Materials for Thermal Insulation

Batteries with a high operating temperature, of about 300 °C, require high-eSiciency insulating jackets to maintain the temperature within an acceptable range. Especially in nonoperating periods, the battery should not cool down. It is requested that batteries should keep their operating temperature window for at least four days. This requires heat loss rates of less than 200 W for a 40 kWh battery. 

The thermal insulation has also to fulfill the further requirements of  

To limit the thickness of the insulation, and thus the battery volume, the battery insulation is usually maintained at a vacuum of 10 mbar or less. This makes possible the use of jackets that are only 15-30 mm thick. 

The factors that must be controlled for efficient insulation are the amounts of heat transferred by radiation, by conduction through the sohd structure, and by conduction through the residual gases. 

The heat loss by radiation increases with increasing temperature, being proportional to 7. This means there is a steep increase in heat loss with increasing temperature. It was found that about 50% of the heat loss of a battery is caused by radiation. In order to reduce the transmission of radiation through the thermal insulating material, opacifiers are added to the insulating material. 

---

Buildings constructed between 1930 and 1950 may contain insulation made with asbestos. Wall and ceiling insulation that contains asbestos is generally found inside the wall or ceiling ( sandwiched behind plaster walls). The asbestos is used as material for thermal insulation, acoustical insulation, and fire protection. Renovation and home improvements may expose and disturb the materials. 

This specification, prepared by the Navy, covers polyphosphazene elastomeric foam material for thermal insulation on piping, in either sheet or tubing form. Polyphosphazene foam has excellent fire-retardant properties and is suitable for use in the range -20 to 180°F (-29 to 82.TC) in tubular form (Form T). Form S covers sheet form. 

Polypropylene staple with permanent three-dimensional helix has been produced by a new processing technology developed by ESL, a British company, in the 1990s [217]. This staple fiber has the same contour as wool. It is particularly useful as a stuffing material for thermal insulation. 

Reim, M., Komer, W., Manara, J., Korder, S., Arduini-Schuster, M., Ebert, H.P. and Fricke, J., Silica aerogel granulate material for thermal insulation and dayUghting. Solar Energy, 2005. 79(2) p. 131-139. 

Processing techniques used for basalt fibers are similar to the traditional techniques used for glass fibers (fabric, filament, staples, glass fiber-reinforced polymer [GFRP]). Thanks to their excellent properties, basalt fibers are employable in heat-resistant as weU as alkaline-resistant products (containers, pipes, GFRP, materials for thermal insulation). 

Mondal B, Basu PK, Reddy BT et al (2009) Oxidized macro porous silicon layer as an effective material for thermal insulation in thermal effect microsystems. In Chakrabarti P, Jit S, Pandey A (eds) International conference on emerging trends in electronic and photonic devices and systems, Lyon, France, pp 202-206... 

Nearly all the expanded polystyrene that is not used for thermal insulation is used for packaging. Uses range from individually designed box interiors for packing delicate equipment such as cameras and electronic equipment, thermoformed egg-boxes to individual beads (which may be up to 5 cm long and about 1 cm in diameter) for use as a loose fill material. There is also some use of thin-wall containers for short-term packaging and conveying of hot food from... 

Oilfields in the North Sea provide some of the harshest environments for polymers, coupled with a requirement for reliability. Many environmental tests have therefore been performed to demonstrate the fitness-for-purpose of the materials and the products before they are put into service. Of recent examples [33-35], a complete test rig has been set up to test 250-300 mm diameter pipes, made of steel with a polypropylene jacket for thermal insulation and corrosion protection, with a design temperature of 140 °C, internal pressures of up to 50 MPa (500 bar) and a water depth of 350 m (external pressure 3.5 MPa or 35 bar). In the test rig the oil filled pipes are maintained at 140 °C in constantly renewed sea water at a pressure of 30 bar. Tests last for 3 years and after 2 years there have been no significant changes in melt flow index or mechanical properties. A separate programme was established for the selection of materials for the internal sheath of pipelines, whose purpose is to contain the oil and protect the main steel armour windings. Environmental ageing was performed first (immersion in oil, sea water and acid) and followed by mechanical tests as well as specialised tests (rapid gas decompression, methane permeability) related to the application. Creep was measured separately. 

Phenol-formaldehyde (PF) was the first fully synthetic macromolecular material ( Bakelite , 1907). In a slightly precured condition and provided with fillers, it is, as a moulding powder, available for processing into end-use articles such as bulb fittings, switch housings, coils, laminated wood and foam for thermal insulation. 

The Fibrous Minerals. The fibrous minerals contain very long silicate ions in the form of tetrahedra condensed into a chain, as shown in Figure 31-6. These crystals can be cleaved readily in directions parallel to the silicate chains, but not in the directions which cut the chains. Accordingly crystals of these minerals show the extraordinary property of being easily unravelled into fibers. The principal minerals of this sort, tremolite, C.a.jMg..Si 022(0H)2, and chrysotile, Mg6Si40u(0H)p/H20, are called asbestos. Deposits of these minerals are found, especially in South Africa, in layers several inches thick. These minerals are shredded into fibers, which are then spun or felted into asbestos yarn, fabric, and board for use for thermal insulation and as si heat-resistant structural material. 

The fibers or the yarn or rovings made therefrom can be processed to fleeces or mats (non-oriented semi-finished product) and textiles, lattices or meshes (oriented semifinished products) and can be utilized as such e.g. for thermal insulation or as filter materials, or in composites with other materials e.g. for fiber-reinforced polymers, metals or ceramics. Fibers are generally marketed after surface treatment (chemical modification, annealing, smoothing) to optimize their application and processing properties. 

Carbon felts are mainly utilized for thermal insulation at high temperatures e.g. in resistive or induction furnaces. Carbon wool is manufactured by decomposing cotton wool or similar materials and is mainly utilized as a packing material for high temperature heat insulation. Its resistance to chemical corrosion makes it suitable as a filter material for corrosive media, as a support for catalysts and for corrosion-resistant linings in chemical plant. 

A different clay derives from the layered mineral talc, Mg3(Si40io)(01T)2. If iron(II) and aluminum replace magnesium and silicon in varying proportions and water molecules are allowed to take up positions between the layers, the swelling clay vermiculite results. When heated, vermiculite pops like popcorn, as the steam generated by the vaporization of water between the layers puffs the flakes up into a light, fluffy material with air inclusions. Because of its porous structure, vermiculite is used for thermal insulation or as an additive to loosen soils. 

Ceramics used for thermal insulation of microwave caskets include alumina, aluminosilicates, mullite, and fused silica, each of which is relatively transparent to microwave radiation and thus have low dielectric loss at room temperature. The insulating materials included in the casket are typically in the form of ceramic fibers, fiberboard, or a granular bed of ceramic... 

Shredded foam may be used as void liII material or thermal insulation or construchon products. Ground PS foam is used in floral vase stuffing, lawn furniture fill, and in plant nurseries as soil lightener to improve aeration. PS foam beads can also be used with concrete to make lightweight insulating material for use in highway road beds, railroad beds, and airport runways. PS foam can also be an oil spill clean-up material. 

Polyethylene has become one of the most widely used materials for electrical insulation due to its excellent dielectric properties and low cost. Original estimates of its probable lifetime using Arrhenius type extrapolation led to lifetime predictions of the order of forty years or more and yet a substantial number of failures in transmission and distribution cables have been observed at times under ten years. For 1977 failures on HMW URD cable totalled 1697 a failure rate of 3,08 per 100 miles while XLP cables were 0.53 per 100 miles and increasing (5). This work was undertaken to find out the role played by the polymer molecule under separate thermal and electrical stress. 

Mastic- A pasty material used as a cement (as for setting tile) or a protective coating (as for thermal insulation or waterproofing)... 

The test methods mostly follow British Standards, but some are more closely related to the ISO tests. Care must be taken to ensure that the correct sample size is u.sed. The determination of water absorption by diffusion is based on the Swiss Standard SIA 279 Part 5.07 [13] (see Section 2.6 below). Similarly the properties of extruded board are specified in BS 3837, Part 2, 1990 [14]. BS 3927, 1986 [15], specifies rigid phenolic foam for thermal insulation in the form of slabs and profiled sections. The material is classified as types A. B. and C. which differ principally in thermal conductivity, water vapor permeability and apparent water absorption. Thermal conductivity is measured by methods described in BS 4370, Part 2, Method 7 [16] or Appendix B of BS 874 [17]. ... 

---