The ever growing environmental issues of fumes, odour and waste disposal have focused increased attention on the need to develop a process to reduce the environmental impact of casting production.
The Geopol inorganic binder system, designed to produce moulds and cores, is a sand binder, cured by adding a liquid hardener. The Geopol system is an ester cured, alumino-silicate geo-polymer.
The process differs from traditional sodium silicates in the way that the bond is formed. It forms an amorphous inorganic polymer, which exhibits higher strengths at lower addition levels (typically 2%). This offers improved flowability of sand, which gives it higher mould density to create a higher quality surface finish and breakdown after casting.
The major benefit of the system is its negligible environmental impact. The system does not emit any VOC’s and hazardous air pollution is minimal. With no phenol, formaldehyde or F.A. there are no hazardous leachates and therefore should not be classified as special waste. On casting no visible fume is witnessed. With virtually no odour, low emissions on moulding, casting and shake-out, it is both operator and environmentally friendly.
This system is yet another tool in the foundryman’s toolbox. It is not the system to replace all other binders but has its place, especially for those foundries either wishing, or being forced, to look to more environmentally friendly systems.
There is a large range of esters making the systems highly flexible with bench life of between two and 30 minutes, and strip times of six to 40 minutes based on typical ester additions of around 14% and silicate additions of just 2%. The system is more tolerant of varying ester levels than the traditional ester/silicates, but with any system it should be managed to provide the best cost and technical benefits.
Higher reclaim levels are possible with the Geopol system with up to 50% possible with mechanical reclamation. When double attrition is available then 70% and even 80% reclaim is possible. In any reclamation system management of the system to avoid fines build up or soda levels going above 0.3% is essential if problems are to be avoided.
Good strip is achieved from good, well maintained patterns. Good shake-out is also achieved in a range of materials from aluminium, cast iron, steels and copper base alloys. Leaded gun metal is a material prone to pin-holing and by changing to Geopol at least two foundries have eliminated pin holes from their LG2/4 alloy castings.
Originating in the Czech Republic, Geopol has been commercially developed by Sand Team, John Winter and Technofond and is now available worldwide, having been proven to transform the working environment in several foundries in Europe, North America, Asia and the Middle East. The binder has been tested in a number of foundries casting ferrous and non-ferrous castings.