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Examining the thermal degradation of polymer binders using FTIR spectroscopy

Grabowska B.

Archives of Foundry Engineering

2010

Vol. 10, iss. 4

43--46

This article discusses the general theoretical basis for examining polymers using FTIR infrared spectroscopy. It presents results of research on using the FTIR to analyse the course of structural changes during the thermal degradation of polymer binders exemplified by a sodium salt of the maleic acid – acrylic acid copolymer. This polymer was selected for the research due to its structure (an aliphatic structure polymer) and its physical chemistry properties (polarity, presence of reactive COO- carboxylic groups). In addition, results of previous research on using acrylic polymers as binders for casting pastes have shown that they can be applied in casting technologies. Results of FTIR examinations were used to determine the structural changes resulting from the gradual degradation consisting in the progressive fragmentation of polymer chains, the formation of new, shorter hydrocarbon chains of various structural arrangements. It was found that the thermal degradation of the initial polymer starts at about 120°C. Examinations of the thermal degradation process are significant, particularly with reference to processes taking place in the casting paste when it comes into contact with liquid metal. In the case of casting paste whose matrix is formed of quartz sand and the binder is a sodium salt of the maleic acid/acrylic acid copolymer, the degradation process of the polymer in the paste starts at about 300°C, and at 450°C the destruction is practically complete.