Mineral wool – the keeper of warmth and silence in the house

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In this Article: The History of Mineral Wool Creation; from what and how mineral wool is made; types, properties and characteristics of mineral wool; which provides mineral wool with heat and sound insulation properties; mineral wool classification; how to deal with negative properties; what to look for when buying.

Laying mineral wool

Among the many worries about your home, the problem of insulation and protection from noise is in the first positions. Summer heat and winter cold – mankind has invented protection from these seasonal phenomena for centuries, but most often relied on heat sources, whether it be an open fire or an electric heater. As for sound insulation, you often get the feeling that you live like in Bulgakov’s “Treatise on Housing” – in a close resemblance to a “telephone receiver” in which sounds often penetrate from everywhere. Insulating materials based on mineral wool will immediately solve two problems – only you should choose them carefully and extremely meticulously.

History of mineral wool

Mineral wool owes its origin to nature – during volcanic eruptions, in addition to lava and scorching clouds, thin threads are formed from molten slag splashes caught in the wind. Noticing this and deciding that such a material would be perfect as a heater, the English industrialist Edward Perry in 1840 reproduced the process of forming threads from blast furnace slag. But they made a gross mistake – the creation of slag wool took place in the open, so some of the fibers produced freely flew around the workshop and the workers were forced to inhale them. As a result, several people were injured, and Perry himself abandoned the idea of ​​producing mineral wool..

History of mineral wool

30 years later, in 1871, industrial production of mineral wool was launched at the metallurgical plant in the German town of Georgsmarienhütte, taking into account the mistakes of Edward Perry.

Mineral wool production technology

The raw materials for stone wool are limestone, diabase, basalt and dolomite, for slag wool – slag waste from blast furnace metallurgy, and glass wool is made from broken glass or from limestone, soda and sand. With the external similarity of, say, stone wool from different manufacturers, its characteristics will differ slightly, since each manufacturer calculates the exact combination of raw materials “for himself”, entrusting the calculation of the exact formula to the technologists of production laboratories and keeping the results in strict secrecy.

It is necessary to formulate the formulation so that the resulting fiber has the maximum quality properties: hydrophobicity and durability, chemical neutrality to metals and materials used in construction and decoration. Possessing these quality characteristics, mineral fiber must have the highest thermal insulation performance, resist any dynamic load. There are two quality criteria that apply to mineral wool – fiber thickness and fiber chemistry. And if exact information on the second criterion is not available to the general public, then the dependence of quality on the thickness of mineral wool fibers is as follows – the thinner the fiber, the higher the thermal insulation properties of the mineral wool.

The production of mineral wool begins with the melting of raw materials, for this the prepared mixture is loaded into cupola furnaces, baths or shaft melting furnaces. Melting temperature in the range 1400-1500 degrees – compliance with the accuracy when heating the initial mixture of components is extremely important, because the length and thickness of the resulting fibers depend on the degree of melt viscosity, which means the dynamic and thermal insulation properties of the mineral wool itself.

Mineral wool production

At the next technological stage, the melt brought to a given viscosity enters the centrifuges, inside which rolls rotate at a speed of more than 7000 rpm, breaking the molten mass into myriads of thin fibers. In the centrifuge chamber, the fibers are coated with synthetic binder components – as a rule, phenol-formaldehyde resins play their role. Then a powerful stream of air throws the formed fibers into a special chamber, where they settle, forming a kind of carpet of a given size.

From the deposition chamber, the fibers are fed to a lamellar or corrugating machine, where the fiber carpet is given a given shape and volume. Next, a carpet of mineral wool is placed in a heat chamber – under the influence of high temperature, the organic binder undergoes polymerization, and the mineral wool itself takes on its final shape and volume. The final heat treatment takes place at strictly defined temperatures – it is at this stage that the strength properties of mineral wool are formed.

At the final stage, polymerized mineral wool is cut into blocks of specified sizes and packaged..

Mineral wool – properties and characteristics

GOST 52953-2008 classifies glass wool, slag wool and stone wool as heat-insulating materials of this group. These types of thermal insulation materials differ not only in the raw material, but also in a number of other parameters: the length and thickness of the fibers; heat resistance; resistance to dynamic loads; hygroscopicity; thermal conductivity coefficient. In addition, it is much easier to work with stone and slag wool than with glass wool – its causticity is widely known, because in the USSR it was used everywhere due to its cheapness.

Mineral wool

Consider the characteristics of each type of mineral wool separately.

Glass wool

The thickness of the glass wool fibers is from 5 to 15 microns, the length is from 15 to 50 mm. Such fibers impart high strength and elasticity to glass wool, practically without affecting the thermal conductivity, equal to 0.030-0.052 W / mK. The optimum heating temperature that glass wool can withstand is 450 ° C, the maximum permissible temperature is 500 ° C, the maximum cooling temperature is 60 ° C. The main difficulty in working with glass wool is its high fragility and causticity. Broken fibers easily pierce the skin, penetrate the lungs and eyes, therefore, goggles and a respirator, disposable overalls (it will not be possible to clean it of glass wool fibers) and gloves are required;

Slag wool

The thickness of the fibers of which is from 4 to 12 microns, the length is 16 mm, among all other types of mineral wool, it can withstand the lowest temperature – up to 300 ° C, above which its fibers are sintered, and the functions of thermal insulation completely cease. Slag wool has a high hygroscopicity, therefore it is not allowed to work on the facades of buildings and for thermal insulation of water pipes. Another disadvantage of slag – blast-furnace slags, from which it is produced, have residual acidity, which, with the slightest moisture, leads to acid formation and the appearance of an aggressive environment for metals. In a dry state, its thermal conductivity is in the range of 0.46 – 0.48 W / m · K, i.e. is the largest among the thermal insulation materials of its group. To top it off, the fibers are slag-like brittle and splintered, like glass wool fibers;

Stone wool

The thickness and length of its constituent fibers is the same as that of slag wool. Otherwise, its characteristics are better – thermal conductivity is in the range of 0.077-0.12 W / m · K, the maximum withstand heating temperature is 600 ° C. Its fibers are not splitting; stone wool is much easier to work with than glass wool or slag wool. Basalt wool, produced from almost the same raw material as stone, has the best characteristics. The only difference is that manufacturers add minerals (limestone, dolomite and clay), charge or blast-furnace slags to the starting material (diabase or gabbro) for stone wool, which increases the fluidity of the melt – the share of mineral and other impurities in the stone wool can be up to 35 %. By the way, it is stone wool that is called mineral wool in construction markets..

In addition to thermal insulation materials related to mineral wool, there is also basalt fiber. It does not contain any impurities or binding components, therefore it can withstand the highest heating (up to + 1000 ° C) and cooling (up to – 190 ° C) temperatures. The absence of a binder does not allow forming sheets or rolls of basalt fiber; this heat-insulating material is used in bulk or stuffed with mats.

Any heat-insulating material related to mineral wool has high sound absorption performance – almost absolute sound absorption in super-thin basalt fiber (STBF).

All types of mineral wool, with the exception of super-thin basalt fiber, contain from 2.5 to 10% of a binder based, as a rule, of phenol-formaldehyde resins. The lower the percentage of this binder contains mineral wool, the less likely the threat of evaporation of phenol, but, on the other hand, the higher the content of phenol-formaldehyde resins gives greater resistance to moisture.

Any type of mineral wool does not burn and does not support combustion – if the temperature exceeds the permissible temperature for this type of mineral wool, its hairs will only fuse together.

Why is mineral wool an effective heat and sound insulator

Thermal insulation of mineral wool is based on two elements: the small diameter of its constituent fibers does not allow the accumulation of heat; the chaotic internal structure forms many air cavities that impede the free transmission of radiant heat. Thermal insulation of rigid mineral wool slabs is ensured by chaotic orientation and arrangement of fibers. By the way, their resistance to dynamic loads will be the higher, the greater the percentage of the forming fibers will be located vertically, i.e. manufacturers of mineral wool boards are forced to find the optimal balance between thermal conductivity and compression resistance.

Applications and grades of mineral wool

Sound insulation with mineral wool is achieved due to its air-cellular internal structure – standing sound waves and acoustic noises are immediately attenuated, because cannot continue to spread.

Applications and grades of mineral wool

Mats and slabs based on mineral wool are used for thermal insulation of straight and curved surfaces – roofs and internal walls, ceilings and partitions, floors of buildings and panel structures. Installation work of mineral wool does not require special skills.

Mineral slabs are classified by density:

Brand P-75

Plates and mineral wool of the P-75 brand, the density of which is 75 kg / m3, insulate unloaded horizontal surfaces, for example, attics of buildings, and in some cases – for thermal insulation of the roof. They are used for insulation of heating system pipelines, gas and oil pipelines;

Brand P-125

The P-125 brand of mineral slabs and wool is used for heat and sound insulation of unloaded surfaces of any spatial position, in the construction of internal partitions, heat insulation of floors and ceilings. Slabs of this brand are used as a middle layer in three-layer brick, aerated concrete, expanded clay concrete walls of low-rise buildings;

PZh-175 brand

Walls and ceilings made of profiled metal sheet and reinforced concrete products (without cement screed) are insulated with a rigid slab of the ПЖ-175 brand;

Brand PPZh-200

Increased rigid plate ППЖ-200 is used to increase the fire resistance of engineering and building structures – otherwise the area of ​​its application is identical to the area of ​​application of ПЖ-175.

Manufacturers produce mineral slabs and wool of lower density than P-75 – accordingly, such products are used mainly on horizontal surfaces, provided that there are no dynamic loads.

Cons of mineral wool

It is not entirely safe to work with products based on it, despite the lack of sharpness in stone wool fibers. A binder based on phenol-formaldehyde resins can release phenol, which is not at all conducive to the health of the household. In addition, the smallest particles of mineral wool fibers will inevitably be lifted into the air during installation, and their penetration into the lungs is highly undesirable..

However, negative aspects can be avoided. In the second case, use a respirator, carefully tighten the entire surface of the laid mineral wool or slab with a vapor-proof pvc film. As for the danger of phenol release – at ordinary temperature, conditionally called “room”, the products of the largest manufacturers of mineral fiber products will not emit phenol.

Mineral slabs

But – the release of phenol is inevitable if the mineral wool is heated to the maximum design temperatures, because at such temperatures, bonds formed by phenol-formaldehyde resins will be lost. So, the choice of products of a large manufacturer will help to solve the problem with phenol in mineral wool, to exclude the possibility of heating the insulation to temperatures exceeding the calculated one, or to build thermal insulation on super-thin basalt fiber that does not contain a binder (the most expensive solution).

What you need to pay attention to when choosing a mineral wool

For a manufacturer – let it be a well-known brand, for example, “Rockwool”, “ISOVER”, “PAROC” or “URSA”. If it becomes possible to purchase mineral wool from a German manufacturer, do it, because German certification bodies are considered the most picky about these products when compared with all other EU countries..

Decide on the density of mineral wool – the higher it is, the more expensive the mineral wool itself. The dependence of the price on density is associated with a large number of fibers in denser mineral wool, respectively, with a large consumption of material during production.

Do not be tempted by the low cost of glass wool and slag wool, because their heat and sound insulation characteristics are the lowest, and installation will not be easy because of the causticity.

Find out if the fibers in a given mineral wool have a vertical orientation or their arrangement is chaotic – in the second case, the heat and sound insulation properties will be higher, and in the first case, the resistance to dynamic loads is higher..

Depending on the type of mineral wool purchased, it must comply with GOST. Here are some of them: for mineral wool slabs – GOST 9573-96; for stitched mats – GOST 21880-94; for slabs of increased rigidity – GOST 22950-95.

And finally, do not trust the claims of sellers that “this mineral wool really has a thickness of 50 mm” – partially open the package and see for yourself!

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