UL temperature index

It is important to know whether a polymer will be stable, that is, whether it will not decompose at a given temperature. There are several measures of thermal stability, the most important of which (from an economic standpoint) is the Underwriters Laboratories (UL) temperature index. 

Unfortunately, there is not at a present a computational method for predicting the UL temperature index. There is a QSPR method for predicting... 

Long-term exposure to high temperature is best described by the Underwriters Laboratory (UL) temperature index. The UL temperature index is ... 

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. 

A high UL Temperature Index of 170°C (for mechanical with impact). 

As with the polysulphones, the deactivated aromatic nature of the polymer leads to a high degree of oxidative stability, with an indicated UL Temperature Index in excess of 250°C for PEEKK. The only other melt-processable polymers in the same league are poly(phenylene sulphides) and certain liquid crystal polyesters (see Chapter 25). 

The temperature index is the maximum temperature that causes a 50% decay of the studied characteristics in the very long term. It is derived from long-term oven-ageing test runs. The UL Temperature Index depends on ... 

The UL temperature index of a specific grade is claimed to be 105°C for electrical and mechanical properties including impact strength. 

The UL temperature indexes for a variety of engineering plastics are in Table 4. Glass-filled PPS compounds exhibit a high UL temperature index, which indicates excellent retention of properties for long-term exposure to high temperature. Other fillers, eg, mineral (talc), may also be used. ... 

Biaxially oriented PPS film is transparent and nearly colorless. It has low permeability to water vapor, carbon dioxide, and oxygen. PPS film has a low coefficient of hygroscopic expansion and a low dissipation factor, making it a candidate material for information storage devices and for thin-film capacitors. Chemical and thermal stability of PPS film derives from inherent resin properties. PPS films exposed to toluene or chloroform for 8 weeks retain 75% of their original strength. The UL temperature index rating of PPS film is 160°C for mechanical applications and 180°C for electrical applications. Table 9 summarizes the properties of PPS film. 

Underwriters Laboratories has authorized temperature Indices of 170OC for the 40% glass-filled PPS and 200 C for the glass-and mineral-filled resin. The glass- and mineral-filled color compounds have a provisional UL Temperature Index of 200OC. 

The most important testing protocol for resistance to deterioration of critical physical properties upon exposure to heat, especially over prolonged periods of time, was designed by the Underwriters Laboratories (UL) [1], The UL temperature index is used to qualify materials for applications (such as use in electrical equipment) regulated by UL. The main purpose of these tests is to ensure that a polymer can be used safely for a prolonged period of time in these applications. A larger value of the UL temperature index implies greater stability, defined in... 

The resistance of commercial polymer grades to thermooxidation is commonly indicated by their UL temperature index (Table 15.1). It shows at which continuous temperature the polymer will serve for 100,000 h, that is, 11.4 years. Will serve in this context means until its impact strength, or strain at break, or other chosen mechanical property is reduced by 50%. 

Relative long-time experiments are often performed according to the Underwriters Laboratories (UL) testing protocol [29]. The results, the retention of certain properties upon exposure to heat, are expressed in UL temperature index values. The time and material consuming UL testing procedure is usually preceded by short-time mass retention measurements, mainly performed with TGA equipment. 

UL temperature index, °C/ /T (electrical) Deflection temperature "C 182 h/ po(°F 264 psi) Dielectric strength (short time), KV/cm (volts/mil) Dielectric constant 60Hzh(fHz Dissipation factor X lCt 60Hz/i04Hz Arc resistance, seconds Oxygen index... 

The polymer has very high tensile strength, an Underwriter s Laboratories (UL) temperature index of 170°C, flame resistance, and low smoke emission. The polymer is resistant to alcohols, acids, and hydrocarbon solvent but will dissolve in partially halogenated solvents. Both glass- and carbon fiber-reinforced grades are available. 

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