Mineral_wool encyclopedia topics

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 fibers 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 fibers conduct heat very well, when pressed into rolls and sheets their ability to partition air makes them excellent heat and sound insulators. Though not immune to the effects of a sufficiently hot fire, the fire resistance of fiberglass, stone wool and ceramic fibers 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 fibers are produced in the same way, without binder. The fiber as such is used as a raw material for its reinforcing purposes in various applications, such as friction materials, gaskets, plastics and coatings.

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 of 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 fiber 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. This effect may depend upon the fiber diameter and length, chemical composition and persistence within the body.

High bio soluble fibers (HT-fibers) are produced that do not cause damage to the human cell. IARC (the International Agency for Research on Cancer) has reviewed the carcinogenicity of man made mineral fibers in October 2002. These newer biosoluble materials have been tested for carcinogenicity and most are found to be non-carcinogenic, or to cause tumors in experimental animals only under very restricted conditions of exposure. The IARC Monographs working group concluded that only the more biopersistent materials remain classified by IARC as possible human carcinogens (Group 2B). These include refractory ceramic fibers, 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 fiber wools including insulation glass wool, rock (stone) wool and slag wool are considered not classifiable as to carcinogenicity to humans (Group 3).

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 fibers. Test results that contravene such results were deemed inadmissible to IARC as submission by whistleblowers are not sanctioned by the party paying for the tests. Still by following common sense and industrial guidelines to prevent breathing of the fibers, it is possible to reduce the likelihood of pathology.