Thermoanalytical tests (TG–DTG–DSC, Py-GC/MS) of foundry binders on the example of polymer composition of poly(acrylic acid)–sodium carboxymethylcellulose

Abstract

The results of thermal analysis (TG–DTG–DSC) of a foundry binder from the BioCo group in the form of a polymer composition of poly(acrylic acid)–sodium carboxymethylcellulose (PAA/CMC-Na) are presented in this article. The range of temperature of degradation has been determined. It was found that as the temperature rises, physical and chemical changes take place in the binder as a result of evaporation of solvent water, release of constitutional water, intermolecular dehydration reactions and decomposition of polymer chains with the formation of gaseous decomposition products. Pyrolysis gas chromatography mass spectrometry method (Py-GC/MS) was used to identify PAA/CMC-Na binder degradation products in a predetermined temperature range based on the previously performed thermal analysis of TG–DTG–DSC. Py-GC/MS tests were also carried out to determine the emission level of gaseous products of the polymeric binder in the context of the processes occurring in the moulding (foundry) sand, in conditions of its contact with liquid metal. In addition, Py-GC/MS tests were carried out for two commonly used foundry binders based on alkaline phenolic resin cured with esters and based on urea-formaldehyde resin with furfuryl alcohol cured with sulphonic acids. The obtained Py-GC/MS results for commercial binders were referred to the results obtained for the new PAA/CMC-Na binder. It was found that the new polymer binder is characterized by the lowest emission level of gaseous products.