Evolved gas analysis of PEP-SET sand by TG and FTIR

Abstract

Thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TG-FTIR) and on-line FTIR were employed in this study, aiming at investigating the pyrolysis characteristic of Polybenzylic Ether Phenolic resin sand mould (PEP-SET sand) and emission gases generated during casting. The non-isothermal pyrolysis of PEP-SET sand can be subdivided into three stages: emission of inherent moisture (below 215°C), thermal decomposition at low temperature (215–315°C) and further cracking process at high temperature (315–432°C). The main emission gaseous products in pyrolysis processes were H2O, CO2, NH3, CH4, C2H6, NO and a little amount of CO, according to the FTIR spectrum analyses. The amount of N-containing pyrolysis products generated from cracking of the CN bond reflects the collapse extent of the binder. The thermal shock tests at different temperatures were performed. Similar to non-isothermal pyrolysis processes, the main gaseous products were CO2, CO, NO, CH4 and C2H6 under thermal shock conditions, and these gases released follow a fixed sequence: concentrations of CO, CO2 and NO firstly increased to the peaks and then decreased with the rising of CH4 and C2H6. At last the CO2 concentration increased again. The major emission oxidizing gas which may induce ignition of Mg melt is CO2 and the environmental hazardous components are NO and NH3.