Burning process, polymer flammability

Substances applied to or incorporated in a combustible material (e.g. organic polymers, nylon, vinyl and rubber, etc.) to reduce flammability. Act by retarding ignition, control/douse burning, reduce smoke evolution. Slow down or interrupt the self-sustained combustion cycle when the heat-flux is limited. Flame retardants (FRs) improve the combustion behaviour and alter the combustion process (cool, shield, dilute, react) so that decomposition products will differ from nonflame retarded articles. FRs are usually divided into three classes ... 

Because of the ease of formation of these flammable pyrolysis products, polyesters have LOI values of 20-22 vol% (see Table 2.4), and hence, burn readily and because of the styrene content, give heavy soot formation. As these resins are cured at room temperature, bromine-containing flame retardants, which would decompose in melt-processed, thermoplastic polymers, may be effectively used. 

However, a common feature of the PNs is that, based on the flammability of various polymers that have been studied with a single nanoadditive, like clay, they can only show a retarded combustion process (i.e., the peak HRR and the average HRR can be lowered), while almost all the carbon sources will eventually burn out in most cases. The total heat released (THR) in CCA is not changed compared with that of the same amount of base polymer. Furthermore, like many flame-retardant composites, an earlier time to ignition (and perhaps also the time to peak HRR) for most PNs than the base polymer is also seen in the CCA experiment.117... 

As one can see from the above discussion, establishing correlation between bench-scale flammability and cable flame tests is a difficult task because of complicated chemical and physical processes involved in the burning and combustion of polymer materials and cables. Much research is still needed to understand fundamental processes governing the flaming combustion of wire and cable compounds in actual cable designs and cable bundles in a given environment. 

Flammability is the ease with which a substance will ignite, causing fire or combustion. Combustion or burning of solid polymers is a complicated process involving physical and chemical phenomena that are only partially understood (Nelson, 2002). It is a sequence of... 

PVA is one of the few linear non-halogenated aliphatic polymers that has a significant char yield (3-5%) when burned. The flammability properties of PVA, the structure of the char and the processes by which char forms, have been studied previously. The data for the performance of the additives individually, combined, and at different concentrations are shown in Table 5.5. Potassium carbonate used alone with PVA (mass fraction of 10%) reduces the peak RHR by 47%, while silica gel used alone with PVA (mass fraction of 10%) reduces the peak RHR by 57%. 

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