What is Coated Abrasives?
Coated abrasives are particles applied to a surface, usually in the form of tapes, sheets, discs and rolls, where the particles are attached to a backing by a binder, and then another layer of binder provides additional support for the particles. Sandpaper is probably the most common type of coated abrasive. Widely used substrates are paper, cloth, vulcanized fibers, and plastic films, which range in particle size from very coarse (~24 mesh) to ultrafine (micron size).
Coated abrasives may be products consisting of a thin layer of abrasive grains attached to a substrate such as paper or cloth, and are available in the form of sheets, discs, coils, specialty materials or strips. Another international standard for coated abrasives is ISO 6344.
Coated abrasives can utilize abrasive grains with high performance and excellent uniformity. Ceramic particles are also self-sharpening for longer life and can be used on materials that are difficult to grind or finish.
What are the ingredients?
The following are the components of the coated abrasives:
Abrasive grains
Coated grinding wheels are developed using abrasive grains. The most common abrasive particles are alumina, zirconium, ceramic, carbide and garnet. Grains are crushed and separated into particle sizes using calibrated sieves. Grain sizes range from 12 (very coarse) to 1200 (very fine). Once the particles are separated into different sizes, they are attached to the backing material using various bonding techniques.
Here are descriptions of the most common abrasive grains:
CERAMIC
It is a high-performance artificial abrasive with a very uniform, high-density grain structure. The extremely durable ceramic is self-sharpening for longer life and easier cuts. Specializes in difficult-to-grind materials.
ALUMINUM OXIDE
It is a challenging, lumpy man-made grain for high-speed grinding and finishing of metal, wood, and other durable materials without excessive cracking or chipping. Resistance to fracture is the main consideration and aluminum oxide will outperform all other coated abrasives.
ZIRCONIUM
Zirconium is an excellent, dense man-made grain for power cutting. Zirconium, which can be a very thick material, has unique self-sharpening properties that give it a long life in large-scale cutting operations.
SILICON CARBIDE
It is a hard, very sharp man-made abrasive suitable for use on non-ferrous and non-metallic materials such as concrete, marble and glass. Carbide is a brittle grain that cuts faster under light pressure than other grains used in coated abrasives.
GARNET
Formed naturally from alumina, garnet may be a relatively strong but fragile bonded structure. Very inconsistent compared to synthetics. It is primarily used in woodworking, as garnet dulls too quickly for metalworking.
How to produce coated abrasives?
Preparatory product manufacturing includes:
Bucket treatment
–Treatment of high-quality cotton cloth, polyester cloth and mixed abrasive cloth by dipping and gluing
–Purpose—to minimize elongation and adjust softness
–Through continuous research and development, VSM is one of the few manufacturers of coated abrasives in the world that has cloth finishing machines and uses them optimally
Resin bonding production
–Production of high-quality phenolic and urea-formaldehyde resins for coated abrasives
Abrasive treatment
— Improve coating performance and abrasive adhesion through proper handling during the forecasting process
–Produce stacked abrasive particles
Large roll production line
As shown in the picture:
Step 1: rolling out the backing
At the start of the production process, abrasive backings are supplied in jumbo rolls with a width between 1450 and 1950 mm. The supplied rolls contain 1500 to 5000 meters of continuous material, depending on the thickness of the backing.
Thanks to the double rolling, the backing can be fed continuously without interrupting the production process. The backing reservoir acts as a buffer to allow sufficient time for roll changes without slowing down at the end of the roll.
Step 2: printing the abrasive paper backing
The backing was printed using flexographic printing. The information printed on the back of the coated abrasive paper contains important information such as product name and grain size details. Depending on the sanding ap plication, safety or legally relevant information is also printed. The serial number ensures that the product can be traced at any time.
Step 3: base coat application
During automated operation, the binder resin is continuously metered and applied across the entire production width. The production speed is 80m/min. For this, the whole process has to adapt to this speed. The primer feed is checked several times to ensure that the product is always of high quality.
Steps 4 and 5: grit coating
After the backing is coated with primer, it enters the “electrostatic coating” core grinding tool production process. The abrasive is transported on the abrasive belt to a charged 90,000 volt “electrostatic field”. Here, the grit attaches itself to the passed scrim backing and adheres to the binder resin. This procedure takes place in a fully air-conditioned environment.
Step 6: pre-drying kiln
During the first drying cycle, the abrasive particles are temporarily fixed by drying the undercoat. According to the recipe, the abrasive remains in the pre-drying kiln for approximately 90 minutes.
Step 7: Size Coating Application
Apply the primer in the glue machine. The abrasive particles are thus permanently affixed to the backing. The integration of the abrasive grains is critical to the quality of the abrasive. According to product requirements, the abrasives can also be dyed for easy differentiation. Additives such as stearates or coolants are also mixed at this stage.
Step 8: pre-drying kiln
Abrasives are baked for approx. 120 minutes in a second drying kiln to ensure optimal curing.
9、10 steps: rolling up the jumbo roll
The abrasive is now rolled up at a constant temperature of up to 100 °C. The finished giant rolls, which can carry up to 3000 meters of continuous abrasive, are now fully post-cured for several hours in giant curing kilns. After the abrasive is fully cured, the giant roll enters the post-processing stage. Here, the abrasive is pushed out again, then crushed, bent and wetted. After this, the completed jumbo is trucked to the manufacturing plant.
References
- https://benchmarkabrasives.com/blogs/news/what-are-coated-abrasives
- https://www.siaabrasives.com/en-ca/expertise/types-of-abrasives/coated-abrasives/production/
- https://onedrive.live.com/?authkey=%21ALeECTYbLIJsoYw&cid=809642C1196FB5C7&id=809642C1196FB5C7%2183528&parId=809642C1196FB5C7%2183518&o=OneUp
