Preparation And Forming Studies Of Conductive Polymer Materials For Granular 3D Printing Application

During the past 30 years,a variety of molding process for 3D printing technology have been developed very fast.Among them,fused deposition molding(FDM)is one of the most widely used 3D printing molding processes attributed to its unique characters.However,the shape and hardness of materials need to be improved for its further development.Therefore,a variety of granular 3D printing equipment based on the principle of fused deposition molding was appeared.The granular 3D printing can meet the requirements of more types of materials.Among them,the widespread use of conductive polymer materials is the most representative.Conductive polymer materials can be specified as structural types and composite types.In generally,one or more conductive fillers were added to pure polymer materials to forming a new type of combined material that meets specific conductive requirements by a certain processing method.This method has been widely used in electronic circuits,electromagnetic shielding and other fields.On the basis of current type of granular 3D printer,the preparation and molding of MWCNTs/TPU conductive polymer materials were performed in this work,which will broaden the material selection range of 3D printing technology,also its application in practice feasibility will be verified.The specific work content is as follows:(1)Co-develop new type of granular 3D printing equipment and optimize the structure.Shortcomings of traditional silk FDM printers will be analyzed and a new type of granular 3D printing equipment for resolving low universality problem of materials will be developed by corporation.The structural shortcomings exist in current equipment will be analyzed,two different forms of support blocks will be designed,the cantilever problem of the two motors and the stability of the equipment will be improved.(2)Preparation of MWCNTs / TPU combined materials and its conductivity test.MWCNTs / TPU composites with filler contents of 3wt%,5wt%,7wt% and 10wt% were prepared by using a twin-screw extrusion method with polyurethane and carbon nanotubes as the base material and conductive fillers respectively.With electron microscope it is observed that the internal dispersion is good;the conductivity test results show that it meets the requirements of the conductor when the filler content is 3wt%,and the maximum conductivity is 7.14S/m when the filler content is 10wt%,and the conductivity is good;the electrical conductivity of different forms of extruded filaments can be considered to satisfy the law of electrical resistance,and the number of melt blends can affect the stability of the electrical conductivity.(3)The mechanical properties of MWCNTs / TPU composites will be tested.A new type of granular 3D printer was used to prepare multiple tensile test specimens of the same standard.Following the principle of one single variable,the test was performed using a universal material tensile strength tester.The different effects of filler content,molding path,temperature and layer height on its tensile strength and elongation at break were explored respectively.In addition,the material matching of process parameters was also examined.(4)A metamaterial absorber will be designed and its performance will be tested.A metamaterial absorber was designed and prepared using MWCNTs/TPU composites.The simulation results show that the absorption rate of the absorber unit is larger than 90% within the two frequency bands of 14.7 ~ 16.4GHz and 16.9 ~ 17.3GHz;the actual test results show that the test sample is in the range of 15.6 ~ 15.8GHz,16.2 ~ 16.5GHz The absorption rates in the three frequency ranges of 17.2 ~ 17.5GHz are more than 90%.The curve trends of the two results are similar,but there is a large gap in the frequency range,which may attribute to the preparation process and material properties.