Calorimetric characterization of the formation of acrylic type bone cements

The formation of acrylic bone cements upon heating was investigated by differential scanning calorimetry (DSC). The effects of the contents of initiators, accelerator, biocompatibilizer, and crosslinking agents on the rate and the heat of polymerization during DSC heating were studied. The rate and the heat of polymerization (ΔH) were characterized by the peak temperature and the area of the DSC exotherm, respectively. It was found that both the rate and heat of polymerization decreased with increasing heating rate. The ΔH was increased considerably with increasing benzoyl peroxide (BPO) initiator concentration from 1 to 10% (w/v), whereas the rate of polymerization was reduced significantly. An increase in azobisisobutyronitrile (AIBN) initiator concentration also induced an increase in ΔH, but the rate of reaction was not affected considerably. The addition of the accelerator promoted the rate of reaction but resulted in a drop in ΔH. The rate of polymerization for the system containing BPO initiator was increased quite significantly with the addition of hydroxyethyl methacrylate (HEMA) biocompatibilizer, while the ΔH was slightly increased. For the system using AIBN as the initiator, the rate of polymerization was decreased slightly and the ΔH dropped significantly with the addition of HEMA. The effect of ethylene glycol dimethacrylate (EGDMA) crosslinking agent was also examined. Polymerization became more rapid with the addition of EGDMA in the bone cement using BPO as the initiator, while it remained approximately constant for the system using AIBN as the initiator. No systematic change in ΔH was observed with the addition of EDGMA in both systems. This study demonstrated that DSC is a potential tool to measure the amount of heat released and also the rate of polymerization for bone cements.