Synergistic Toughening Of Epoxy Resin By Carboxyl Terminated Liquid Nitrile Rubber And Organic Particles

Epoxy resin is a thermosetting resin used in various fields,such as coating,adhesives.It is also applied in the automotive,aerospace,and construction industries,as the matrix of a variety of composites.However,epoxy also features the undesirable properties of brittleness and poor impact resistance because of its’structure,which limits its application in many fields.Therefore,toughening epoxy resin has been a focus of research.There are many materials used for toughening epoxy resin,among which carboxyl terminated liquid nitrile rubber(CTBN)toughening epoxy resin is a traditional and sophisticated method of toughening.In this article,on the basis of rubber toughening epoxy resin(E-54),β-cyclodextrin and cellulose nanoparticles are added as the third phase for synergistic toughening.The results show that it could balance the strength and toughness of epoxy resin.The key to a good toughening effect of nanoparticles lies in their dispersibility and compatibility with epoxy resin matrix.In this article,carboxymethyl-β-cyclodextrin(CM-β-CD)was prepared by nucleophilic substitution method,and the method was used to modify the surface ofβ-cyclodextrin.Nano-sized oxidized cellulose was prepared by TEMPO-Na Br-Na Cl O.The method improved the dispersion of cellulose in the system to a certain extent.The chemical information or particle size of the particles were characterized by infrared spectroscopy and dynamic light scattering.The results showed that the modification of the two particles was successful.Different proportions of CM-β-CD or TEMPO oxidized cellulose and carboxyl-terminated nitrile rubber were added to the epoxy resin and blended to prepare a ternary composite material.Tensile testing machine,scanning electron microscope(SEM),X-ray photoelectron spectroscopy(XPS)and dynamic thermomechanical analysis(DMA)were used to study the mechanical properties,thermal stability and cooperative toughening mechanism of the system.The results showed that the toughening effect of CM-β-CD and carboxyl-terminated liquid nitrile rubber toughened epoxy resin was better than some common nanoparticles and rubber toughened epoxy resin.Compared with the impact strength of the CTBN/E-54 system,the CM-β-CD/CTBN/E-54 system was significantly improved,and the T_g was also improved.When the content of CM-β-CD was 1.0 wt%,the impact strength and tensile strength were increased by 78.2%and 4.25%,respectively.When the mass fraction of oxidized cellulose was 0.2 wt%,compared with E-54 system,the impact strength of TEMPO oxidized cellulose/CTBN/E-54 composites was improved greatly(39.5%).The Young’s modulus,T_g and elongation at break of the system had been improved to varying degrees.It could be found that CM-β-CD and oxidized cellulose nanoparticles were more uniformly dispersed in the resin matrix by SEM,and the rubber particles on the fractured surface showed an obvious"sea-island"two-phase structure.In addition,microcracks and radial cracks indicate that the two kinds of nanoparticles had a significant toughening effect in the system.