The influence of polyacid molecular weight on some properties of glass-ionomer cements.

The influence of the molecular weight of the poly(acrylic acid) component on some properties of glass-ionomer cement has been investigated. The results can be explained by treatment of glass-ionomer cements as thermoplastic composites. Many of the concepts of polymer science can be applied successfully in a qualitative way to these cements, including the ideas of entanglements and reptation. Molecular weight of the polyacid had a pronounced influence on setting rate, acid erosion rate, toughness, fracture toughness, and wear resistance. The chain length of the polyacid was found to be an important parameter in formulation of a cement, and the higher the molecular weight, the better the properties. However, in practice the molecular weight is limited by viscosity, and some balance has to be achieved among concentration, molecular weight, and viscosity.