Recyclable 3D Printing Of Epoxy Composite And Its Application In Shape Memory Materials

Epoxy resin is one of the most widely used thermosetting resins.Because of its excellent mechanical performance and low cost,it has been widely used in many areas.The molding of traditional epoxy resins is mostly based on molds,such as injection molding,casting,and compression molding,which are not only time-costing,but also inapplicable for complex shapes.The introduction of additive manufacturing technology into the epoxy molding can solve the above problems and improve the reliability of manufacture.In this thesis the 3D printing of epoxy resin materials is studied and an epoxy resin/graphene composite ink for direct ink writing(DIW)technology is developed.Also,the performance of the 3D printed epoxy composites is examined,and the recycling and application of these composites are investigated.Epoxy resin/graphene composite that can be used for DIW technology is prepared by using few-layered graphene nanoplatelets as the thixotropic agent and functional filler.Graphene can transform the epoxy precursor into a gel ink with viscoelasticity and shear thinning.A composite ink with the graphene content of 10 wt.%is prepared,and the 3D printing parameters,such as diameter of printing needle,air pressure,centrifugal time of the ink,are further optimized.With the new ink,3D printing of epoxy/graphene composite products with good molding performance,high fineness and freely adjustable structure are realized.The properties of the 3D printed epoxy/graphene composite material is studied.We carry out thermal analysis on composite materials and pure epoxy resin materials by thermogravimetric analysis and differential scanning calorimetry.Experimental results show that the electrical and thermal conductivities of the composites are improved significantly as compared with pure epoxy,but the mechanical strength shows isotropy.Besides,the effect of 3D printing path on material properties is investigated by testing the performance of the samples with different printing directions.In addition,the shape memory properties of epoxy resin and the high electrical and thermal conductivity properties of graphene are integrated to obtain the thermally induced shape-memory materials and safety switches with designable shapes,fast response,and adjustable shape response modes,which broadens the application of epoxy resin.A recyclable 3D printing technology of thermosetting resin is also developed in this thesis.The crushed epoxy resin/graphene composite powder is used as a co-thixotropic agent,together with graphene,for adjusting the rheological properties of the epoxy resin precursor to realize the DIW.The rheological property of the inks and mechanical,thermal,and electrical properties of the printed materials with different formulations are studies to screen out the optimized ink.Repeated cycling is carried out and the test results indicate that the performance of the 3D printed recycled materials shows little change.This technology provides a recyclable 3D printing electrical and thermal conductive thermosetting composite,and opens an new way for the sustainable development of thermosetting resin and new molding method.