Monomer systems for the gelcasting of foams

The association of the gelcasting process with the aeration of ceramic suspensions allowed the development of a novel category of porous ceramics with unprecedented mechanical properties. One of the critical points in the processing of porous ceramics by this route involves the setting of the foams, which is based on a gelling reaction by the in situ polymerization of organic monomers dissolved in the liquid phase. A variety of monomeric systems that are known to be suitable gelling agents for setting ceramic suspensions into dense forms were investigated in this work, with a view to the production of ceramic foams. These systems, namely ammonium acrylate, N-hydroxymethylacrylamide, methacrylic acid, methacrylamide and methylene-bysacrylamide, were studied considering the main requirements to produce ceramic foams, which include short setting time and high wet green strength. The effects of monomer type on powder dispersion, reaction kinetics, and green strength of wet and dried gelled bodies were investigated. The results revealed that the chemical characteristics of each system can affect the dispersion and rheological properties of suspensions. Polymerization kinetics and wet and dry mechanical strength varied markedly, depending on the type of monomer used.