Coated abrasives main components are abrasive grains, backing materials and resins.
The backing is the foundation of the product and when choosing a backing you will also choose what can be done with the product. The backing material not only carries the abrasive layers, it must also transfer the sanding power through to the surface. This means that larger abrasive grains demand more power and, therefore, also need a stronger backing material.
Paper backing - The different weight of the paper, as well as the latex content, determines the flexibility and waterproof properties of the coated abrasives. The light weight papers are more flexible, while the heavy weight papers are stronger and tear resistant. The addition of 30% latex in the paper, makes the coated abrasive waterproof and suitable for wet sanding applications.
Cloth backing - Cloth backing is made of Cotton fibres, or a mixture of Cotton and Polyester fibres, or polyester fibres only. Cloths are tear-resistant and very flexible. According to the density of the yarns, cloths are categorised in more flexible and less strong cloth abrasives (like J-type), or less flexible but very strong cloth abrasives (like X-type).
Film backing - Extremely thin layer of a polyester special treated backing, very flexible and tear-resistant mainly used for finishing and sanding applications.
Foam backing - Foam backing is a polyether-based material, adhered to the paper or the cloth abrasives, in order to make them suitable for sanding profiled surfaces. Due to the unique absorbance properties of the foam, the finishing result is guaranteed and the final surface is free of deep scratches and irregularities.
NET backing - The Net Mesh consists of Polyamide and Polyester yarns, creating a special net structured backing. Due to the unique pattern of the combs and mesh combination, this backing is ideal for manufacturing non-clogging coated abrasives with outstanding dust-extraction properties.
Fibre backing - Fibre backing is made of vulcanised cotton fibres, creating a very hard and robust backing, with great mechanical strength and heat resistance. It is suitable for coated abrasives in heavy-duty applications.
Make Coat & Size Coat
The ‘Make Coat’ and ‘Size Coat’ are layers of resin. The Make Coat is the first layer on which the abrasive grains are applied, while the Size Coat is added to keep the grains firmly in place.
A key factor in producing flexible abrasives is the amount of resin that is applied. A low amount of resin results in an aggressive product but with restricted working lifespan. Increasing the amount of resin increases the products working lifespan.
A constant research and development program has enabled Mirka to continually enhance the performance of its products. By optimising the construction of our products we have been able to provide innovative and cost effective solutions that meet the demanding requirements of modern customers.
Amount of Grains The performance is greatly affected by the amount of abrasive grains used. For example, less grains results in an open coating which is highly resistant to clogging, whereas more grains produce a closed coating with good stock removal and a smooth surface finish.
Grit Sizes Different grit sizes are used for different purposes. Therefore, grit sizes are sorted during manufacture. Abrasive products can be made with different grit size standards such as FEPA, ANSI and GOST. Mirka uses grains according to the FEPA standards – Federation of European Producers of Abrasives. Products produced according to this standard are recognised by the ‘P’ mark – for example P80. Grain size is determined by passing them through sieves that are measured in ‘threads- per-inch’. W hen it comes to micro grains, the threads-per-inch measure- ment is a theoretical amount.