The development of theoretical relationships between some handling parameters (setting time and setting temperature), composition (relative amounts of initiator and activator) and ambient temperature for acrylic bone cement

Abstract

Commercially available acrylic bone cements are two-component systems based on the polymerization of methyl methacrylate around poly(methyl methacrylate) particles. When benzoyl peroxide (BPO), which is the initiator, in the powder component meets accelerator (N,N-dimethyl-p-toluidine (DMpT)) in the liquid component, radicals are produced, initiating the polymerization. This solidifies the cement. In this work, kinetic expressions have been developed that describe the relationship between bone cement setting time on the one hand, and BPO and DMpT concentrations on the other. Changes in setting time with ambient temperature follow a complex relationship, because both the polymerization process (initiation, propagation, and termination) and the swelling and dissolution of the polymer particles contribute to setting. The contribution of polymer swelling and dissolution to the setting process was determined by developing a relationship between the doughing time, which is substantially independent of DMpT or BPO concentrations, and ambient temperature. A value of 64 kJ mol(-1) was found for the activation energy for this process. An activation energy for the overall setting process of 68 kJ mol(-1) was determined from setting-time measurements over several ambient temperatures. This indicates that the sensitivity of setting time to temperature depends more on swelling and dissolution than on the polymerization process.

Bone cement product and failure in total knee arthroplasty

“…The new bone cements are almost identical to the old ones, but the small differences may be due to new suppliers of monomers, copolymers, and gentamicin—and/or slightly changed production procedures. Such minor changes in the chemical properties of the ingredients could affect the end-product (Kühn 2000, Milner 2004, Dall et al. 2007a and b).…”

Preparation and physico‐mechanical, thermal and acoustic properties of flexible polyurethane foams based on hydroxytelechelic natural rubber

“…Clinically, the final curing of the bolus occurs at a temperature closer to 37°C than to the operating room temperature (typically, 21°C). t set and T max of an acrylic bone cement are affected by a host of variables, such as ambient temperature,12, 55 composition,55 and LPR,12 Furthermore, T max is markedly influenced by the amount of cement used, due to an auto‐acceleration effect of the polymerization reaction. These considerations make it very difficult to relate the present t set and T max values to setting times and maximum exotherm temperatures that may be obtained during VP or KP.…”

In vitro comparison of Refobacin-Palacos R with Refobacin Bone Cement and Palacos R + G

“…Intrinsic factors that can vary slightly between batches of the same cement and alter the handling characteristics are the sizes (and therefore relative surface areas) of polymer beads, and also the concentrations of BPO initiator and DMPT accelerator (Milner 2004). Because the chemical composition of the polymer and co-polymer and their relative proportions can vary from batch to batch, the end product reaching the customer will depend on the in-house quality control process of the cement producing company.…”