Síntese e caracterização de poliésteres de glicerol e acido adípico

Abstract

Due the large increase in biodiesel production and consequently the increase of its main byproduct, glycerol is emerging as a great potential for various applications. Glycerol has three sites (three hydroxyl groups) which can react with other molecules (dicarboxylic acids), under specific conditions, giving polycondensation reactions to obtain aliphatic polyesters. The present work aims to synthesize and characterize polyesters from polycondensation reaction of adipic acid with glycerol. The polyesters were prepared by adding the monomers at different stoichiometric ratios in vacuum and environment pressure, with different catalysts: dodecylbenzene sulfonic acid (DBSA), stannous chloride and DBSA/SnCl2 mixture. The polymerization and formation of polyester was confirmed by infrared spectra that showed characteristic bands of the ester group. Quantitative solubility tests were performed, using water, hexane, chloroform, tetrahydrofuran (THF), N-methyl pyrrolidone (NMP), methyl ethyl ketone (MEK) and dimethylsulfoxide (DMSO) as solvents. These test confirmed that the polyesters are insoluble and crosslinked. The samples were exposed to environments temperature and humidity, to check the natural degradation. Was observed that the polyesters obtained with DBSA as catalyst degrades more quickly compared to others. The samples, initially rubbery and solid, became a viscous liquid, probably due to acid hydrolysis of ester groups. The thermal behavior of the samples was studied by thermogravimetric analysis. Was observed that the main onset of thermal degradation, with a large mass loss, for all samples, occur from 200 to 400 °C. By application of elemental analysis and NMR 11-I and 73C spectra was possible propound the croslinked strutural of the polyester.