Surface Hydrophobicity Of Silicone Rubber Research Articles

Study on the Effect of Cleaning and Swelling Action of Cleaning and Repairing Agents on the Properties of Silicone Rubber

Silicone rubber composite materials are prone to fouling under outdoor conditions for a long time, leading to a decrease in hydrophobicity and even the occurrence of pollution flashover. Generally, the silicone rubber surface is cleaned and repaired with cleaning and repair agents, which can quickly restore its hydrophobicity to the factory state and even reach HC1. Under the action of cleaning and repairing agents, silicone rubber will undergo a certain swelling effect. This article conducts in-depth research on the impact of the cleaning and swelling effect of cleaning and repairing agents on the performance of silicone rubber. Research has found that this cleaning and repairing agent can significantly improve the surface hydrophobicity of silicone rubber. When silicone rubber is immersed in the cleaning and repairing agent for up to 10 hours, its surface undergoes swelling equilibrium, where the evaporation volume and swelling index remain unchanged. Through testing its mechanical properties, it was found that its tear resistance and fracture performance have been improved to a certain extent, with growth rates of 23.36% and 2.55%, respectively; Through electrical performance testing, it was found that its volume resistivity and dielectric strength were both improved to a certain extent, with volume resistivity and dielectric strength increased by 16.5% and 14.3%, respectively. Moreover, after reaching swelling equilibrium in the cleaning and repairing agent, the hydrophobicity of silicone rubber did not decrease, and it can still maintain HC1 for a long time, exhibiting good hydrophobicity.

Influence of AC corona discharge on the hydrophobicity of silicone rubber surface in high-speed airflow environment

Corona discharge is one of the key factors that lead to the hydrophobicity loss of silicone rubber insulators used on the roof of high-speed trains. Based on the artificial experimental wind-tunnel platform, influences of AC corona intensity and airflow velocity on the hydrophobicity distribution of the silicone rubber surface were studied. According to the corona discharge phenomena and measured discharge current, influences of airflow velocity and voltage on the characteristics of corona discharge in a high-speed airflow environment were discussed. Results reveal that the hydrophobicity distribution on the silicone rubber surface shifts along the airflow direction in the high-speed airflow environment when the voltage is relatively high. When ionization zone develops to the needle-plate gap, the discharge path is deflected to the direction of airflow, which is responsible for the change of the hydrophobicity distribution. It is notable that the deflection distance decreases with the increase of airflow velocity. This is attributed to the fact that the electrons with variable horizontal distance from the electron to the plate electrode center are subjected to different electric field forces, resulting in different influences of high-speed airflow on them. These results are of engineering and theoretical significance for insulators used in high-speed railways.

Increasing the surface hydrophobicity of silicone rubber by electron beam irradiation in the presence of a glycerol layer

A cost-effective and scalable silicone rubber (SR) modification technology for increasing its surface hydrophobicity is urgently needed to enhance the stability of global power systems. In this work, an easily accessible method was developed to increase the surface hydrophobicity of silicone rubber, which was established by high-energy electron beam irradiation in the presence of a layer of glycerol. Although glycerol is a highly hydrophilic alcohol, the contact angle of silicone rubber can be surprisingly increased by 19.9% with the irradiation treatment of glycerol. Despite a high hydroxyl content being observed, a network structure formed on the silicone rubber surface is responsible for the increase in hydrophobicity. Control experiments and molecular dynamics (MD) simulations were also conducted to shed light on the underlying mechanism. This method has some intrinsic advantages, such as cost-effectiveness, easy operation and nontoxicity of glycerol; thus, it is expected to be applicable in large-scale industrial production and modification of silicone rubber.

Super-hydrophobic zinc oxide/silicone rubber nanocomposite surfaces

This study presents comparative assessments on hydrophilic and hydrophobic ZnO nanoparticles and their deposition methods on the surface hydrophobicity of silicone rubber (PDMS) and glass substrates. The influence on the surface hydrophobicity and wettability of all the variables regarding the deposition methodologies and the interaction of the nanoparticles with the substrates were within the scope of this study. The different surfaces created by spraying, dipping and drop-pipetting deposition methods were assessed by static contact angle measurements and contact angle hysteresis from advancing and receding angles, as well as by the calculation of the sliding angle and the surface energy parameters. An accurate methodology to determine the contact angle hysteresis was proposed to obtain repetitive and comparative results on all surfaces. All the measurements have been correlated with the morphology and topography of the different surfaces analysed by FE-SE microscopy. The spray-deposition of hydrophobic ZnO nanoparticles on PDMS resulted in super-hydrophobic surfaces, exhibiting hierarchical structures with micro- and nanometer features which, together with the low surface energy, promotes the Cassie-Baxter wetting behavior. This study provides the fundamental approach to select critically the most promising combination in terms of materials and deposition techniques to create silicone-based super-hydrophobic surfaces with potential to be applied in high voltage outdoor insulation applications.

Influence on hydrophobicity of silicone rubber surface by introducing fluorocarbon functional groups

Hydrophobic modification on surface of silicone rubber (SIR) by CF4 radio frequency inductively coupled plasma is discussed. Static contact angle, atomic force microscopy and X-ray photoelectron spectroscopy were used in characterizing the hydrophobic property, surface appearance and chemical composition of the modified SIR. The results show that the improvement of surface hydrophobic property on modified SIR is attributed to the introduction of fluorocarbon functional groups (C–CFn, n = 1, 2, 3) and fluosilicic structures (Si–F and Si–F2) during the treatment.

Surface degradation of silicone rubber nanocomposites due to DC corona discharge

Corona discharge is recognized as one of the mechanisms that can influence the surface hydrophobicity of Silicone Rubber (SR) because of the chemical changes that occur on its surface. In this study SR samples were exposed to positive and negative DC corona for 25 and 50 hours using a needle-plane electrode system. Hydrophobicity changes were monitored using a sessile drop contact angle measurement facility. The physical changes on the surface were studied using Scanning Electron Microscopy (SEM) and surface roughness measurements. The effect of positive dc corona was found to be different from that of negative dc corona. Significant surface degradation and loss of hydrophobicity was found in the case of negative dc corona exposed samples. Significant improvement in the above mentioned properties were obtained by adding small quantities of nSIL into the SR matrix.

Hydrophobic recovery of repeatedly plasma-treated silicone rubber. Part 1. Storage in air

Silicone rubber is used for a wide variety of biomedical and industrial applications due to its good mechanical properties, combined with a hydrophobic surface. Frequently, however, it is desirable to alter the surface hydrophobicity of silicone rubber. Often this is done by plasma treatments but the effects are usually transient. In this study, surfaces of medical grade silicone rubber have been repeatedly modified by means of oxygen, argon, carbon dioxide, and ammonia RF plasma treatments with a 24 h time interval in between treatments. Treated samples were stored in air prior to surface characterization by water contact angle measurements, X-ray photoelectron spectroscopy (XPS), streaming potential measurements, and profilometry for surface roughness. The carbon percentage of the surfaces decreased after plasma treatment, while the silicon and oxygen percentages increased irrespective of the plasma used. The formation of Si-O-Si bridges between siloxane chains after plasma treatment was demonstrated by the appearance of a new component in the Si2p peak but the degree to which this occurred differed per gas. Streaming potential measurements in a 10 mM potassium phosphate buffer indicated a more negatively charged surface for treated samples compared to untreated samples (-23.3 mV at pH 7.0). Surface roughness increased slightly for repeatedly plasma-treated samples from RA = 0.35 μm to RA = 0.46 μm, while scanning electron microscopy showed the presence of several 'cracks' spanning the surface after repeated treatment. Argon, carbon dioxide, and ammonia plasmas significantly reduced the advancing water contact angle from 115° to 58°, 72°, and 85°, respectively, on a more permanent basis (especially when the treatments were repeated after recovery). Oxygen plasma effects on water contact angles generally disappeared within 5 h, also after repeated treatment.