Flammability testing dripping

Higher irradiation levels give better reproducibility, more clearly defined ignition, and shorter measurement times, but correspond to more developed fires. Thus particularly for flame-retarded polymers, a smaller irradiation level often corresponds better to the fire protection goals addressed. Cone calorimeter results for the HRR at small irradiances correspond to flammability tests such as LOI and UL 94, if a reasonable set of materials are compared and the behavior is not dominated by dripping effects. Thus different considerations govern the choice of external heat flux.76 77... 

Different regulations, such as those of the Federal Aviation Administration, Department of Transportation, and local building codes, mandate that the designs of certain products comply with specific flammability test requirements. Flame-retardancy requirements generally include limits on flame spread, burning time, dripping, and smoke emission. A multitude of flammability tests have been developed, with more than 100 known just in the United States. The most common ASTM tests are given in Table 4-17. 

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. 

The UL flammability ratings describe the relative ease of ignition and combustibiUty of plastics. Tests include the measurement of flame propagation, time to self-extinguish, melt and drip with and without flame, and oxygen indexes. Some engineering plastics, eg, polyetherimides, are, as ranked by this test, inherently nonflammable. Others can be made nonflammable by compounding with flame retardants (ERs) such as bromine... 

The flammability of the three polyarylethers 7, 8, and 10 was measured using the UL-94 V test, and all three samples obtained a V-0 rating when mixed with 1 wt.%1 PTFE as an antidrip additive. It is important to note that the samples were tested without antidrip additive, and did not burn but dripped excessively, making characterization impossible. It was observed that while these polymers where subjected to prolonged exposure to the Bunsen burner flame, the fire never consumed them. The UL-94 sample results are shown in Table 3. 

The burn results for polymers 15 and 19 show that the polymers are inherently flame retardant with low base flammability (Table 4). The polymer dripped but did not ignite the cotton when it was subjected to the UL-94 flame test, and with the addition of 1 wt% PTFE, it did not drip. The PCFC results show that these polymers have a high heat release capacity when compared with the BPC carbonates and aryl ethers, but it is still significantly less than that of the base commodity polymers, such as polyethylene or polystyrene (Table 5). 

The test method of ASTM D 3801-1980 is also practically identical to the Vertical Burning Test for Classifying Materials 94V-0, 94V-f or 94V-2 but only the combustion times and the observation of dripping are recorded without any flammability rating of the material. 

Less efforts have been devoted to the problems of dripping. This phenomenon is normally observed in the test procedures of flammability (cf. Section 3) and some specific methods will be reviewed in Section 4.3. 

Drums Store flammable liquids in closed containers or dmms. Dispense flammable liquids from drums by gravity or suction pump, not by pressurizing the dmm. Valves for gravity dispensing must have recognized testing laboratory approval and close automatically. There must be drip containers to catch leaking fluids. 

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