Design And Construction Of Superhydrophobic Structure On The Surface Of Silicone Rubber

Superhydrophobic materials were inspired from natural bionic research and have great potential in the fields of anti-fouling,attenuation,and anti-icing.However,it is often difficult to balance excellent superhydrophobicity and good mechanical stability.There is still a huge challenge to fabricate stable and durable superhydrophobic materials.Here,vulcanized silicone rubber ws used as the substrate.Utilizing the swelling characteristics of vulcanized silicone rubber,inorganic nanoparticles are generated“in situ”on the surface of silicone rubber to build a rough structure,based on interface diffusion reaction and sol-gel technology.The effects of the preparation processes on the surface morphology,superhydrophobic properties and durability were investigated,and the drainage and self-cleaning properties of superhydrophobic silicone rubber were also discussed.Firstly,an aqueous solution of n-butylamine was used as a rubber swelling agent,and tetrabutyl titanate(TBT)was used as the precursor of the sol-gel reaction.The rough structure of TiO₂ was constructed by“in-situ”growth on the surface of vulcanized silicone rubber(SR)by the sol-gel method.After surface modification with stearic acid(SA),the contact angle(CA)reached 158.5°,and the rolling angle(RA)was 4.5°.Scanning electron microscopy(SEM)showed that the surface of the sample was composed of a single layer of nano-scale spherical TiO₂ particles,and the TiO₂ particles were“embedded”in the rubber surface instead of being“adsorbed”.The mechanical stability was characterized by linear abrasion on sandpaper,which could withstand 100 cycles of wear while maintaining superhydrophobic properties.Constructing a micro-nano composite structure is another way to improve the stability of superhydrophobicity.Polyacrylamide(PAM)was added during rubber mixing.Due to the poor compatibility of PAM and silicone rubber,it will gradually precipitate on the rubber surface.The rough structure was prepared by the above sol-gel method.The PAM particles on the surface of the vulcanized rubber were coated with TiO₂ particles to construct a TiO₂/PAM micro-nano composite structure.The sandpaper linear abrasion experiment proved that the TiO₂/PAM micro-nano composite structure superhydrophobic material could withstand 200 cycles of wear,which is twice that of the previous group of TiO₂ superhydrophobic rubbers.In order to further improve the stability,the silane coupling agent Si-69 and KH550were added during the mixing of the silicone rubber to link the particles and the SR matrix molecular chain through chemical bonding to increase the bonding strength.The addition of 1phr Si-69 or KH550 made the superhydrophobic silicone rubber could tolerate 3200and 600 wear cycles respectively,and the superhydrophobic samples show excellent mechanical wear resistance.Finally,using transparent silicone rubber(PDMS)as the matrix,by controlling the sol-gel reaction time and temperature,a single-layer rough structure was prepared,and a transparent superhydrophobic silicone rubber with a contact angle of 159.3° and a rolling angle of 4.9°was obtained.Prepared by sol-gel method to construct superhydrophobic structure on the surface of vulcanized rubber is simple,controllable and excellent in super-hydrophobic mechanical durability,providing a new idea for the industrial application of super-hydrophobic materials.