Analysis of the decomposition of an anhydride-cured epoxy resin by subcritical hydrolysis

The decomposition of an anhydride-cured epoxy resin by subcritical hydrolysis is studied under variation of reaction temperature, decomposition duration and water volume using a batch reactor. Within the framework of a design of experiment, the process is evaluated by the gravimetric decomposition of the epoxy resin clearly showing that temperature is the most important factor. Duration and water volume have only smaller positive effects. The mass loss mechanism of the cube-shaped specimens corresponds to a heterogeneous surface degradation where material is only lost from the outer areas. The determination of glass transition temperatures after the experiments demonstrates that the water hardly affects the center of the epoxy cubes. Therefore, a core-shrinking model is successfully applied for analysis of the decomposition kinetics. The product distribution in the aqueous phase reveals a large number of organic compounds. Higher temperatures, longer durations and lower water volumes lead to an increase in decomposition product complexity and concentrations, but the degradation pathways are apparently not affected.