Pyrolysis Reaction Pathways of Waste Epoxy-Printed Circuit Board

Abstract

This article elucidates pyrolysis reaction pathways of waste epoxy-printed circuit boards (e-PCBs). Non-isothermal thermogravimetric analyses showed that waste e-PCBs decomposed via a series of reactions distinguished by three apparent reaction regions. The first-stage reaction ( <250°C) can be accounted for by the cleavage reaction of N-containing cross-linkage between brominated epoxy resin (BER) and non-brominated epoxy resin (NBER). Evolved gas analysis-mass spectrometry (EGA-MS) showed that the second-stage reaction (250-500°C) can be represented by two independent decomposition reactions of BERs and NBERs to yield thermally stable intermediates. BERs decomposed more rapidly (250-350°C), whereas NBERs decomposed over broader temperature regions (250-500°C) with slower decomposition rates. Multi-shot gas chromatography/mass spectrometry also indicated that brominated compounds, brominated phenol and brominated bisphenol A, are generated mainly at lower temperature zones of the second-stage region, whereas phenols and branched phenols are generated at higher temperature zones. Steady but slow conversion of intermediates was carried out over the conversion of 0.9. At the third-stage reaction, thermally stable intermediates were converted slowly to char as a result of HBr release from intermediates.

VOCs elimination and health risk reduction in e-waste dismantling workshop using integrated techniques of electrostatic precipitation with advanced oxidation technologies

“…As well known, PCBAs are manufactured mainly with epoxy or phenol resin containing a fire retardant, such as tetrabromobisphenol-A (TBBPA) [32]. At a high combustion temperature (>400 • C in the rotary incinerator), the single bond between carbon atom and benzene ring in TBBPA may be broken or substituted by other radicals during the heating, releasing a large amount of AHs [33].…”

Analysis of rejects from waste printed circuit board processing as an alternative fuel for the cement industry

“…The TGA and derivative thermogravimetric curves (Figures 3 and 4) showed that the degradation temperature for the thermal breakdown of resins or paper laminate maximizes around 320°C in all cases. The first fast decomposition region ranges from 250°C to 350°C, peaking around 310–320°C, whereas the second slow decomposition region starts after 400°C, peaking around 500°C, which would represent the presence of components from FR-2 and FR-4 boards (Evangelopoulos et al, 2015; Kim et al, 2013, 2015). The NMFC shows a decomposition region from 350°C to 450°C, which represents the decomposition of phenolic resin.…”

“…Researchers have shown that the combustion of flame retardent-2 (FR-2) and flame retardant-4 (FR-4) type boards occurs in two distinct temperature ranges. A fast decomposition step of resins occurs from 250°C to 370°C, followed by a slow combustion process after 500°C (Evangelopoulos et al, 2015; Kim et al, 2013). The Fourier-transform infrared spectroscopy spectrum of the evolved products during the decomposition step shows the presence of low molecular weight compounds such as carbon monoxide, carbon dioxide, ammonia, hydrogen bromide, methane, and water molecules, and high molecular weight compounds such as phenol, dioxins, furans, benzene and their derivatives along with char residue.…”

Co-Pyrolysis of PCB with Cotton Stalk: Product Characterisation

“…Some authors presented TBBA degradation mechanism and release of brominated compounds in their research (Grause et al, 2008; W. J. Kim et al, 2013). Moreover, Furans are highly toxic components and they are present in PCB oil in the form of Benzofuran, 2-isopropenyl-3-methyl-, Dibenzofuran, and 2(5H)-furanone, 3-hydroxy-4,5-dimethyl-(total of 1.44 % area) but their quantity decreased to 0.78 % area with co-pyrolysis, see Table 2.…”

“…Additionally, it contains a large amount of volatile matter and lower O/C (Madhu et al, 2018); Kim et al, 2013) which gives an expectation of high bio-oil yield with improved quality (W. J. Madhu et al, 2018).…”