Coated abrasives of the “three elements”: substrate, abrasive, binder. Each element has different properties and different types of materials to choose from.
(1) Classification of abrasive
Abrasive is the main body of the grinding and polishing effect of coated abrasives. Abrasives must have these basic properties: a certain hardness, a certain strength, appropriate crushing, a certain physical and chemical stability, abrasive can be divided into natural abrasive and artificial abrasive two categories. Coated abrasives commonly used varieties of abrasives are as follows:
Brown corundum: the main component is alumina, the appearance of brown or tan, high hardness, good toughness, can withstand a lot of pressure, with high temperature resistance, oxidation resistance, corrosion resistance, good chemical stability and other characteristics, is very widely used.
White corundum: the main component is alumina, the appearance is white, hardness is higher than brown corundum, brittle, toughness is lower than brown corundum, abrasive grains are easy to fracture, good sharpness.
Black silicon carbide: the main component is silicon carbide, black appearance, high hardness, brittle, sharp abrasive good.
Zirconium corundum: the main composition is alumina and alumina eutectic, the appearance is grayish white or grayish brown, with good toughness and wear resistance, suitable for high-speed heavy load grinding and grinding of metal materials processing.
In addition, there are ceramic abrasive, glass sand, garnet and so on.
The coated abrasives have special requirements for the chemical composition, particle size, particle shape, bulk density, hydrophilicity of the abrasives. The abrasives used by the coated abrasives should use the coated abrasives special abrasives, namely P abrasives.
(2) Classification of binder
Binder is the role of bonding abrasive and substrate, so that the abrasive has a certain shape and strength. The adhesive in coated abrasives is generally composed of substrate treatment agent, adhesive, compound adhesive and so on. The function of the substrate treating agent is mainly to improve the physical and mechanical properties of the substrate, ensure the good quality of the coating and planting sand, and endue the product with good performance. According to the different use requirements of products, the substrate treatment is divided into non-water resistant treatment and water resistant treatment, and the substrate treatment agent should be adapted to it. Adhesive is a coating that binds the abrasive to the substrate and plays a role in bonding and fixing the abrasive.
The compound adhesive is coated with a layer of binder on the fixed abrasive particles, which is surrounded by the abrasive particles, so as to further strengthen the adhesive strength between the abrasive particles and the substrate, and ensure that the abrasive particles can withstand the extrusion and impact of the grinding force in the grinding process and not easy to fall off. The main factors that affect the bond strength of coated abrasives are the type and quantity of binder. The main adhesive used by coated abrasives are animal glue, synthetic resin, etc. Examples: leather gum, formaldehyde resin, phenolic resin, epoxy resin, alkyd resin, etc.
Animal glue: good bonding property, easy to use, but not water resistant, easy to be affected by moisture. Pulse aldehyde resin: simple to manufacture, low cost, bonding properties, moisture resistance and mildew resistance than animal glue. Phenolic resin: high bond strength, water resistance, acid resistance, good weather resistance, especially the use of water-soluble phenolic resin, make it become one of the most important adhesives coated abrasives industry. Epoxy resin, alkyd resin: good bonding performance, good water resistance, but need to use organic solvents, more used in the production of water resistance sandpaper.
(3) The classification of the substrate
The main types of substrates are paper, cloth, steel paper, composite substrate, non-woven fabric, etc.
Paper: coated abrasive paper is made of particularly strong and ductile fiber, according to different needs made of different quality and specifications of varieties. The price of paper is cheaper, generally do not need to undertake substrate processing, the amount is very large.
Cloth: Fabric made from fibers and woven to form certain tissues. Cloth in coated abrasives in the most widely used substrate, good flexibility, high strength, but the need for strict substrate treatment. Cloth because of the different types of fiber to form different varieties, coated abrasive cloth in the current mainly cotton cloth, blended cloth, polyvinegar cloth, etc. Cloth because of the different formation of different types of organization, coated abrasives with cloth organization is currently mainly 1/1, 2/1, 3/1, 4/1, etc., different coated abrasives choose different organizations of cloth.