The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Philippe Cassagnau - One of the best experts on this subject based on the ideXlab platform.
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Compatibilization of silicone/Fluorosilicone blends by dynamic crosslinking and fumed silica addition
Polymer, 2018Co-Authors: T. Métivier, Philippe CassagnauAbstract:Abstract The aim of this work is to study the compatibility of silicone/Fluorosilicone blends by exploring two compatibilization strategies. First, the crosslinking of the blend under shearing conditions leads to a reduction in the size of the Fluorosilicone domain and hence to an effective stabilization of the morphology under shear and long time annealing. The refinement of the morphology in the dynamic crosslinking step is most likely due to a decrease in the viscosity ratio coming from preferential crosslinking of the Fluorosilicone phase. However, the formation of a copolymer between silicone and Fluorosilicone at the blend interface cannot be totally excluded. Secondly, the silicone/Fluorosilicone blend was compatibilized by the addition of silica particles whose surface is hydrophilic or hydrophobic. Fumed hydrophilic silica allows to reduce the size of the Fluorosilicone phase up to 500 nm while its hydrophobic counterpart is ineffective. This observation has been attributed to the specific hydrogen and dipolar interactions of the silicone and the CF3 group with the silanol present on the surface of the hydrophilic silica. The compatibilization mechanism is supposed to be due to a decrease in the interfacial tension and to a reduction of the coalescence phenomenon.
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Foaming behavior of silicone/Fluorosilicone blends
Polymer, 2018Co-Authors: T. Métivier, Philippe CassagnauAbstract:Abstract An alternative approach, based on vinyl-PDMS/Fluorosilicone blends, has been developed to improve the CO2 foaming behavior of silicone elastomers. For this purpose, a dynamic crosslinking process has been used to compatibilize these silicone blends and to improve their strain hardening behavior under biaxial deformation. As a result, fine cells (65 μm) have been achieved using gaseous CO2 in a one-step batch foaming process. Actually, the dispersed Fluorosilicone domains act as nucleating sites allowing the formation of higher nuclei densities which reduce the overall bubble size by competitive nuclei growth. This new formulation strategy has allowed us to develop silicone foams with equivalent properties (cell and foam densities) to foams prepared by supercritical CO2.
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foaming behavior of silicone Fluorosilicone blends
Polymer, 2018Co-Authors: T. Métivier, Philippe CassagnauAbstract:Abstract An alternative approach, based on vinyl-PDMS/Fluorosilicone blends, has been developed to improve the CO2 foaming behavior of silicone elastomers. For this purpose, a dynamic crosslinking process has been used to compatibilize these silicone blends and to improve their strain hardening behavior under biaxial deformation. As a result, fine cells (65 μm) have been achieved using gaseous CO2 in a one-step batch foaming process. Actually, the dispersed Fluorosilicone domains act as nucleating sites allowing the formation of higher nuclei densities which reduce the overall bubble size by competitive nuclei growth. This new formulation strategy has allowed us to develop silicone foams with equivalent properties (cell and foam densities) to foams prepared by supercritical CO2.
T. Métivier - One of the best experts on this subject based on the ideXlab platform.
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Compatibilization of silicone/Fluorosilicone blends by dynamic crosslinking and fumed silica addition
Polymer, 2018Co-Authors: T. Métivier, Philippe CassagnauAbstract:Abstract The aim of this work is to study the compatibility of silicone/Fluorosilicone blends by exploring two compatibilization strategies. First, the crosslinking of the blend under shearing conditions leads to a reduction in the size of the Fluorosilicone domain and hence to an effective stabilization of the morphology under shear and long time annealing. The refinement of the morphology in the dynamic crosslinking step is most likely due to a decrease in the viscosity ratio coming from preferential crosslinking of the Fluorosilicone phase. However, the formation of a copolymer between silicone and Fluorosilicone at the blend interface cannot be totally excluded. Secondly, the silicone/Fluorosilicone blend was compatibilized by the addition of silica particles whose surface is hydrophilic or hydrophobic. Fumed hydrophilic silica allows to reduce the size of the Fluorosilicone phase up to 500 nm while its hydrophobic counterpart is ineffective. This observation has been attributed to the specific hydrogen and dipolar interactions of the silicone and the CF3 group with the silanol present on the surface of the hydrophilic silica. The compatibilization mechanism is supposed to be due to a decrease in the interfacial tension and to a reduction of the coalescence phenomenon.
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Foaming behavior of silicone/Fluorosilicone blends
Polymer, 2018Co-Authors: T. Métivier, Philippe CassagnauAbstract:Abstract An alternative approach, based on vinyl-PDMS/Fluorosilicone blends, has been developed to improve the CO2 foaming behavior of silicone elastomers. For this purpose, a dynamic crosslinking process has been used to compatibilize these silicone blends and to improve their strain hardening behavior under biaxial deformation. As a result, fine cells (65 μm) have been achieved using gaseous CO2 in a one-step batch foaming process. Actually, the dispersed Fluorosilicone domains act as nucleating sites allowing the formation of higher nuclei densities which reduce the overall bubble size by competitive nuclei growth. This new formulation strategy has allowed us to develop silicone foams with equivalent properties (cell and foam densities) to foams prepared by supercritical CO2.
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foaming behavior of silicone Fluorosilicone blends
Polymer, 2018Co-Authors: T. Métivier, Philippe CassagnauAbstract:Abstract An alternative approach, based on vinyl-PDMS/Fluorosilicone blends, has been developed to improve the CO2 foaming behavior of silicone elastomers. For this purpose, a dynamic crosslinking process has been used to compatibilize these silicone blends and to improve their strain hardening behavior under biaxial deformation. As a result, fine cells (65 μm) have been achieved using gaseous CO2 in a one-step batch foaming process. Actually, the dispersed Fluorosilicone domains act as nucleating sites allowing the formation of higher nuclei densities which reduce the overall bubble size by competitive nuclei growth. This new formulation strategy has allowed us to develop silicone foams with equivalent properties (cell and foam densities) to foams prepared by supercritical CO2.
Miguel F. Refojo - One of the best experts on this subject based on the ideXlab platform.
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Intravitreal silicone and Fluorosilicone oils: pathologic findings in rabbit eyes.
Acta Ophthalmologica, 2009Co-Authors: J. Carlos Pastor, María I. López, M.a. Saornil, Miguel F. RefojoAbstract:The effects of medical-grade intraocular silicone and commercial-grade Fluorosilicone oils were studied in rabbit eyes. The experimental model consisted of lensectomized and vitrectomized eyes that did not undergo further treatment (Group 1), and three groups of lensectomized and vitrectomized eyes that were injected intravitreously 3 months earlier with medical-grade silicone oil of 1000 cs (Group 3), and 10 000 cs (Group 4). The silicone oil-injected eyes developed proliferative membranes. The Fluorosilicone oil caused an intravitreous inflammatory reaction with vacuolated macrophages present around the oil that may have been due to the higher concentration of low-molecular-weight components found in the oil.
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Histopathology of rabbit eyes with silicone-Fluorosilicone copolymer oil as six months internal retinal tamponade
Experimental Eye Research, 2005Co-Authors: Motoaki Doi, Miguel F. RefojoAbstract:Abstract Silicone-Fluorosilicone copolymer oil has low viscosity (175–185 cSt) and is heavier than water (density, 1·16 g cm−3). Short term retinal tolerance (within 2 months) of the silicone-Fluorosilicone copolymer oil has been reported to be the same as that of currently used intraocular silicone oil. Ocular response of the purified silicone-Fluorosilicone copolymer oil were examined clinically and histopathologically from 2·5 months to 6 months after vitreous cavity injection in rabbit phakic eyes, and compared the oil tolerance with that of purified silicone oil (0·97 g cm−3, 5000 cSt). The effects in anterior chamber also were examined within 4 weeks of the silicone-Fluorosilicone copolymer oil injection in different rabbits. Silicone-Fluorosilicone copolymer oil recovered from the vitreous cavity at 6 months was analysed for cholesterol and retinol content by high performance liquid chromatography. Because of its low viscosity, silicone-Fluorosilicone copolymer oil was easy to inject and remove from the vitreous cavity with a 20-G needle. After the vitreous injection, discrete droplet formation by the silicone-Fluorosilicone copolymer oil occurred more easily than by silicone oil. Medullary ray detachment was seen in a silicone oil-, and some silicone-Fluorosilicone copolymer oil-injected eyes at 4–6 months. Histopathologically, after 3–6 months disappearance of outer plexiform layer and disorganization of the photoreceptor layer of silicone oil-, and silicone-Fluorosilicone copolymer oil-injected eyes were seen in the superior and the inferior retina, respectively. Migration of the photoreceptor cell nuclei to the photoreceptor layer was found in the inferior retina of silicone-Fluorosilicone copolymer oil-injected eyes at 5–6 months. Small droplets ingested by mononuclear cells were found in the vitreous cavity or preretina at 4–6 months in silicone-Fluorosilicone copolymer oil-injected eyes. After the anterior chamber injection, silicone-Fluorosilicone copolymer oil induced endothelial cell damage in the area where the oil contacted continuously. Retinol and cholesterol were identified in silicone-Fluorosilicone copolymer oil removed from the vitreous cavity. Silicone-Fluorosilicone copolymer oil may be useful as an intraoperative device in retinal detachment surgery and as a short term (up to about 2 months) retinal tamponade but we do not recommend it for long term retinal tamponade.
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Histopathology of rabbit eyes with intravitreous silicone-Fluorosilicone copolymer oil.
Experimental Eye Research, 1994Co-Authors: Motoaki Doi, Miguel F. RefojoAbstract:Silicone-Fluorosilicone copolymer oil is characterized by being heavier than water (density, 1.16 g cm-3) and low viscosity (175-185 centistokes) compared with currently used intraocular silicone oils (density, 0.97 g cm-3 and 1000-5000 centistokes). This oil is potentially useful as an operative tool and a tamponade on the inferior retina in complicated retinal detachment. We evaluate the ocular response clinically and histopathologically within 8 weeks in rabbit phakic eyes to the purified silicone-Fluorosilicone copolymer oil after vitreous cavity injection, and compared the oil tolerance with purified silicone oil (0.97 g cm-3, 5000 centistokes) and perfluorotetradecahydrophenanthrene for ophthalmic use (Vitreon, 2.03 g cm-3, 8.03 centistokes) which are currently used as operative tools and as internal retinal tamponade agents in retinal detachment surgery. Because of their low viscosity, silicone-Fluorosilicone copolymer oil and perfluorotetradecahydrophenanthrene were easier to inject into the eye than silicone oil. Silicone-Fluorosilicone copolymer oil and perfluorotetradecahydrophenanthrene occupied the inferior portion in the eye, and silicone oil occupied the superior portion. Fewer discrete oil droplets and weaker vessel attenuation of medullary rays than in the perfluorotetradecahydrophenanthrene-injected eyes were seen in silicone-Fluorosilicone-copolymer-oil-injected eyes. Histopathologically, all retinas injected with silicone-Fluorosilicone copolymer oil were normal within 4 weeks. The silicone-Fluorosilicone copolymer oil dispersion did not induce histopathological changes within 8 weeks. However, thinning or disappearance of the outer plexiform layer was seen in the inferior retina in some silicone-Fluorosilicone-copolymer-oil-injected eyes at 6-8 weeks. A similar effect was found in the superior retina of a silicone-oil-injected eye at 8 weeks. More severe changes such as thinning or disappearance of the outerplexiform layer, thinning and disorganization of the photoreceptor layer, and migration of the receptor cell nuclei to the photoreceptor layer were found in the inferior retina of perfluorotetradecahydrophenanthrene-injected eyes after 2 weeks. Intraocular silicone-Fluorosilicone copolymer oil tolerance until about 2 months post-injection is similar to silicone oil and better than perfluorotetradecahydrophenanthrene. Silicone-Fluorosilicone copolymer oil may be useful intraoperatively and as a temporary vitreous substitute in cases of inferior retinal detachment.
Santanu Chattopadhyay - One of the best experts on this subject based on the ideXlab platform.
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The synergistic effect of Fluorosilicone and silica towards the compatibilization of silicone rubber and fluoroelastomer based high performance blend
Journal of Polymer Research, 2020Co-Authors: Sipra Khanra, Debabrata Ganguly, Sanjoy Kumar Ghorai, Debottam Goswami, Santanu ChattopadhyayAbstract:Fluoroelastomer and silicone rubber lie in the two different poles of elastomer family in terms of polarity. Hence, combining them in a single material and making it as at least technologically compatible substance is a great challenge. In this article, the compatibilization effect of Fluorosilicone rubber (block copolymer) (trifluoropropylpolydimethylsiloxane) with various loading of modified silica filler on the novel advanced polymer architecture based fluoroelastomer (copolymer of hexafluoropropylene, vinylidene fluoride, and tetrafluoroethylene) and silicone rubber (poly methylvinylsiloxane) blends has been studied in details. The mechanical properties show significant improvement at room temperature (13%) and remarkably more at high temperature (54%) for the compatibilized system. Tan delta peak shifting in DMA study indicates better compatibilization for 2.5 phr loading of Fluorosilicone and 15 phr loading of silica at 50/50 blend ratio. The reduction in domain size (from ⁓3 μm to ⁓200 nm) of the fluorocarbon phase by the synergistic effect of silica and Fluorosilicone proves the decrease in interfacial tension and better compatibilization. This blend can be judiciously applicable in the sealing system as oil and fuel resistant O-rings and gaskets for a very wide range of temperature.
Yukun Chen - One of the best experts on this subject based on the ideXlab platform.
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thermoplastic vulcanizate based on poly vinylidene fluoride and methyl vinyl silicone rubber by using Fluorosilicone rubber as interfacial compatibilizer
Materials & Design, 2015Co-Authors: Yanpeng Wang, Baofeng Lin, Xingquan Liang, Yukun ChenAbstract:Abstract To successfully fabricate a thermoplastic vulcanizate (TPV) based on poly (vinylidene fluoride) (PVDF) and high loading level of methylvinyl silicone rubber (MVSR), stabilizing the phase structure during blending is a challenge due to the distinct interface properties of the two materials. Herein, we report a feasible method to fabricate a desired PVDF/MVSR TPV by using Fluorosilicone rubber (FSR) as an interfacial compatibilizer. We found that the FSR was self-assembly migrated from MVSR phase toward PVDF phase and finally located at the interface between PVDF and MVSR, forming core–shell-like spherical particles with a rough surface, and surprisingly, the crosslinked rubber particles were connected by fiber-like elastomeric materials which bonded onto the surfaces of the particles. The excellent property of repeat processing of the PVDF/MVSR/FSR TPV with such novel phase morphology makes it a potential alternative of Fluorosilicone rubber in future.