Surface Modification Of Silicone Rubber Research Articles

Surface modification of silicone rubber by CF4 radio frequency capacitively coupled plasma for improvement of flashover

The flashover performance of insulating materials plays an important role in the development of high-voltage insulation systems. In this paper, silicone rubber (SIR) is modified by CF4 radio frequency capacitively coupled plasma (CCP) for the improvement of surface insulation performance. The discharge mode and active particles of CCP are diagnosed by the digital single-lens reflex and the spectrometer. Scanning electron microscopy and x-ray photoelectron spectroscopy are used for the surface physicochemical properties of samples, while the surface charge dissipation, charge accumulation measurement, and flashover test are applied for the surface electrical characteristics. Experimental results show that the fluorocarbon groups can be grafted and the surface roughness increases after plasma treatment. Besides, the surface charge dissipation is decelerated and the positive charge accumulation is inhibited obviously for the treated samples. Furthermore, the surface flashover voltage can be increased by 26.67% after 10 min of treatment. It is considered that strong electron affinity of C–F and increased surface roughness can contribute to deepening surface traps, which not only inhibits the development of secondary electron emission avalanche but also alleviates the surface charge accumulation and finally improves the surface flashover voltage of SIR.

Study on surface modification of silicone rubber for composite insulator by electron beam irradiation

In order to improve the outdoor service life of composite insulators, the effect of electron beam irradiation on SIR is studied. In this paper, the silicone rubber was treated by two different doses of electron beam irradiation, and the accelerated aging test of 1000 h high temperature, high humidity and strong sunlight was carried out in the multi factor aging test chamber. At the same time, the physical and chemical properties such as physical tensile properties, hydrophobicity, optical microscope, scanning electron microscope (SEM), Attenuated Total internal Reflection Fourier Transform Infrared Spectrometer(ATR-FTIR) and crosslinking density were analyzed. The results showed that after low electron beam irradiation dose (40 kGy) treatment, the crosslinking density of silicone rubber increased by 8.8 times, and after 1000 h aging treatment, the crosslinking density of low irradiated(40 kGy) silicone rubber is still 6 times higher than that of unirradiated silicone rubber. Based on the analysis of the test results, the surface modification mechanism of silicone rubber under electron beam irradiation and aging is proposed. The research observation results demonstrate the influence of electron beam irradiation and aging on silicone rubber. Related research provides a novel idea for improving the service life of insulators.

Controlled surface modification of silicone rubber by gamma-irradiation followed by RAFT grafting polymerization

The formation of biofilms on the surface of some biomaterials causes problems that can have a negative impact on human health. Various studies have been carried out for the modification of polymeric biomaterials; however, with conventional methods of modifying surfaces with radiation-induced grafts, obtaining uniformly distributed grafts over the entire surface is not facilitated, so the mechanical properties are strongly affected by the modification. In this study, silicone rubber (SR) films were modified with 2-hydroxyethyl methacrylate (HEMA) and with oligo(ethylene glycol) methyl ether methacrylate, Mn = 300 g mol−1 (OEGMA300) using the oxidative pre-irradiation method with gamma-irradiation followed by reversible addition-fragmentation chain transfer (RAFT) grafting polymerization. The copolymers of SR-g-PHEMA and SR-g-poly(HEMA-co-OEGMA300) were synthesized with various grafting percentages and these could be adjusted to obtain a thin grafted layer. The grafted samples were characterized by FTIR-ATR spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), light microscopy, swelling in water, contact angle, and dynamic mechanical analysis (DMA); in addition, the non-grafted polymer formed in the RAFT copolymerization reactions was analyzed by gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (NMR). The results confirmed the presence of PHEMA and poly(HEMA-co-OEGMA300) on the surface of SR films, uniformly grafted by the use of a chain transfer agent (CTA). The uniform layer of hydrophilic grafts in the SR films generates a surface capable of forming a water barrier on the surface, without significantly compromising the elastic properties of the SR; furthermore, the grafted thin layer was capable of loading biologically active molecules like curcumin. Modified SR films loaded with curcumin may decrease the possibility of biofilm formation. The described approach of oxidative gamma pre-irradiation followed by RAFT controlled grafting may be of interest for the modification of biomaterials in a controlled way, in the case of silicone for instance for catheters or aesthetic implants.

Superhydrophobic micro-nano structures on silicone rubber by nanosecond laser processing

This paper demonstrates laser surface modification of silicone rubber using an economic and efficient nanosecond fibre laser. The resulting surface morphology shows that micro-nano structures leading to an increase in the surface slope were formed after processing. The effect of laser power on the surface wettability was investigated demonstrating that the contact angle of the silicone rubber surface increased with increasing laser fluence. The water contact angle on the treated surface reached ~160° with a rolling-off angle of ~3° when the laser fluence reached 10 J cm−2. After laser processing, both the roughness and root mean square slope of the silicone rubber surface increased with increasing fluence and reached maximum at a fluence of 10 J cm−2. An analysis of the pre- and post processing surfaces suggested there were no significant compositional changes, but there were some micro-structural changes to the polymer chain, namely, cleavage of the Si–O–Si bonds. It is thus proposed that the hierarchical micro-nano structures and hence the change in the root mean square slope of the silicone rubber surface induced by laser irradiation are the primary reasons for its superhydrophobicity. The preparation of superhydrophobic silicone rubber can have important applications in self-cleaning, anti-icing, and anti-pollution.

Photochemical Surface Modification of Silicone Rubber into Photoluminescent Material by 193 nm ArF Excimer Laser Irradiation

A transparent, flexible silicone rubber ([SiO(CH3)2]n) surface was photochemically modified into a photoluminescent material using a 193 nm ArF excimer laser. The photomodified silicone rubber emitted white light under a 325 nm He–Cd laser or a 375 nm light-emitting diode. The chemical bonding of the photomodified silicone rubber was found to be similar to that of a silica-like silicone, as analyzed by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The photoluminescence of the rubber originated from oxygen deficiency centers and peroxy centers of the silica structure in the photomodified silicone rubber. Fine particles 200 nm in diameter were also formed in the photomodified silicone rubber to enhance the intensity of the photoluminescence.

CF 4 radio frequency plasma surface modification of silicone rubber for use as outdoor insulations

For further prolonging the serve life of silicone rubber (SIR) for outdoor insulation and increasing its resistance of pollution flashover, surface modifications of SIR were carried out via CF 4 capacitively coupled plasma at radio frequency (RF) power of 60, 100 and 200 W for a treatment time up to 20 min under CF 4 flow rate of 20 sccm. Static contact angle measurement was employed to estimate the change of hydrophobicity of the modified SIR. The variation of the surface functional groups of the modified SIR was observed by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrum and X-ray photoelectron spectroscopy (XPS). The surface topography was observed by atom force microscopy (AFM). The results indicate that the static contact angle of SIR surface is improved from 100.7° to 150.2° via the CF 4 plasma modification, and the super-hydrophobic surface of modified SIR, which corresponds to a static contact angle of 150.2°, appears at RF power of 200 W for a 5-min treatment time. According to the results, it is suggested that the formation of super-hydrophobic surface is ascribed to the co-action of the increase of roughness created by the ablation reaction of CF 4 plasma and the formation of [ SiF x (CH 3) 2− x O ] n ( x = 1, 2) structure produced by the direct attachment of F atoms to Si.

Surface Modification of Silicone Rubber by CF4 Radio Frequency Plasma Immersion

Silicone rubber samples were treated by CF(4) capacitively coupled plasma at radio frequency (RF) power of 60, 100 and 200 W for a treatment time up to 20 min under CF(4) flow rate of 20 sccm, respectively. Static contact angle, ATR-FTIR and XPS, and AFM were employed to characterize the changes of surface on hydrophobicity, functional groups, and topography. The results indicate the static contact angle is improved from 100.7 to 150.2, and the super-hydrophobic surface, which corresponds to a static contact angle of 150.2, appears at RF power of 200 W for a 5 min treatment time. It is suggested that the formation of super-hydrophobic surface is ascribed to the co-action of the increase of surface roughness created by the ablation reaction of CF(4) plasma and the formation of [-SiF (x) (CH(3))(2-x) -O-] (n) (x = 1, 2) structure produced by the direct attachment of F atoms to Si.

Surface Modification of Silicone Rubber After Corona Exposure

This paper describes the surface modification of high temperature vulcanized silicone rubber (HTV-SR) resulting from corona discharges under atmospheric pressure. In this study, a plate-shaped HTV-SR specimen was exposed to corona stress generated by a needles-plane electrode system; further, physicochemical analyses were conducted on the surface layer of SR before and after corona discharge treatment. The results showed that the plasma impingement from the corona discharge can cause physical and chemical damages to the SR surface. In addition, it was demonstrated that instead of hydrophobic CH3 groups, hydrophilic OH groups that are byproducts of ageing may be formed on the surface of aged SR; further, the corona discharge plays an important role in the loss of hydrophobicity.

Surface modification of silicone rubber by ion beam assisted deposition (IBAD) for improved biocompatibility

AbstractWe studied the preparation of antimicrobial silicone rubbers of improved interfacial strength, which could be formed with the ion beam assisted deposition (IBAD) technique for coating metallic or inorganic materials (silver (Ag), Copper (Cu), and Hydroxyapatite(HAp)/TiO2) on the silicone surface. Those coating materials provide high product safety as well as outstanding antimicrobial activity. The deposition methodology is composed of pre‐etching with oxygen gas, vaporizing the coating materials, and post‐treatment with Ar ion. With the evaporation of the coating materials, the Ar beam was focused on the substrate to assist deposition. It was found out that the ion assisting depositions in the IBAD process give a prominent enhancement in adhesion between silicone rubbers and coatings of Ag and Cu. The HAp/TiO2 coating layer was easily dissolved in aqueous saline solution. All deposited layers display high antimicrobial activities against Staphlococcus aureus (ATCC 6538) and Escherichia coil (ATCC 25,922), showing 99.9% reduction of bacteria, respectively. In a cytotoxicity test, the Ag and HAp/TiO2 coated silicone shows a decrease of cytotoxicity, while the Cu coating leads to a slight increase of cytotoxicity. The result on the surface modifications of silicone rubber will be employed in further study for applications of medical or rehabilitation devices. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1095–1101, 2005

Surface modification of silicone rubber with poly(ethylene glycol) hydrogel coatings

AbstractHydrogel coatings of monoacrylated poly(ethylene glycol) (PEG) methyl ethers of different molecular weights were attached to silicon rubber surfaces and crosslinked with hexanediol diacrylate or ethoxylated trimethylolpropane diacrylate by UV polymerization. The wetting, evaluated with the water contact angles, correlated with the surface oxyethylene chain density, which was evaluated with the ESCA >CO/CH2 ratio obtained from the C(1s) peak. As measured by the ESCA N(1s) peak, bovine serum albumin formed very thin protein adsorbates on the PEG‐coated surfaces. A strong correlation was found between low protein adsorption and a high >CO/CH2 ratio of the PEG‐coated substrate. The PEG‐coated silicon rubber also demonstrated very low cell and platelet adhesion. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1486–1492, 2004

Laser surface modification of silicone rubber to reduce platelet adhesion in vitro

To improve the blood compatibility, the surface of polydimethylsiloxane (PDMS) films were irradiated using a CO2-pulsed laser. Acrylamide (AAm) was grafted onto a pre-irradiated surface. The AAm-grafted and laser-treated films were characterized using different techniques. Platelet adhesion and activation onto the AAm-grafted PDMS, laser-treated (ungrafted) and unmodified PDMS film surfaces were compared. Data from in vitro assays indicated that the platelet adhesion was reduced on the AAm-grafted PDMS and laser treated PDMS films in comparison with the unmodified PDMS. The laser-irradiated sample showed the minimum platelet adhesion. It seems that laser irradiation onto a silicone rubber surface is a versatile technique to produce anti-thrombogenic surface for biomaterial applications.

Bulk and surface modification of silicone rubber for biomedical applications

AbstractAttempts have been made to modify the surface and bulk properties of polydimethylsiloxane (PDMS) polymers to improve their properties for biomedical applications. Laser‐induced surface grafting of poly(2‐hydroxyethyl methacrylate) (PHEMA) and a sequential method for preparation of interpenetrating polymer networks (IPNs) of PDMS/PHEMA were used for surface and bulk modifications, respectively. A major difference between these two methods and other modification techniques is their unique potentiality to modify a specific section of a polymeric sample. The modified PDMS samples have been studied by attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, water contact angle measurement, scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), and platelet adhesion measurement.© 2002 Society of Chemical Industry

Surface modification of silicone rubber by gas plasma treatment

Silicone rubber films were surface-modified with O2, Ar, or NH3 plasma in either a bell-jar-type or a tubular-type reactor to investigate the effect of the plasma treatment conditions on the hydrophilicity, peel strength, and chemical composition of the film surface. ESCA spectra of the modified films were used to calculate the elemental ratios of oxygen to carbon and nitrogen to carbon. In the bell-jar-type reactor, the order of hydrophilicity improvement was found to be O2 > Ar > NH3 plasma. NH3 plasma treatment at 10 W for 2 min resulted in the highest enhancement of peel strength. The contact angle of water on the modified surface increased with storage humidity. However, the peel strength decreased with the storage time.

Surface modification of silicone rubber by ion implantation

A study has been made on the wettability, structure, and chemical states of ion implanted silicone rubbers. C +, N 2 +, O 2 +, and Ar + ion implantations were performed at energies of 50 and 100 keV at room temperature. The fluences ranged from 10 12 to 10 17 ions/cm 2. Ion implantation caused the surface roughness to increase 2–3 times. Wettability was estimated by means of the sessile drop method using water, of which the results showed that the contact angle of water decreased from 98.9° to 48° as the fluence increased. The results of XPS measurements showed that implanted elements formed a Gaussian-like distribution, host elements were redistributed and no change in binding energies of O 1s, C 1s and Si 2p occurred. Results of FT-IR-ATR showed that ion implantation broke up original chemical bonds to form new radicals, the amounts of which are related to the fluences. It is concluded that the change in wettability may be caused by formation of new radicals rather than roughening of the surface under ion implantation.