Thermal and dynamic mechanical characterization of acrylic bone cements modified with biodegradable polymers



In this work, a thermal and a dynamic mechanical study of new formulations self-curing acrylic bone cements is reported. The basic formulation of poly(methylmethacrylate) (PMMA)-based acrylic bone cements has been modified with biodegradable polyesters such as poly(l-lactic acid), poly(β-hydroxybutyrate), and different kinds of thermoplastic starches. Differential scanning calorimetry (DSC) (dynamic and isothermal conditions), thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), and scanning electron microscopy (SEM) were used to determine the influence of the biodegradable polymer in the behavior of the biomedical formulations. DSC assay revealed a strong dependence of the polymerization enthalpy (ΔHcur) with increasing solid : liquid ratio and a low influence of the nature of the added biodegradable polymer on glass transition. TGA analysis showed the different mechanism of PMMA-biodegradable polymer interaction depending on the solubilization of the added polymer in methylmethacrylate monomer during curing. DMTA showed the reinforcing capacity of segregated phases of the polymer included in the cement. The solubilization of aliphatic polyesters in the resulting PMMA polymerized phase led to a drop in mechanical stiffness observed from storage modulus (E′) profiles. Moreover, tan δ shifts to higher temperatures (4–7°C) during a second scan, confirming the presence of residual monomer content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013