Studies on the Gases Emission under High Temperature Condition from Moulding Sands Bonded by Modified Starch CMS-Na

Emission of gases under high temperature after pouring molten metal into moulds, which contain the organic binder or other additives (solvents or curing agent), may be an important factor influencing both on the quality of the produced castings, and on the state of environment. Therefore, a comprehensive studies of the emitted gases would allow to determine restrictions on the use of the moulding sands in foundry technologies, eg. the probability of occurrence of casting defects, and identify the gaseous pollutants emitted to the environment. The aim of the research presented in this paper was to determine the amount of gases that are released at high temperatures from moulding sands bonded by biopolymer binder and the quantitative assessment of the emitted pollutants with particular emphasis on chemical compounds: benzene, toluene, ethylbenzene and xylenes (BTEX). The water-soluble modified potato starch as a sodium carboxymethyl starch with low (CMS-NaL) or high (CMS-NaH) degree of substitution was a binder in the tested moulding sands. A tests of gases emission level were conducted according to the procedure developed at the Faculty of Foundry Engineering (AGH University of Science and Technology) involving gas chromatography method (GC). The obtained results of the determination of amount of BTEX compounds generated during the decomposition process of starch binders showed lower emission of aromatic hydrocarbons in comparison with binder based on resin Kaltharz U404 with the acidic curing agent commonly used in the foundries.