Horizontal burning

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. 

BS 4735. Assessment of Horizontal Burning Characteristics of Small Specimens of Cellular Plastics and Cellular Rubber Material When Subjected to a Small Flame, BSI, London. 

Minimum oxygen concentration needed for burning at 20°C. h V. vertical burning HB, horizontal burning. 

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. 

In this test, a small sample of material (127 mm x 13 mm, or 5 in. x 0.5 in.) is exposed vertically to a small Bunsen burner-type flame from underneath (in the UL 94 V test) and the results show a rating, ranging from V-0 (best), through V-l, V-2 to B (for Burn). Materials with a B rating on the UL 94 Vertical test can also be tested in the less severe UL 94 HB (for horizontal burning), where the assessment is whether a flame spread rate of 4in./min is achieved. It is the most widely used fire-test specification for plastic materials, especially fire-retarded ones, and forms the basis of the famous Yellow Card used by ULs to list the plastic materials. The results from these tests are almost invariably found in a variety of specifications and data sheets. 

ASTM D 4986 Standard Test Method for Horizontal Burning Characteristics of Cellular Polymeric Materials... 

ASTM D 5132, Standard Test Method for Horizontal Burning Rate of Polymeric Materials Used in Occupant Compartments of Motor Vehicles, Annual Book ASTM Standards, American Society for Testing and Materials, West Conshohocken, PA. 

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. 

BS 4755. Laboratory method of test for assessment of the horizontal burning characteristics of specimens no larger than 150 mm x 50 mm x 15 mm (nominal) of cellular plastics and cellular rubber materials when subjected to a small flame. 

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]. 

ISO 9772 1994 [27] determines horizontal burning eharaeteristies of small eellular specimens subjected to a small flame. The ends of pieces of cellular materials, 150 X 50 X 13 mm, are supported horizontally on a wire grid and are exposed to a (lame 38 mm high, from a wing tap burner for 60 seconds. The burn distance, time, and burn rate are determined. The Appendix gives a classification for cellular materials as FHl. FH2, or FT13 see Fig. 7. 

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. 

In contrast to the considerable number of fire tests for plastics, there are relatively few fire tests specifically for rubbers as such. There are a number of tests for rubber products including cable insulation, hoses of various types, and cellular products. In some cases, e.g.. cellular products, the test relates to both cellular plastics and rubbers, e.g.. BS 4735 and ISO 3582. Horizontal burning characteristics when subjected to a small flame or BS 5111. Determination of smoke generation. For convenience, these have been described in the section dealing with plastics tests, Other tests for rubber products include ISO 8030 [51], Flammability of rubber hoses for underground mining, ISO 3401 [52], Conveyor belts Flame retardation specification and test method, and BS 5173, Part 103 [53], Fire rc.sistance of plastics and rubber hoses and hose assemblies, and linings of hoses, etc. 

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

UL94 H-B Horizontal burning on 3-mm sample at less than 76mm/minute, or for less than 127mm length For partial-duty, monitored appliances and decorative materials material considered self-extinguishing ... 

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

Included in the horizontal tests is the horizontal burn (HB) test. This takes place on solid polymers such as plastics. Cellular elastomers are evaluated according to the horizontal foam (HE) test. Horizontal burn foam (HBF) is the minimal rating assigned in this test, followed by horizontal foam-2 (HF-2) and horizontal foam-1 (HF-1) (the most stringent). 

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