Translucent insulation materials

Transparent or translucent insulating materials (TIMs) can provide light or solar gains without view. TIMs typically have thermal properties similar to conventional opaque insulation and are thicker than conventional insulating glass units, providing significant resistance to heat transfer. 

Encasing constructions can be used with several membrane layers to form an intermediate space that can be filled with air or another insulating material, making U-values from 2.7 to 0.8 W/m K possible. U-values down to even 0.2 W/m can be obtained by using opaque, flexible mineral fibre fills or translucent insulating material, for example blister foils, as well as reflecting intermediate layers which are commonly used in space technology (ref LPS see Rg. 3.12). 

One of the most promising options of flexible insulation materials to be used for translucent foil structures involves granular silica aerogel as insulation material - see Fig. 12.2 (Cremers, 2008). Not only does aerogel have excellent thermal-insulation properties (see r-values and /-values in Fig. 12.3), but it is translucent as well. 

Due to the absence of a stabilising pressurisation in mechanically tensioned structures, another type of aerogel insulation is employed. This version is a fleece made of two-component fibres which is sprinkled with aerogel particles. This produces a flexible and pressure-resistant mat which has highly favourable insulating properties. This fleece can be used both in combination with transparent ETFE foils and with translucent membrane materials such as PTFE-coated, glass-fibre fabric - see Fig. 12.4. The... 

In case of the thermal insulation, the technical limits are nearly reached today and a further improvement will affect aspects like the units transparency (yiP - Vacuum Insula-ti(Mi Panels) or their maximum size, not mentioning the costs. A functional transparent vacuum insulating unit with U-values of 0.1 W/(m K) is not available by now due to the technical problems of keeping the system permanently gas-tight. Therefore, the use of translucent Silica Aerogels, as a highly efficient insulating material inside the/Gf/ s cavity, represents the best possible thermal insulation at the moment. 

White and translucent hard material used as abrasive for grinding. Excellent electric insulator and also wear resistant. Insoluble in water and in strong mineral acids, readily soluble in strong alkali hydroxides, attacked by HE or NH HEj. Owing to its corrosion resistance, in inert atmosphere, in molten metals such as Mg, Ca, Sr, Ba, Mn, Sn, Pb, Ga, Bi, As, Sb, Hg, Mo, W, Co, Ni, Pd, Pt, and U it is used as crucible container for these liquid metals. Alumina is readily attacked in an inert atmosphere by molten metals such as Li, Na, Be, Al, Si, Ti, Zr, Nb, Ta, and Cu. Maximum service temperature 1950°C... 

SILICA AEROGEL AS A TRANSLUCENT THERMAL INSULATING MATERIAL... 

On the other hand, silica aerogel has also optical function, translucent or transparent, as described in another section (Chapter 3). This excellent thermal insulating material is most ideal for solar energy application. 

Hollomon s ethos, combined with his ferocious energy and determination, and his sustained determination to recruit only the best researchers to join his group, over the next 15 years led to a sequence of remarkable innovations related to materials, including man-made diamond, high-quality thermal insulation, a vacuum circuit-breaker, products based on etched particle tracks in irradiated solids, polycarbonate plastic and, particularly, the Lucalox alumina envelope for a metal-vapour lamp. (Of course many managers besides Hollomon were involved.) A brilliant, detailed account of these innovations and the arrangements that made them possible was later written by Guy Suits and his successor as director, Arthur Bueche (Suits and Bueche 1967). Some of these specific episodes will feature later in this book, but it helps to reinforce the points made here about Hollomon s coneeption of broad research on materials if I point out that the invention of translucent alumina tubes for lamps was... 

Polyethylene. The most straightforward process for the production of polymers from ethylene is that of the direct polymerization of the olefin. The polymerization process usually requires pressures and temperatures of 15,000 to 30,000 pounds per square inch and 200° to 300° C., and may be effected in either gas or liquid phase reactions (9). The polymer of molecular weight above 20,000 is the white, translucent plastic, polyethylene, widely used in electrical insulation, packaging material for foods, cosmetics and pharmaceuticals, liners for paper bags, etc. Articles molded from polyethylene are semirigid or rigid, depending on their thickness, but in thin films the material has excellent flexibility, even at relatively low temperatures. 

Fused quartz or silica tubes are used as insulators through which the wires of a rare-metal couple are threaded, and as outer protecting tubes. The molten quartz may be drawn and worked like glass or the material may be ground and pressed, with a suitable binder, into the proper form and fired in a manner similar to that employed for the manufacture of porcelain. These tubes are translucent like china. Trans-... 

Already many lightweight membrane structures are in existence, and an increasing number of them are planned for the future, e.g. football stadium roofs. For such structures the combination of materials produces widely differing properties. Some projects are very cost-effective, while others are used for more expensive building constructions. Some constructions are of a temporary nature, some are erected at a fixed location some are required to be portable, while others may remain in place for decades. Textile roofs or walls may be open or closed according to the time of day or the position of the sun others stay fixed in one position. Some materials are required to have high translucency others may be designed for maximum insulation. 

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