Abstract
The authors decomposed an epoxy resin cured with an amine by using a nitric acid solution, and extracted compounds were recovered by ethyl acetate to be added to the virgin epoxy resin and cured with an acid anhydride. The cured resin showed good mechanical properties. In this study, aiming at the appearance of 4 peaks in the molecular weight distribution of the extracted compounds, each peak component was fractionated by chromatography. The compounds of 4 kinds with respectively different molecular weight distribution were added to the virgin epoxy resin individually and cured with the acid anhydride to evaluate mechanical properties. Generally speaking, the higher the molecular weight of the extracted component, the better were the mechanical properties and thermal stability. Decomposing conditions for efficiently obtaining the extract with high molecular weight were investigated with respect to the concentration of nitric acid solution and the proceeding time of decomposition. The extract from the compounds which decomposed by a high conc. nitric acid for a short time contained plenty of the high molecular weight component. It became clear that there was a correlation between the content of high molecular weight component and the mechanical strength of recycled materials.
