mineral wool

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Building joint with incomplete firestop made of rockwool packing that still requires topcaulking.

Rockwool stud cavity insulation in drywall assembly under construction.

Common insulation applications in an apartment building.

A rockwool pipe covering applied to a steel pipe for a fire test.

Cubes made of rock wool which could be used for hydroponics

Mineral wool, mineral fibres or man-made mineral fibres are fibres made from natural or synthetic minerals or metal oxides. The latter term is generally used to refer solely to synthetic materials including fibreglass, ceramic fibres and rock or stone wool. Industrial applications of mineral wool include thermal insulation, filtration, soundproofing, and germination of seedlings.

History

Slag wool was first made in 1840 in Wales by Edward Parry but the harmful effects on the workers caused production to be abandoned.^[1] It was first produced commercially in 1871 at the Georg-Marien Hutte in Osnabruck Germany.

Manufacture

Stone wool is a furnace product of molten rock at a temperature of about 1600 °C, through which a stream of air or steam is blown. More advanced production techniques are based on spinning molten rock on high speed spinning wheels somewhat like the process used to prepare cotton candy. The final product is a mass of fine, intertwined fibres with a typical diameter of 6 to 10 micrometers. Mineral wool may contain a binder, often food grade starch, and an oil to reduce dusting.

Usage

Though the individual fibres conduct heat very well, when pressed into rolls and sheets their ability to partition air makes them excellent heat insulators and sound absorbers. Though not immune to the effects of a sufficiently hot fire, the fire resistance of fibreglass, stone wool and ceramic fibres makes them common building materials when passive fire protection is required, being used as spray fireproofing, in stud cavities in drywall assemblies and as packing materials in firestops.

Mineral wools are unattractive to rodents but will provide a structure for bacterial growth if allowed to become wet.

Other uses are in resin bonded panels, growth medium in hydroponics, filler in compounds for gaskets, brake pads, in plastics in the automotive industry and as a filtering medium.

Mineral fibres are produced in the same way, without binder. The fibre as such is used as a raw material for its reinforcing purposes in various applications, such as friction materials, gaskets, plastics and coatings.

The heat that the material can withstand is:

^[2]

In hydroponics

Mineral wool products can hold large quantities of water and air that aids root growth and nutrient uptake in hydroponics; their fibrous nature also provides a good mechanical structure to hold the plant stable. The high natural pH of mineral wool makes them initially unsuitable to plant growth and requires "conditioning" to produce a wool with an appropriate, stable pH.

Safety of material

Precautions need to be taken when handling a fibre product as it can be absorbed into the body by inhalation. It can also irritate the eyes, skin and respiratory tract. Prolonged exposure could lead to long term effects and it is considered a possible carcinogen to humans, similar to asbestos. This effect may depend upon the fibre diameter and length, chemical composition and persistence within the body.

IARC (the International Agency for Research on Cancer) has reviewed the carcinogenicity of man made mineral fibres in October 2002.^[3] The IARC Monograph's working group concluded that only the more biopersistent materials remain classified by IARC as "possibly carcinogenic to humans" (Group 2B). These include refractory ceramic fibres, which are used industrially as insulation in high-temperature environments such as blast furnaces, and certain special-purpose glass wools not used as insulating materials. In contrast, the more commonly used vitreous fibre wools including insulation glass wool, rock (stone) wool and slag wool are considered "not classifiable as to carcinogenicity in humans" (Group 3).

High bio soluble fibres (HT-fibres) are produced that do not cause damage to the human cell. These newer biosoluble materials have been tested for carcinogenicity and most are found to be non-carcinogenic, or to cause tumours in experimental animals only under very restricted conditions of exposure. The IARC Monograph's working group "elected not to make an overall evaluation of the newly developed fibres designed to be less biopersistent such as the alkaline earth silicate or highalumina, low-silica wools. This decision was made in part because no human data were available, although such fibres that have been tested appear to have low carcinogenic potential in experimental animals, and because the Working Group had difficulty in categorizing these fibres into meaningful groups based on chemical composition."^[4]

The EU risk and safety phrases associated with this material in general are:

• R38 – Irritating to the skin
• R39 – Danger of very serious irreversible effects
• R40 – Possible risk of irreversible effects
• S36/37 – Wear suitable protective clothing and gloves.

All European produced rock (stone) wool and glass wool is bio soluble and R39 and R40 do not apply. For these products only the risk phrase R38 remains. This irritation to the skin however is not a chemical irritation but only a temporal mechanical irritation, comparable with exposure of the skin to straw, grass or hay.

Controversy exists over these rulings, as the majority of test results upon which they are based have typically been provided by the industry that makes the fibres. Test results that contravene such results were deemed inadmissible to IARC as submission by whistleblowers^[who?] are not sanctioned by the party paying for the tests^{[citation needed]}. Still, by using common sense to prevent breathing of the fibres and following industrial guidelines, it is possible to reduce the likelihood of pathology.

See also

• Risk and Safety Statements

References

External links

Wikimedia Commons has media related to: Thermal insulation

• Rock Wool material safety data sheet

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