Synthesis And Properties Of A Low Shrinkage Epoxy Curing Agent

Epoxy resin have certain volume shrinkageIn the process of curing. The volume contraction leading to residual stress is generated in the material so as to affect the performance of resin matrix composites and service life. Scholars at home and abroad mainly have added expansive monomer in the epoxy resin to solve the problems of the epoxy resin curing shrinkage volume. Epoxy resinexpanding curing agent to research report has been observed.In this dissertation, on the basis of the extensive review of the research progress of epoxy curing agents, a new curing agents was developed to overcome the difficultiesin the practicalapplication ofthe expanding monomer and volume shrinkage originated the loss of dimensional stability.This article prepared ethylenediaminetetraacetic dianhydride(EDTAD) and optimizeditssynthesis, and its cure shrinkageandcuring kineticswas in-depthresearched, the main work as follows:(1) the optimalsynthesis processforthe synthesis ofEDTADwas determined by orthogonal experimentmethod.reactiontemperature 85℃,reaction time28 h,the molarratio of1:7.The two characteristic absorption peaksof cyclic acid anhydrideappearsin1808cm-1and1762cm-1,and the volume shrinkageof cured epoxy resin wasmeasuredbya density method, when themass fraction of55%EDTAD, the Minimal volumeshrinkagewas 0.251%.DMP-30 promoted the curing reaction rate, at the same time, greatly reduce the curing of the tensile strength, bending strength and impact strength. EDTAD/DGEBA system of the average tensile strength, bending strength and impact strength are 69.2 MPa, 55.5 MPa and 4.38 KJ/m2. When the content of EDTAD was 55%, the maximum tensile strength was 82.3MPa, the content of EDTAD was 50%, the maximum bending strength and the maximum impact strength were 69.4MPa, 5.23KJ/m2, respectively. EDTAD/DGEBA/DMP-30 system of theaverage tensile strength, bending strength and impact strength are 36.2MPa, 43.0 MPa and 2.17 KJ/m2.When the content of EDTAD was 55%, the maximum tensile strength was 47.5MPa, the content of EDTAD was 50%, the maximum bending strength and the maximum impact strength were 50.5MPa, 2.76KJ/m2, respectively.(2) TheDGEBA/EDTAD reactions was investigatedindetailwithanisothermal differential scanning calorimetry(DSC). Kamal model canbetterdescribereaction rate in the reaction-controlled stage; Kamalcontainingdiffusionfactormodelcansimulatethe curingreaction ratefor the entireconversionrange. In addition,ananalysisofthereactionmechanismswiththeisoconversionalmethod showed thattheactivationenergyofthe curing reaction closelyrelatestothefractionalconversion.(3) The nonisothermal reaction of DGEBA/EDTAD/DMP-30 was inspected by using DSC. theoptimumcuring process was determined. The result was showed that: Theoreticalgeltemperature of the firststage of theTgel = 93.2℃,the theorycuring temperatureTcure = 119.2℃ and post-cure temperature theoryTpost = 121.8℃,the secondstage theorygelling temperatureTgel = 249℃,curing temperaturetheoryTcure = 253.95℃and post-cure curing temperaturetheoryTpost= 257.3℃.(4) Themolecular structureof EDTAD was studiedby quantumchemistry. The result showed that its moststablestructurein line withthe six-membered ring.wasasymmetricthree-dimensionalconfigurationspaceand Mulliken atomicnegative chargeis mainlydistributed in thetwo tertiarynitrogen atoms,respectively,-0.378128and-0.432320. itsbond angledistributionswere about109.5°.EDTAD curing epoxy resin in the process of bond length increases, in conformity with the expansive monomer polymerization mechanism.