HB21L man-made mineral stone wool fibers for friction and sealing materials

Short Description:

Rock wool fiber HB21L, an inorganic silicate fiber, is made of basalt, diabase and dolomite by blowing or centrifugation at high temperature. It is grey-green and pure. To promote its dispersion and adhesion, we mix a little liquid phenolic resin. Finally it is yellow-green. After fixing length and shot removal, a mass of fine, intertwined fibres are created.

Since the matrix in the friction material is an organic phenolic resin, and the rock wool fiber is an inorganic reinforcing fiber, there is a problem of poor interfacial bonding between the rock wool fiber and the matrix resin. Therefore, we usually use surfactants to modify the surface of rock wool fibre, which can improve its compatibility with organic binders.Since rock wool and its products are light and fibrous materials and are produced by dry method, a certain amount of dust will be generated during the processing of raw material melting, product cutting and etc. Dust can irritate to the skin. The fiber after surface treatment can inhibit the fine dust in the mixture to reduce the irritation of the dust to the skin and improve the working environment. 

Product Detail

Product Tags




Test Result



SiO2+Al2O3 (wt%)



CaO+MgO (wt%)



Fe2O3 (wt%)



Others(max; wt%)



Ignition loss (800±10℃,2H; wt%)








Long-term using temperature



Fibre diameter numerical average(μm)



Fibre length weighted average(μm)



Shot content (>125μm)



Specific density(g/cm3)



Moisture Content(105 ℃±1℃,2H; wt%)



Surface Treatment Content(550±10℃,1H; wt%)




Asbesto Detection



RoHS Directive(EU)

10 substance of RoHS


Safety Date Sheet(SDS)





Friction materials

Sealing materials

Road construction

Coating materials

Insulation materials

Our rock wool mineral fibers are suitable for industrial structural reinforcements such as friction, sealing, road engineering, coatings. For many years our rock wool mineral fibres have been used in automotive friction materials (disc pads and linings) to improve comfort, safety and durability. Brake linings made from our fiber products have many notable features such as braking stably, high temperature properties, little abrasion, low (no)noise and long life.


● Asbestos Free
Our fine rock wool fibre is friendly and safe for human and environment without asbestos. It is non-radioactive and passed non asbestos testing.

● Low shot content
The nature of the production process means that for every fibre, there is a small non-fibrous particle called “shot”. Our fibre is made of pure rock , so it is stable because of stable chemical compositions of its raw materials. In our production process, we can reduce the shot content lower to 1% after testing. Low shot content can bring about low wear and noise on brake materials.

● Excellent dispersion and combination
We put a variety of surface treatments on the fibres, which makes it compatible to different binder systems. That can be an adhesion promotor, surfactant, or even a rubber layer. With the different surface modifiers, we can engineer the fibres for a range of binder systems and applications. It can be well combined with resin.

● Dust suppression
After surface treatment, fibres can inhibit fine dust in the mixture to reduce its irritation of skin and improve the working environment.
High temperature resistant,  moisture and abrasion resistant.

Note: We can customize fiber according to clients special needs.

How to distinguish between slag wool and rock wool

The same points

Rock wool and slag wool belong to the same mineral wool. There are many things in common, like production process, fiber shape, alkali resistance, thermal conductivity, non-combustibility, etc. People usually refer to rock wool and slag wool as mineral wool, so it is easy to regard the two as the same thing, which is a misunderstanding. Although they are both mineral wools, there are some differences that cannot be ignored. The main reason for these differences is the difference in raw material composition.

The difference between them

The main raw material of slag wool is generally blast furnace slag or other metallurgical slag, and the main raw material of rock wool is basalt or diabase. Their chemical compositions are quite different.

1) Comparison of chemical composition and acidity coefficient between rock wool and slag wool.
From a professional point of view, the acidity coefficient is generally used as the main indicator to distinguish rock wool from mineral wool. The acidity coefficient MK of rock wool is generally greater than or equal to 1.6, and can even be as high as 2.0 or more; The MK of slag wool can generally only be maintained at about 1.2, and it is difficult to exceed 1.3.

2) The performance difference between rock wool and slag wool.

Rock wool has a high acidity coefficient, and its chemical stability, high temperature resistance, and corrosion resistance are superior to mineral wool. Slag wool should not be used in humid environments, especially in cold insulation projects. Therefore, only rock wool can be used in the thermal insulation system inside the building, and slag wool cannot be used. When the working temperature of the slag wool reaches 675℃, the density of the slag wool becomes smaller and the volume expands due to physical changes, so that the slag is pulverized and disintegrated, so the temperature of the slag wool should not exceed 675℃. Therefore, slag wool cannot be used in buildings. The temperature of rock wool can be as high as 800 ℃ or more.

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