Horizontal burning tests

Air Products, a manufacture of latex binders, has completed a comprehensive study of flame retardants for latex binder systems. This study evaluates the inherent flammability of the major polymer types used as nonwovens binders. In addition, 18 of the most common flame retardants from several classes of materials were evaluated on polyester and rayon substrates. Two of the most widely recognized and stringent small scale tests, the NFPA 701 vertical burn test and the MVSS-302 horizontal burn test, are employed to measure flame retardancy of a latex binder-flame retardant system. Quantitative results of the study indicate clear-cut choices of latex binders for flame retardant nonwoven substrates, as well as the most effective binder-flame retardant combinations available. 

The UL 94 standard specihes bench-scale test methods to determine the acceptability of plastic materials for use in appliances or other devices with respect to flammability under controlled laboratory conditions. The test method that is used depends on the intended end-use of the material and its orientation in the device. The standard outlines two horizontal burning tests, three vertical burning tests, and a radiant panel flame spread test. The most commonly used test method described in the UL 94 standard is the 20-mm Vertical Burning Test V-0, V-l, or V-2. The method is also described in ASTM D 3801. A schematic of the test setup is shown in Figure 14.3. 

For samples that cannot meet the requirements for the UL 94 V test, the UL 94 HB horizontal burn test is a possibility. Flame spread in the horizontal orientation is much slower than for the vertical test. Two marks are made on the bar at 25.4 and 101.6 mm from the free end of the specimen. After the flame has been applied for 30 s, the burn rate between the reference marks... 

Five grades are defined Standard (SD), High (HD), Extra High (EHD), Ultra High (UHD). and Impact Sound (ISD). Type A differs from Type N in that it is flame retarded to pass the horizontal burn test BS 4735 [12]. The properties expected for these various grades are specified in tables such as that partially depicted in Table 2. 

These two tests are similar to those defined in BS 2782, Part 1, Method 140A (20). This test is similar to the UL94 [21] Vertical burning (UL94, VO, VI. V2) and horizontal burn tests (UL94HB). The horizontal test is similar to ASTM D635 [22], while the vertical test is defined in ASTM D3801 [23]. 

It should be noted that the small flame vertical and horizontal burn tests (usually referred to in its L L 94 format), together with the oxygen index lest, are probably the most widely used small flame tests for plastics materials. They are also used with rubber materials. 

GNP gross national product (GDP replaced HBT horizontal burn test... 

Flame spread (rating) — horizontal burning test UL 94, ISO 1210 lEC 707 140, 213... 

This standard test method is similar to prEN ISO/FDIS 11925-2 test. In the test, both horizontal burning (HB) and vertical burning (V) behaviors of 127-mm (5-in) long, 13-mm (0.5-in) wide, and up to 13-mm (0.5-in) thick material samples are examined. Horizontal burning test is performed for 94HB classification of materials. The sample used is placed on top of a wire gauge and ignited by a 30-s exposure to a Bunsen burner at one end. 

FIGURE 9.26 Linear burning rates of epoxy samples obtained according to the UL-94 horizontal burning test only LDH-based nanocomposites (i.e., epoxy + LDHl and epoxy + LDH2) show self-extinguishing properties (the front flame did not reach the first mark at 25 mm or extinguished in the first 30 mm of the specimen). 

Thermosetting nanocomposites exhibit a reduced rate of heat release compared to neat polymer. However, the approach to nanocomposites itself is not sufficient to comply with the actual fire test standards. For this reason, traditional flame retardants are currently used in combination with nanofillers, and researchers are focusing on the individuation of synergistic systems. As an alternative to the most common cationic clays, anionic clays show improved performance in terms of flame retardancy. Epoxy nanocomposites based on anionic clay exhibit unique self-extinguishing behavior in a UL-94 horizontal burning test never observed before in a pure nanocomposite. The formation of a continnous intu-mescent ceramic layer on the surface of a polymer during combustion reduces the heat release rate to a higher extent than do montmorillonite nanocomposites. 

Figure 30 shows typical dripping behavior of unfilled LDPE and a LDPE/LDH composition (PE-LDH5) at comparable time after the first 10 s flame application. The UL94 horizontal burn test showed better flammability performance of the LDPE/LDH nanocomposites as compared to the pure polyethylene. 

Fig. 31 Influence of LDH loading on the rate of burning during UL94 horizontal burn test (at each composition, the average of three measurements were taken) (Reprinted from [135], with permission from Elsevier)...

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