Underwriters

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. 

Many grades of acetal resins are Hsted in Underwriters Eaboratories (UL) Kecogni d Component Directory. UL assigns temperature index ratings indicating expected continuous-use retention of mechanical and electrical properties. UL also classifies materials on the basis of flammability characteristics homopolymer and copolymer are both classified 94HB. 

Tests for Flammability of Plastic Materialsfor Parts in Devices and Appliances, UL-94, Underwriters Laboratories, Northbrook, lU., 1991. 

CAL = California MVSS = Motor Vehicle Safety Standard UL = Underwriter s Laboratory. 

UE 910 Standardfor Safety, Test Methodfor Fire and Smoke Characteristics of Electrical and Optical Fiber Cables used in Air Handling Spaces, Underwriters Laboratories, Inc. Northbrook, lU., 1985. 

Until 1990 the EPA maintained a Hst of chemicals suitable for potable water treatment ia the United States. Siace then the entire question of certification and standards has been turned over to a group of organi2ations headed by the National Sanitation Eoundation, which has issued voluntary standards. As of January 1992, standards had been issued for most of the principal inorganic products, but only for two polymers, poly(DADMAC) and Epi-DMA (epichl orohydrin dimethyl amine) polymers (78). Certifications for commercial products meeting specified standards are issued by the National Sanitation Eoundation, Underwriter Laboratories, and Risk Eocus/Versar (79). 

Health and Safety Factors. Sulfur hexafluoride is a nonflammable, relatively unreactive gas that has been described as physiologically inert (54). The current OSHA standard maximum allowable concentration for human exposure in air is 6000 mg/m (1000 ppm) TWA (55). The Underwriters Laboratories classification is Toxicity Group VI. It should be noted, however, that breakdown products of SF, produced by electrical decomposition of the gas, are toxic. If SF is exposed to electrical arcing, provision should be made to absorb the toxic components by passing the gas over activated alumina, soda-lime, or molecular sieves (qv) (56). 

The limiting oxygen index of Tefzel as measured by the candle test (ASTM D2863) is 30%. Tefzel is rated 94 V-0 by Underwriters Laboratories, Inc., in their burning test classification for polymeric materials. As a fuel, it has a comparatively low rating. Its heat of combustion is 13.7 MJ/kg (32,500 kcal/kg) compared to 14.9 MJ /kg (35,000 kcal/kg) for poly(vinyHdene fluoride) and 46.5 MJ /kg (110,000 kcal/kg) for polyethylene. 

In 1976, Ashland Od (Ashland Synthetic Fuels, Inc.) was awarded the prime contract to constmct a 540 t/d H-coal pdot plant adjacent to its refinery at Cadettsburg, Kentucky, by an industry—government underwriting consortium. Constmction was completed in 1980 (112). The pdot-plant operation ended in eady 1983. 

Underwriters Laboratories Inc., Standards forA.cetylene Generators No. 297 Portable Medium Pressure, May 1973 No. 408 Stationay Medium Pressure, May 1973. 

Each segment of the insulated wire and cable industry has its own set of standards, and cables are built to conform to specifications provided by a large variety of technical associations such as The Institute of Electrical Electronic Engineers (IEEE), The Insulated Cable Engineers Association, (ICEA), National Electrical Manufacturers Association (NEMA), Underwriters Laboratories (UL), Rural Electrification Administration of the U.S. Department of Agriculture (REA), Association of Edison Illumination Companies (AEIC), MiUtary Specifications of the Department of Defense (MIL), American Society for Testing and Materials (ASTM), National Electrical Code (NEC), etc. 

Underwriters Laboratories, Spec. Subject 15 for Power-limited Circuit Cable Class 2, (NEC article 725), Melville, N.Y. 

Underwriters Laboratories 333 Pfingsten Road Northbrook, Id. 60062 Standards for Safety is ahst of more than 200 standards that provide specifications and requirements for constmetion and performance under test and in actual use of a broad range of electrical apparatus and equipment, including household appHances, fire-extinguishing and fire protection devices and equipment, and many other nongenerady classifiable items, eg, ladders, sweeping compounds, waste cans, and roof jacks for trader coaches. 

Underwriters Laboratories (UL) is an independent, nonprofit organisation that develops standards for safety in electrical products. UL 746 A, B,... 

Flammability. Most nylons ate classified V-2 by the Underwriters Laboratory UL-94 test, which means that these nylons are self-extinguishing within a certain time-scale under the conditions of the test. They achieve this performance by means of giving off burning drips. 

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

Kecogni d Component Directory, Vol. 2, Underwriters Laboratories Inc., Northbrook, Dl., 1994. 

National Board of Fire Underwriters, Chem. Eng. Nem25, 1594 (1947). 

Fire and Wind Hazards. Weather resistance of roof covetings is not necessarily correlated to fire and wiad resistance. Underwriters Laboratory and the Factory Mutual System test and rate fire and wiad hazard resistance, and some durabiUty tests. Organic felt or fiber glass mat base shingles are commonly manufactured to meet minimum UL requirements, which, ia addition to minimum mass, require wiad and fire resistance properties. 

A. F. Matson, R. E. Dufour, andj. E. Breen, Survey of Available Information on Ignition of Wood Exposed to Moderately Elevated Temperatures, Bulletin of Research 51, Part II, Underwriters Laboratories, Inc., 1959. 

According to the National Board of Fire Underwriters, activated carbons normally used for water treatment pose no dust explosion ha2ard and are not subject to spontaneous combustion when confined to bags, dmms, or storage bins (64). However, activated carbon bums when sufficient heat is appbed the ignition point varies between about 300 and 600°C (65). 

For physical, thermal, electrical, and mechanical properties, ASTM test methods are employed (28). Flammability ratings are often based on Underwriters Laboratories (UL) standards (29). UL flammabiUty ratings given ia this article are aot iateaded to reflect the hazards preseated by the resias uader use coaditioas. Typical properties are givea ia Table 3. More details and additional properties are given ia Refereaces 5 and 31—33. 

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. 

Polymeric Materials—Eong Term Property Evaluations, UE 746B, 2nd ed.. Underwriters Laboratories, Inc., Northbrook, HI., 1979, pp. 6—26. 

Underwriters Laboratories (UL) UL 51, UL343, ULI08I, UL448, ULI247... 

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