The die pressing of ceramic powder samples is a high packing process of small grains in stiff forms under the influence of uniaxial action of external pressure.
The disadvantages of pressing are trying to be minimized by selecting suitable materials for making molds, favorable pressing parameters, and by optimizing the rheological properties of the molded ceramic powders. Polymeric organic binders provide the pressed powders with appropriate thickening capabilities and the molded ceramic samples with mechanical strength. These binders should, at their minimal quantity, provide such rheological properties which would cause a decrease in the friction forces between the powder particles and matrix, simultaneously providing the green samples with high mechanical strength. These binders are added most often in a 0.5-3 wt. % amount with respect to the ceramic powder.
Water soluble polymeric binders such as poly(vinyl alcohol), methylcellulose and poly(oxyethylene) glycol are most often used in the pressing of ceramic powders. A disadvantage of this type of binders is the small mechanical strength of the samples obtained with them, which precludes the processing of samples in the green state
Various types of polymers, often of hydrophobic properties, prepared in the form of water dispersions, are more and more often used in recent years. Polyacrylic, polyurethane and polyvinyl emulsions are most often used. Studies on the application of water thinnable binders comprising inbuilt amphiphilic macromonomers playing the role of hydrophilizing agents and internal plasticizers intended for alumina molding are presented. The results of studies on the application in the alumina pressing of a new group of acrylic-allyl binders and the effect of water soluble carboxyalumoxanes as coupling agents and polyurethane dispersions applied in molding are also presented.
This work was supported by the Polish State Committee for Scientific Research