Preparation And Properties Of 3D Printing Silicone Rubber Based On Thiol-ene Curing

Silicone rubber material is the first rubber material to achieve 3D printing.In recent years,3D printing silicone rubber has been widely researched and applied in the fields of flexible electronics,software robotics,biomedicine and other advanced materials.However,the reported 3D printing silicone rubber has disadvantages such as low mechanical strength,easy collapse during printing,difficulty in using heavy metal catalysts,and difficulty in functional modification,which limits its application.Therefore,it is of great significance to carry out research on new 3D printing silicone rubber material systems and printing processes.In this paper,liquid silicone rubber material which has been reacted and cured by thiol-ene reaction was developed,and 3D printing was successfully realized.The application of flexible conductive materials was preliminarily studied.The thiol-ene click reaction can react rapidly under UV and does not require heavy metal catalysts,which is of great significance for expanding the application of silicone rubber in biomedical fields,and the system is very suitable for 3D printing methods.First,a novel liquid silicone rubber was successfully prepared under UV by using medium molecular weight Vinyl terminated polydimethylsiloxanes and poly[(mercaptopropyl)methylsiloxanel.In order to better adapt to the 3D printing method,the effects of the amount of silica,the viscosity of the base rubber,the sulfhydryl content of the cross-linking agent,the mechanical properties and rheological properties of the liquid silicone rubber were investigated.The obtained UV-curable liquid silicone rubber has good mechanical properties;its tensile strength can reach 7 MPa and elongation at break can reach 560%.The addition of fumed silica not only improves the mechanical properties of the silicone rubber,but also changes the viscosity of the liquid silicone rubber,so that the silicone rubber has shear rheological properties.In order to solve some shortcomings in the current 3D printing silicone rubber methods,such as collapse and low mechanical strength.A new method of UV-assisted DIW 3D printing of silicone rubber has been developed.Inks containing UV-curable silicone and nanocomposites are used for direct ink writing(DIW)3D printing.First,each layer is printed followed by ex situ UV curing,this is to solve the problem of collapse caused by low mechanical properties of the ink.Finally,a UV curing is carried out to ensure that the silicone rubber is completely cured.In order to better perform 3D printing,the printing parameters were explored;including PDMS ink viscosity,air pressure,printing speed and lighting time per layer.At the same time,in order to verify the printing effect of the system,three-dimensional materials of various complicated shapes were printed and the mechanical properties of the 3D printed materials were studied.It was found that the tensile strength of the printed materials could reach 8 MPa and had excellent mechanical properties.In order to expand the application of 3D printing silicone rubber,the polydimethylsiloxane sponges was successfully printed by UV-assisted DIW printing method,and its conductive function was performed.The polydimethylsiloxane sponges has excellent shape retention ability,high hydrophobicity,excellent compression capability and fast recovery rate,and can control the porous silicone rubber by precisely controlling the aperture and wall thickness of the multi-pile silicone rubber by controlling the printing program.A flexible conductive material having good electrical conductivity can be obtained by coating a mixed conductive solution of graphene and carbon nanotubes on the surface of the polydimethylsiloxane sponges.