| Because of its excellent performance,epoxy resin has been widely used in paint coating,adhesives,electronic components,composites,structural parts and other fields in recent years.Unfortunately,its brittle texture,poor thermodynamic performance,not flame retardant and other shortcomings hinder its practical applications.The study found that doping nanoparticles or grafting molecular chains can effectively improve these shortcomings.In order to systematically explore the influence of nano-particles and graft modification on the properties of epoxy resin,a series of epoxy resin matrix composites were prepared in this paper,and the conclusions were drawn as follows:Firstly,a series of bisphenol A epoxy resin(BAER)-4'4-disphenyl methane disocyanate(MDI)-polyethylene glycol(PEG)copolymers were synthesized by two-step polymerization.And then the mechanical and thermal properties of modified epoxy resin including a five-membered heterocycle,oxazolidone,had been studied.The obtained results indicated that the copolymers had the fusion enthalpy and crystallization enthalpy from60 °C to 120 °C,and the sample modified by PEG2000 showed the smallest extent of supercooling in comparison to ones modified by PEG4000 and PEG6000.Although it was found that the modified BAER system exhibited lower glass transition temperature,it would not limit its application in electronic packaging materials.Based on scanning electron microscope(SEM),the fracture surfaces of the samples were completely changed from a brittle behavior of unmodified epoxy to a ductile behavior for the modified ones.By this way,the new measure served a two-fold purpose of providing phase transition enthalpy and better mechanical properties,which developed polymer materials to apply in electronic packaging materials.Secondly,we synthesized a high-specific surface area Co-based metal organic framework by a solvothermal method.Then it was combined with a commonly used electronic packaging material(bisphenol A epoxy resin,E-44)in order to improve the thermal stability and enhance the fire safety of the latter.Compared with other common MOFs,the obtained results indicated that the peak heat release rate(PHRR)values of EP/6%Co-MOF decreased by 78.5%,and that the total smoke production notably decreased as well,by using a cone calorimeter test.Based on thermogravimetry-mass spectrum(TG-MS)and the combustion residue analysis,the mechanism behind the enhancement in the flame retardancy and overall thermostability of our epoxy resin composites was rationalized as a combined effect from the catalytic effect of MOF,and its thermal barrier effect.The effective flame retardancy behavior of composites showed a potential applicability of our approach for developing polymer materials to use in fire safety applications.Finally,in order to fabricate a layered porous structure with high fracture toughness,by mimicking nature cuttlefish bone(CB),we proposed a new anisotropy material composite.This bioinspired quaternary layered material consisted of epoxy resin(EP),CB,dopamine hydrochlorides(DA),graphene oxide(GO),which was based on three-step fabrication process involving infiltration of EP into the CB-DA-GO scaffolds.In this study,we firstly developed a biomimetic cuttlefish bone,which mimicked the cuttlefish diving state of the bone,by filling the holes with EP.Except from the advantages of well-defined structure,green and environmental protection,low cost and rational electrical conductivity,the proposed EP-CB-DA-GO composites exhibited exceptional fracture toughness,which was3.41 times that of pure epoxy.In addition,due to the anisotropic CB scaffold,this biomimetic material was capable of anisotropic conductivity which can be used to detect cracks.Our bioinspired strategy provides a promising approach to combine excellent mechanical properties with functional properties to fabricate high-performance composites. |
PDF Full Text Request