| Silicone rubber is an organic silicone elastomer which main chain is composed of Si-O-Si bond and side chain is composed of organic groups.The highly ionized Si-O bond,controllable polymerization chain length and crosslinking degree make silicone rubber with high elasticity,high and low temperature resistance,aging resistance and biocompatibility and other excellent characteristics,which are widely used in biomedical products,functional coatings,electronic and optical devices,aerospace,soft robot and other fields.At present,silicone rubber products manufacturing process is given priority to with the traditional mold processing,which has the high cost,complex craft,time-consuming and low level of controlled shortcomings,therefore,the research development of silicone rubber advanced forming technology to effectively solve the traditional process of the rapid prototyping,personalization and bottleneck problems such as high precision processing areas.3D printing technology is a rapid prototyping technology that realizes 3D structure through 3D drawing software modeling and layer by layer printing.Compared with traditional manufacturing methods,3D printing has the advantages of diversification,high precision,short time consumption and saving of raw materials.However,due to the poor rheological properties and low photocuring rate of silicone rubber,the research on 3D printing silicone rubber is relatively slow compared with other materials.Although a variety of 3D printing silicone rubber material technologies based on light curing,direct writing and other technologies have been developed at home and abroad,and have shown good application potential in performance control,there are shortcomings such as material customization and process specialization,and the related material technologies are not highly compatible with the commonly used silicone rubber.Therefore,based on commercially available silicone rubber precursors,this thesis carried out research on 3D printing silicone rubber and its properties based on light curing and direct writing technology.The main research work includes the following three parts:1.Digital light processing(Digital Light Processing,DLP)3D printing silicone rubber and its performance study.Different ratios of silicone rubber ink were prepared by mercapto-ene click reaction.Q630 silicone rubber was used as matrix ink,B1002 provided double bond,mercapto silicone oil provided sulfhydryl group and adjusted viscosity.TPO-L was selected as initiator,and the ideal viscosity of photosensitive resin ink was tested to be 5Pa·s ～ 10Pa·s.Furthermore,the tensile properties of ink were studied.For inks with different proportions,the tensile properties of photocured samples and photothermal dual-cured samples and the tensile properties of photocured samples with different TPO-L content were mainly displayed.The experimental results showed that when the content of PDMS was 70%,the tensile properties of ink,including Young’s modulus,tensile strength and ultimate strain,are the most outstanding.The tensile properties of photothermal double cured ink were better than those of pure photocured ink.The tensile properties increased first and then decreased with the increase of TPO-L content,and the optimum tensile properties were obtained when the TPO-L content was 1%.2.Direct writing(DIW)3D printing silicone rubber and its mechanical behavior design and regulation.DIW printing ink was prepared by mixing SE1700 silicone rubber precursor and diallyl maleate inhibitor.The analysis of rheological properties of ink shows that the ink had obvious thinning phenomenon,which could guarantee the extrusion of ink nozzle.Under the action of low shear force,the storage modulus(G ’)of the ink was much larger than the loss modulus(G ")of the ink.The thixotropic viscosity and thixotropic modulus had good thixotropic recovery,indicating that the ink had good self-support.The ink was formed by DIW 3D printing and cured at 150 ℃ for 1h,showing the best mechanical properties.It was found that the diameter,pattern and printing spacing of DIW 3D printing had an effect on the compressive mechanical properties of silicone rubber samples.When the printing needle was 400μm,the printing pressure was 0.15 Mpa,the platform speed was 5mm/s,and the line spacing was determined,the compression performance was best when the printing pattern Angle was 0-90°.Other printing conditions remain unchanged,when the print pattern(0-90°)was determined,the greater the line spacing,the worse the compression performance.When the line spacing was 1.2mm,the platform width exceeds 16%.Considering the practical application of silicone rubber material,the stress-strain curve was more ideal.3.Study on structure and mechanical properties of DIW 3D printing multi-hole silicone rubber foam.By adding sodium chloride into DIW 3D printing silicone rubber ink as pore-forming agent,3D printing silicone rubber foam with traditional microporous structure was realized by solution-dissolution method,and the effect of different sodium chloride content on its compressive mechanical properties was studied.The rheological behavior test of ink showed that the addition of sodium chloride changes the shear viscosity of ink,but the viscosity still decreases with the shear rate.The storage modulus increased with the increase of sodium chloride content,and the storage modulus(G ’)>> loss modulus(G ").The thixotropic viscosity and thixotropic modulus of ink had good recovery,no obvious loss,and meet the requirements of printing.After curing at 200 ℃ for 1h,the 3D printed sample was soaked in water to remove sodium chloride to obtain microporous silicone rubber foam.Compression tests showed that with the increase of sodium chloride content,porosity increases,elastic modulus and yield stress decrease,relaxation rate decreases,and stress relaxation performance increases. |
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