Analysis of Pyrolysis Products during Thermal Decomposition of Organic Components in Ceramic Green Bodies

Abstract

For improved quality and machinability of ceramic green bodies the use of organic additives is necessary. During the debinding process the polymers are thermally decomposed and partially emitted as ecotoxicologically relevant components. The aim of this study was to determine and to quantify these compounds during pyrolysis with the ultimate goal of reducing the emission of undesirable pyrolysis products. Four organic polymers frequently used in ceramics industry were investigated: polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyethylene glycol (PEG) and latex. The decomposition experiments were carried out using a tube furnace. Cylindrical green bodies, mainly Al 2 O 3 but also SiC, containing a common amount of 5 mass % of organic additives were pressed and heated. To gather the different volatile decomposition products, a branched sampling system with different adsorbents was developed. After elution of these adsorbents separation and quantification of the pyrolysis products were performed using GC/MS and HPLC. The main pyrolysis products of the three aliphatic organic additives are low molecular mass aldehydes in particular the potentially carcinogenic form-, acet-, and crotonaldehyde in the range of mg/g. According to the used polymer, the concentration of aromatic compounds varies over a wide range from μg/g to mg/g. While the pyrolysis of PEG results in nearly undetectable concentrations of aromatics, mono-, di-, and trimers of ethylene glycol, 2-methyl-1,3-dioxolan and 1,4-dioxan are formed in concentrations in the range of mg/g. The formation of the potentially carcinogenic 1,4-dioxan could be of toxicological relevance.