| Because the cured cycloalipHatic epoxy resin has excellent pHysical and chemical properties,high bond strength,high hardness,good toughness,excellent dielectric properties and a small curing shrinkage,it is widely used in various fields of national economic life.The cured carbon fiber composite material plays an important role in the automotive lightweight,wind power generation and aerospace industries.However,the post-treatment of the epoxy resin is very troublesome,and it causes great pollution to the environment.Especially after the composite materials are used,the useful materials therein cannot be effectively recovered.It causes huge waste and increase cost.As the consumption of non-renewable resources and the environmental pollution become more and more serious,designing degradable epoxy resin has become a good solution.In this thesis,the chemical unstable acetal groups were introduced into a highly cross-linked density epoxy resin network through molecular design using3-cyclohexene-1-methanoland4-?Trifluoromethyl?benzaldehyde,benzaldehyde,p-tolualdehyde,Anisic aldehyde,respectively.The synthesis of CF3-ER,H-ER,CH3-ER and CH3O-ER with acetaldehyde and degradable was designed and synthesized by the reaction of acetaldehyde and epoxidation.The synthesized epoxy monomers were characterized by FTIR,1H NMR,13C NMR and MS.Two methods of curing epoxy and cationic initiated epoxy curing by anhydride were used in this thesis,and curing kinetics of different curing methods were studied.The synthesized epoxy resin was cured with HMPA which is the anhydride curing agent,and the corresponding curing procedure was determined by Kissinger theoretical calculation:100°C/2 h+170°C/2 h+200°C/2 h.The synthesized epoxy was cured with KWM-753 which is the initiator,and the curing procedure was also confirmed:70°C/8 h+80°C/1 h+100°C/2h+120°C/2 h+140°C/2 h.The CFRCs were made with HMPA by using a suitable process.The DMA,TGA,flexural properties,fracture properties,and degradation properties of the cured epoxy resins were analyzed and discussed.The mechanical properties and degradation recovery performance of the CFRCs were tested.The Tg of the anhydride cured epoxy is significantly higher than the Tg of the cationic cured epoxy.The initial degradation temperature of epoxy resin cured by cation initiated or anhydride is 300°C or even more than300°C.All four epoxy cures have good mechanical strength.In the degradation experiments,the degradation rate was faster and faster as the increase ability of pushing the electrons of substituent.With the decrease of acidity and pH,the degradation rate will be faster and faster.Cation-cured epoxy degrades faster than anhydride-cured epoxy.The CFRCs also have good mechanical properties.After the CFRCs were degraded,the result of single fiber tensile and SEM test show that the carbon fiber can remained intact and can be reused many times.This is very important for the recovery of composite materials and some precious metals. |
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