The Experts below are selected from a list of 8559 Experts worldwide ranked by ideXlab platform
Henrik Hillborg - One of the best experts on this subject based on the ideXlab platform.
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Oxidative Surface Treatment of Silicone Rubber
Silicone Surface Science, 2012Co-Authors: Henrik Hillborg, Ulf W. GeddeAbstract:The mechanisms behind the loss and Recovery of Hydrophobicity of silicone rubber after exposure to oxidative surface treatments, such as UV irradiation, corona or plasma, are presented. Initially, polar groups are introduced into the surface region, mainly in the form of silanol groups. The oxidation then proceeds towards a vitrified silica-like surface layer. The formation of complex buckling patterns, formed by the mechanical stress difference between the silica-like layer and the rubbery bulk opens the way to a wide range of new applications, such as gratings and flexible electronics. The main challenge is to address the Hydrophobic Recovery process after an oxidative surface treatment. In some applications, such as high-voltage outdoor insulation materials, this Recovery is desired but usually it is not. The most common methods of inhibiting Hydrophobic Recovery are extraction of the silicone rubber to remove extractable oligomers, storage of oxidized silicone rubber in water directly after treatment, or the grafting of polar species onto the oxidized surface.
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Hydrophobic stability of silicone rubber after water immersion
2007 Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, 2007Co-Authors: Henrik Hillborg, Andrej Krivda, Xavier Kornmann, P Meier, L. E. SchmidtAbstract:The Hydrophobic stability of a virgin HTV silicone rubber formulation and corresponding formulations after initial 'accelerated ageing' by water immersion during 410 h at 23 or 90degC has been compared. This is in order to investigate the influence of moisture/water ingress on the Hydrophobic Recovery after corona discharges and after deposition of artificial pollution layers. The 'aged' materials exhibited a slower Hydrophobic Recovery after exposure to corona discharges, but on the other hand they exhibited a faster Hydrophobic transfer through artificial pollution layers. Scanning electron microscopy revealed a significant surface erosion, exposing individual filler particles; even though no significant surface oxidation was observed using X-ray photoelectron spectroscopy. Moreover, the extractable amounts of silicone oils were analyzed using chromatography. It was found that both the amount and the types of the extractable silicones were similar for both virgin and 'aged' materials. The observed differences in Hydrophobic Recovery rates were explained primarily by the difference in surface roughness between aged and virgin samples. Finally, it was concluded that cyclic silicone oligomers (D4 and D5) were responsible for the initial Hydrophobic transfer effect through the artificial pollution layer.
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Hydrophobic Recovery of uv ozone treated poly dimethylsiloxane adhesion studies by contact mechanics and mechanism of surface modification
Applied Surface Science, 2005Co-Authors: A. Oláh, Henrik Hillborg, Julius G VancsoAbstract:Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus of this study was to apply the Johnson–Kendall–Roberts (JKR) contact mechanics approach to investigate PDMS samples prior to and following UV/ozone surface treatment. A gradual formation of a hydrophilic, silica-like surface layer with increasing modulus was observed with increasing UV/ozone exposure. A subsequent Hydrophobic Recovery after UV/ozone exposure was observed, as indicated by increasing contact angles. This supports the hypothesis that the Hydrophobic Recovery is mainly caused by the gradual coverage of a permanent silica-like structure with free siloxanes and/or reorientation of polar groups. PDMS containing a homogenously dispersed filler (Sylgard 184), exhibited a decreasing surface roughness (by AFM) when the oxidized surface region “collapsed” into a smooth SiOx layer (final surface roughness <2 nm). PDMS containing heterogeneously distributed, aggregated filler particles (Sylgard 170), exhibited an increasing surface roughness with treatment dose, which was attributed to the “collapse” of the oxidized surface region thus exposing the contours of the underlying filler aggregates (final surface roughness 140 nm). A dedicated device was designed and built to study the contact mechanics behavior of PDMS prior to, and following surface treatment. The value of the combined elastic modulus obtained for PDMS lens and semi-infinite flat surface system showed an increase in full agreement with the formation of a silica-like layer exhibiting a high elastic modulus (compared with untreated PDMS). The work of adhesion observed in JKR experiments exhibited an increasing trend as a function of treatment done in agreement with contact angle data. JKR experiments showed Hydrophobic Recovery behavior as anticipated from contact angle measurements. Single pull-off force measurements by JKR and numerical analysis of full-approach JKR curves were in quantitative agreement regarding practical work of adhesion values.
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Hydrophobic Recovery of UV/ozone treated poly(dimethylsiloxane): adhesion studies by contact mechanics and mechanism of surface modification
Applied Surface Science, 2004Co-Authors: A. Oláh, Henrik Hillborg, G. Julius VancsoAbstract:Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus of this study was to apply the Johnson–Kendall–Roberts (JKR) contact mechanics approach to investigate PDMS samples prior to and following UV/ozone surface treatment. A gradual formation of a hydrophilic, silica-like surface layer with increasing modulus was observed with increasing UV/ozone exposure. A subsequent Hydrophobic Recovery after UV/ozone exposure was observed, as indicated by increasing contact angles. This supports the hypothesis that the Hydrophobic Recovery is mainly caused by the gradual coverage of a permanent silica-like structure with free siloxanes and/or reorientation of polar groups. PDMS containing a homogenously dispersed filler (Sylgard 184), exhibited a decreasing surface roughness (by AFM) when the oxidized surface region “collapsed” into a smooth SiOx layer (final surface roughness
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nanoscale Hydrophobic Recovery a chemical force microscopy study of uv ozone treated cross linked poly dimethylsiloxane
Langmuir, 2004Co-Authors: Henrik Hillborg, A. Oláh, Nikodem Tomczak, Holger Schonherr, Julius G VancsoAbstract:Chemical force microscopy (CFM) in water was used to map the surface Hydrophobicity of UV/ozone-treated poly(dimethylsiloxane) (PDMS; Sylgard 184) as a function of the storage/Recovery time. In addition to CFM pull-off force mapping, we applied indentation mapping to probe the changes in the normalized modulus. These experiments were complemented by results on surface properties assessed on the micrometer scale by X-ray photoelectron spectroscopy and water contact-angle measurements. Exposure times of <_30 min resulted in laterally homogeneously oxidized surfaces, which are characterized by an increased modulus and a high segmental mobility of PDMS. As detected on a sub-50-nm level, the subsequent "Hydrophobic Recovery" was characterized by a gradual increase in the pull-off forces and a decrease in the normalized modulus, approaching the values of unexposed PDMS after 8-50 days. Lateral imaging on briefly exposed PDMS showed the appearance of liquid PDMS in the form of droplets with an increasing Recovery time. Longer exposure times (60 min) led to the formation of a hydrophilic silica-like surface layer. Under these conditions, a gradual surface reconstruction within the silica-like layer occurred with time after exposure, where a hydrophilic SiOx-enriched phase formed <100-nm-sized domains, surrounded by a more Hydrophobic matrix with lower normalized modulus. These results provide new insights into the lateral homogeneity of oxidized PDMS with a resolution in the sub-50-nm range.
Julius G Vancso - One of the best experts on this subject based on the ideXlab platform.
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Hydrophobic Recovery of uv ozone treated poly dimethylsiloxane adhesion studies by contact mechanics and mechanism of surface modification
Applied Surface Science, 2005Co-Authors: A. Oláh, Henrik Hillborg, Julius G VancsoAbstract:Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus of this study was to apply the Johnson–Kendall–Roberts (JKR) contact mechanics approach to investigate PDMS samples prior to and following UV/ozone surface treatment. A gradual formation of a hydrophilic, silica-like surface layer with increasing modulus was observed with increasing UV/ozone exposure. A subsequent Hydrophobic Recovery after UV/ozone exposure was observed, as indicated by increasing contact angles. This supports the hypothesis that the Hydrophobic Recovery is mainly caused by the gradual coverage of a permanent silica-like structure with free siloxanes and/or reorientation of polar groups. PDMS containing a homogenously dispersed filler (Sylgard 184), exhibited a decreasing surface roughness (by AFM) when the oxidized surface region “collapsed” into a smooth SiOx layer (final surface roughness <2 nm). PDMS containing heterogeneously distributed, aggregated filler particles (Sylgard 170), exhibited an increasing surface roughness with treatment dose, which was attributed to the “collapse” of the oxidized surface region thus exposing the contours of the underlying filler aggregates (final surface roughness 140 nm). A dedicated device was designed and built to study the contact mechanics behavior of PDMS prior to, and following surface treatment. The value of the combined elastic modulus obtained for PDMS lens and semi-infinite flat surface system showed an increase in full agreement with the formation of a silica-like layer exhibiting a high elastic modulus (compared with untreated PDMS). The work of adhesion observed in JKR experiments exhibited an increasing trend as a function of treatment done in agreement with contact angle data. JKR experiments showed Hydrophobic Recovery behavior as anticipated from contact angle measurements. Single pull-off force measurements by JKR and numerical analysis of full-approach JKR curves were in quantitative agreement regarding practical work of adhesion values.
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nanoscale Hydrophobic Recovery a chemical force microscopy study of uv ozone treated cross linked poly dimethylsiloxane
Langmuir, 2004Co-Authors: Henrik Hillborg, A. Oláh, Nikodem Tomczak, Holger Schonherr, Julius G VancsoAbstract:Chemical force microscopy (CFM) in water was used to map the surface Hydrophobicity of UV/ozone-treated poly(dimethylsiloxane) (PDMS; Sylgard 184) as a function of the storage/Recovery time. In addition to CFM pull-off force mapping, we applied indentation mapping to probe the changes in the normalized modulus. These experiments were complemented by results on surface properties assessed on the micrometer scale by X-ray photoelectron spectroscopy and water contact-angle measurements. Exposure times of <_30 min resulted in laterally homogeneously oxidized surfaces, which are characterized by an increased modulus and a high segmental mobility of PDMS. As detected on a sub-50-nm level, the subsequent "Hydrophobic Recovery" was characterized by a gradual increase in the pull-off forces and a decrease in the normalized modulus, approaching the values of unexposed PDMS after 8-50 days. Lateral imaging on briefly exposed PDMS showed the appearance of liquid PDMS in the form of droplets with an increasing Recovery time. Longer exposure times (60 min) led to the formation of a hydrophilic silica-like surface layer. Under these conditions, a gradual surface reconstruction within the silica-like layer occurred with time after exposure, where a hydrophilic SiOx-enriched phase formed <100-nm-sized domains, surrounded by a more Hydrophobic matrix with lower normalized modulus. These results provide new insights into the lateral homogeneity of oxidized PDMS with a resolution in the sub-50-nm range.
A. Oláh - One of the best experts on this subject based on the ideXlab platform.
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Hydrophobic Recovery of uv ozone treated poly dimethylsiloxane adhesion studies by contact mechanics and mechanism of surface modification
Applied Surface Science, 2005Co-Authors: A. Oláh, Henrik Hillborg, Julius G VancsoAbstract:Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus of this study was to apply the Johnson–Kendall–Roberts (JKR) contact mechanics approach to investigate PDMS samples prior to and following UV/ozone surface treatment. A gradual formation of a hydrophilic, silica-like surface layer with increasing modulus was observed with increasing UV/ozone exposure. A subsequent Hydrophobic Recovery after UV/ozone exposure was observed, as indicated by increasing contact angles. This supports the hypothesis that the Hydrophobic Recovery is mainly caused by the gradual coverage of a permanent silica-like structure with free siloxanes and/or reorientation of polar groups. PDMS containing a homogenously dispersed filler (Sylgard 184), exhibited a decreasing surface roughness (by AFM) when the oxidized surface region “collapsed” into a smooth SiOx layer (final surface roughness <2 nm). PDMS containing heterogeneously distributed, aggregated filler particles (Sylgard 170), exhibited an increasing surface roughness with treatment dose, which was attributed to the “collapse” of the oxidized surface region thus exposing the contours of the underlying filler aggregates (final surface roughness 140 nm). A dedicated device was designed and built to study the contact mechanics behavior of PDMS prior to, and following surface treatment. The value of the combined elastic modulus obtained for PDMS lens and semi-infinite flat surface system showed an increase in full agreement with the formation of a silica-like layer exhibiting a high elastic modulus (compared with untreated PDMS). The work of adhesion observed in JKR experiments exhibited an increasing trend as a function of treatment done in agreement with contact angle data. JKR experiments showed Hydrophobic Recovery behavior as anticipated from contact angle measurements. Single pull-off force measurements by JKR and numerical analysis of full-approach JKR curves were in quantitative agreement regarding practical work of adhesion values.
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Hydrophobic Recovery of UV/ozone treated poly(dimethylsiloxane): adhesion studies by contact mechanics and mechanism of surface modification
Applied Surface Science, 2004Co-Authors: A. Oláh, Henrik Hillborg, G. Julius VancsoAbstract:Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus of this study was to apply the Johnson–Kendall–Roberts (JKR) contact mechanics approach to investigate PDMS samples prior to and following UV/ozone surface treatment. A gradual formation of a hydrophilic, silica-like surface layer with increasing modulus was observed with increasing UV/ozone exposure. A subsequent Hydrophobic Recovery after UV/ozone exposure was observed, as indicated by increasing contact angles. This supports the hypothesis that the Hydrophobic Recovery is mainly caused by the gradual coverage of a permanent silica-like structure with free siloxanes and/or reorientation of polar groups. PDMS containing a homogenously dispersed filler (Sylgard 184), exhibited a decreasing surface roughness (by AFM) when the oxidized surface region “collapsed” into a smooth SiOx layer (final surface roughness
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nanoscale Hydrophobic Recovery a chemical force microscopy study of uv ozone treated cross linked poly dimethylsiloxane
Langmuir, 2004Co-Authors: Henrik Hillborg, A. Oláh, Nikodem Tomczak, Holger Schonherr, Julius G VancsoAbstract:Chemical force microscopy (CFM) in water was used to map the surface Hydrophobicity of UV/ozone-treated poly(dimethylsiloxane) (PDMS; Sylgard 184) as a function of the storage/Recovery time. In addition to CFM pull-off force mapping, we applied indentation mapping to probe the changes in the normalized modulus. These experiments were complemented by results on surface properties assessed on the micrometer scale by X-ray photoelectron spectroscopy and water contact-angle measurements. Exposure times of <_30 min resulted in laterally homogeneously oxidized surfaces, which are characterized by an increased modulus and a high segmental mobility of PDMS. As detected on a sub-50-nm level, the subsequent "Hydrophobic Recovery" was characterized by a gradual increase in the pull-off forces and a decrease in the normalized modulus, approaching the values of unexposed PDMS after 8-50 days. Lateral imaging on briefly exposed PDMS showed the appearance of liquid PDMS in the form of droplets with an increasing Recovery time. Longer exposure times (60 min) led to the formation of a hydrophilic silica-like surface layer. Under these conditions, a gradual surface reconstruction within the silica-like layer occurred with time after exposure, where a hydrophilic SiOx-enriched phase formed <100-nm-sized domains, surrounded by a more Hydrophobic matrix with lower normalized modulus. These results provide new insights into the lateral homogeneity of oxidized PDMS with a resolution in the sub-50-nm range.
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Nanoscale Hydrophobic Recovery: A chemical force microscopy study of UV/ozone-treated cross-linked poly(dimethylsiloxane).
Langmuir : the ACS journal of surfaces and colloids, 2004Co-Authors: Henrik Hillborg, A. Oláh, Nikodem Tomczak, Holger Schonherr, G. Julius VancsoAbstract:Chemical force microscopy (CFM) in water was used to map the surface Hydrophobicity of UV/ozone-treated poly(dimethylsiloxane) (PDMS; Sylgard 184) as a function of the storage/Recovery time. In addition to CFM pull-off force mapping, we applied indentation mapping to probe the changes in the normalized modulus. These experiments were complemented by results on surface properties assessed on the micrometer scale by X-ray photoelectron spectroscopy and water contact-angle measurements. Exposure times of
G. Julius Vancso - One of the best experts on this subject based on the ideXlab platform.
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Hydrophobic Recovery of UV/ozone treated poly(dimethylsiloxane): adhesion studies by contact mechanics and mechanism of surface modification
Applied Surface Science, 2004Co-Authors: A. Oláh, Henrik Hillborg, G. Julius VancsoAbstract:Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus of this study was to apply the Johnson–Kendall–Roberts (JKR) contact mechanics approach to investigate PDMS samples prior to and following UV/ozone surface treatment. A gradual formation of a hydrophilic, silica-like surface layer with increasing modulus was observed with increasing UV/ozone exposure. A subsequent Hydrophobic Recovery after UV/ozone exposure was observed, as indicated by increasing contact angles. This supports the hypothesis that the Hydrophobic Recovery is mainly caused by the gradual coverage of a permanent silica-like structure with free siloxanes and/or reorientation of polar groups. PDMS containing a homogenously dispersed filler (Sylgard 184), exhibited a decreasing surface roughness (by AFM) when the oxidized surface region “collapsed” into a smooth SiOx layer (final surface roughness
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Nanoscale Hydrophobic Recovery: A chemical force microscopy study of UV/ozone-treated cross-linked poly(dimethylsiloxane).
Langmuir : the ACS journal of surfaces and colloids, 2004Co-Authors: Henrik Hillborg, A. Oláh, Nikodem Tomczak, Holger Schonherr, G. Julius VancsoAbstract:Chemical force microscopy (CFM) in water was used to map the surface Hydrophobicity of UV/ozone-treated poly(dimethylsiloxane) (PDMS; Sylgard 184) as a function of the storage/Recovery time. In addition to CFM pull-off force mapping, we applied indentation mapping to probe the changes in the normalized modulus. These experiments were complemented by results on surface properties assessed on the micrometer scale by X-ray photoelectron spectroscopy and water contact-angle measurements. Exposure times of
Iskender Yilgor - One of the best experts on this subject based on the ideXlab platform.
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hydrophilization of silicone urea copolymer surfaces by uv ozone influence of pdms molecular weight on surface oxidation and Hydrophobic Recovery
Polymer, 2013Co-Authors: Sevilay Bilgin, Mehmet Isik, Emel Yilgor, Iskender YilgorAbstract:Abstract Hydrophilization of polydimethylsiloxane–urea copolymer (PSU) surfaces and the extent of Hydrophobic Recovery were investigated as a function of; (i) UV/ozone (UV/O) exposure time, (ii) the aging period after UV/O exposure, (iii) sample preparation method, and (iv) polydimethylsiloxane (PDMS) soft segment molecular weight of the copolymer (1500, 3000 and 11,000 g/mol). All copolymers had a constant urea hard segment content of 15% by weight. Samples were prepared by three different methods, which were; solution casting, spin-coating and electrospinning. XPS spectra clearly showed transformation of PDMS into SiO 2 and sub-oxides, which increased gradually with increasing UV/O exposure time. XPS and ATR-FTIR measurements also revealed that the copolymer based on PDMS-11000 displayed the highest amount of SiO 2 formation and overall surface modification. Static water contact angle values of the spincoated silicone–urea copolymer films decreased significantly from 110° to 43° after 3 h of UV/O exposure. Interestingly, the Hydrophobicity of the electrospun fibers was retained under similar UV/O exposure conditions, most probably due to the preserved surface roughness. Hydrophobic Recovery was evaluated after 2 months of storage at ambient conditions. The slowest Recovery was observed for spin-coated copolymer film based on PDMS-11000, due to higher amount of surface oxidation and formation of a thicker SiO 2 barrier layer.
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Hydrophilization of silicone–urea copolymer surfaces by UV/ozone: Influence of PDMS molecular weight on surface oxidation and Hydrophobic Recovery
Polymer, 2013Co-Authors: Sevilay Bilgin, Mehmet Isik, Emel Yilgor, Iskender YilgorAbstract:Abstract Hydrophilization of polydimethylsiloxane–urea copolymer (PSU) surfaces and the extent of Hydrophobic Recovery were investigated as a function of; (i) UV/ozone (UV/O) exposure time, (ii) the aging period after UV/O exposure, (iii) sample preparation method, and (iv) polydimethylsiloxane (PDMS) soft segment molecular weight of the copolymer (1500, 3000 and 11,000 g/mol). All copolymers had a constant urea hard segment content of 15% by weight. Samples were prepared by three different methods, which were; solution casting, spin-coating and electrospinning. XPS spectra clearly showed transformation of PDMS into SiO 2 and sub-oxides, which increased gradually with increasing UV/O exposure time. XPS and ATR-FTIR measurements also revealed that the copolymer based on PDMS-11000 displayed the highest amount of SiO 2 formation and overall surface modification. Static water contact angle values of the spincoated silicone–urea copolymer films decreased significantly from 110° to 43° after 3 h of UV/O exposure. Interestingly, the Hydrophobicity of the electrospun fibers was retained under similar UV/O exposure conditions, most probably due to the preserved surface roughness. Hydrophobic Recovery was evaluated after 2 months of storage at ambient conditions. The slowest Recovery was observed for spin-coated copolymer film based on PDMS-11000, due to higher amount of surface oxidation and formation of a thicker SiO 2 barrier layer.
