Maximum temperature of use

Vacuum-deposited and electroplated coatings are pure metal with no chemical bond to the underlying surface. The properties will be those of pure aluminium. The presence of lacquer, in the case of vacuum-deposited coatings will, however, afford resistance to the passage of electricity and limit the maximum temperature of use. 

The Tg will determine the maximum temperature of use of the material as a rigid thermoplastic. For amorphous rubbers the will determine the minimum temperature. 

A summary of the chemical and abrasion resistances, and approximate operational temperature ranges of elastomers is given in Table 18.16. Further details of specific chemical resistances are given in Table 18.17. The maximum temperature of use will always be dependent on the chemical conditions prevailing. Abrasion resistance can be affected by the chemical environment if the exposed surface properties are changed by adsorption or chemical attack. The rate of material loss by abrasion will also vary according to temperature as the resilience etc. is dependent on prevailing temperature conditions. 

As previously stated, polyurethanes do not have the degree of chemical resistance enjoyed by the other elastomers. Specially designed chemical resistant polyurethanes are suitable for use in dilute non-oxidative acids and salts, but are not normally suitable for alkalis. They show good resistance to oils and solvents. Maximum temperature of use is usually about 80°C, but this temperature is very dependent on the chemical environment. 

The best fit to the Arrhenius plot can be found by the least squares method (applied to In t or log t) and extrapolated to find the time to the threshold value (tu) at a temperature of interest (Tu). To obtain an estimate of the maximum temperature of use, extrapolate the line to a specified reaction rate or time to reach a threshold value. 20,000 or 100,000 hours duration and 50% change as the threshold value are commonly used for establishing a general maximum temperature of use. 

To obtain an estimate of the maximum temperature of use, extrapolate the line to a specified reaction rate or time to reach the threshold value. 20,000 hours is commonly used as the time for establishing a general maximum temperature of use. 

ISO 11346, Rubber, vulcanized or thermoplastic - Estimation of life-time and maximum temperature of use from an Arrhenius plot, 1997. 

The reaction was carried out using Nafion-H and polystyrene sul-phonic acid resin catalyst at 180°C and 140°C, respectively, which are their maximum temperatures of use 2-nitrotoluene solvent and 10% w/w catalyst. Conversions of 20% and 1.5% were obtained at the end of six hours indicating that higher temperatures will be necessary to achieve appreciable rates on these catalysts. Since these catalysts are not structurally stable above the respective temperatures, they appear to be unsuitable for this application. The reaction was also carried out using triflic acid as catalyst at various temperatures. The results are shown in Fig.3. Surprisingly, the reaction did not proceed beyond 40% conversion in spite of the high acidity of the catalyst. 

The parameter most often used to indicate the maximum temperature of use is the temperature-index , introduced by the American Underwriters Laboratories Inc., and, therefore, also named the U.L. index . Since, for different applications, degradation affects the performance of polymers in different ways, different values of the UL index are attributed to one and the same polymer, for instance for electrical insulation and for impact strength. 

Known amounts of salt(s) of catalytic metals are dissolved in aqueous solutions and impregnated into carrier materials. The wet mass is dried at 110°C and calcined in air at 300-500°C, releasing the decomposable salt components and depositing the metal oxide on the surface within the depths of the porous carrier. For many oxidation reactions the catalyst is now ready for use but for hydrogenation it is necessary to reduce the impregnated metal oxide or salt chemically. Usually this is accomplished by flowing H2, under conditions consistent with the maximum temperature of use for the reaction of interest. 

Material Type of bond Bond con- tent (%) Moisture content (%) Maximum temperature of use (°C) Cold compres- sive strength (MPa) Bulk density (gcm ... 

Most reactive extrusion has dealt with polymers that can be difficult to handle by other techniques.68 Polymers can be cross-linked, grafted with other monomers, and so on. Extrusion cross-linking of polyethylene wire coating raises the maximum temperature of use. Polypropylene degrades in this process, but can be cross-linked successfully if mul-... 

The maximum temperature of use for NICALON- or TYRANNO-fiber reinforced glasses and glass-ceramic is limited by the transformation temperature of the glass phases, i.e., about 500 °C for SiCAiorosilicate-glasses,... 

Table 10.5 Recommended maximum temperatures of use for selected fired refractories...

Property Density kgm Shear Shear modulus strength Resistance to smoke and flame LOI Water absorption % Form Ability Maximum Temperature of use °C... 

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