Fire retardant tests

The most extensive body of tests are provided under the auspices of ASTM Standard methods. Specific ASTM test designations and descriptions are available (48). The other compendium of fire-retardant tests are contained ia Federal Test Method Standards 191A (49). 

During the course of this work, 27 interior fire-retardant paints have been developed and evaluated. Formulations and test results are shown for two of the best of these (Tables III and IV), together with the results obtained for JAN-P-702 (Table VII). Formulation and fire-retardance test results are shown in Table V for interior paint 3, while data for interior paint 4 are given in Table VI. 

Another thermocouple and pyrometer indicate the flame temperature at the coating surface. The burner setup is designed to apply the desired temperature for the given period of time. For example, a temperature of 1750 F. can be reached in 1 minute and then held constant tor 0.5 hour. Figure 3 is a photograph of a typical fire-retardant test setup. 

Figure 3. Typical Fire-Retardant Test Setup...

Platy nano-particles, such as nano-clays and micas, have some potentially useful flame retardant effects, and are currently receiving a lot of attention for this application. This topic has recently been reviewed [34, 35]. The other forms of nano-particle do not seem to have the same effectiveness. This subject, which was briefly treated in Chapter 6, is discussed in more detail here, but the earlier chapter should be referred to for details of fire retardant tests, especially the cone calorimeter which is widely used in studies involving nano-plate fillers. 

Obviously, polymer/Ceo nanocomposites offer novel strategies for developing flame retardant polymeric materials. However, they do not behave well in traditional fire retardation tests, such as LOI and the UL test. Thus, in the future, more work needs to be done on this problem and the synergistic effects of Ceo and other traditional fire retardants. 

Polymer-clay nanocomposites that have the best fire-retardant performance evaluated by the cone calorimeter have clay particles oriented parallel to the surface of the sample. Vertical fire retardant tests (UL-94) of these samples do not demonstrate improved performance because the edges of the particles are exposed to the fire. The edges of clay are very thin (approximately 1 nm). Hence, the mechanisms predicated on barriers provided by the clay are not applicable. Mechanisms associated with increased melt viscosity are apparent with vertical fire-retardant testing. Dripping during the burning of the vertical samples is greatly reduced [3]. 

The assessment of the contribution of a product to the fire severity and the resulting hazard to people and property combines appropriate product flammabihty data, descriptions of the building and occupants, and computer software that includes the dynamics and chemistry of fires. This type of assessment offers benefits not available from stand-alone test methods quantitative appraisal of the incremental impact on fire safety of changes in a product appraisal of the use of a given material in a number of products and appraisal of the differing impacts of a product in different buildings and occupancies. One method, HAZARD I (11), has been used to determine that several commonly used fire-retardant—polymer systems reduced the overall fire hazard compared to similar nonfire retarded formulations (12). 

Handbook of Fire Retardant Coatings and Fire Testing Services, Technomic, Lancaster, Pa., 1990. 

The Fire Tests for Flame Resistant Textiles and Films, issued by the National Fire Protection Association (NFPA) ia 1989, is the method most used by iadustrial fire-retardant finishers (ca 1993) (50). It has been approved by the American National Standards Institute. 

The surface burning characteristics (flame spread index and smoke developed index) for wood and wood products as measured by American Society for Testing and Materials (44) can be reduced with fire retardant treatments, either chemical impregnation or coatings (48). Fire retardant treatments also reduce the heat release rate of a burning piece of wood (49,50). The heat release rates (51) of the burning materials are an important factor in fire growth. 

Flammability. The fire hazard associated with plastics has always been difficult to assess and numerous tests have been devised which attempt to grade materials as regards flammability by standard small scale methods under controlled but necessarily artificial conditions. Descriptions of plastics as selfextinguishing, slow burning, fire retardant etc. have been employed to describe their behaviour under such standard test conditions, but could never be regarded as predictions of the performance of the material in real fire situations, the nature and scale of which can vary so much. 

At present there is no small-scale test for predicting whether or how fast a fire will spread on a wall made of flammable or semiflammable (fire-retardant) material. The principal elements of the problem include pyrolysis of solids char-layer buildup buoyant, convective, tmbulent-boundary-layer heat transfer soot formation in the flame radiative emission from the sooty flame and the transient natme of the process (char buildup, fuel burnout, preheating of areas not yet ignited). Efforts are needed to develop computer models for these effects and to develop appropriate small-scale tests. 

The feasibility of using these elastomeric foams as fire retardant thermal insulation has been demonstrated by a Department of the Navy-National Bureau of Standards Test Program (54). 

A basic scientific investigation of fire retardancy, however, remained to be initiated by Gay-Lussac in France at the request of King Louis XVIII in 1821 who was again interested in reducing the flammability of theater curtains. This researcher noted that the ammonium salts of sulfuric, hydrochloric and phosphoric acids were very effective fire retardants on hemp and linen and that the effect could be improved considerably by using mixtures of ammonium chloride, ammonium phosphate and borax. This work has withstood the test of time and remains valid to this day. Thus the basic elements of modern fire retardant chemistry had been defined early in recorded history and remained the state of the art until early in the twentieth century. The most effective treatments for cellulosic materials being concentrated in Groups III, V and VII elements. 

When samples are exposed vertically to a flame or another heat source, some materials melt and drip, and do not burn up completely. This will cause their smoke results to be artificially low [9]. Burning samples horizontally makes material performance comparisons in a small scale test more logical because the entire sample will be burnt in every case. This is very relevant when dealing with fire retarded materials which do not melt or drip, and will thus, yield similar smoke production results in the vertical and horizontal modes. 

Fire retardant treatment, for wood, 26 348 Fire science, 11 450 Fire test methods, 11 449—450 Fire test terminology, 19 588 Fire-tube furnaces, 12 319—320, 327 Firing, of ferrites, 11 73 Firming agents, 12 32 as food additives, 12 57 First aid and rescue, 21 858 First aid, for nitric acid exposure, 17 192 First failure, time to, 26 987 First falling rate period, 23 67 First-generation ionic liquids, 26 837-838, 841, 865... 

Since combustion is subject to many variables, tests for flame retardancy may not correctly predict flame resistance under unusual conditions. Thus, a disclaimer stating that flame retardancy tests do not predict performance in an actual fire must accompany all flame-retardant products. Flame retardants, like many organic compounds, may be toxic or may produce toxic gases when burned. Hence, care must be exercised when using fabrics or other polymers treated with flame retardants. 

A very good description of fire-retardant textiles is given in. Kirk Othmer (Ref 7) Tests for Fire-resistance and Flammability,... 

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