Influence of alkali metal ions on the fracture properties of glass polyalkenoate (ionomer) cements.

The influence of substituting sodium for calcium on the properties of glass polyalkenoate cements was investigated. Two series of glass compositions based on PSiO2 x QAl2O3 x 0.75P2O5 x (1 - Z)CaO x XCaF2ZNa2O were studied. The fluorine content was fixed at X = 0.50 and 0.75 and the sodium content varied by altering Z. The glass polyalkenoate cements formed from these glasses were characterized using a linear elastic fracture mechanics (LEFM) approach. In addition, compressive strengths of the cements were determined. The properties of the cements based on the high fluorine content glasses (X = 0.75) were relatively insensitive to sodium content. The Young's modulus, un-notched fracture strength and fracture toughness of the cements produced with the lower fluorine content glasses (X = 0.5) reduced with sodium content, which was consistent with sodium acting to disrupt ionic cross-linking in the polyacrylate matrix. The compressive strength was not as dependent on sodium content as the LEFM parameters.