| Silicone materials are widely used in aerospace,medical,military industry,transportation,light industry and other fields,as it have many excellent properties which includes weather resistance,flame retardant,hydrophobicity,corrosion resistance,high elasticity,high and low temperature resistance,and so on.With the rapid development of the 5G communication intelligence era,conductive silicone composites have shown potential application and received extensive attention from academia and industry in recent years.However,the processing methods is mainly dependent on the mechanical blending,which requires a large number of conductive fillers to construct the conductive network in the silicone matrix,and there are some problems to be solved urgently.Firstly,the addition of conductive fillers limits the mobility of silicone molecules and induces the difficulty and cost of preparation.Secondly,the polarity of conductive fillers and silicone molecules are quite different,and this easily produces agglomerates and thus seriously influences the electrical and mechanical properties of the composites.In addition,the conductive network in the silicone matrix is difficult to alter,which would produce a poor sensitivity.Therefore,it is urgent to develop facile technologies or methods to prepare conductive/hydrophobic silicone composites with excellent mechanical property.For such purpose,this paper designs and develops two types of carbon nanofibers/silicone composites with different structures and morphologies(swelling and assembly of carbon nanotubes(CNTs)network on the surface of silicone rubber and construction of carbon nanofibers(CNFs)network in silicone aerogels dried at room temperature).The regulation of its surface hydrophobicity/conductivity has been systematically studied,and then related strain sensing and oil/water separation were explored.The main research content is briefly described as follows:(1)Swelling and assembly of carbon nanotubes network on the surface of silicone rubber:herein the hydrophobic and conductive silicone rubber composites were prepared with the help of the swelling phenomenon of the polymer and the effect of ultrasound which assembles one-dimensional carbon nanotubes on the surface of silicone rubber.Firstly,the influence of different solvents on the swelling behavior of the matrix was studied,and then the influence of the degree of swelling on the surface layer of the CNTs embedded in the matrix was explored.The results revealed that the amount and depth of the embedded CNTs into the surface layer of the matrix increased with the increase of its swelling degree.Then,the effects of the ultrasonic duration,CNTs'concentration,CNTs'length and diameter on the assembly of CNTs into the surface layer of the substrate were in detail investigated.Based on the resistance value,it was found that the effect of assembling the CNTs into the surface layer of silicone rubber is the most ideal under the conditions of ultrasound for 3 h,CNTs concentration of 1.5 mg·m L-1,CNTs length within 30?m,CNTs diameter within 5-20 nm,etc..Based structure characterization and analysis,the CNTs on the micro-nano structure of the substrate's surface layer are assembled and evenly distributed to form an interconnected conductive path.The presence of CNTs layer improved hydrophobic property and adjustable sensitivity of the silicone rubber without altering the mechanical property.The CNTs layer showed a good structure stability in different acid/base/salt solutions,which can promote the applicability of the as-prepared conductive silicone rubber.(2)Construction of carbon nanofibers network in silicone aerogels at room temperature:The key factors for the preparation of aerogels by drying at room temperature are related with the enhancement of the gel network framework and the reduction of surface tension.Therefore,we choose poly(methylhydridosiloxane)(PMHS)and vinylmethyldimethoxysilane(VMDMS)as the raw materials.The hydrosilylation reaction occurs under the Karstedt catalyst to obtain the gel precursor,and then the wet gel is prepared by the sol-gel method.Through extending the aging time and low surface energy solvent replacement,the superhydrophobic silicone aerogel was prepared by drying at room temperature.Then,the influence of the amount of solvent and tetramethylammonium hydroxide catalyst on the microstructure of aerogels in the sol-gel process were investigated,and the density,high and low temperature resistance,thermal insulation performance,mechanical properties,hydrophobic performance and oil-water separation performance of the aerogels were in detail characterized and discussed.The results showed that the lowest volume density of the prepared aerogels was about 73 mg·cm-3,which was much lower than most aerogels prepared by drying at room temperature.And the mechanical property of the aerogels is excellent and can be effectively tailored.In addition,the water contact angle of the silicone aerogels reached up to 165°,showing excellent hydrophobic and lipophilic property,which can be used to separate oil/water mixtures in different environments.Further,CNFs was added in the precursor to prepare a conductive/superhydrophobic silicone aerogel composites.The pressure-sensitive test of the aerogel confirmed that the CNF/silicone aerogels had a very high sensitivity and the resistance change rate is close to 100%under 20%strain compression.Clearly,the multifunctional CNF/silicone aerogels developed here are promising in various applications from the oil/water separation to the strain sensor fields. |
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