Effect of the loading of organomodified clays on the thermal and mechanical properties of a model dental resin


Mat. Res.




Experimental dental resins composed of triethyleneglycol dimethacrylate, urethane dimethacrylate, ethoxylated bisphenol-A-dimethacrylate and bisphenol A glycidyl methacrylate containing an organoclay as filler were prepared by photopolymerization. The addition of organoclay fillers results in slower polymerization rates (0.59 and 0.24 mol L-1 min-1, for the formulations without and with 15% of organoclay, respectively) and lower degrees of conversion (0.50 and 0.35 for the formulations without and with 15% of organoclay), as determined by photocalorimetry. The influence of the organoclay on the thermal and mechanical properties of the resins was evaluated using thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) techniques. The (tan δ) and E´ curves indicate the formation of more rigid materials and the damping curve data indicates more homogeneous materials. An increase of storage modulus, E’, was observed for composites with the higher organoclay filler contents. These effects are due to the higher viscosity of the systems with organoclay, resulting in a lower mobility of the radicals during the propagation step of polymerization, as well as to the scattering of the incident photopolymerizing radiation, which lowers the amount of initiation centres.

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