Low pressure injection moulding of ceramic suspensions

Injection moulding has received a significant attention for manufacturing o f precise, complex shaped parts which could not be obtained by other method s. However, this technique implies the use of polimeric transport vehicles, associated to some problems that limit its use, such as the high working t emperature (120 degrees C-200 degrees C), the complex and expensive machine ry, the high injection pressures (7-150 MPa), the moulds corrosion, the lon g cycles for burning out, etc. These characteristics are the responsible fo r the low industrial use of this process, only available for big companies. An useful alternative to reduce costs and process complexity is the low pr essure injection moulding. It has been stated that this technique can be us ed from aqueous suspensions, thus largely facilitating handling, machinery and reducing costs. This technique allows to decrease the content of polyme ric materials down to 2-3 vol%, respect to 20-50 vol%, tipically employed i n the high pressure technique, in such a way that it is not necessary a spe cific treatment for burning out, and then the number of rejected parts is l ower. In this work, the advantages and limitations of the low pressure injection moulding (LPIM) process in water are described focusing critical parameters for the obtention of alumina parts, such as the rheological properties of the suspension at the injection temperature and the influence of the gellin g additive.