Glass wool

Glass wool is an insulating material made from glass fiber arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation properties. Glass wool is produced in rolls or in slabs, with different thermal and mechanical properties. It may also be produced as a material that can be sprayed or applied in place, on the surface to be insulated.

Principles of function

Gases possess poor thermal conduction properties compared to liquids and solids^[2][3] and thus make good insulation material if they can be trapped in materials so that much of the heat that flows through the material is forced to flow through the gas.^[4] In order to further augment the effectiveness of a gas (such as air) it may be disrupted into small cells which cannot effectively transfer heat by natural convection. Natural convection involves a larger bulk flow of gas driven by buoyancy and temperature differences, and it does not work well in small gas cells where there is little density difference to drive it, and the high surface area to volume ratios of the small cells retards bulk gas flow inside them by means of viscous drag.

In order to accomplish the formation of small gas cells in man-made thermal insulation, glass and polymer materials can be used to trap air in a foam-like structure. The same principle used in glass wool is used in other man-made insulators such as rock wool, Styrofoam, wet suit neoprene foam fabrics, and fabrics such as Gore-Tex and polar fleece. The air-trapping property is also the insulation principle used in nature in down feathers and insulating hair such as natural wool....

Manufacturing process

Natural sand and recycled glass are mixed and heated to 1,450 °C, to produce glass. The fiberglass is usually produced by a method similar to making cotton candy, by forcing it through a fine mesh by centrifugal force, cooling on contact with the air. Cohesion and mechanical strength are obtained by the presence of a binder that “cements” the fibers together. A drop of binder is placed at each fiber intersection. The fiber mat is then heated to around 200 °C to polymerize the resin and is calendered to give it strength and stability. Finally, the wool mat is cut and packed in rolls or panels, palletized, and stored for use.

Uses

Glass wool is a thermal insulation material consisting of intertwined and flexible glass fibers, which causes it to "package" air, resulting in a low density that can be varied through compression and binder content (as noted above, these air cells are the actual insulator). Glass wool can be a loose-fill material, blown into attics, or together with an active binder, sprayed on the underside of structures, sheets, and panels that can be used to insulate flat surfaces such as cavity wall insulation, ceiling tiles, curtain walls, and ducting. It is also used to insulate piping and for soundproofing.