RESUMO
The synthesis of many polycarboxylic acids is reported. An account is given of their stability in aqueous solution and the properties of cements formed by their reaction with ion-leachable glasses. A copolymer of acrylic and itaconic acids was found to combine several favorable characteristics.
Assuntos
Resinas Acrílicas/síntese química , Cimentos Dentários/síntese química , Cimentos de Ionômeros de Vidro/síntese química , Cimento de Policarboxilato/síntese química , Ácidos Carboxílicos/análise , Fenômenos Químicos , Físico-Química , Géis , Cimentos de Ionômeros de Vidro/análise , Metacrilatos , Peso Molecular , Cimento de Policarboxilato/análise , Polímeros , SuccinatosRESUMO
The oscillating rheometer is a valuable instrument for studying the effects of additives on the setting behavior of a cement system. Using this instrument, it was found that certain chelating comonomers, the hydroxycarboxylic acids, could improve the setting characteristics of the glass-ionomer cement system when added to the PAA solution. The acid chelates probably assign the extraction of metal ions from the glass and also tend to hold them in solution, preventing premature ion binding of the polyanion chains. The effect is to increase the rate of hardening without reducing the working time, which may indeed by slightly increased. Tartaric acid, the most effective of the comonomers, can form a chelate bridge between aluminum atoms, and this metal complex probably acts as a flexible bridge structure linking polyanion chains. This mechanism offers some steric advantages over a simple salt bridge.
