Adhesion phenomena between particles according to the content of organic binder in core for thin-wall casting.

ABSTRACT

The content of organic binder in a core for thin-wall casting has been controlled to investigate the adhesion phenomena of inorganic binder between starting particles, as directly related to the mechanical and thermal properties of the core. The inorganic binder precursor was composed of tetraethyl orthosilicate and sodium methoxide as the silicon dioxide and sodium oxide precursors, respectively. Poly(vinyl alcohol), a hydrophilic polymer, was used as an organic binder. The particles coated with the inorganic precursor were sculpted with the organic binder and then the prepared core samples were heated at 1000 degrees C for 1 h. The core samples prepared with the optimum content of organic binder show the highest fracture strength. This may be due to the enhancement of adhesion by the glass phase formed between starting particles. However, when too much or too little organic binder is employed, the strength values of the core samples are significantly decreased. This is because the network structure of the glass phase is not inadequately created or the glass phase is not uniformly developed between starting particles, resulting in the insufficient contact between starting particles during the convert process.