Thermal endurance

Isophthahc (y -phthahc) acid [121 -91 -5] (IPA) is selected to enhance thermal endurance as well as to produce stronger, more resiUent cross-linked plastics that demonstrate improved resistance to chemical attack. TerephthaUc (p-phthaUc) acid [100-21-0] (TA) provides somewhat similar properties as isophthahc acid but is only used in selective formulations due to the limited solubiUty of these polyester polymers in styrene [100-42-5] (see Phthalic acid AND OTHERBENZENEPOLYCARBOXYLIC ACIDS). 

Insulation having high thermal endurance has been made from vitreous siUca fibers (see Ablative materials). Such material forms the basis for the 30,000 iasulatiag tiles, 125-mm thick, that protect the aluminum skin of the space shuffle. The tiles add a minimum of weight because the density of the iasulation is only 144 kg/m (9 lb/fT), similar to balsa wood. 

NEMA standards do not give any fixed maximum operating temperature by any class of insulation. Briefly, NEMA states that insulation of a given class is a system that can be shown to have suitable thermal endurance when operated at the temperature rise shown in the standard.s for that type of machine. Standards for synchronous motors and indue tioii motors with a 100% service factor specify 80°C rise by resistance... 

Insulation systems are divided into classes according to the thermal endurance of the system for temperature rating purposes. Four classes of insulation systems are used in motors and generators, namely, classes A, B, F, and H. These classes have been established in accordance with IEEE Std. I. 

Class A—An insulation system that, by experience or accepted test, can be shown to have suitable thermal endurance when operating at the limiting Class A temperature specified in the temperature rise standard for the machine under consideration. 

Parylene The melting point of these film and coating plastics ranges from 290 to 400° C (554 to 752°F), and Tg from 60 to 100°C (14 to 212°F). Their cryogenic performances are excellent. Physical properties are unaffected by thermal cycles from 2°K to room temperature. Good thermal endurance in air, absence... 

The boiler A can be made from an ordinary laboratory conical flask a side arm is added and then the top of the flask is drawn off and rounded— if a laboratory filter suction flask is available, and has suflident thermal endurance for a boiler, the side arm already exists and need only be lengthened. 

IEC 60216, Parts 1-5, Guide for the determination of thermal endurance properties of electrical insulating materials, 1990-2001. 

IEC 60216, Electrical insulating materials - Properties of thermal endurance, 1990-2001. 

The American standard ASTM D-2307 [12] provides a test method for measuring Relative thermal endurance properties of film insulated magnet wire . The ageing philosophy is similar to that required by IEC 60216 [9] and is based on the Arrhenius ageing model. Oven ageing is carried out at three specific temperatures. The samples are twisted wire... 

ASTM D-2307, Standard Test Method for Thermal Endurance of Film-Insulated Round Magnet Wire, 2001. 

The only procedure to have been standardised generally is application of the Arrhenius relation (see below). IEC 21662 is a guide to evaluating the thermal endurance of electrical insulating materials and ISO 257863 applies the same principle to determining time/temperature limits to plastics. In both cases, the accent is more on finding maximum service temperatures rather than extrapolating to normal ambient temperature. Use of the same... 

Flexibilizers generally cannot be used to counteract internal stress in high temperature adhesive because of their relatively low glass transition temperature and thermal endurance properties. However, most high-temperature adhesive systems incorporate metallic fillers (generally aluminum powder) to reduce the coefficient of thermal expansion and degree of shrinkage. 

The hydrolytic stability and very high thermal endurance of this plastic in conjunction with a good balance of mechanical properties suit it for hot water and food handling equipment, range components, TV applications, alkaline battery cases, and film for hot transparencies. The unmodified product is transparent with a slightly yellow tint. Low flammability and low smoke suite it for aircraft and transportation applications. As with the other amorphous polymers, susceptibility to attack by organic solvents is a deficiency. 

The ability to withstand thermal shock resulting from sudden changes in temperature is important for technical applications of glass. The thermal endurance of inorganic glass, studied mainly by Schott and Winkelmann [24] (see also refs. [1] and [25]), is a very complex property. The investigations have led to the definition of a coefficient of thermal endurance F ... 

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