Three Dimensional Printing Craft And Mechanical Properties Optimization For Room Temperature Vulcanized Liquid Silicone Rubber

Room-temperature-vulcanization Liquid Silicone Rubber(RLSR)material is often used in the manufacture of flexible circuit board substrates for wearable device.However,traditional processing techniques limit the improvement of forming precision and make it difficult to process complex structures.3D printing is a novel manufacturing method for RLSR wearable device.In this paper,RLSR is taken as the research object.The range of extrusion pressure and extrusion speed and the relationship curve are obtained by combining experimental test with fluid simulation.On the basis of orthogonal experiment,the importance of each parameter affecting the printing process is clarified and the printing process parameters are optimized.To optimize printing structure,the effect of printing sample structure on its mechanical properties is studied.The RLSR modification method was studied to improve the printing performance and mechanical properties of the sample.The details are as follows:According to characteristics of flexible wearable 3D printing materials,by comparing the printing effects of silicone,RLSR,latex and polydimethylsiloxane,RLSR was selected as the printing material,and the printing process of RLSR material was simulated numerically to determine the relationship between material outlet flow rate and pressure,and the range of velocity variation was determined.According to the variation range of the material outlet speed,the extrusion type 3D printer is used as the printing platform to carry out the optimal printing parameters.The orthogonal test method is used to determine that the printing temperature is 20?,stirred for 30 s,vulcanization period is 10-30 min,speed is 8 mm/s,and the curing time of each layer is 2 s.Judging the influence weight of each printing parameter on the experimental results,it is concluded that the influence of printing temperature on the experimental results is the highest,and the influence weight is 45%.By designing different grid structures,the effect and mechanical strength of different grid shapes and density on the printing comprehensively results are studied.Entropy method is used to evaluate the three indexes of densities,tensile strength and printing difficulty.The weights of each index in the final evaluation results are 24.49%,57.35%and 18.16%.Comprehensive evaluation of the impact of grid structure on the above indicators show that the best mechanical performance is obtained when the width of print edge is between 75%and 85%of the print needle's diameter,and the printing structure is 45-135 or 0-45-90-135.In order to improve the three dimensional printing and mechanical properties of RLSR,modified silica materials are prepared by surface activation of precipitated silica,fumed silica and quantitative polyethylene glycol(PEG).Modified silica and RLSR composites are prepared by mechanical blending method.The pressure change/material continuous extrusion printing time,dynamic printing linewidth change rate,tensile elasticity and impact elasticity are taken as evaluation indexes.It is concluded that the fumed silica is the best to improve the printing performance and mechanical properties of RLSR.Orthogonal experiment is used to optimize the modification ratio of fumed silica.It is found that the amount of silica gel had the greatest influence on the properties of the material.The optimum mass ratio of silicone rubber,PEG and fumed silica is 300:30:1.