Polymers, burning products

When a composite propellant composed of ammonium perchlorate (AP) and a hydrocarbon polymer burns in a rocket motor, HCl, CO2, H2O, and N2 are the major combustion products and small amounts of radicals such as OH, H, and CH are also formed. These products are smokeless in nature and the formation of carbon particles is not seen. The exhaust plume emits weak visible light, but no afterburning occurs because AP composite propellants are stoichiometrically balanced mixtures and, in general, no diffusional flames are generated. 

Propylene-Butylene Motor Polymer This product is the most predominant of those made by polymerization of the olefins from cracked gases. It is a clean-burning fuel having a... 

Tign for PMMA and unsaturated polyester is 310 and 390 °C, respectively. From these results it follows that PMMA and similar products are more easy to ignite and to burn than unsaturated polyesters, under a given external heat flux qe. It is interesting to note that q0 ign values, obtained from flame spread experiments in this manner, are consistent with the q0 ign values determined from direct ignitability tests. This is an evidence of the validity of the treatment of flame spread on a surface as a continuous gas-phase ignition of polymer decomposition products. 

For eliminating or minimizing the fire hazards from the burning products (determined by measuring the flammability of the polymers and comparing the values with the specified limits)... 

Thermochromatography is useful in studying flame-resistant materials, e.g., cellulose fibres [122]. Phosphorus-containing antipyrenes increase the amount of water present in the degradation products, which, in turn, increases flame resistance of a polymer. The amount and composition of the burning products should also be taken into account in characterising the flame resistance of cellulose fibres [123]. In the thermochromatograms... 

As shown in the burning cycle, a polymer burns via the vapour phase combustion of the volatile products produced during its thermal oxidative degradation. The vapour phase combustion is a free radical process which can be simplified and expressed as follows, where RCH3 is representative of the hydrocarbon undergoing combustion ... 

The intumescent char acts essentially as a physical barrier to heat and mass transfer between the flame and the burning material. Thus, the process of pyrolysis of the polymer that produces combustible volatile products to feed the flame is reduced by a decrease in temperature, caused in turn by a lower heat supply from the flame. The diffusion of the volatile products towards the flame is hindered with further reduction of the flame feed. Furthermore, whatever may be the role of oxygen in the combustion process, its diffusion towards the polymer burning surface is also hindered, This series of events can lead to an interruption in the self-sustained combustion process because the flame is starved. 

The purpose of this section is to give an up to date overview of the effects which some iron compounds have on flammability and smoke production when polymers burn in air. A glance at chemical abstracts indexes under iron, iron compounds or iron chemistry shows thousands of scientific papers appearing every year however, very few of these deal with the use of iron compounds as flame retarding/smoke suppressing additives for polymers. The recent chemistry of iron has been reviewed by Silver [1] but again there are few comments on the potential uses of iron compounds in polymers. 

When exposed to sunlight, it is converted to a white insoluble resin, disacryl. Oxidized by air to propenoic acid small amounts of hy-droquinone will inhibit this. Bromine forms a dibromide which is converted by barium hydroxide into DL-fructose. The acrid odour of burning fats is due to traces of propenal. It is used in the production of methionine and in controlled polymerization reactions to give acrolein polymers. ... 

Incineration of a collection of polymers with 10 different kinds of brominated flame retardants has been studied under standardized laboratory conditions using varying parameters including temperature and air flow. Polybrominated diphenyl ethers like the deca-, octa-, and pentabromo compounds yield a mixture of brominated dibenzofurans while burning in polymeric matrices. Besides cyclization, debromination/hydrogenation is observed. Influence of matrix effects and burning conditions on product pattern has been studied the relevant mechanisms have been proposed and the toxicological relevance is discussed. 

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