Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Process Analysis of PMMA Dental Resins Scraps Depolimerization: Optimization of Reaction Time and Temperature

Version 1 : Received: 5 October 2021 / Approved: 6 October 2021 / Online: 6 October 2021 (09:19:43 CEST)

A peer-reviewed article of this Preprint also exists.

dos Santos, P.B., Jr.; Ribeiro, H.J.S.; Ferreira, A.C.; Ferreira, C.C.; Bernar, L.P.; Assunção, F.P.C.; de Castro, D.A.R.; Santos, M.C.; Duvoisin, S., Jr.; Borges, L.E.P.; Machado, N.T. Process Analysis of PMMA-Based Dental Resins Residues Depolymerization: Optimization of Reaction Time and Temperature. Energies 2022, 15, 91. dos Santos, P.B., Jr.; Ribeiro, H.J.S.; Ferreira, A.C.; Ferreira, C.C.; Bernar, L.P.; Assunção, F.P.C.; de Castro, D.A.R.; Santos, M.C.; Duvoisin, S., Jr.; Borges, L.E.P.; Machado, N.T. Process Analysis of PMMA-Based Dental Resins Residues Depolymerization: Optimization of Reaction Time and Temperature. Energies 2022, 15, 91.

Journal reference: Energies 2021, 15, 91
DOI: 10.3390/en15010091

Abstract

In this work, the cross-linked PMMA-based dental resins scraps were submitted to pyrolysis to recover MMA (Methylmethacrylate). The thermal degradation of cross-linked PMMA-based dental resins scraps was analyzed by TG/DTG to guide the operating conditions in pilot scale. The pyrolysis experiments carried out in a reactor of 143L, at 345, 405, and 420°C, 1.0 atmosphere. The reaction liquid products obtained at 345°C, physicochemical characterized for density, kinematic viscosity, and refractive index. The chemical composition of liquid products obtained at 345°C, 30, 40, 50, 60, 70, 80, and 110 minutes, at 405°C, 50, 70, and 130 minutes, and at 420°C, 40, 50, 80, 100, 110, and 130 minutes determined by GC-MS. The experiments show that liquid phase yields were 55.50%, 48.73%, and 48.20% (wt.), at 345, 405, and 420°C, respectively, showing a smooth sigmoid behavior, decreasing with increasing temperature, while that of gas phase were 31.69%, 36.60%, and 40.13% (wt.), respectively, increasing with temperature. The liquid products density, kinematic viscosity, and refractive index obtained at 30, 40, 50, 60, 70, 80, and 110 minutes, varied between 0.9227 and 0.9380 g/mL, 0.566 and 0.588 mm2/s, and 1.401 and 1.414, respectively, showing percentage deviations between 0.74 and 2.36%, 7.40 and 10.86%, and 0.00 and 0.92%, respectively, compared to standard values for density, kinematic viscosity, and refractive index of pure MMA at 20 °C. The GC-MS identified in the reaction liquid products at 345, 405, and 420°C, 1.0 atm, esters of carboxylic acids, alcohols, ketones, and aromatics, showing concentrations of MMA between 83.454 and 98.975% (area.). For all the depolymerization experiments, the concentrations of MMA in the liquid phase, between 30 and 80 minutes, reach purities above 98% (area.), decreasing drastically with increasing reaction time after 100 minutes, thus making it possible to depolymerize the cross-linked PMMA-based dental resins scraps by pyrolysis to recover MMA. The optimum operating conditions to achieve high MMA concentrations, as well as elevated yields of liquid reaction products were 345 °C and 80 minutes.

Keywords

PMMA; Pyrolysis; Plastics Wastes; Depolymerization; Distillation; Recovery of Methylmethac-rylate

Subject

ENGINEERING, Biomedical & Chemical Engineering

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