Rubber plastics thermal decomposition

The overwhelming majority of foams are TPs, but TSs are also foamed with CBAs, although some of them do create problems. Popular TS foams are made from polyurethane, polyester, phenolic, epoxy, and rubber. Thermal decomposition of the blowing agent with certain plastics such as TS polyesters cannot be applied in this system because the heat of polymerization is not high enough to induce decomposition. But chemical reactions simultaneously produce gas and free radicals they typically involve oxidation and reduction of a hydrazine derivative and peroxide. The reactions are catalyzed by metals, which can be used repeatedly. 

The polymers of rubber plastics have unsaturated hydrocarbon chain structure, since they are polymerized from alkadienes. The general formula of poly(l,3-butadiene) or butadiene rubber (BR) and polyisoprene or natural rubber (NR) is drawn in Scheme 12.5, where X is hydrogen in BR and methyl group in synthetic polyisoprene or NR. The free radical mechanism of thermal decomposition starts by homolytic scission of the alkyl C-C bonds. Two primary macroradicals (4 and 5) are formed for which the rearrangement... 

Thermal processes are mainly used for the feedstock recycling of addition polymers whereas, as stated in Chapter 2, condensation polymers are preferably depolymerized by reaction with certain chemical agents. The present chapter will deal with the thermal decomposition of polyethylene, polypropylene, polystyrene and polyvinyl chloride, which are the main components of the plastic waste stream (see Chapter 1). Nevertheless, the thermal degradation of some condensation polymers will also be mentioned, because they can appear mixed with polyolefins and other addition polymers in the plastic waste stream. Both the thermal decomposition of individual plastics and of plastic mixtures will be discussed. Likewise, the thermal coprocessing of plastic wastes with other materials (e.g. coal and biomass) will be considered in this chapter. Finally, the thermal degradation of rubber wastes will also be reviewed because in recent years much research effort has been devoted to the recovery of valuable products by the pyrolysis of used tyres. 

Contact with metals and some metal compounds may cause polymerization. Attacks most rubbers, plastics, and coatings. May accumulate electrical charges and cause ignition of its vapors. Thermal decomposition releases deadly hydrogen cyanide gas and nitrogen oxides. On small fires, use alcohol-resistant foam, dry chemical, or COj extinguishers. 

HEXACHLOROBUTADIENE or HEXACHLORO-l,3-BUTADIENE (87-68-3) C4C1 CliC=CClCCl=CCIj Combustible liquid (flash point 195°F/90°C autoignition temp 1125°F/607°C Fire Rating 1). Unless inhibited, may form unstable peroxides in storage. Reacts strongly with oxidizers, aliuninum powder may cause fire and explosion. Mixtures with bromine perchlorate forms heat-, friction-, and shock-sensitive explosive compound. Attacks aluminum, and some plastics and coatings decomposes rubber. Thermal decomposition releases toxic and irritating chloride fumes. On small fires, use dry... 

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