The formation and hydrolytic stability of metal ion- polyacid gels

A wide range of metal oxide—polyacid cements have been studied to determine the influence that the nature of the cation and polymer structure have on their formation and water stability. The formation of water‐stable products depends markedly upon the type of oxide and polyacid employed and some typical examples of rapid‐setting ionomer cements with varying degrees of water resistance have been listed. Poly(ethylenesulphonic acid) has been found to be a poor cement former compared to polycarboxylic acids. The stability in water of these systems appears to be dependent on a number of factors, including the nature of the metal ion—polyanion bonding, the size of the cation and the presence of other potential ligands on the polymer. To aid a fuller understanding of the influence of the cation—polyanion bonds on the properties of cements made from CaO and CdO with poly(acrylic acid) or ethylene‐maleic acid copolymer, stability constants for Ca2+ and Cd2+ with these polyacids have been determined. Cd2+ is bound much more strongly than Ca2+ to the macroanions of these polyacids and poly(acrylic acid) appears to be a more effective cation binder than ethylene—maleic acid copolymer.