Study On Superhydrophobic Surface Of Silicone Rubber Induced By Nanosecond Laser And Analysis Of Anti-icing Property

Silicone rubber is widely used in the power industry due to its high electrical and thermal insulation properties.Silicone rubber could still be hydrophobic because of the ability to recover its hydrophobicity even after being polluted on the surface.However,the hydrophobicity of the silicone rubber surface would be lost gradually and the ability to recover hydrophobicity declines significantly at low humidity.It is difficult to prevent effectively the adsorption of moisture and pollutants,resulting in the pollution flash of silicone rubber insulators under high voltage.In this paper,a method of preparing silicone rubber superhydrophobic surface solely by nanosecond laser was proposed in this paper,which is efficient,green and stable.The superhydrophobic surface's anti-icing and anti-frosting properties were investigated.The transition mechanism of wettability from hydrophobic to superhydrophobic on silicone surface rubber was analyzed.The superhydrophobic surface morphology of silicone rubber was observed by scanning electron microscopy.The results reveal that a hierarchical structure was formed on the surface after being processed,shows a fish scale type structure.It can be observed that a sponge-like micro and nano structure where particles with a size of~150nm appeared to be gathered to form irregular aggregates.Cracking,ablation and vaporization are the likely mechanisms involved in the rearrangement of the surface matter into this complex structure.To evaluate if there has been significant change in surface chemistry,EDS was used to measure Carbon(C),Oxygen(O)and Silicon(Si)before and after processing and the data shows slight increases after processing in C and O whilst there is a slight reduction in Si.It can be explained by the adsorption of Adventitious Carbon by the processed surface which since the processed surface has greater surface area,means increased O and C levels compared to the unprocessed surface and that the Si signal is attenuated in the processed surface also by the presence of more Adventitious Carbon compared to the unprocessed surface.The results suggest that laser exposure is causing some break down of the siloxane backbone causing a shift in the Si-O-Si stretching frequencies,but with no obvious change in functionality.The change in wetting behavior is due to the change in morphology and not a chemical process.The effects of laser fluence on the surface morphology and wettability of rubber adhesive were analyzed.The experimental results show that the trend of the surface's behavior to water,as measured by the water contact angle,is entirely consistent with the extensive formation of micro-nano structures on surface and in full compliance with the Cassie model.During the process of thermal cracking,the surface roughness also increases with the increase of fluence and reaches a maximum of~11?m at a fluence of9.5J/cm~2 and at this point,the surface of the silicone rubber appears de-adhered from the bulk and torn due to the heat.As the fluence continues to increase,the surface is further broken down into fine particles,forming a new surface and the roughness decreased to a stable value of~8.2?m.The contact angle increases up to~158°with low rolling-off angle of~3°and reaches a stable value,therefore the wettability of the sample surfaces transform into superhydrophobic from hydrophobic when the pulse fluence increases to10J/cm~2.The microstructure composed of particles increases the roughness of the sample surface and is considered the main factor for the change of wettability for silicone rubber.The anti-icing and anti-frosting properties of surface of silicone rubber were studied by using a refrigeration device.The icing process and delayed time of water droplets on the superhydrophobic silicone rubber surface at low temperatures were recorded using a camera.The relevant mechanisms of anti-icing and anti-frosting on superhydrophobic surfaces were analyzed.The appearance time and the morphology differences for frost crystals between superhydrophobic surface and ordinary surface were studied by using a microscope.The results show that although the contact angle of the superhydrophobic surface of the silicone rubber decrease at low temperatures,the superhydrophobic surface can significantly delay the icing and frosting time,which has a significant anti-icing and anti-frosting effect.