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Coated abrasives – abrasive structure

The structure of a coated abrasive consists of up to five main components: backing, base coat, abrasive grit, size coat as well as an additional coating.

Backing

The first of these components is the backing. Paper, cloth, plastic films, vulcanised fibre, foam or a combination of paper and cloth are used as backing for coated abrasives.

The backing gives the abrasive very specific grip and adhesion, stretch, tear resistance, tensile strength, flexibility and stability properties.



Base coat

We use only environmentally-friendly, water-soluble binder systems. We mainly use phenol and urea resins, which, depending on application, are flexibilised using different dispersions such as synthetic resins or hide glue. These systems enable us to manufacture very hard, high-performance abrasives on the one hand, as well as highly flexible finishing products on the other.

The base coat is used to prefix the abrasive grits in the required position and distribution on the backing material. Softer, more elastic or harder, tougher binder resins are used depending on the application of the abrasive. The hardness of the bonding agent affects the aggressiveness and the lifetime of the abrasive.



Abrasive grit


The most common materials used for the production of abrasive grits are aluminium oxide and silicon carbide in their various forms. Minerals such as zirconia alumina, ceramic aluminium oxide and diamond are also used. The hardness and resilience of the abrasive grits determine the properties and the applications of the abrasive. An abrasive coating can be open or closed depending on grit size and grit quantity.

The key minerals are summarised below:

Garnet
For wood and manual sanding.

Emery
For precious metals and fine sanding.

Brown aluminium oxide
For metal.

Semi-friable aluminium oxide
For metal and wood.

White aluminium oxide
For wood and manual sanding.

Silicon carbide
For grey cast iron, stone, hardwood, glass and particle board.

Zirconia alumina
For alloyed steel.

Ceramic aluminium oxide
For high-alloy steel.

Diamond
For stone, concrete, glass, grey cast iron and carbide.

Size coat




The size coat permanently bonds the abrasive grits to each other and to the backing material.

Softer, more elastic or harder, tougher binder resins are used depending on the application of the abrasive. The hardness of the bonding agent affects the aggressiveness and the lifetime of the abrasive.



Additional coating




The final step involves applying additional materials to complete the abrasive structure. This extends the lifetime of the abrasive or (if an active cooling agent is added) prevents glazing of the grit tips.

Stearate, for example, minimises the clogging tendency of the abrasive. Coolants prevent glazing of the grit tips.