| To implement the "carbon peaking and carbon neutrality goals",the country has launched the "Three UHV AC projects and nine UHV DC projects"high-voltage transmission project,which aims to solve the problem of clean energy power consumption by transmitting electricity across geographical areas.Therefore,reliable and stable high-voltage transmission-insulated electrical equipment is an important guarantee for the realization of electrical transport.Epoxy is widely used as insulation material for high-voltage equipment due to its excellent insulation and mechanical properties.However,the rigid network created by the epoxy curing leads to easy fatigue fracture and reduced toughness,which can lead to cracking and partial discharge in electrical products such as transformers,transformers,reactors,and switches,causing electrical accidents.There has been a lot of research into toughening epoxy resins,including the addition of liquid rubber,thermoplastics,nanoparticles,core-shell particles,and flexible chain segments to epoxy resins to toughen them,but there has been less research into the electrical properties of toughened composites.This thesis aims to prepare toughened epoxy resin composites with high elongation at the break without any reduction in tensile strength,Young’s modulus,and electrical properties,with the following main research:(1)Dimethyl 3,3’-dithiodipropionate/epoxy resin composites(EP-DTDP-X)were prepared based on a flexible chain segment toughening method.Due to the increased cross-link density of the system and the introduction of flexible chain segments,EP-DTDP-2 toughens best,increasing elongation at the break by 104%and tensile strength by 16.1%compared to pure EP.The electrical properties were not affected,with the EP-DTDP-3 composite achieving the highest breakdown strength(37.6 kV/mm),an increase of 11.2%over the pure epoxy resin(33.8 kV/mm).(2)Carbon nanotube-terminated carboxylated nitrile rubber/epoxy resin composites(C-C/EP)were prepared based on nanoparticle and liquid rubber toughening methods.The "island-like structure" triggers a plastic cavity growth mechanism that increases the elongation at break of the 15wt%C-C/EP composite by 85.4%compared to the pure epoxy resin and achieves a tensile strength of 67.1 MPa.The electrical properties are less affected,with the 15wt%C-C/EP composite showing an 11.3%reduction in breakdown strength.(3)A titanium oxide-polybutylene acrylate/epoxy resin composite(TiO2-PBA/EP)was prepared based on a core-shell particle toughening method.The TiO2 core provides dispersion and high modulus,offsetting the strength-reducing effect of the soft shell,and the PBA flexible shell absorbs fracture energy,bridging cracks.The elongation at break of the 0.3wt%TiO2-PBA/EP composite was 21.1%higher than that of the pure epoxy resin,and the tensile strength reached 64.7 MPa.The soft shell of TiO2-PBA core-shell particles hinders the passage of charges and the breakdown voltage of TiO2-PBA/EP composites is increased. |
