Research On Direct 3D Printing Functional Composite Based On Shear Thinning And Its Application Performance

3D printing(also known as additive manufacturing（AM）has become one of the important development directions of manufacturing technology because it can reduce waste,energy consumption,and production time,and also support mass customization of complex equipment.According to the 3D printer system,at present,the publicly reported 3D printing technologies mainly include adhesive spraying（BJ）,material spraying（MJ）,photopolymerization（DLP 、SLA）,powder sintering and melting（SLS）,energy deposition（DED）and sheet lamination（LOM）,melt extrusion（FDM）,direct ink writing（DIW）,etc.Among these 3D printing technologies,direct ink writing（DIW）is the most common am technology because it applies to more materials,in which almost any material can be constructed into complex 3D shapes through this technology,such as ceramic,polymer,metal,or composite（or multi-material）structures.As we all know,the design and synthesis of ink is the most important part of DIW technology.Unfortunately,many functional or composite materials that have been proved to be widely used in industry cannot be applied to DIW technology.This is because it is difficult to design and prepare functional or composite ink materials with good shear thinning effect and high modulus.So far,only a few kinds of literature have reported "real" multi-material or composite structures.In addition,the organic solvent or water content of ink materials is usually high,while the solid content is usually low to achieve good shear thinning performance.Therefore,after drying,degreasing and curing,it is easy to cause the micropore and size change of DIW structure.These problems limit the practical application of DIW technology in the industry.So far,DIW technology is mainly small-scale manufacturing in the laboratory.Aiming at the above problems,this paper designs a new type of DIW ink.Combined with the independently developed DIW 3D printing equipment based on a spiral extrusion mechanism,it constructs the 3D structures of different material systems.Compared with the traditional DIW ink,it has high universality and can be combined with almost any material to form DIW printing ink,with high solid content,high density of 3D printing structure,few holes,and excellent comprehensive performance,It has a wide application prospect in practical industry.The main research results and innovations are as follows:（1）A supramolecular interaction gel system composed of triethanolamine and ammonium oleate is reported.It has good strength and excellent shear thinning effect.It is suitable for DIW 3D printing ink.More importantly,almost any material（such as rubber,plastics,ceramics,metals and composites）can be integrated into the ink system,and then 3D printing can be carried out by shear thinning DIW method.In addition,the solid content of the ink system is higher than 80%,which avoids the formation of porous structure during the drying process of 3D printing structure and the size change after molding.Using the ink system and 3D printing method,a flexible pressure sensor based on natural rubber / magnetic composite is constructed for real-time monitoring of human health.This work provides a new method for developing 3D printing materials for various practical applications.（2）Based on the supramolecular interaction gel system composed of triethanolamine and oleic acid,the composite DIW printing ink of glass fiber（GF）and nitrile rubber（NBR）was designed,and the GF/ NBR composite material with GF orientation（such as 0 degrees,45 degrees,and 90 degrees）was constructed by combining with the self-developed 3D printing equipment.The influence of GF orientation on the mechanical properties and thermal conductivity of the composite material in the NBR matrix was systematically explored.The results show that the tensile strength of GF / NBR Composites with 90 ° GF orientation is333.3% and 246.7% higher than that of GF composites with 0 ° orientation or disorder,respectively.In addition,we evaluated the heat dissipation performance of 90 ° oriented GF /NBR Composites and found that the temperature of LED devices and computer CPUs covered by this heat dissipation material decreased by about 8.1 ℃ and 4.1 ℃ respectively.This study provides a general method for large-scale preparation of polymer composites with orderly arrangement and distribution of fiber fillers,which can be used in various applications.（3）Based on the supramolecular interaction gel system composed of ammonium oleate,the Al2O3 DIW printing ink was designed and prepared.Combined with the self-developed3 D printing equipment,the size controllable porous Al2O3 ceramic material with millimeter,micron,and nanoscale structure was constructed.Mm and μ The influence of M-scale on the mechanical and thermal insulation properties of porous ceramics.The results show that 3D printing foam ceramics with millimeter-level pores and smaller micron pores have better thermal insulation and lower compressive strength.In addition,we evaluated the application of the porous Al2O3 ceramic material with a multi-level structure in chip insulation.The results show that the chip temperature is reduced by about 20 ° C with the thermal insulation material.This study provides a new method to construct multi-stage porous alumina ceramics with accurate and adjustable size,solves the problem that the size of traditional ceramic materials is difficult to be accurately controlled due to its brittleness,and opens up a new application of porous alumina ceramics in portable equipment or consumer electronics.