Underwriters Laboratories ratings

Underwriters Laboratory rating a material is aged at various temperatures and a propery is monitored, e.g., tensile strength. 

Nylon-SAN, which has a high impact strength of 16 ft.-lb/in. of notch (854 J/m), has received a UL (Underwriters Laboratory) rating of 104°C. The nylon-arylate blend is transparent and has a heat-distortion temperature under load (264 Ibf/in. ) value of 154°C. 

Figure 4. Maximum continuous use temperatures of some engineering thermoplastics based on Underwriters Laboratories ratings...

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. 

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. 

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. 

Over the years many attempts have been made to provide some measure of the maximum service temperature which a material will be able to withstand without thermal degradation rendering it unfit for service. Quite clearly any figure will depend on the time the material is likely to be exposed to elevated temperatures. One assessment that is being increasingly quoted is the UL 746B Relative Temperature Index Test of the Underwriters Laboratories (previously known as the Continuous Use Temperature Rating or Index). 

In the absence of fire retardants the material has a limiting oxygen index of 27.5 and may bum slowly. Only some grades will achieve a UL 94 V-1 rating. The Underwriters Laboratories continuous use temperature index is also somewhat low and similar to the polyarylates with ratings of 135-140°C (electrical) and 105°C (mechanical with impact). Initial marketing has emphasised comparisons with the aliphatic nylons for the reasons given in the previous... 

A somewhat low Underwriters Laboratories Temperature Index rating of 120-130°C. 

The Underwriters Laboratories (UL) tests are recognized by various industries to provide continuous temperature ratings, particularly in electrical applications. These ratings include separate listings for electrical properties, mechanical properties including impact, and mechanical properties without impact. The temperature index is important if the final product has to receive UL recognition or approval. 

Underwriters Laboratories Inc. (UL), UL 555S. Safety Leakage Rated Dampers for Use in Smoke Control Systems. Second Edition, UL, Northbrook, IL, 1994. 

The electrical electronics market dictates some specific regulations. Among them a typical example is the UL (Underwriters Laboratories) requirements related to the long-term service temperature and the fire rating. 

Underwriters Laboratories (UL) also approves and rates storage tanks. Factors including tank wall thickness, type of metal used, welding procedure, venting, supports, pressure ratings, and other related topics are specifically defined in the approval codes. Guidelines which relate directly to the storage of flammable and combustible materials are provided under UL Code 142. 

The American Society for Testing Materials (1) has described this test. The Underwriters Laboratories, Chicago, has test equipment as described above. The Forest Products Laboratory, Madison, Wise., has built a smaller tunnel, approximately 1 foot wide and 8 feet long. As far as the writers know, this type of tester has not been installed in any private industrial or commercial testing laboratories. This severely restricts the rate of accumulation of test data by this method. In spite of this, classifications by this method are being incorporated in various building codes. 

The Underwriters Laboratories (UL) tests are recognized by various industries to provide continuous temperature ratings, particularly in... 

Many grades of acetal resins are listed in Underwriters Laboratories (UL) Recognised Component Director)1. 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. 

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