The Study Of Design,Preparation And Curing Kinetics Of An Epoxy Resin With Flexible Side Chains

It is an effective method to control the structure of thermosetting epoxy resin by curing,which is characterized by well design and easily operation.Among the many epoxy curing agent,the anhydride has good properties,such as,low toxicity,viscosity,better heat resistance and dielectric properties.Therefore,the epoxy/anhydride system has obvious advantages in wind power generation,electronic packaging and vehicle manufacturing.With the development of large size of wind blade,the high power of electronic devices and the high-speed traffic,the demand for high performance of epoxy resin is more and more urgent,and the limitation stronger rigidity and poor toughness of anhydride curing system is more and more obvious,thus,largely limited its application in some areas.So the toughness of epoxy/anhydride system becomes the current research focus.In this study,a series of epoxy resins with different lengths of flexible side chains were synthesized by adopting different long-chain amines reacted with epoxies.The relationship between the length,content of side chains and the mechanical properties,thermal properties and curing behavior was studied.Then,the epoxy/anhydride system with excellent tensile strength and impact strength,high elongation,good thermal stability was successfully prepared.The specific research contents are as follows:We used normal bisphenol A type epoxy resin(E-51)and n-butylamine,n-octylamine,dodecylamine and octadecylamine as raw materials to prepare the epoxy resins with different lengths of flexible side chains and different degrees of polymerization.The results of infrared tacking,titration of epoxy value and mass spectrometry proved that the modified epoxy resin was successfully prepared.Then,we adopted methyl hexahydrophthalic anhydride(MHHPA)as curing agent,DMP-30 as the accelerator to react with the modified epoxy resin.A series of test found that compared with the unmodified epoxy resin-anhydride system,the glass transition temperature of the modified epoxy resin-anhydride system decreased with the increase of the length and content of the side chain.On the other hand,the strength,elongation at break and impact strength gradually increased,the epoxy/anhydride system which the molar ratio of octadecylamine to epoxy resin was 2:10,compared with pure epoxy curing system,the tensile strength,elongation at break and impact strength increased by 18.68%,127%and 32.4%.The toughness was significantly improved.The heat resistance was greatly improved with the increase of the side chain length.The toughening mechanism was studied by using scanning electron microscopy(SEM)to characterize the tensile fracture Surface.The curing kinetics of epoxy-anhydride system was studied by using non-isothermal DSC method.The activation energy obtained by FWO method and Kissinger method is closer,and increased with the increase of conversion rate.The activation energy of the modified epoxy resin system is lower than the unmodified epoxy resin system.The accelerator content affect the activation energy of the system.As the accelerator content increased,the activation energy of the system decreased.The non-isothermal curing behavior of the systems can be described by SB(m,n)model,the non-autocatalytic reaction order m is much lower than the autocatalytic reaction order n,indicating that the autocatalytic reaction play a leading role in the epoxy-anhydride system.The accelerator content has a certain effect on the reaction,the system of non-autocatalytic reaction series had increased with the accelerator content increases.