Preparation And Curing Kinetics Of Epoxy Resin/carboxyl-terminated Butadiene-Acrylonitrile Rubber Composites

Epoxy resin is one of the most widely used thermoset resins owing to its excellent properties including mechanical,processing and adhesion performance,but the brittleness of cured epoxy resin limits its applications in many fields.Thus,it is of importance to modify epoxy resin.In this study,the diglycidyl ether of bisphenol-A(DGEBA)-based epoxy resin was chosen as matrix resin,Methylhexahydrophthalic anhydride(MeHHPA)and 2,4,6-tris(dimethylaminomethyl)phenol(DMP-30)were respectively used as curing agent and curing accelerator,modifier(liquid carboxyl-terminated butadiene-acrylonitrile rubber(CTBN)),compound modifier(CTBN and polyimide resin(PI))were used to toughen epoxy resin.The effect of introduced modifier on the performance and morphology of materials were investigated.Meantime,the curing kinetics was also concerned.There were three main parts as follows:1.Epoxy resin was modified by CTBN.Based on the results of mechanical test,it was found that with the increase of the amount of CTBN,the impact strength,fracture strength and elongation at break were enhanced but the elastic modulus and glass transition temperature(T_g)were reduced.It was observed the phase separation between CTBN and epoxy resin matrix formed‘sea island structure'though the morphology of cured epoxy resins with different amount of CTBN.When the amount of CTBN was increased,the size of rubber particles was larger;resulting in the impact cross-section of cured epoxy resins was rougher.The cured epoxy with 30phr CTBN possessed optimal comprehensive properties.2.Epoxy resin was modified by CTBN/PI.The Izod impact strength,the fracture toughness and elongation at break of DGEBA were significantly increased,while the modulus decreased slightly.The better integrated properties of the composites with20-30phr CTBN and 1.5-2phr PI were achieved.Under the same content of CTBN(30phr),it was evident that the rubber particles reached the largest when the amount of PI was up to 1.5phr compared to the PI with different addition for the effect of phase structure.It was also found that the appropriate amount of PI enhanced the storage modulus and heat resistance of composites through the mechanical,DMA and TGA test.3.For E51?E51/CTBN?E51/CTBN/PI system,curing process was studied by non-isothermal differential scanning calorimeter(DSC)and then curing kinetics parameters were calculated and the best curing process was further confirmed though Kissinger,Ozawa and Crane methods.It was demonstrated that the introduction of CTBN and PI decreased the activation energy of curing reaction.Varying the curing process and the amount of curing accelerator could control the size of rubber particles,leading to enhancement of the performance of E51/CTBN/PI composite.