Combustion plastics

Acrylics are combustible plastics, and the fire precautions normally used with other combustibles must be observed in handling, storing, and using them. The fire hazards of acrylic installations can be kept within acceptable levels by complying with building codes, applicable Underwriters Laboratories standards, and the established principles of Fire safety. 

Acrylic Acid-Trinitrophenylecter, such as C,H,N,0, polymerized by heating to ca 100° with dibenzoyl peroxide, yields an exp or readily combustible plastic Ref H.A.Bruson G.B.Butler, USP 2,407, 131(1946) CA 41,288(1947)... 

Polyethylene is one of the most combustible plastics, and laboratory tests appeal to show that its applications as containers would enhance the fire hazard. Surprisingly, however, the contrary was shown by model fire tests carried out in Hungary to... 

Polyolefins, as pure hydrocarbons, are among the most combustible plastics with an oxygen index of 17 to 18 per cent and heat of combustion of 40 to 45 MJ/kg. Their flame spread rate is high both horizontally and vertically. An unpleasant side effect of their combustion is dripping of the low-viscosity burning melt, which may contribute to a further propagation of fire. The smoke production of this burning is small. 

Polyamides are less combustible plastics due to their chemical composition. Unfilled and unmodified PA 6 and PA 66 are rated V-2 according to UL 94, with an oxygen index of about 25 per cent without any added agents. One peculiarity is that glass fibres, mineral fillers, and some additives (such as the impact modifiers) actually enhance the flammability of polyamides they are rated only HB when not flame-retarded. A drawback of polyamides is dripping during the combustion. 

Annual Proceedings of the Safety Seminars, Dept, of Defense, Explosive Safety Board, Washington, D.C. International symposia on explosives and closely related subjects are excellent sources of information, ie, international symposia on detonation symposia on combustion symposia on chemical problems connected with the stabiUty of explosives international pyrotechnics seminars symposia on compatibiUty of plastics and other materials with explosives, propellants, and pyrotechnics, and processing of explosives, propellants, and ingredients and symposia on explosives and pyrotechnics Mineral Industy Surveys, U.S. Bureau of Mines, Pittsburgh, Pa. Periodic pubhcations dedicated primarily to explosive studies in Propellants and Explosives Journal of Ha yardous Materials, and apparent consumption of industrial explosives and blasting agents in the United States. 

Fire Resista.nce. Many fillers, particularly inorganic oxides, are noncombustible and provide a measure of passive fire resistance to filled plastics by reducing the volume of combustible matter in the filled composition. Depending on their density, they may also serve as insulation. 

Another factor potentially affecting the market for halogenated fire retardants is the waste disposal of plastics (see Wastes, industrial). As landfiU availabihty declines or becomes less popular, two alternatives are incineration and recycling (qv). The nature of the combustion products from halogenated products requires carefiil constmction and maintenance of incinerators (qv) to avoid damage to the incinerator itself and a pubHc health problem from the exhaust. The ease of recycling used products also has a potential effect on fire retardants. 

The use of flame retardants came about because of concern over the flammabiUty of synthetic polymers (plastics). A simple method of assessing the potential contribution of polymers to a fire is to examine the heats of combustion, which for common polymers vary by only about a factor of two (1). Heats of combustion correlate with the chemical nature of a polymer whether the polymer is synthetic or natural. Concern over flammabiUty should arise via a proper risk assessment which takes into account not only the flammabiUty of the material, but also the environment in which it is used. 

Standard Test MethodforMeasuring the Minimum Oyrggen Concentration to Support Candle-like Combustion of Plastics, ASTM D2863-87, ASTM, Philadelphia, Pa., 1987. 

The high fluorine content contributes to resistance to attack by essentially all chemicals and oxidizing agents however, PCTFE does swell slightly ia halogenated compounds, ethers, esters, and selected aromatic solvents. Specific solvents should be tested. PCTFE has the lowest water-vapor transmission rate of any plastic (14,15), is impermeable to gases (see also Barrierpolymers), and does not carbonize or support combustion. 

Flammability. The results of small-scale laboratory tests of plastic foams have been recognized as not predictive of their tme behavior in other fire situations (205). Work aimed at developing tests to evaluate the performance of plastic foams in actual fire situations continues. All plastic foams are combustible, some burning more readily than others when exposed to fire. Some additives (131,135), when added in small quantities to the polymer, markedly improve the behavior of the foam in the presence of small fire sources. Plastic foams must be used properly following the manufacturers recommendations and any appHcable regulations. 

Flammability. Plastic foams are organic ia aature and, therefore, are combustible. They vary ia their respoase to small sources of ignitioa because of composition and/or additives (255). AH plastic foams should be handled, transported, and used according to manufacturers recommendations as weU as appHcable local and national codes and regulations. 

Toxicity. The products of combustioa have beea studied for a number of plastic foams (257). As with other organics the primary products of combustion are most often carbon monoxide and carbon dioxide with smaller amounts of many other species depending on product composition and test conditions. 

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. 

The long-term effects of CECs and HCECs leaking into the environment have been discussed. Combustion where aU ceUular plastics can evolve smoke containing carbon monoxide and in certain cases cyanide and other toxic gases from various constituents involved in thein manufacture is also a consideration. 

Emissions During Disposal and Incineration. The increasing use of modem incinerators to dispose of domestic waste results in complete combustion of plasticizers to carbon dioxide and water. The preponderance of plasticizer going into landfiUs is as plasticized PVC. Once a landfiU has been capped anaerobic conditions prevail and it is biologically relatively inactive. Under these conditions the main route by which organic components are removed from the landfiU contents is by ingress of water, extraction, and subsequent loss of water from the site to the environment. 

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