Polyurethane burning

Plastics in general (including all forms) are sensitive to high temperatures, among the more resistant being fluorocarbon resins, nylon, phenolics, polyim-ides, and silicones, though even these soften or melt above 260C. Other types (cellulosics, polyethylene, acrylic polymers, polystyrene) are combustible when exposed to flame for a short time and still others (polyurethane) burn with evolution of toxic fumes. 

Laboratory experiments using rodents, or the use of gas analysis, tend to be confused by the dominant variable of fuel—air ratio as well as important effects of burning configuration, heat input, equipment design, and toxicity criteria used, ie, death vs incapacitation, time to death, lethal concentration, etc (154,155). Some comparisons of polyurethane foam combustion toxicity with and without phosphoms flame retardants show no consistent positive or negative effect. Moreover, data from small-scale tests have doubtful relevance to real fine ha2ards. 

Sohd rocket propellants represent a very special case of a particulate composite ia which inorganic propellant particles, about 75% by volume, are bound ia an organic matrix such as polyurethane. An essential requirement is that the composite be uniform to promote a steady burning reaction (1). Further examples of particulate composites are those with metal matrices and iaclude cermets, which consist of ceramic particles ia a metal matrix, and dispersion hardened alloys, ia which the particles may be metal oxides or intermetallic compounds with smaller diameters and lower volume fractions than those ia cermets (1). The general nature of particulate reinforcement is such that the resulting composite material is macroscopicaHy isotropic. 

These materials not only have a good resistance to burning and flame spread but are also able to withstand service temperatures of up to 150°C. At the same time polyisocyanurate foams have the very good hydrolytic stability and low thermal conductivity associated with rigid polyurethane foams. 

Paraffin gauze dressing Perforated film absorbent dressing Polyurethane foam Burns, scaids, grafts Postoperative wounds Burns, ulcers, grafts. Any combination of dry heat, gamma-radiation and ethylene oxide... 

Various polymeric materials were tested statically with both gaseous and liquefied mixtures of fluorine and oxygen containing from 50 to 100% of the former. The materials which burned or reacted violently were phenol-formaldehyde resins (Bakelite) polyacrylonitrile-butadiene (Buna N) polyamides (Nylon) polychloroprene (Neoprene) polyethylene polytriflu-oropropylmethylsiloxane (LS63) polyvinyl chloride-vinyl acetate (Tygan) polyvinylidene fluoride-hexafluoropropylene (Viton) polyurethane foam. Under dynamic conditions of flow and pressure, the more resistant materials which binned were chlorinated polyethylenes, polymethyl methacrylate (Perspex) polytetraflu-oroethylene (Teflon). 

The low value of 1.0 in Table VII for the rigid Polyurethane foam in the box-methods may be explained by low ventilation rate. The experiment is over in less than 1 minute and most of the material is combusted during that period. The ventilation rate becomes to low to generate a "normal" ratio of C02/C0 for fast burning materials. In this particular case the oxygen concentration become very close to 0 oxygen. 

POLYURETHANE FOAM SHEETS OR BLOCKS. These are required to resist ignition source 5 (17 gram wood crib) of BS5852 Part 2 except that the flames may penetrate the full depth of the specimen and that the mass loss (due to burning and liquid residues falling from the test rig) shall not exceed 60 grams. 

These criteria were developed by the UK PU foam industry and were intended to differentiate the melamine or exfoliated graphite containing combustion modified PU foams from the standard, high resilience and flame retarded (chloro and bromo phosphate) containing PU foams (Table IV). This distinction was required because large scale burning tests of real arm chairs and furnished rooms had demonstrated the superiority of the combustion modified polyurethane foams. 

K.T. Paul, D.A. King, The Burning Behaviour of Domestic Upholstered Chains Containing Different Types of Polyurethane Foam. 

Burning polyurethane (foam stuffing in furniture and mattresses)... 

A. Jaumotte, "Remarks on the Burning Mechanism and Erosive Burning of Ammonium Perchlorate Propellants , Ibid, pp 689-93 G2) G.K. Adams et al, "Combustion of Propellants Based on Ammonium Perchlorate , Ibid, p 693-705 Hj) J.Hershkowitz, F. Schwartz J.V.R. Kaufman, "Combustion of Loose Granular Mixtures of Potassium Perchlorate and Aluminum , Ibid, pp 720-27 H2) L.A. Dickinson et al, "Erosive Burning of Polyurethane Propellants in Rocket Engines , Ibid, pp 754-59 H ) S. Kumagai... 

Several of the urethane polymers are known for their thermal stability. Probably related to the thermal stability are the slow burning rates that have been obtained with some of the propellant formulations based on polyurethanes. 

Composition (wt. %) NH4CIO4 67 aluminum 17 CuO202, a burning rate accelerator 0.1 sulfur, stabilizer 0.1 N-phenylnaphthylamine, stabilizer 0.1 Fe(AA)3 0.015 HAA 0.009 polyether-polyurethane binder containing 25% isodecyl pelar-gonate 15.68%. 

Contrary to the general trend described above, hydroxyl terminated polybutadiene (a polyurethane) has a burning rate curve which bends concave downward below 0.3 atm. (Figure 16), and the extinction pressure of this propellant is rather high (0.18 atm.). The burned surface of extinguished samples of this propellant had a glistening black appearance. 

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