Investigation of the thermal decomposition of printed circuit boards (PCBs) via thermogravimetric analysis (TGA) and analytical pyrolysis (Py–GC/MS)

Published Date
September 2015, Vol.115:337–343, doi:10.1016/j.jaap.2015.08.012

Author 

Panagiotis Evangelopoulos ^,

Efthymios Kantarelis

Weihong Yang

Royal Institute of Technology (KTH), Department of Material Science and Engineering, Brinellvägen 23, 100 44 Stockholm, Sweden

Received 10 April 2015. Revised 10 August 2015. Accepted 12 August 2015. Available online 19 August 2015. 

Highlights

• Identification of two degradation steps of printed circuit boards (PCBs) via TGA experiments.
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  Identification of several pyrolysis products, which the most abundant was phenol and phenolic compounds.
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  Correlation of the product yields according to the temperature conditions.
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  Possible reaction pathways of the degradation of brominated epoxy resin was proposed.
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  Production of benzofuranic structures at higher temperatures remains a significant challenge.

Abstract 

The purpose of this study is to experimentally investigate the pyrolytic behavior of printed circuit boards (PCBs) waste fraction at a temperature range of 400 °C to 900 °C by means of thermogravimetric analysis (TGA) and analytical pyrolysis (Py–GC/MS) was carried out. The experimental results reveal that the chemical composition of the PCBs and the relatively high ash content (=79% w/w) are strongly connected with the high quantity of metals and ceramic materials. The main decomposition of PCBs occurs between 250 °C and 370 °C. The pyrolysis of PCBs showed a varying production of aromatic compounds such as phenol, bromophenol, styrene, methylstyrene, and bisphenol A as well as non-aromatic compounds such as acetone and bromomethane, which are strongly related with the initial chemical composition of PCBs. Moreover, Py–GC/MS revealed that temperature increase favours the production of aromatic hydrocarbons, while the phenol which is the most abundant compound produced, shows an opposite trend, as a result of its further decomposition to simpler products. Furthermore, brominated compounds produced, such as bromomethane and bromophenol, are derived from the flame retardant used during the manufacturing process and in that case the Py–GC/MS showed a slight decrease of brominated compounds with increase in temperature.

Keywords

Pyrolysis

Printed circuit boards

Py–GC/MS

TGA

PCBs

e-Waste

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  Corresponding author.
  
  

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