The Effect Of Acid/Base Catalyst On Degradation Behavior Of Epoxy Resin In Nearcritical Water

Epoxy resins are widely used in adhesives, printed circuit boards and as the matrix of advanced composites that have found increasing applications in aerospace and aeronautical industries. However, wastes of thermosetting resins have caused many environmental problems, because they were difficult to dispose arising from their networks. Therefore, the recycling of epoxy resins is an imminent problem.In this paper, the decomposition behavior of bisphenol A type epoxy resin cured with DDM and MeTHPA in water at nearcritical conditions is studied. Experiments are devised in order to identify the signi?cant process parameters that affect epoxy resin recovery potential including temperature, time, catalyst species and concentration. The decomposition rate of resin could reach 100% at lower temperatures under nearcritical water conditions through the use of potassium hydroxide, sulfuric acid and phosphotungstic heteropoly acid as catalyst. KOH can improve the decomposition rate of epoxy resin efficiently and reduce the yield of char.Solid residues are collected and analysed by infrared spectroscopy (IR) and compared with those obtained from the thermal decomposition processes. The liquid product distribution is analyzed using gas chromatography mass spectroscopy (GC-MS). Phenol, substituted phenols, bisphenol A and fragments of curing agent are found as the main compounds in liquid product.From the results, the mechanism of the decomposition of the resin in nearcritical water is discussed. The possible ways of the product formation are predominantly based on hydrolysis processes, the decomposition mechanisms of E-51/DDM and E-51/MeTHPA are envisaged as the ether and crosslink bonds cracking. The addition of catalyst can change the path of decomposition reaction. H2SO4 and PW can accelerate the scission of ether bond of E-51/DDM, while KOH can accelerate the scission of crosslink bond of E-51/DDM. KOH can accelerate the scission of ether bond of E-51/ MeTHPA, while the scission of ester bond is restrained, H2SO4 and PW only facilitate the scission of ether bond.