A room-temperature autonomically-healing PMMA bone cement: influence of composition on fatigue crack propagation rate

To test two hypotheses. First, autonomic healing is achievable in a commercially available poly (methyl methacrylate) bone cement brand that is widely used to anchor total joint replacements. Secondly, in this self-healing cement, the fatigue crack propagation (FCP) rate is critically dependent on the relative amount of the mass of the healing agent (endo-isomer of dicyclopentadiene (DCPD) embedded in poly (urea-formaldehyde) (PUF) microcapsules (diameter = 226 plusmn; 51 mu;m)) (MDM) to that of the catalyst (a first-generation Grubbsrsquo; catalyst) (MGC). (Note that, in this work, the term, ldquo;autonomic healingrdquo; or ldquo;self healingrdquo;, refers to the ability of the material, after having been damaged during service, due to formation of cracks, for example, to restore its initial mechanical performance without the need for any external intervention).

The strategy that was developed by White et al. for room-temperature autonomic healing of a neat polymeric material was used. The DCPD-filled PUF microcapsules and the catalyst were blended with the cementrsquo;s powder in a mortar bowl using a polymeric spatula, and the blended powder mixture and the cementrsquo;s liquid monomer were mixed under a partial vacuum. FCP tests were performed on specimens of seven study groups: the control cement (CMWTM1), four sets having different values of MDM/MGC, one set in which only the DCPD-filled microcapsules were blended with the CMWTM1 powder, and one set in which only the Grubbsrsquo; catalyst was blended with the CMWTM1 powder.

An index of the self-healing achieved, as computed using the estimated FCP rates, was within the range reported in the literature for autonomically-healing neat polymeric materials. Furthermore, the variation of the estimated FCP rate with MDM/MGC suggests that changes in this rate is critically dependent on change of MDM/MGC.

The results supported both of the study hypotheses.