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నైరూప్య

Recovery of MMA by Depolymerization of PMMA-Based Dental Resins Scraps Rosettes (Retraction Note)

Armando Costa Ferreira, Haroldo Jorge da Silva Ribeiro, Paulo Bissi dos Santos Jr, Maria Elizabeth Gemaque Costa, Conceição de Maria Sales da Silva, Douglas Alberto Rocha de Castro, Marcelo Costa Santos, Sergio Du-voisin, Jr, Luiz Eduardo Pizarro Borges, Nélio Teixeira Machado

This work aims to investigate the influence of temperature on the recovery and purity of Methyl Methacrylate (MMA) by depolymerization of Polymethyl Methacrylate (PMMA) dental resins scraps. The experiments were carried out at 350˚C, 400˚C, and 450˚C, 1.0 atm. in laboratory scale, using a borosilicate glass reactor of 125 mL. The density, kinematic viscosity, acidity and refractive index of liquid products were determined experimentally. The chemical compositions of liquid products were determined by GC- MS. The experiments show liquid phase yields between 48.76% and 94.74% (wt.), showing a 1^st order exponential growth behavior, increasing with increasing temperature, while that of solid phase (coke) varied between 0.68% and 38.83% (wt.), showing a 1st order exponential decay behavior, decreasing as the temperature increases. The measure liquid products density, kinematic viscosity, and refractive index are close to those of pure MMA at 20˚C, showing percent errors between 0.0% and 0.42%, 6.54% and 7.81%, and 0.28% and 0.42% for density, kinematic viscosity, and refractive index, respectively. The GC-MS analysis identified Methyl Methacrylate (MMA) and Ethylene Glycol Dimethyl Methacrylate (EDGMA). The concentrations of Methyl Methacrylate (MMA) varied 94.20% and 95.66% (area), showing a smooth increase with increasing de-polymerization temperature. The pyrolysis of PMMA dental resins scraps has proven to be an effective method to recover high amounts of MMA with high purity.