Study On Influence Of The Crosslinking Structure Of Epoxy Resins On The Decomposition Characteristics In Nearcritical Water

Epoxy resin possesses excellent electrical insulating and physico-mechanical properties.It can be prepared into paints,adhesives,electrical and electronic materials,composite materials and construction materials,and has been widely used in various fields of the national economy.With the resulting waste volume growing rapidly,it has caused many environmental problems,and they need to be solved urgently.This paper mainly studies the degradation behavior and the decomposition rules of different crosslinking structure of epoxy resin systems in nearcritical water,and sets forth a variety of reaction mechanism of resin systems based on analyzing the composition of decomposition products.A macrokinetics model concerning the decomposition of different crosslinking structure epoxy in near-critical water is set up,which provides a theoretical basis for the industrialized production of epoxy resin degradation.This paper also analyzes the degradation behaviors of DGEBA and aliphatic amine curing agent triethylene tetramine(E-51/TETA),DGEBF and triethylene tetramine(GY282/TETA),TGDDM and triethylene tetramine(AG-80/TETA)in nearcritical water,and discusses the influence of chemical structures of epoxy resin on the degradation behaviors of the curing system.The experiment mainly deals with the effect of the process parameters,such as the reaction temperature,the reaction time on the decomposition rate of the resin system.The experimental results show that in nearcritical water,the completely decomposed degree of difficulty of three systems is AG80/TETA(350 ℃)> GY282(305 ℃)> E-51/TETA(300℃),when the ratio(resin: water)is 1g:10m L and the reaction time is 60 min.In addition,the degradation behaviors of DGEBA and the anhydride curing agent of methyl hexahydrophthalic anhydride(E-51/Me HHPA),DGEBA and in the presence of a promoter(E-51/Me HHPA/BDMA),DGEBA and aromatic amine curing agent of dapsone(E-51/DDS)in nearcritical water are studied respectively,and the influence of chemical structure of curing agent on the degradation behavior of epoxy resin is also discussed in the paper.The experiment mainly analyzes the reaction and the effect of the parameters on the decomposition rate of the resin system,such as the reaction temperature,the reaction time.The experiment proves that in nearcritical water,the completely decomposed degree of difficulty of the three systems is E-51/DDS(340 ℃)> E-51/Me HHPA(285 ℃)> E-51/Me HHPA /BDMA(275℃),when the ratio(resin: water)is 1g:10m L and the reaction time is 60 min.Testing methods such as infrared spectrometry,gas chromatography-mass spectrometry,nuclear magnetic resonance and gel permeation chromatography are used to characterize the degradation products of each system,to analyze the bond breaking position of epoxy resin,and to infer the possible degradation mechanisms.The testing results show that the discrepancies between the crosslinking density and resin molecular structure are the important factors leading to the different decomposition temperatures of the curing system,that is,when the crosslink density is big,the degradation temperature is high.At the same time,the chemical structure of curing system also affects the degradation temperature.When the curing systems contain rigid benzene ring structure,the degradation temperature is relatively high,and when the curing systems contain aliphatic or cyclic structure,the degradation temperature is relatively low.However,the degradation temperature also affects degradation products and mechanism.When the degradation temperature is high,the products tend to form small molecular compounds or cyclic compounds,and when the degradation temperature is low,the products tend to form a relatively larger molecular weight prepolymer.The dynamic model of non-steady state kinetics is adopted in the experiment to analyze the degradation process of curing system.The results verify that the decomposition process is a second order reaction.The reaction rate constants of E-51/TETA,GY282/TETA,AG-80/TETA,E-51/Me HHPA,E-51/MeHHPA/BDMA and E-51/DDS at different temperatures are calculated respectively,and the apparent activation energy is also calculated by using the Arrhenius equation.