Influence of poly(acrylic acid) content on the fracture behaviour of glasspolyalkenoate cements

A linear elastic fracture mechanics approach (LEFM) was used to study glass polyalkenoate cements as a function of the poly(acrylic acid) content. Cem ent specimens were tested at three time intervals after mixing; one, seven and twenty eight days. Two series of cements were investigated one with a g lass volume fraction of 0.4 and the other with a glass volume fraction of 0 .5. The fracture toughness, toughness, Young's modulus and un-notched fract ure strength increased significantly with the percentage polyacid content. The Young's modulus increased with time for ail the cement samples studied. In many cases the moduli values at twenty eight days were twice the values at one day. This is consistent with increased ionic crosslinking of the po lyacrylate matrix. The toughness increased with the polyacid content as pre dicted by the chain pull-out model for fracture and did not change signific antly on increasing the glass volume fraction from 0.4 to 0.5. Fracture tou ghness and Young's modulus increased significantly with glass volume fracti on consistent with the residual glass particles acting as a reinforcing fil ler. (C) 1998 Kluwer Academic Publishers.