Thermal Insulation Index

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. 

In terms of fire safety, there are no fire resistance requirements and all interior surfaces must comply with the FSI of 200 in the Steiner tunnel test, ASTM E 84,114 or a radiant panel index of 200 in the radiant panel test, ASTM E 162.55 Thermal insulation materials, other than foam plastics, must meet an ASTM E 84 Class A requirement (i.e., FSI < 25 and SDI < 450) and loose-fill insulation must meet the same requirements as the building codes, which are mostly based on smoldering tests (as the materials tend to be cellulosic). Foam plastic insulation must be treated as in the building codes as well (see Table 21.13) it cannot be used exposed (expensive foam that meets the NFPA 286 test is not used in manufactured housing) and must meet an ASTM E 84 Class B requirement behind the thermal barrier. 

The next detector often used in liquid chromatography is the refractive index detector. This detector uses the property of the sample molecules to bend or refract light. The disadvantage of these detectors in comparison to UV detectors is that refractive index detectors are less sensitive than the UV detectors. Refractive index depends strongly on the temperature of the sample. This is why the refractive index detector must be well thermally insulated. A scheme of the analysis cell of the refractive index detector is shown in Figure 2.23. 

Sources are often surrounded by a thermally insulated enclosure to reduce noise caused by refractive index gradients between the hot air near the source and cooler air in the fight path. Short-term fluctuations in spectral output are usually due to voltage fluctuations and can be overcome by use of a stabilized power supply. Long-term changes occur as result of changes in the source material due to oxidation or other high temperature reactions. These... 

Kusan-Bindels and Friedrichs [57] have discussed the measurement of this property in rigid polyisocyanurate foams. An increase in the thermal insulation index of this polymer improves temperature stability and mechanical properties, even at 250 °C. 

Sol-gel techniques are being employed to fabricate components not only for mainstream applications such as photonics, thermal insulation, electronics and microfluidics, but also for more exotic applications such as space dust and radiation collectors [1]. Methods have been developed to tailor the physical properties of sol-gel materials to the requirements of a specific application. For example, porosity and pore size distribution can be controlled by forming micelles in a sol [2-4-] gels can be made hydrophobic by derivatizing the otherwise hydrophilic pore walls with hydrophobic moieties [5] superhydrophilicity can be obtained by ultraviolet irradiation [6, 7] mechanical strength can be increased by cross-linking the oxide nanoparticles that make up the gel [1, 8, 9], and optical properties can be controlled by adding chromophores and nanoparticles to control index of refraction, absorption and luminescence [10-12]. 

The techniques presented here allow to produce ultralight materials with anisotropic properties. Optical absorption and emission, hydrophobicity mechanical strength and index of refraction can be tuned within the same monolith. Conceivable applications of our technique include fabrication of photonic devices, membranes, radiation collimators, fuel cell electrodes as well as hierarchically structured materials that combine mechanical strength with the acoustic and thermal insulation properties of conventional aerogels. 

A photonic device is also found in the literature (Wang et al. 2007) using the thermal insulation properties of porous Si in a photonic crystal reflector for mid-infrared applications. It uses an alternate high-porosity/low-porosity multilayer structure with the high-porosity layers fully oxidized and the low-porosity layers partially oxidized in order to achieve good thermal insulation properties and at the same time enough contrast of the refractive index. 

In recent years, epoxy resins have been nsed to realize optical disk matrices, lenses and prisms. However, the refractive index of conventional epoxy resins is low and their applications as optical materials where a high refractive index is reqnired are limited. For this reason, many efforts are being dedicated to synthesizing new optical epoxy resins characterized by a high refractive index, good mechanical properties and optimal thermal insulation. 

Vitreous sihca has many exceptional properties. Most are the expected result of vitreous sihca being an extremely pure and strongly bonded glass. Inert to most common chemical agents, it has a high softening point, low thermal expansion, exceUent thermal shock resistance, and an exceUent optical transmission over a wide spectmm. Compared to other technical glasses, vitreous sihca is one of the best thermal and electrical insulators and has one of the lowest indexes of refraction. 

Thermal Properties. Thermal properties include heat-deflection temperature (HDT), specific heat, continuous use temperature, thermal conductivity, coefficient of thermal expansion, and flammability ratings. Heat-deflection temperature is a measure of the minimum temperature that results in a specified deformation of a plastic beam under loads of 1.82 or 0.46 N/mm (264 or 67 psi, respectively). Eor an unreinforced plastic, this is typically ca 20°C below the glass-transition temperature, T, at which the molecular mobility is altered. Sometimes confused with HDT is the UL Thermal Index, which Underwriters Laboratories estabflshed as a safe continuous operation temperature for apparatus made of plastics (37). Typically, UL temperature indexes are significantly lower than HDTs. Specific heat and thermal conductivity relate to insulating properties. The coefficient of thermal expansion is an important component of mold shrinkage and must be considered when designing composite stmctures. 

Fluorine-containing polymers exhibit unique chemical and physical properties and high performance that are not observed with other organic polymers. They possess high thermal stability, high chemical stability, a low coefficient of friction, low adhesion, water and oil repellency, low refractive index, and outstanding electric insulation. In addition, there have recently been new expectations of selective permeability, piezoelectricity, and biocompatibility. 

Potassium titanate has a high refractive index and a low thermal conductivity. Moreover, its size is in the right range to scatter infrared radiation. Thus it has potential use as an insulating and ir-reflective material. Other potential applications of potassium titanate include its use as a filtration medium, a reinforcement material for organic polymers, and an asbestos replacement in friction brakes. Between 1965 and 1972, pigmentary potassium titanate was manufactured in the United States (108). 

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