Fluorosilicone Polymers Research Articles

Facile and Efficient Synthesis of Fluorosilicone Polymers by Using an Optimized Gradient Ring-Opening Reaction.

Fluorosilicone rubber is essential for sealing in extreme temperatures and non-polar environments due to its exceptional adaptability. However, achieving a high yield of fluorosilicone polymers with medium and high fluorine content remains a challenge. Herein, a facile gradient strategy is developed that involves modifying the method of cyclic monomer addition based on the rate of ring-opening polymerization (ROP), to improve yield and adjust fluorine content precisely. The polymerization process is designed and tailored based on the reaction rates of anionic ring-opening polymerization (AROP) and cationic ring-opening polymerization (CROP) via an efficient gradient strategy. The effects of the polymerization process on the viscosity and yield of vinyl fluorosilicone polymers and hydrofluorosilicone polymers are investigated and optimized. Notably, the as-prepared vinyl-terminated fluoromethylsilane with 60% fluorine content (FMS-Vi-60F) has a high yield (86.6%) and high viscosity (150000 mPa·s) in a short reaction time, which is superior to previous methods. Clearly, the gradient ring-opening method developed in this work provides a facile and efficient synthesis for fabricating fluorosilicone polymers with a high yield and tunable fluorine content.

Facile synthesis of UV-curable fluorosilicone polymers and coatings with good corrosive resistance on account of the reaction of disulfide bonds with vinyl groups

A new UV curing strategy is introduced into the curing field of fluorosilicone polymers. This strategy is predicated on the reaction of sulfur radicals generated from disulfide bonds with vinyl groups under the presence of UV light. Here, we engineered and synthesized a kind of novel fluorosilicone polymers (FS-SS) with disulfide bonds and vinyl groups. The disulfide bonds contained in FS-SS undergo photocleavage under ultraviolet irradiation, generating sulfide radicals, which can interact with vinyl groups to complete the curing reaction. Subsequently, the UV curing behavior of coatings on the basis of the novel polymers and photo-initiator 1173 was investigated by FT-IR spectroscopy and a possible UV-curable reaction mechanism based on disulfide bonds and vinyl groups was proposed. The results showed that curing reactions based on disulfide bonds and vinyl groups can reach a relatively high degree of reaction in a short period of time in terms of reaction rate. However, the lower conversion rate of the reaction may be due to the fact that the sulfur radicals generated by disulfide bonds are more inclined to form disulfide bonds rather than undergo addition reactions with vinyl groups. Subsequently, a series of fluorosilicone coatings with good optical transparency (transmittance above 90 %), good hydrophobicity (the lowest value of surface energy is 21.54 mN/m), lower roughness value (Ra values was in the region of 2.24 nm– 12.2 nm) and high temperature resistance were prepared by utilizing this curing strategy. Furthermore, the applicable experiment of fluorosilicone coatings to protect tinplate as anti-corrosive coatings was also performed. The corrosive resistance results formalize its practical value for possible application as preventive coatings.

Parallel Amperometric and Potentiometric Multianalyte Detection in a Microfluidic System

The adoption of microfluidic technologies in electrochemical biosensor development has enabled quantitative biomarker monitoring that use significantly lower volumes of reagents and samples, miniaturized electrodes, and inexpensive fabrication techniques, while presenting opportunities for multianalyte detection. We describe the fabrication of amperometric and potentiometric biosensors on a multichannel, platinum screen-printed electrode (SPE) and demonstrate their operation in parallel on a microfluidic multianalyte electrochemical sensor array (µMESA) platform.Working electrodes (WEs) of an SPE were were modified with either enzymes or ion selective membranes (ISMs) for amperometric or potentiometric measurements respectively. Oxidase enzymes were dissolved in an osmium (II) bis(2,2'-bipyridine)chloride-poly(vinylimidazole-allylamine) redox polymer and immobilized on four WEs. The use of this osmium-based electron transfer mediator has been previously reported to lower the oxidation potential of analytes and to improve overall sensor performance. The remaining four WEs were modified by electrodeposition of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), an intrinsically conductive polymer. Solid contact ISMs were prepared by combining ionophores, lipophilic ion exchangers, and a fluorosilicone polymer, and drop casting the mixtures on PEDOT:PSS-coated WEs. Plasticizer-free ISMs improve sensor lifetime by lowering the glass transition temperature and eliminating leaching of plasticizers from the ISM. By utilizing these strategies, we fabricated amperometric sensors for glucose and lactate, and potentiometric sensors for K+ and Ca2+ ions. Glucose is a primary substrate for energy metabolism while lactate is a major metabolite and signaling molecule. K+ ions maintain cell membrane physiology and homeostasis whereas Ca2+ ions serve as messengers during muscle activity and neurotransmission.Sensor characteristics like sensitivity, selectivity, linear range, and operational longevity for each biosensor were assessed using chronoamperometry or chronopotentiometry techniques on a potentiostat/potentiometer instrument. The results indicate that the sensor fabrication strategies described, in combination with our µMESA platform, can be used to measure changes in metabolite concentrations under laminar flow. Ultimately, this versatile technology may provide novel insights into complex physiological and pathological processes in biological systems.

Preparation and characterization of high molecular weight vinyl-containing poly[(3,3,3-trifluoropropyl)methylsiloxane

Prior to crosslinking and vulcanization, fluorosilicone rubber is a linear polymer. This linear polymer contains 3,3,3,-trifluoropropyl methyl siloxane links, a few methyl vinyl siloxane links, and is formed by co-polymerization of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl) cyclotrisiloxane (D3F) with 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (V4) under alkaline conditions. To improve the performance of fluorosilicone rubber, three key points should be considered during the synthesis of vinyl-containing high-molecular-weight linear fluorosilicone polymers (fluorosilicone raw rubber): first, avoid the generation of low molecular weight equilibrium by-products; second, eliminate the influence of impurities; and third, increase the copolymerization participation rate of monomer V4. From the three aspects above, this study optimized the reaction conditions for the synthesis of high-molecular-weight linear fluorosilicone polymers containing vinyl. Various factors influencing polymerization were thoroughly investigated. These factors include the initiation system, accelerator, equilibrium reaction, feeding ratio, feeding sequence, neutralization mode, impurity content, etc.

Room temperature nondestructive encapsulation via self-crosslinked fluorosilicone polymer enables damp heat-stable sustainable perovskite solar cells

Encapsulation engineering is an effective strategy to improve the stability of perovskite solar cells. However, current encapsulation materials are not suitable for lead-based devices because of their complex encapsulation processes, poor thermal management, and inefficient lead leakage suppression. In this work, we design a self-crosslinked fluorosilicone polymer gel, achieving nondestructive encapsulation at room temperature. Moreover, the proposed encapsulation strategy effectively promotes heat transfer and mitigates the potential impact of heat accumulation. As a result, the encapsulated devices maintain 98% of the normalized power conversion efficiency after 1000 h in the damp heat test and retain 95% of the normalized efficiency after 220 cycles in the thermal cycling test, satisfying the requirements of the International Electrotechnical Commission 61215 standard. The encapsulated devices also exhibit excellent lead leakage inhibition rates, 99% in the rain test and 98% in the immersion test, owing to excellent glass protection and strong coordination interaction. Our strategy provides a universal and integrated solution for achieving efficient, stable, and sustainable perovskite photovoltaics.

Design, synthesis and properties of trifluoromethyl polysiloxane oxetane monomers

The oxetane is widely used in cationic photopolymerization, while fluorosilicone polymers combine the advantages of organosilicone and organofluorine. In this study, a series of trifluoromethyl polysiloxane oxetane monomers with different chain length (XE-FSin, n = 3, 6, 9) was designed and synthesized by a simple two-step synthesis procedure, and low-cost and easily available raw materials. XE-FSin exhibited good photopolymerization property and ability to boost the photopolymerization of the alicyclic epoxy monomers, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (E4221) and 1,2-epoxy-4-vinylcyclohexane (VOH). The final conversions of the alicyclic epoxy group and the oxetane group of the systems with XE-FSi3 after 900 s of the irradiation reached up to 80.8 % and 75.2 %, respectively. The introduction of XE-FSin improved the thermal stability, glass transition temperature (Tg) and tensile property of the UV-cured film because of the presence of trifluoromethyl group and polysiloxane chain. The surface of the UV-cured film of XE-FSi9-0.5 % system had the highest water contact angle that was 108.4°. The tensile strength and elongation at break of the UV-cured film of XE-FSi3-0.5 % system were 0.85 MPa and 67.87 %, respectively, and three times more than those of XE-FSi3-0 % as the blank control. With the increase of the chain length of XE-FSin, the Tg, adhesion force and pencil hardness of the UV-cured film had no significant changes.

A facile preparation method of UV rapid curing fluorosilicone coatings with good hydrophobicity and excellent corrosion resistance based on thiol-ene click reaction

As reported herein, UV rapid curing fluorosilicone coatings with good hydrophobicity and corrosion resistance were developed with a novel fluorosilicone polymer possessing thiol functional groups (PTFPMS-SH) and a series of fluorosilicone polymers having different vinyl content (PTFPMS-Vi). The chemical structures of the prepared polymers (PTFPMS-Vi and PTFPMS-SH) were first characterized by FT-IR (fourier infrared transform spectroscopy) and 1H NMR (nuclear magnetic resonance), confirming the successful synthesis of expected polymers. Subsequently, the curing process, basic properties, thermal properties and surface properties of the UV cured fluorosilicone coatings were investigated. Moreover, the application of the fluorosilicone coatings as anti-corrosion coatings in the field of circuit boards were also preliminarily explored. The results show that the photocuring reaction based on the thiol-ene reaction for the preparation of fluorosilicone coatings is very effective because the conversion rate of carbon‐carbon double bonds can reach more than 95 % within 5 s under UV irradiation. These obtained fluorosilicone coatings exhibit transparency higher than 90 %. The contact angle of the obtained coatings ranges from 100° to 110°, showing their excellent hydrophobicity. Furthermore, the fluorosilicone coatings with outstanding corrosion resistance show their potential application worth as protective coatings for electronic devices.

Preparation of Fluorosilicone Triblock Copolymers and Microphase Separation Behavior on Surfaces

Fluorosilicone polymer is a new type of structure of the fluorine silicon block polymer. Because it combines the excellent properties of organic silicone and organic fluorine compounds, it has a wide range of uses and becomes a hot issue in the field of materials. In the paper, A series of novel poly(2,2,3,4,4,4-hexafluorobutyl methacrylate)-block-poly(dimethylsiloxane)-block-poly(2,2,3,4,4,4-hexafluorobutyl methacrylate)s (PHFBMA-b-PDMS-b-PHFBMA) were synthesized by atom transfer radical polymerization (ATRP) with different molecular weight prepared polydimethylsiloxane macroinitiator as raw materials. The effects of the fluorine and silicone content on the hydrophobic and oleophobic properties of prepared triblock copolymers were also investigated. The structure and composition of the copolymers were analyzed and identified by infrared spectroscopy (IR) and nuclear magnetic resonance (NMR). The average molecular weight and molecular weight distribution of the prepared PHFBMA-b-PDMS-b-PHFBMA were evaluated by gel permeation chromatography (GPC). The surface energy of the triblock copolymers was calculated from the contact angle reaches as low as 10.43 mN/m through the Owens-Wendt-Rabel-Kaelble method, with the fluorine content of triblock polymer was 19.0 wt%. Atomic force microscopy (AFM), differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS) indicated that there were Obvious nanoscopically microphase separation on the surface of the prepared triblock copolymers and the fluoride contents in the block polymer of the fluorine silicon block were more likely to migrate to the surface.

Fluorosilicone polymers with tailored mechanical, acid resistant and adhesive properties: Role of ultrasonication and functionally active single walled carbon nanotubes

Abstract Though fluorosilicone polymers (FSP) are known for their excellent solvent resistance and broad service temperature, reports on single walled carbon nanotube (SWCNT) incorporated FSP coatings that are resistant to oxidative environments and at the same time possessing good adhesive characteristics are rare. In this paper we report some interesting results when functionalized single walled carbon nanotubes (FSWCNTs) were incorporated into FSP matrix where the nanotube chosen is the one having minimum defects with the maximum amount of functional groups attached on its surface. Ultrasonication is the process adopted for nanotube incorporation where the conditions were first optimized by subjecting the mixture to ultrasonication for different extent of time. Next, the concentration of FSWCNT in the FSP matrix is varied to optimize the nanotube loading. An ultrasonication time of 30 min and FSWCNT concentration of 0.1% displayed the highest storage modulus values which is taken as the basis for the second part of the study where the optimization of extent of functionalization of SWCNT was validated. Here, FSP nanocomposites were prepared using pristine SWCNT, SWCNT functionalized for 30 min (lower than optimum duration), SWCNT functionalized for 4 h (optimum duration) and SWCNT functionalized for 24 h (higher than optimum duration). Among the nanocomposites, the one containing optimally functionalized SWCNT (that is, SWCNT functionalized for 4 h) displayed superior adhesive properties and resistance to corrosive environment. The reason for this behaviour is established using computational studies where better interaction between FSWCNT and FSP matrix was shown when the nanotubes were functionalized for 4 h. Swelling studies were carried out to prove the role of better interaction of cyclic siloxane units of FSP with hydroxyl functionalities of optimally functionalized SWCNT along with free trifluoropropyl pendants in imparting excellent resistance to corrosive acidic environments. Lap shear strength evaluation on aluminium substrate proved the capability of FSP/FSWCNT nanocomposite as a promising adhesive.

Preparation of hydrophobic organic-silicanano composites

ABSTRACTIn this paper, we use silica nanoparticles modified by methacryloxy propyl trimethoxylsilane (KH570) as the core material, and employ polymers including hexafluorobutyl methacrylate (HFMA), dodecafluoroheptyl methacrylate (DFMA) and acrylic ester as the shell materials to prepare the hydrophobic inorganic–organic hybrid nanocomposites with a seed emulsion polymerization strategy. The size, morphologyandproperties of the core-shell structured nanoparticles are investigated by TEM and SEM. The results showthat the polymer nanocomposite has three concentric layers with silica nanoparticles in the center, acrylic polymer as the internal shell and fluorosilicone polymer as the outmost shell. By controlling the ratio of the silica nanoparticles and monomers, we can achieve each composite particle has the core-shell structure with silica nanoparticles as the core and the thin layer of fluorosilicone polymer as the shell. Compared with the traditional polymer film, the nanocomposite film shows a hydrophobic property with a contact angle of up to 100 degree. Therefore, it is feasible to prepare hydrophobic organic–inorganic nanocomposites using the method proposed here.

Synthesis and Application of Fluorosilicone Polymer

The structure, properties, synthesis methods and application of siloxane fluorinated polyacrylate polymers,side chain fluorinated silicone polymer and fluoro-silicone block copolymers are discussed. Fluorosilicone polymers has excellent physical property such as low and high temperature resistance, hydrophobic oleophobic property, lubricity etc. It is an advanced material.

Rheology, adhesion, and debonding mechanisms in fluorosilicone polymer gels

AbstractPolymer gels are complex materials used in myriad applications and industries including foods, consumer products, and adhesives. We examine the rheology and adhesion characteristics of three fluorosilicone gels of varying equilibrium modulus. Adhesion is studied in terms of confinement and separation velocity or initial strain rate. Further, the role of debonding mechanism on the adhesion properties is also elucidated. At low initial strain rates or low degrees of confinement, interfacial failure dominates while at high initial strain rates or high degrees of confinement bulk cavitation is the dominant debonding mechanism. We also report for the first time a transition region where both interfacial failure and bulk cavitation are observed. The adhesion results are explained in light of the rheological properties of the gels examined. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40034.

Synthesis and thermal stability of hybrid fluorosilicone polymers

Aromatic hybrid fluorosilicones, such as perfluorocyclobutane aromatic polyethers, have higher thermal stability than typical polysiloxanes. While these polyethers decompose by homolytic cleavage of the oxygen–perfluorocyclobutane bond, the enhanced thermal stability of the polyethers may, in part, arise from this oxygen through the anomeric effect. To determine the effect of the ether oxygen on thermal stability, two perfluorocyclobutane aromatic units, one with and one without the oxygen, were modeled. To confirm the results experimentally, a series of hybrid fluorosilicones based on the latter were synthesized by thermocyclodimerization of 1-bromo-4-(trifluorovinyl)benzene, metal–halogen exchange, and condensation with one of 1,3-dichlorotetramethyldisiloxane; 1,7-dichlorooctamethyltetrasiloxane; or chlorine-terminated poly(dimethylsiloxane). The degradation temperature (T1%) was lower (∼240°C) than the comparable polyethers (∼430°C). These results demonstrate the importance of the ether oxygen to the stability of perfluorocyclobutane aromatic polyethers through a number of effects including the anomeric effect and enhancing the strength of the silicon-aromatic bond.

Synthesis and characterization of novel polysiloxane-grafted fluoropolymers

Fluorosilicone polymers combine the properties of both fluorocarbons and siloxanes, yielding materials with unique properties. Novel crosslinked fluorosilicone polymers were synthesized by grafting diisocyanate-terminated polydimethylsiloxane (PDMS) to hydroxyl-functionalized fluoropolymers of poly(tetrafluoroethylene-co-vinyl acetate-co-vinyl alcohol) (PTFE-VAc-VA), as confirmed by elemental bulk and surface analysis. The fluorosilicone polymers containing 34 mol% of TFE were thermally stable with a degradation temperature of 267 °C. Fluorosilicone films were found to be more hydrophobic than the parent, non-grafted fluoropolymers; dynamic advancing and receding water contact angles for PTFE-co-VAc-co-VA-g-PDMS were 104° ± 1° and 61° ± 1°, respectively, whereas for PTFE-co-VAc they were 90° ± 2° and 59° ± 2°. The combined properties of thermal stability and hydrophobicity suggest that these fluorosilicones may be useful for coating and paint applications.Key words: fluoropolymers, fluorosilicone, polydimethylsiloxane, supercritical carbon dioxide.

Fluorosilicone elastomer based on the poly[(3,3,3‐trifluoropropyl)methyl‐siloxane‐co‐(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)methylsiloxane

AbstractFluorosilicone elastomer based on the poly[(3,3,3‐trifluoropropyl)methylsiloxane‐co‐(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)methylsiloxane] was studied. First, the synthesis of fluorosilicone polymer based on the poly[(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)methylsiloxane] (PNFHMS) was examined by the polymerization of 1,3,5‐tris(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)‐1,3,5‐trimethylcyclotrisiloxane (C4F9D3) by sodium hydroxide. On the contrast of the polymerization of the commercially available 1,3,5‐tris(3,3,3‐trifluoropropyl)‐1,3,5‐trimethylcyclotrisiloxane (CF3D3), the polymerization of C4F9D3 with sodium hydroxide resulted in the formation of 1,3,5,7‐tetrakis(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)‐1,3,­5,7‐tetramethylcyclotetrasiloxane : [C4F9CH2CH2(CH3)SiO]4 (C4F9D4) as the major product. It was due to the easy occurrence of the depolymerization by the back‐biting mechanism, because C4F9D4 is more stable ­than 1,3,5,7‐tetrakis(3,3,3‐trifluoropropyl)‐1,3,5,7‐tetramethylcyclotetrasiloxane : [CF3CH2CH2(CH3)SiO]4 (CF3D4). The above result made us to conclude that it was difficult to apply the polymer based on PNFHMS to heat vulcanizable elastomers and to investigate the elastomer based on the poly[(3,3,3‐trifluoropropyl)methylsiloxane‐co‐(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)methylsiloxane]. C4F9D3 and CF3D3 were co‐polymerized successfully by sodium hydroxide and formulated with the silica treated by CF3D3. The use of silica treated with methylsilyl unit failed, because creep‐hardening phenomenon occurred. This elastomer was evaluated about some mechanical properties, and the resistance to organic solvents, and a fuel. The advantage that can be detected from the introduction of [C4F9C2H4‐(CH3)SiO] unit was that the resistance to the polar solvents such as acetone and dimethylformamide was improved. Copyright © 2001 John Wiley & Sons, Ltd.

Surface tension of poly(fluoroalkylsilsesquioxane)s

AbstractPoly(3,3,3‐trifluoropropylsilsesquioxane) (Prf‐T) and poly(3,3,4,4,5,5,6,6,6‐nonafluorohexylsilsesquioxane) (Hxf‐T) were synthesized via the hydrolysis of trichloro‐3,3,3‐trifluoropropylsilane and trichloro‐3,3,4,4,5,5,6,6,6‐nonafluorohexylsilane, respectively. The related resin‐like fluorosilicone polymers containing dimethylsiloxy units were also prepared. Contact angle measurements were carried out after the polymers were crosslinked by condensation. The solid surface tensions were determined from the combined Owens‐Wendt/Young equation using water and methylene diiodide contact angles. The value obtained for Prf‐T resin (20 mN/m) is similar to the value for poly(methylsilsesquioxane) as the unfluorinated silsesquioxane analogue (21,5 mN/m). On the other hand, the Hxf‐T polymer shows a very low surface tension, 7 mN/m, lower than that of the corresponding polysiloxane with linear structure, poly[methyl‐(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)siloxane]. The surface tensions based on other approaches, such as the Girifalco‐Good‐Fowkes‐Young equation and the Zisman critical surface tension of wetting, were also determined.

Nonionic Fluorosilicone Surfactants

New fluorosilicone surfactants have been prepared. The focus has been on branched disiloxane and trisiloxane hydrophobes having 3,3,3-trifluoropropyl and 3,3,4,4,5,5,6,6,6-nonafluorohexyl radicals with poly(oxyethylene) hydrophiles. Their performance as aqueous surfactants was evaluated and compared to conventional methylsiloxane surfactants of similar structure. Critical micelle concentrations and equilibrium and dynamic aqueous surface tensions were measured. The behavior parallels that of the related fluorosilicone polymers in the liquid rather than in the solid state. The trifluoropropyl surfactants are less effective at lowering equilibrium aqueous surface tension, while the nonafluorohexyl surfactants have similar effectiveness to the methyl surfactants. Wettability tests were also carried out on polyethylene films. The wetting power generally correlated with equilibrium surface tension lowering ability.

Surface tension of poly[(1H,1H,2H,2H‐heptadecafluorodecyl)methylsiloxane

AbstractPoly[(1H,1H,2H,2H‐heptadecafluorodecyl)methylsiloxane] (PHDFDMS) was synthesized and the solid surface tension of its cross‐linked films was obtained from water, methylene iodide and various alkanes contact angle data. The value obtained from the Owens and Wendt geometric mean approach using water and methylene iodide data is 7,0 mN/m, the lowest value yet reported for a preformed fluorosilicone polymer. Surface tension values obtained from alkane contact angle data are higher, for example, the Zisman critical surface tension of wetting is 14,9 mN/m. These values fit the trends of other similar fluorinated polymers with the exception of a previous report that PHDFDMS has an anomalously high surface tension.

Fluoroelastomers

Abstract The importance of fluorine in polymer chemistry has been known since the discovery of poly (tetrafluoroethylene) in 1938. Highly fluorinated polymers are very stable and have remarkable resistance to oxidative attack, flame, chemicals, and solvents. This stability has been attributed to the strength of the carbon—fluorine bond compared to that of the carbon—carbon bond, to steric hindrance, and to strong Van der Waals forces. The synthesis of elastomeric polymers containing enough fluorine to impart a significant degree of stability was not achieved until the mid-1950's. Since then a multitude of fluoroelastomers have been reported, but, of these, only certain copolymers of vinylidene fluoride, and fluorosilicone polymers have become commercially important. Recently, however, perfluoroelastomers based on perfluoro (alkyl vinyl ethers) and tetrafluoroethylene have been shown to possess an even greater degree of high temperature stability than do the fluoroelastomers hitherto available. These perfluoroelastomers also are essentially inert to most chemicals and solvents. Copolymers of perfluoro (alkyl vinyl ethers) with partially fluorinated monomers also have been developed that give better flexibility at low temperature. These polymers, now at the developmental stage, appear to be the forerunners of a new generation of superior high-performance elastomers. The discussion that follows will concern firstly, the commercial fluoroelastomers; secondly, those that show commercial promise and might be considered semi-commercial or at the developmental stage but which are available only in limited developmental quantities; and thirdly, those reported in the literature that, so far at least, have been of research interest only. In this last category, polymers will not be included which contain so little fluorine that performance characteristics are not substantially enhanced. For example fluoroprene [poly(2-fluorobutadiene)] and copolymers with nonfluorinated, olefin monomers in which the latter predominate will not be included.

Fluorosilicones as High Temperature Elastomers

Abstract Two types of fluorosilicone polymers are described, the poly(fluoroalkyl)-siloxanes and the hybrid fluorocarbon silicones. The first type, represented by the structure (CF3CH2CH2SiMeO)n exhibits good solvent resistance, thermal and oxidative stability and is commercially available in the form or rubber, sealants and fluids. The second type, is in the research stage and has demonstrated much improved stability especially under confined heating conditions.