Estudo dos Mecanismos de Despolimerização Térmica do Poli (Metacrilato de Metilo).:  Escolha de solventes compativeis com o PMMA

Nsingi Ngoma

Key information

Authors:

Nsingi Ngoma (Nsingi Ngoma António)

Supervisors:

Carlos Carvalheira (Carlos Carvalheira); João Carlos Moura Bordado (João Carlos Moura Bordado)

Published in

10/17/2007

Abstract

The mechanism of depolymerisation of the PMMA was studied in this work as well as the incidence of formation of by-product with negative effect in the yield of MMA. A bibliographical study of patents and processes for depolymerisation of the PMMA was described. A theoretical and experimental study of dissolution of the PMMA in different organic solvent was developed, for selection of solvent that can serve of base for acrylic adhesive preparation. The depolymerisation mechanism of PMMA has been studied for more than 6 decades. It consists of three distinct stages: the initiation, depropagation and termination. The initiation can occur by chain end scission, random chain scission, or by elimination of metoxicarbonil side-chains, originating macro-radicals that during the depropagation promote the formation of the MMA. The PMMA degrades thermally almost exclusively in MMA with yields up to 97%. The main by-product are CO2, CO, CH4, CH3OH, light Hydro-carbons and char. The amount of by-products depends on the temperature of depolymerisation. The processes of depolymerization of the PMMA are based on the pyrolysis, differentiating for the way as the necessary heat to the reaction is transmitted. Two groups are distinguished: processes of direct heating and processes of indirect heating. The forecast of dissolution PMMA made from the three-dimensional method of Hansen and of the energy of Gibbs, agrees with experimental results, except in the cases of the Nitrometane and Acetonitrile. As potential solvents for the acrylic adhesive preparation we can use: CH2Cl2/CH3NO2; CHOOCH3/CH3NO2; CHOOCH2CH3/CH3NO2; CH3COOCH3/CH3NO2; CH3COOCH2CH3/CH3NO2; CH3COOCH3/C3H7NO; CH3COOCH2CH3/C3H7NO and CH3COO(CH2)3CH3 /C3H7NO