Fire performance

The performance of fibre-reinforced plastics is assessed in relation to the various phases in the development of a fire. Tests relating to the phases are described and material response discussed. A strategy is outlined w hich requires both attention to the design and the material choice. This may well limit the properties available to the designer. 

Human tolerance to these characteristics varies widely and so the rate of build-up is an important consideration in designing a suitable strategy 

A major difference between thermosets and thermoplastics is that the latter may drip, causing burns or fires on anything underneath. 

The data describe measurements of the response of materials to the types of flame or radiant heat flux. These need however to be related to the usage of the material in a component or structure. 

A series of tests is required to characterize the reaction of products to different fire situations. Such tests are most useful when a range of ignition sources and heating conditions can be used so results based on a restricted range of tests should be used with caution. For example, a product may react entirely differently when exposed to a high heat flux than it does when tested with a low heat flux. 

The peak heat release rate (PHRR) in parhcular has been used to determine and compare the fire performance of nanocomposites, as this measurement gives information about the size of the fire and the approximate fire hazard [25]. 

While the PHRR of PS-MMT nanocomposites is usually reduced over unfilled PS, most studies have not shown a significant decrease in the THR, and so at this time the modified clay on its own is not sufficient to provide complete flame 

Surfactant (Tables 13.1-13.3) Clay loading Time to ignition PHRR (IdW/m ) (% reduction) Time to PHRR THR (M) m )  

PS-MMT nanocomposites have exhibited improved mechanical properties, including tensile, impact, rheological, and barrier properhes. The thermal and fire properties have also been improved upon addition of MMT, but it is evident that for all physical properties the morphology of the nanocomposite ultimately determines the level of improvement in properties. 

These studies have helped to develop a level of understanding of the importance of the interplay between the clay modification, the polymerization technique, the 

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Elame-spread and smoke-density values, and the less often reported fuel-contributed semiquantitive results of the ASTM E84 test and the limited oxygen index (LOI) laboratory test, are more often used to compare fire performance of ceUular plastics. AH building codes requite that ceUular plastics be protected by inner or outer sheathings or be housed in systems aH with a specified minimum total fire resistance. Absolute incombustibHity cannot be attained in practice and often is not requited. The system approach to protecting the more combustible materials affords adequate safety in the buildings by aHowing the occupant sufficient time to evacuate before combustion of the protected ceUular plastic. 

Phosphate Esters. The principal advantage of phosphate esters is the improved fire retardancy relative to phthalates. The fire performance of PVC itself, relative to other polymeric materials, is very good due to its high halogen content, but the addition of plasticizers reduces this. Consequendy there is a need, in certain demanding appHcations, to improve the fire-retardant behavior of dexible PVC. 

Patents have appeared (33,34) which show formulations containing PMMA emulsion polymer and PMMA suspension polymer combined with benzyl butyl phthalate and octyl benzyl phthalate. It is likely that polymers of this type will require highly polar plasticizers in order to have both adequate compatibiHty and adequate gelation. When replacing PVC appHcations the use of large quantities of phosphate plasticizers is sometimes required to give equivalent fire performance. 

Building code requirements for fire performance are mainly concerned with noncombustibiUty (41), fire endurance (42,43), and surface burning characteristics (44). Wood, even in its treated form, does not meet the building code requirements for a noncombustible material. However, for some specific apphcations where noncombustible materials are required, the codes permit the substitution of fire retardant treated wood. 

Over the years plastics users have demanded progressively improving fire performance. By this is meant that plastics materials should resist burning and in addition that levels of smoke and toxic gases emitted should be negligible. That a measure of success has been achieved is the result of two approaches ... 

Groupe TBI is investing about FFr3m to build a 15,0001/ y aromatic polyester polyols plant on a greenfield site at Issoire, near Lyons. The novel, patented process uses postconsumer waste bottles made from PETP as feedstock. PU and modified PIR foams made using the APPs have excellent fire performance and good dimensional stability. GROUPE TBI... 

The symposium was planned as a state-of-the-art meeting, focusing on the basic science. Program areas included high heat polymers, fire performance of polymers, hazard modeling, mechanism of flammability and fire retardation, char formation, effects of surfaces on flammability, smoke assessment and formation mechanisms, and combustion product toxicity. 

Polyester resins. The fire-performance characteristics of unsaturated polyester resins are of utmost importance in many application areas, particularly in the construction, transportation and electronics industries ( 1 3). Consequently, these plastics represent one of the major growth areas for fire retardants in recent years ( 1 4). 

NELSON Effects of Coatings on the Fire Performance of Plastics... 

Coatings can significantly alter the fire performance properties of plastics. A 2-mil coating can reduce the value for a more flammable substrate by an order of magnitude while more flame retardant substrates can see a doubling of the Ig value. 

Clearly 2 to 5 mil coatings can significantly alter fire performance. Proper evaluation and choice of coating for fire performance is an important, and often missed, opportunity. 

G.L. Nelson, M.L. Bosarge, K.M. Weaver, Effect of EMI Coatings on the Fire Performance of Plastics, Part II, Proceedings of the Thirteenth International Conference on Fire Safety, January 11-15, 1988, 12, 367-378 (1988). 

Synergistic Fire Performance between a Zinc Coating and a Modified Poly(phenylene oxide)... 

Test results show that thin coatings (2-5 mils) can significantly effect the fire performance of plastic substrates. Most EMI coatings decrease ignitability test results. Coatings tend to level diverse flame spread and ease of extinction performance. A 2-mil coating can reduce the 1, value in ASTM E162 Radiant... 

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