Epoxy resin pyrolysis products

Bromocresol purple (5.2...6.8) glutamic and ketoglutaric acids [217], halide and halate anions [91,218, 219] preservatives [220, 221] products of pyrolysis of epoxy resins [222] 5-aminodibenzocyclo-heptane derivatives [223] phenylalkanolamines, eph-edrine [224]... 

Thermoset plastics have also been pyrolysed with a view to obtain chemicals for recycling into the petrochemical industry. Pyrolysis of a polyester/styrene copolymer resin composite produced a wax which consisted of 96 wt% of phthalic anhydride and an oil composed of 26 wt% styrene. The phthalic anhydride is used as a modifying agent in polyester resin manufacture and can also be used as a cross-linking agent for epoxy resins. Phthalic anhydride is a characteristic early degradation product of unsaturated thermoset polyesters derived from orf/io-phthalic acid [56, 57]. Kaminsky et al. [9] investigated the pyrolysis of polyester at 768°C in a fiuidized-bed reactor and reported 18.1 wt% conversion to benzene. 

There is a common feature of the polymer composition in PC, PPO, epoxy and phenol-formaldehyde resin, all contain phenoxy moieties in their repeating unit. Hence, it is not unexpected that the major pyrolysis products of these plastics are phenols. The reason of the production of phenolic compounds is the higher bonding energy of the C-0 linkage in the phenoxy moiety related to that of other bonds along the polymer chain. 

Pyrolysis Products of Flame-retarded Epoxy Resin... 

Information about the composition of the sample material can be significantly increased if the paints have been derivatized during pyrolysis. Tetramethyl-ammonium hydroxide (TMAH) is used as a derivat-izing reagent for structure elucidation of alkyd, unsaturated polyester, epoxy, and phenol-formaldehyde resins. The derivatization of paints, whose pyrolysis products elute at very low retention times (such as formulations based on polyvinylacetate... 

Significant effort has recently been put in for the elimination of polymer wastes from electric and electronic equipment (WEEE) by pyrolysis. WEEE includes mainly epoxy resins and styrene polymers. They often contain brominated aromatics, which are highly contaminant. However, their elimination by simple thermal treatments is no longer possible as one of the most important drawbacks in dealing with thermal treatment of WEEE is the likely production of supertoxic halogenated dibenzodiox-ins and dibenzofurans. A pyrolysis method at low temperature range was developed, which limited the formation of such toxic by-products and reduced pyrolysis costs, even at relatively long residence times in the reactor. 

In epoxy resin, the combination of ATH and phosphonium-modified clay additives showed superposition or even synergetic behavior for nearly all fire retardancy properties. Schartel et al. suggested that the presence of ATH resulted in an increase in residues and a small decrease in effective heat of combustion because of dilution of the pyrolysis products [24], Both fire retardancy mechanisms have their primary source in the conversion of ATH into aluminum oxide, which increased the residues, and water, which diluted and cooled the flame zone. In addition, the presence of organophosphorus decreased the effective heat of combustion through a gas phase. Most of the phosphorus was liberated during polymer pyrolysis and influenced the Are behavior through flame inhibition. 

PyGC cannot be fully exploited for identification of unknown compounds in complex matrices, such as cured epoxy resins. It is impossible to identify unknown resins by pattern recognition. In those cases identification of pyrolysis products requires postchromatographic detection (MS, FTIR, AED) to collect structural information. 

It is generally accepted that degradation of epoxy resins starts by dehydration of secondary alcoholic groups followed by homolytic scission of the formed allylic bond [34, 35]. There have been various studies carried out for the brominated epoxy resin treatment. In the study of Balabanovich [33], brominated epoxy resin produces gases and oil as pyrolysis products at the temperature of about 100 °C. However, these pyrolysis volatiles are contaminated by brominated phenols, brominated alkanes, and HBr, which is a difficult point for pyrolysis of brominated epoxy resin. 

Based on analysis of products distribution [25], it was concluded that there were two kinds of decomposition action hydrolysis mainly at lower temperature and pyrolysis mainly at higher temperature. At low-temperature stage, the brominated epoxy resin was mainly decomposed into bisphenol A, brome-phenol, isopropyl phenol monomer, etc., while at high-temperature stage, the brominated epoxy resin was mainly decomposed into phenol, o-cresol, p-cresol, and other small molecule compormds without bromine. 

Products obtained by pyrolysis of other polymers is reviewed in Table 4.5. Some specific applications of the chromatography-MS technique to various types of polymers include the following PE [34,35], poly(l-octene) [29], poly(l-decene) [29], poly(l-dodecene) [29], CPE [36], polyolefins [37, 38], acrylic acid-methacrylic acid copolymers [39, 40], polyacrylate [41], nitrile rubber [42], natural rubbers [43, 44], chlorinated natural rubber [45, 46], polychloroprene [47], PVC [48-50], polysilicones [51, 52, 53], polycarbonates [54], styrene-isoprene copolymers [55], substituted olystyrene [56], PP carbonate [57], ethylene-vinyl acetate [58], Nylon 66 [59], polyisopropenyl cyclohexane-a-methyl styrene copolymers [60], cresol-novolac epoxy resins [61], polymeric flame retardants [62], poly(4-N-alkyl styrenes) [63], polyvinyl pyrrolidone [64], polybutyl-cyanoacrylate [65], polysulfides [66], poly(diethyl-2-methacryl-oxy) ethyl phosphate [67, 68], polyetherimide [69], bisphenol-A [70], polybutadiene [71], polyacenaphthalene [72], poly(l-lactide) [73], polyesterimide [74], polyphenylene triazine [75], poly-4-N-vinyl pyridine [76], diglycidylether-bisphenol-A epoxy resins [77], polyvinylidene chloride [78] and poly-p-chloromethyl styrene [79]. 

Electrical and electronic devices are made utilizing several various types of plastic materials, thus when discarded their waste is difficult to recycle. The plastics employed in housing and other appliances are more or less homogeneous materials (among others PP, PVC, PS, HIPS, ABS, SAN, Nylon 6,6, the pyrolysis liquids of which have been discussed above). However, metals are embedded in printed circuit boards, switches, junctions and insulated wires, moreover these parts contain fire retardants in addition to support and filler materials. Pyrolysis is a suitable way to remove plastics smoothly from embedded metals in electrical and electronic waste (EEW), in addition the thermal decomposition products of the plastics may serve as feedstock or fuel. PVC, PBT, Nylon 6,6, polycarbonate (PC), polyphenylene ether (PPO), epoxy and phenolic resins occur in these metal-containing parts of EEW. 

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