· Metodos de moldeo y materiales ·
P J Davies and W D Griffiths
Department of Metallurgy and Materials, School of Engineering, University of Birmingham, UK
67th World Foundry Congress
Entrapment of liquid polystyrene degradation products during filling is
detrimental to the quality of Aluminium Lost Foam castings. In this study,
the degradation of expanded polystyrene under different heating
conditions, and the ability of two pattern coatings of different permeability
to absorb the partially degraded liquid polymer, was determined using gel
permeation chromatography and scanning electron microscopy. It is
suggested that, with the degradation of the polystyrene to a sufficiently low
molecular weight liquid, significant absorption of the liquid polystyrene can
occur with each coating. A number of simple plate patterns were cast in a
real-time x-ray facility to determine the effect of each coating type on filling
behaviour and casting quality. Similar tensile properties were found in
each case, although the high permeability coating was associated with a
filling velocity about twice that associated with the low permeability
coating.
