production industry is continuously innovating to deliver high-quality products with enhanced brightness, gloss, opacity and surface quality for better printing. Manufacturers also need eco-friendly, recyclable and environmentally viable products, including reducing the necessity for extreme water consumption.
Paper and board production facilities rely on kaolin clay as control agents that reduce water consumption and pollution. Kaolin helps improve the cost-effectiveness and eco-friendliness of conventional pulp and paper processes, leading to cleaner and higher-quality pulp and paper. As a particulate filler, it fills and coats paper products to improve their smoothness, gloss and printability. Not only does kaolin help make more attractive paper, but it can also extend fiber and improve the products’ overall longevity, durability and strength.
Kaolin’s natural crystal size, shape and structural distribution make it an exceptional filling and coating product. Compared to other mineral fillers that decrease in strength as they become smaller, kaolin doesn’t lose its strength effects as its particle size decreases.
Kaolin in Polymeric Materials
In manufacturing polymers, including rubbers and plastics, kaolin’s natural properties make this clay ideal as a natural filler and additive. As kaolin binds to polymers during processing, it naturally enhances mechanical properties, including strength, impact and flexibility. Kaolin gives plastics and rubbers desirable properties, like better resistance to tears and abrasions. It also improves these products’ tensile strength and prevents warping. Kaolin offers enhanced chemical and electrical resistance. Overall, kaolin is an effective filler and reinforcer to improve rubber and plastics’ durability and rigidity, extending product longevity and quality.
Kaolin also helps extend pigment and produce sharper colors in polymers, while helping enhance the final products’ smoothness and brightness. It can improve production, including by increasing curing rates while reducing cure times. These qualities provide manufacturers with overall cost-effectiveness and productivity.
Learn more about how AMI’s kaolin clay products can serve the rubber industry.
Kaolin in Fiberglass
Kaolin is vital in Fiberglas production. Factories rely on high-quality kaolin to weave and reinforce Fiberglass products, including as a reinforcing filler for continuous-filament Fiberglass. Kaolin provides alumina, which is necessary for improving products’ surface durability. Fiberglass acts as a natural filler, thanks to its layered structure that adds density without increasing weight. Kaolin keeps Fiberglass lightweight yet strong, giving it better structure and durability.
Kaolin is also a desirable mineral in the manufacturing of Fiberglass insulation. Thanks to its low thermal conductivity, it maximizes the product’s insulative quality. Kaolin is an ingredient in many other Fiberglass or Fiberglass-containing products, including cars, boats, aircraft, circuit boards, air filters, tanks, pipes and building materials.
Fiberglass manufacturers use kaolin to improve product quality, optimize their manufacturing processes, increase cost-effectiveness and maximize production.
Learn more about the use of kaolin products in the Fiberglas industry.
Kaolin in Agriculture
Kaolin offers many uses for the agricultural industry, including in crop protectants, seed coatings and solar protectants. Crop protectant forms a barrier film, which acts as a broad spectrum agricultural crop protectant for controlling damage from listed insects, mite, and disease pests.
Similarly, solar-protectant products containing kaolin also act as a barrier to reduce environmental stress, including heat and solar exposure. The film barrier reduces crop sunburn while also encouraging photosynthesis.
Another use for kaolin products in agriculture is with coatings that protect seeds and increase their size, which improves handling and planting ability. Coated seeds also have better germination success and can withstand adverse climate conditions.
Discover the benefits of AMI’s approved kaolin products for the agricultural industry.
Kaolin’s Uses in Adhesives
As with other industrial products, kaolin is also a filler and additive in manufacturing adhesives, sealants and caulks. Kaolin’s natural properties make it a useful ingredient in manufacturing adhesives, particularly its unique particle size and shape, which allow kaolin minerals to extrude well and settle slowly. Kaolin is also low-residue and low-moisture and low oil absorption, all of which make it an excellent filler. Kaolin also helps extend and reinforce pigments in caulks and sealants.
Kaolin provides wet strength, whiteness and film strength in adhesives while also maintaining flow. It helps fill in the substrate to enhance overall strength and durability. Additionally, kaolin reduces shrinkage and controls viscosity modification, increasing binding abilities while improving the barrier properties necessary in manufacturing sealants. All these properties improve the cost-effectiveness of adhesive and sealant products.
For more information on kaolin uses in adhesives, sealants and caulks, contact AMI today.
Kaolin in Paints and Coatings
To produce high-performing and long-lasting paints and coatings, manufacturers need additive ingredients that extend pigment and stabilize the mixture. Kaolin products are beneficial in many applications, from primers and wood stains to enamels and sealers.
Kaolin enhances paints’ and coatings’ appearance, offering increased gloss and sheen control and enamel holdout. Kaolin is also ideal for enhanced whiteness and brightness. For specific paints and coatings, kaolin is also excellent for giving products additional properties like improved corrosion and scrub resistance.
Besides its aesthetic qualities, kaolin also offers performance-enhancing benefits. Kaolin helps prevent settling and maintains a long and stable shelf life. Kaolin-based coatings and paints may have improved dispersion, smoothness and stability. They may also be weather-resistant, particularly in applications like automotive and traffic paints.
Explore the benefits of kaolin products in paints and coatings.
Kaolin in Wastewater Treatment
Wastewater treatment facilities need safe and effective chemical treatments such as kaolin to remove impurities and toxins and return clean, potable water back to the water cycle.
One study found that kaolin was highly effective at removing numerous contaminants from wastewater, including chloride and iron. Kaolin has superior adsorption properties, particularly in adsorbing metal ions. The study ultimately found that even after six repeated applications, kaolin continued exhibiting excellent recyclable and reusable properties, therefore making it a suitable treatment to apply to the wastewater removal of heavy metals.
Because wastewater treatment processes are so expensive to operate, finding cost-effective options is paramount to these operations’ viability. Kaolin products may offer an affordable and practical alternative to traditional wastewater treatment minerals.
Contact AMI About Our Kaolin Mineral Products Today
Kaolin clay is a highly versatile, effective, and beneficial natural mineral with diverse uses and applications across a range of industries. If you are looking for mineral ingredients to optimize your manufactured products, consider the advantages of kaolin clay.
Active Minerals International is a premier global supplier of kaolin clay products. From mining to processing to distribution, AMI delivers high-quality kaolin products for ceramics, paints and coatings, agriculture products, concrete systems and more. Contact us today for a free quote on kaolin products for your industry. Call us at 410-825-2920 or fill out an online form.