Introduction

Poly(acrylic acid) and its salts have been known to have useful binding properties for some thirty years; they have been used for soil consolidation (Lambe & Michaels, 1954; Hopkins, 1955; Wilson & Crisp, 1977) and as a flocculant (Woodberry, 1961). The most interesting of these applications is the in situ polymerization of calcium acrylate added to soil (de Mello, Hauser & Lambe, 1953). But here we are concerned with cements formed from these polyacids.

The polyelectrolyte cements are modern materials that have adhesive properties and are formed by the cement-forming reaction between a poly(alkenoic acid), typically poly(acrylic acid), PAA, in concentrated aqueous solution, and a cation-releasing base. The base may be a metal oxide, in particular zinc oxide, a silicate mineral or an aluminosilicate glass. The presence of a polyacid in these cements gives them the valuable property of adhesion. The structures of some poly(alkenoic acid)s are shown in Figure 5.1.

The polyelectrolyte cements may be classified by the type of basic powder used to form the cement.

1. The metal oxide cements (Section 5.6)

2. The zinc polycarboxylate cement (Section 5.7)

3. The mineral ionomer cements (Section 5.8)

4. The glass–ionomer or glass polyalkenoate cement (Section 5.9)

Only two of these materials are of practical importance: the zinc polycarboxylate cement of Smith (1968) and the glass–ionomer cement of Wilson & Kent (1971). Both are used in dental applications and both have been used as bone cements.