Coated abrasives classification and properties

- Jun 02, 2018-

Abrasives are known as "industrial teeth," and coated abrasives are known as "industrial beauticians." In most books and textbooks in China, the definition of coated abrasive is a tool that can be used to grind and polish the abrasive by bonding it to a flexible material such as cloth or paper. The classification includes the cloth. Rolls, sheets, ribbons, discs, and exotics made from substrates such as paper, paper, and non-woven fabrics.

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1:Coated abrasive basic knowledge

1.1: Coated Abrasives Definition and Structure

Coated Abrasives: Abrasives that are adhered to a bendable substrate with an adhesive. The structure of coated abrasives, as shown in Figure 1

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The three elements of the coated abrasive are: substrate, abrasive, and binder.

Substrate: Carrier for abrasives and binders. 

Abrasive: Grinding and polishing of the abrasive body

Binder: It acts as a bonding abrasive and substrate, giving the tool a certain shape and strength. 

The nine major characteristics of coated abrasives: substrate, substrate processing, abrasives, grain size, sand density, binder, bond strength, shape, size.

2: The composition of the three elements of the coated abrasive tool.

The "three elements" of the coated abrasive tool is the substrate, abrasive, and the adhesive. Each element has different properties and different model materials to choose from.

(1): Classification of Substrates: Substrates are carriers for abrasives and adhesives in coated abrasives. It is the dominant factor in the flexibility of coated abrasives, and it is also the main feature that distinguishes it from other abrasives. The types of substrates include paper, cloth, steel paper, composites, and non-woven fabrics. Paper: The paper for coated abrasives is made of particularly strong and tough fibers. It is made to meet the different needs of different quality and specifications. Paper is cheaper and generally does not require substrate processing.

(2) Types of Abrasives Abrasives are the main subject of abrasive and abrasive polishing by coated abrasives. The abrasive must possess these basic properties: certain hardness, certain strength, proper crushability, certain physicochemical stability. Abrasives can be divided into natural abrasives and artificial abrasives.

The types of abrasives commonly used for coated abrasives include: Brown fused alumina (A): The main component is alpha-AI2O3. The appearance is brown or brown. The hardness is high and the toughness is good. It can withstand a lot of pressure, and it has high temperature resistance and resistance. Corrosion, good chemical stability and other characteristics, a very wide range of applications.

White fused alumina (WA): The main component is AI2O3, the appearance is white, hardness is higher than brown corundum, brittle, low toughness than corundum, abrasive easy to crack, sharp and good.

Black silicon carbide (C): The main component is SIC, the appearance of black, high hardness, brittleness, and good sharpness of the abrasive.

Zirconium Corundum (ZA): The main components are α-AI2O3 and AI2O3-Zr eutectics, the appearance of gray or gray brown, with good toughness and wear resistance, suitable for high-speed heavy-duty grinding and processing of difficult-to-grind metal materials.

In addition, there are ceramic abrasives, glass sand, garnet and so on. The special requirements for the chemical composition, particle size, particle shape, bulk density, hydrophilicity, etc. of the abrasive on the coated abrasives, the abrasive used for the coated abrasives shall be coated with a special abrasive for the coated abrasives.

(3) Classification of Adhesives - Adhesives act as bonding abrasives and substrates, giving the abrasives a certain shape and strength. 

The adhesive in the coated abrasives is generally composed of a substrate treatment agent, a primer, a sizer, and the like. The role of the substrate treatment agent is mainly to improve the physical and mechanical properties of the substrate, to ensure a good quality of coated sand, giving the product a good performance. According to the different application requirements of the product, the substrate treatment consists of non-water treatment and water treatment, and the substrate treatment agent should be adapted accordingly. Primer is a coating that binds the abrasive to the substrate and acts as a bond and a fixed abrasive. Glue is to apply a layer of adhesive on the fixed abrasive particles to surround the letter to further strengthen the bond strength between the abrasive particles and the substrate to ensure that the abrasive particles can withstand the grinding force during the grinding process. Squeeze and impact and not easy to fall off role.

The main factor affecting the bond strength of the coated abrasive is the type and amount of the binder. The adhesives used in the coated abrasives include: animal glues, synthetic resins, etc. Example skin glue, urea formaldehyde resin, phenolic resin, epoxy resin, alkyd resin, etc.  Animal glue: good adhesion, easy to use, but not water, easy to damp. Urea-formaldehyde resin: simple to manufacture, low cost, adhesive properties, moisture resistance and mold resistance are superior to animal glue. Phenolic resin: high bond strength, good water resistance, acid resistance and weather resistance, especially the use of water-soluble phenolic resin, making it one of the most important adhesives for the coated abrasive industry. Epoxy resin, alkyd resin: good adhesion, good water resistance, but the use of organic solvents, more than the production of water-resistant sandpaper.

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