Article

Fluoroelastomers: Synthesis, properties and applications

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Abstract

The review seeks to cover recent developments in the area of fluorinated elastomers. It reports that, except for isolated cases, most fluoroelastomers are synthesized by radical co-, ternary or tetrapolymerizations. Hence, after reminding the most known syntheses of fluoroalkenes involved in the preparation of these fluoropolymers and recent achievements of block, graft and alternating copolymers, several academic laws and concepts (e.g. kinetics) of the copolymerization are presented. The section dealing with the synthesis of fluoroelastomers is divided into two parts: the first one covers the preparation of fluorinated copolymers containing tetrafluoroethylene, while the second one extensively describes the preparation of fluoroelastomers based on vinylidene fluoride. This section also points out recent syntheses on novel reactive functional trifluorovinyl or vinyl ether monomers for easy curing of original fluoropolymers. Then, heteroatom-containing fluoroelastomers are briefly summarized. Various methods of curing are reported in the following section while the next one describes ingredients used in formulations of fluoroelastomeric systems. This review also covers compounding and processing of this class of fluoropolymers. Finally, a summary of various properties and applications of fluoroelastomers is presented showing how such products resistant to severe conditions are useful in modern industries.

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... Fluoroelastomers exhibit exceptional chemical resistance 48,49 , and thus serve as a useful benchmark for assessing the performance of our encapsulation approach in extreme pH environments. We fabricated NFC devices encapsulated with fluoroelastomer (thickness: 100 µm) and performed a soaking test at various pH environments (pH 1.5, 4.5, 7.4, and 9.0) (Fig. S10). ...
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Thesis
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Article
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Article
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Chapter
This chapter is an update to the earlier Science of Synthesis contribution describing methods and strategies for the synthesis of 1,1-dihaloalk-1-enes. This update focuses on the preparation and polymerization of 1,1-difluoroalk-1-enes, including trifluorovinyl functional monomers. Radical additions of chain-transfer agents onto commercially available fluoroalkenes are described, followed by their chemical modification to yield original fluorinated monomers. These monomers are further involved in radical (conventional or controlled) copolymerizations with vinylidene fluoride (1,1-difluoroethene) or chlorotrifluoroethene to achieve high-value-added materials.
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Contemporary applications require protection against overheating and electromagnetic radiation interference, preferably with reduced mass and enhanced basic performance, such as flammability or chemical or UV resistance. Materials exhibiting all these functions can be designed, but there is often not just one but several different materials with advanced processing requirements; therefore, a simple manufacturing method providing percolation path formation involving powder mixing and hot pressing of terpolymer comprising tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride monomeric units (THV)-based nanocomposites is presented here. Graphene nanoplatelets (GNPs) and multiwalled carbon nanotubes (MWCNTs) were used as fillers to improve the basic matrix properties. The addition of the carbon fillers yielded electromagnetic interference (EMI) shielding effectiveness SE TOT = 23 dB for the GNP filler, SE TOT = 17 dB for the MWCNT/GNP filler, and SE TOT = 7.4 dB for the one wt% MWCNT filler (for a 1 mm sample thickness at 5 GHz). The best series (GNP-based) was also subjected to further investigations: the thermal conductivity reached κ = 1.65 W/mK, providing an over 800% enhancement, and simultaneously, the electrical conductivity reached σ = 1.49 S/cm. Moreover, comprehensive studies of structural and thermal properties were carried out for all series, including filler dispersion analysis.
Chapter
Fluorinated elastomers (FEs) are unique materials bearing exceptional properties and involved in High Tech applications (electronics, car, aerospace, and petrochemical industries and microelectronics) where they resist to stringent conditions, showing peculiar softness and resilience over a wide range of temperatures. This article mainly reports on (per)fluorocarbon elastomers, fluorophosphazenes, fluorosilicones, and perfluoropolyethers as well as controlled thermoplastic elastomers for which several properties and applications are provided.
Article
The aging behavior and degradation mechanism of fluoroelastomers (FKM) after exposure to thermal air, commercial lubricating oil, and the corresponding base oil at elevated temperatures were investigated. The FKMs immersed in oil and exposed to air are denoted by FKM‐O and FKM‐A, respectively. The crosslinking densities of the samples were determined by equilibrium swelling and dynamic mechanical analyses, and the results were different. Compared to the performances of FKM‐A, noticeable changes in the mechanical and swelling performances of FKM‐O were observed, attributed to the severe deterioration induced by both the lubricating oil and the high‐temperature. The FTIR results revealed that the dehydrofluorination induced by the oil caused the fracture of the CF bonds, and the degradation of the oil itself exerted negative impacts on the properties of the FKM. The findings of this study will facilitate the development of FKMs with degradation‐resistant properties for various applications.
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Suspensions of magnetic particles with diameters in the nanometer range exhibit longterm sedimentation stability as well as the possibility of magnetic field induced control of their properties and flow. One of the most famous field induced effects is the change of viscosity of the fluids due to the action of magnetic influences. An explanation of these effects on basis of microscopic models is a challenging field of actual experimental and theoretical research. Within this article the state of knowledge on magnetoviscous effects in magnetic fluids will be summarized and in particular the experimental methods used to obtain related results will be discussed.
Article
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Several fluorocarbon polymers were irradiated with Co/sup 60/ gamma radiation at doses up to 10/sup 22/ ev/g. The polymers studied included polytetrafluoroethylene, polytrifluoroethylene, polychlorotrifluoroethylene, a copolymer of tetrafluoroethylene with hexafluoropropylene, and several rubbery vinylidene fluoride copolymers. G-values were measured for volatile products, for free radicals detected by electron spin resonances, and, in the case of polychlorotrifluoroethylene, for scissions. The course of degradation or crosslinking was followed by zero-strength-time and tensile-strength measurements. It was found that for polytetrafluoroethylene and its hexafluoropropylene copolymer the presence of air accelerated scission drastically. The mechanism of the radiation-induced changes is discussed in terms of free-radical intermediates. (auth)
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The synthesis of a new fluorinated bis-silalkylene polysiloxane is achieved in three steps: hydrosilylation of a vinylchlorosilane by a fluorinated dihydrosilane, hydrolysis of the subsequent bis-chlorosilane and polycondensation of the bis-silanol issued from hydrolysis.All the products are identified by I.R., 1H, 19F and 29Si NMR spectroscopy. The thermal properties of this new kind of fluorosilicone are evaluated by Differential Scanning Calorimetry (DSC) and by Thermogravimetric analysis (TGA) and they are compared to other previously prepared fluorosilicones. The new polymer is comparable to the classical poly trifluoropropylmethylsiloxane but it is much less thermostable than our previous hybrid fluorosilicones.
Article
Two types of fluorosilicone polymers are described, the poly(fluoroalkyl) siloxanes and the hybrid fluorocarbon silicones. The first type, represented by the structure (CF//3CH//2CH//2SiMeO)n exhibits good solvent resistance, thermal and oxidative stability and is commercially available in the form of rubber, sealants and fluids. The second type, of a complex molecular structure, is in the research stage and has demonstrated much improved stability especially under confined heating conditions.
Article
Kinetics of homopolymerization of some substituted nitrostyrenes and their copolymerization with styrene has been studied. The contributions of electronic effect of substituents on activity of nitrostyrenes under study were separated using the derivation of one- and two-factor correlations of rate constants of homo- and copolymerization and σ-constants of substituents. The dependence of polarity and resonance stabilization of these monomers on the donor-acceptor properties of substituents was shown.
Article
The development of two new fluoroelastomers, FKM-5927 and FKM-5958, and their improvement in performance over current commercially available solvent-resistant type fluoroelastomers is highlighted. FKM-5927 shows improved processability and room temperature compression set resistance, maintaining the excellent fluids resistance associated with peroxide curing. FKM-5958 shows excellent low temperature flexibility and compression set resistance maintaining the outstanding fluids resistance of the solvent-resistance type fluoroelastomers.
Article
A discussion is presented of the influence of equipment on processing parameters and shapes. In addition, the effect of temperature and processing aids are assessed. It is shown that higher screw speeds result in higher output and higher die swells. An important effect is observed for die swell after oven post cure. It confirms that stress is very much dependent on die length and that longer die lengths result in lower swells.
Article
Reactivity of nitro- and aminosptyrenes in the course of radical copolymerization with styrene was considered. Copolymerization constants and microstructure of binary and ternary copolymers. m-nitrostyrene-m-aminostyrene, m-nitrostyrene-p-aminostyrene, m-nitrostyrene-p-dimethylaminostyrene, p-nitrostyrene-m-aminostyrene, p-nitrostyrene-p-aminostyrene, p-nitrostyrene-p-dimethylaminostyrene, styrene-p-nitrostyrene-p-aminostyrene, styrene-p-nitrostyrenes-p-dimethylaminostyrene, styrene-p-nitrostyrene-m-aminostyrene, were determined. The influence of substituents on reactivity of nitro- and aminostyrenes, microstructure of macromolecular chains of the copolymers formed, their viscosity and solubility, was shown.
Article
When fluoroelastomers were introduced to the industry the emphasis was on heat and fluid resistance and processability was considered less important. Since that time huge advances have been made and some modern fluoroelastomers can be processed with an ease approaching that of nitrile rubber. Recent developments in polymer design, curing and process aid technology have resulted in the basis for a new range of Viton terpolymers which will allow shorter cycle times and reduced mould fouling/ sticking with no adverse effect on physical properties over currently available types.
Article
New perfluorinated thermosetting resins which exhibits high tensile modulus at high temperature are presented. Highly crosslinked polymers were obtained from a divinyl ether, 2-trifluoromethyl-4,6-bis(perfluoro-4-oxa-5-hexenyl)-1,3,5-triazine (TAVE-2) and a trivinyl ether, 2,4,6-tris(perfluoro-4-oxa-5-hexenyl)-1,3,5-triazine (TAVE-3) after bulk radical polymerization and curing. Tensile modulus of TAVE-3 was very high event a t 200 °C. Thermal stabilities of their thermosets were low due to unstable groups produced during polymerization or unreacted trifluorovinyl oxy groups. A prepolymer, poly(perfluoro-1-cyano-4-oxa-5-hexene) (PCNVE), having cyano groups in the side chains was also cured by means of cyclotrimerization of the functional groups.
Chapter
Fluorinated polymers have achieved commercial importance as thermoplastics, elastomers, membranes, and coatings due to their unique combination of properties. The highly fluorinated plastics, in particular, have high thermal stability, low dielectric constant, low moisture absorption, excellent weatherability, low flammability, low surface energy, and outstanding resistance to most chemicals. The presence of only strong1 C—F and C—C bonds in perfluoropolymers imparts a high degree of oxidative and hydrolytic stability which extends to a remarkable degree to less highly fluorinated analogs.
Chapter
The term fluorinated membranes generally refers to ion-exchange membranes composed of perfluorinated polymeric backbones. An overview of both the fundamental properties and the technological aspects of perfluorinated membranes is available.1 The first perfluorinated membranes, Nafion® membranes, were developed and commercialized by Du Pont in the early 1970s. They were made of the perfluorinated sulfonic acid ionomer called XR resin.2 Nafion® was first employed as a separator in fuel cells that were used in space exploration, and then as ion-exchange membranes that opened the way to the innovative electrolytic process for chlor-alkali production.3
Chapter
Although discovered more than 50 years ago, fluoropolymers are still growing in terms of production volume and of introduction of new compositions to meet industrial needs. Also, they still represent an active field of research holding great promise for new discoveries in the form of macromolecules with unusual properties. As a class fluoroelastomers account for less than ten percent of total fluoropolymer production, which is dominated by PTFE (mainly) and related crystalline fluoroplastics (see Chapter 15).
Article
This paper is concerned with a newly developed fluorine containing polymer which has outstanding abrasion, scratch, chemical, and creep resistance, even at high temperatures. It has survived extended use testing at temperatures as high as 500 degree F. The polymer can be prepared by suspension or emulsion copolymerization of hexafluoroisobutylene (HFIB) and vinylidene fluoride (VF//2). Free-radical initiators are used to carry out the desired copolymerization. The discussion contains the following topics: preparation of new fluoropolymer; fluorocopolymer structure; fluorocopolymer properties (tabulated); potential applications (particularly in coating on various substrates).
Article
The history of fluoroelastomer development is briefly traced and the technology of many of today's fluoroelastomer products is discussed. An important theme in current research is the synthesis of fluoroelastomers with improved low temperature properties. The preparation of perfluorinated elastomers from perfluorovinyl ethers with glass transition temperatures as low as minus 76 degree C is discussed. Plasticization of these materials with perfluorinated polyether oils is also described.
Article
The validity of the copolymer composition equation for the copolymerization of macromers with small monomers for the preparation of graft copolymers has been examined. The reactivity ratios of high molecular weight macromers r1 cannot be determined experimentally with sufficient accuracy whereas those of small monomers r2 may be calculated by r2=ln(1-p2)/ ln(1-p1), where p1 and p2 are the respective conversions of the macromer and small monomer. A single experimental datum obtained even at high conversions may be used. The error of the method can be readily calculated.
Article
This paper presents an investigation of the peroxide cure of TFE-P elastomer, including the use of cure promoters and a discussion of the mechanism of the crosslinking reaction. Experimental data are presented which show the C//2F//4-C//3H//6 copolymer is susceptible only to peroxide and is not crosslinked at all by other reagents. The peroxide vulcanization is greatly accelerated by some coagents, and triallyl isocyanurate was found to be the best cure promoter. The vulcanizate obtained by using a combination of alpha , alpha prime -bis-(t-butylperoxy)-p-diisopropylbenzene with triallyl isocyanurate as curative exhibits good mechanical properties together with excellent heat and chemical resistance. The mechanism of the vulcanization reactions seems to involve a chain reaction which greatly increases the efficiency of the vulcanization reaction by the peroxide.
Article
The vinylidene fluoride(VDF)-hexafluoropropylene(HFP) copolymers are well-known fluorocarbon elastomers which have excellent thermal, oil and chemical stability. Due to their inert structure, curing is more difficult compared with the hydrocarbon elastomers such as styrene-butadiene copolymer, acrylonitrile-butadiene copolymer etc. It is known that two curing recipes described below are practically usable for these fluorocarbon elastomers.
Article
New polymer backbones are needed to solve the problem of amine attack. This paper reports on such a new polymer backbone. In the first part of this article, the backbnone chemistry of fluorocarbon elastomers is discussed. In the second part, a new experimental polymer, with a proprietary cure system is presented. In the final part of this paper, experimental data is presented that display the excellent chemical resistance of this novel polymer system over conventional fluorocarbon elastomers. (from paper)
Chapter
Asahi Chemical started research and development of the ion-exchange membrane chlor-alkali process in 1966. Research was carried out on the effects of the type of ion-exchange group, ion exchange capacity, degree of crosslinking, membrane structure, caustic concentration, and many other parameters on current efficiency, operation voltage, etc. In 1969, a benchscale plant started operation based on a three compartment process using hydrocarbon membrane. Further study on fluorinated monomers and polymers started in 1970, to improve the chemical stability of the membrane. After intensive research and development work, Asahi Chemical filed the basic patents of fluorinated carboxylic acid membrane and carboxylic and sulfonic acid membrane and the related electrolysis processes in 1974 (1 - 8). In April 1975, Asahi Chemical started operation of a membrane chlor-alkali plant with a capacity of 40,000 MT/Y of caustic soda using Nafion perfluorosulfonic acid membrane. In 1976, this membrane was replaced by perfluorocarboxylic acid membrane
Article
Since the discovery more than 50 years ago of the first fluoropolymer, poly(tetrafluoroethylene), many fluorinated polymers have been developed. Their unique properties-ie high thermal stability and chemical inertness-make them suitable for use in various applications-in artificial joints, blood vessels etc; in fabrics, rendering them resistant to oil, water, and stains; in polyeletrolytes and electrical insulation; in lubricating oils and greases; in lenses and optical fibres; in sports clothing and space suits; and in bearings, valves, and gaskets.
Article
Recent advances in the automotive, petroleum, and energy-related industries have created applications for high-performance elastomers, which often require chemically resistant elastomers with improved high-temperature operating capability. Fluoroelastomers are uniquely capable of withstanding high temperatures in conjunction with aggressive chemicals, fuels, and lubricants. While a number of reviews concerning fluoroelastomers have been published in the last three years, this paper will concentrate on recent developments that have improved fluoroelastomers to meet the requirements of new high-performance applications. Three types of fluorine-containing elastomers—fluorocarbon, fluorosilicone, and fluoroalkoxyphosphazene (phosphonitrilic)—are commercially available. The fluorocarbon elastomers have the highest fluorine content, with general grades having between 53 and 70% fluorine. The high fluorine content of these specialty elastomers imparts exceptional resistance to attack by fuels, oils, and corrosive chemicals. The excellent resistance to high-temperature aging for extended periods of time results in a temperature use range of −46 to 320°C. Fluoro-carbon elastomers are produced in the United States by 3M (“Fluorel” Brand fluoroelastomer) and Du Pont (“Viton” Brand fluoroelastomer) and outside the United States by Montedison (Italy, “Technoflon” Brand fluoroelastomer), Daikin (Japan, “Daiel” Brand fluoroelastomer), and Asahi Glass (Japan, “Aflas” Brand elastomer, a copolymer of tetrafluoroethylene and propylene). Fluorosilicone and fluoroalkoxyphosphazene elastomers contain 30–40% fluorine. Although the fluorine content of these elastomers is less than that of fluorocarbon elastomers, it is high enough to provide moderate chemical resistance to many fluids. The flexible nature of the heteroatoms of the polymer chain backbone in fluorosilicone and fluoroalkoxyphosphazene elastomers results in excellent low-temperature flexibility, giving them a temperature use range of −54 to 230°C. Fluorosilicone elastomers are produced by Dow Corning (“Silastic”) and General Electric (“FSE”), while fluoroalkoxyphosphazene elastomers are produced by Firestone (“PNF”). This paper is a discussion of developments in fluorocarbon elastomer technology that have led to successful use in demanding applications which require high-performance elastomeric parts. Typical properties of fluorocarbon elastomers and improved properties resulting from cure system development and variations in the fluorine content of this type of elastomer will be presented. Applications for fluorocarbon elastomers in the automotive, petroleum, and energy-related industries will be illustrated.
Article
Resistance of polymers to hydrazine-type fuels, Hybaline A-5, nitrogen tetroxide, and fluorine-containing oxidizers was investigated. Elastomers found suitable for application in hydrazine-type fuels and Hybaline A-5 environments are butyl and ethylene propylene rubbers. Carboxy-nitroso rubber is recommended for long term exposure to nitrogen tetroxide at 165° F while resin-cured butyl rubber is satisfactory for limited application. Fluorocarbon plastics and silicone rubber are most suitable for use with oxygen difluoride, and Teflon, polyethylene, and ethylene propylene rubber with a perchloryl fluoride-tetrafluorohydrazine mixture. Chlorine trifluoride is a very reactive oxidizer and Teflon, Kel-F 81, and uncured nitroso rubber gum are suitable only for limited application.
Article
The prediction of monomer reactivity ratios is greatly improved by the use of the Revised Patterns of Reactivity Scheme. The application of this scheme is described and a table of the necessary parameters for 143 monomers is provided. A check on the parameters is presented which consists of using them to predict r11, necessarily equal to unity.
Article
This paper concerns a study on a fluoroelastomer containing tetrafluoroethylene, propylene and epoxy groups (from a small amount of glycidyl vinyl ether). This provides a room-temperature vulcanizable fluoroelastomer useful as an anticorrosive coating material with good storage stability when dissolved in the proper solvents. The study also includes the high-temperature vulcanization recipe for the terpolymer to facilitate the molding of articles of complex shapes. The mechanical and chemical properties of the high-temperature vulcanizate obtained are similar to those of the tetrafluoroethylene-propylene binary system vulcanized by peroxide.
Article
During the course of evaluation of bis-peroxycarbamates as crosslinking agents for elastomers, hexamethylene-N,N'bis(tert-butyl peroxycarbamate), HBTBP, was found to be suitable as a crosslinker in Viton grades of fluoroelastomers. The subject matter of this paper is the use of HBTBP as a crosslinking agent for fluoroelastomers. Best results were obtained when HBTBP was used as a curative in Viton GF (FKM-G) and this stimulated further studies on the mechanism of crosslink formation in this fluoroelastomer. Compounding studies, nitrogen tests, and crosslink measurements were used to postulate possible routes of crosslink formation based on free-radical processes.
Article
Homopolymerizations and copolymerizations of isopropyl perfluorooctylethyl fumarate (IPFOF) and isopropyl perfluorohexylethyl fumarate (IPFHF) were performed with radical initiators in bulk and in several solvents at 50°C to 150°C. The overall activation energy for the polymerization of IPFHF was 104.2 kJ mol-1. The reduced viscosities (ηsp/C) and glass transition points (Tg) for the polymers were 0.26 dl g-1 (in trifluoroacetic acid at 30°C) and about 42°C, respectively. The monomer reactivity ratios (r1, r2) in the copolymerizations of IPFOF (or IPFHF) with styrene or methyl methacrylate, and Alfrey-Price Q, e values were determined. Some of the copolymers contained about 10.0 dl g-1 of ηsp/C and about 70°C of Tg.
Article
This is a comprehensive review of knowledge related to fluorine-containing polymers of rubbery types. The following topics are discussed in detail - monomers and polymerization; compounding and processing; vulcanizate properties of ″Kel-F″ elastomers, ″Technoflon″ , ″Silastic″ LS brand fluorosilicone rubber, ECD-006 perfluoroelastomer, carboxynitroso elastomers, and triazine elastomers. Applications of fluorocarbon and fluorosilicone elastomers are indicated.
Article
In the reported study of curing mechanism of fluoroelastomers with peroxide, the cure system comprise an aliphatic peroxide, an appropriate coagent, and an acid acceptor. The preferred coagent is triallylisocyanurate but other compounds having two or three olefinic groups attached to hetero atoms such as N, Si, or O are also effective. The concentration of the curesite monomer affects the rate, state, and stability of the cure. A cure mechanism is proposed in which the initiation step involves radical formation from peroxide decomposition and addition of the radicals to the coagent. Propagation involves the abstraction of bromine atoms from polymer molecules by coagent radicals to give fluorocarbon polymer radicals, which, in turn, add to coagent molecules to generate new radicals. This type of mechanism is supported by the cure characteristics, by the nature of the coagents, by analysis of the volatile by-products emitted during the cure, and by ESR data on model compounds.
Article
This is a bibliography-based review of theory and practice of alternating copolymerization in which alternating copolymers can be prepared by several methods, which may be classified in two categories; one is the alternating addition of monomers in copolymerization and the other is the copolymerization via a 1:1-intermediate or a stable monomer complex composed of two monomer units. The survey is presented under headings - principle of alternating copolymerization; alternating copolymerization of donor monomer and acceptor monomer; donor-acceptor monomer complex with complexing agent; alternating copolymerization of olefin and diolefin by Ziegler-type catalyst; alternating copolymerization of cyclic monomer via zwitterion intermediate; property and application of alterenating copolymers (glass transition temperature of acrylonitrile-butadiene alternating copolymer, melting point and tensile properties).
Article
A brief description of the synthesis and characterization of these new polymers has been presented in the forms of chemical, chromatographical, spectroscopical, physical testing, and rheological studies. The main object of this paper has been to provide an introduction t the art of processing, vulcanization, and reinforcement of these elastomers to produce useful commercial items. These fluoroelastomers can be processed on conventional equipment for dry-mixing rubber. Vulcanization can be effected with either organic peroxides or sulfur-accelerator cure systems. These vulcanizates can be reinforced with silicas, carbon blacks, or silane-treated clays to give stocks with a wide range of modulus, strength, hardness, and service temperatures ( minus 80 to 400 F) in many service fluids and atmospheres. The exceptional solvent resistance, low temperature flexibility, and wide temperature service range indicate that phosphonitrilic fluoroelastomers should find use in items such as O-rings, arctic fuel hose, lip seals gaskets, and vibration damping services.
Article
Light scattering and viscosity measurements of poly(vinylidene fluoride), (PVF2), were made in three solvents; namely, N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP). The following relations between the intrinsic viscosity, [η], (in deciliters per gram) and the weight-average-molecular weight, M̄w, were obtained: [η] = 17,8·10−6 M̄(in DMA at 125°C), [η] = 31,7·10−6 M̄ (in DMF at 125°C) and [η] = 48,8·10−6 M̄ (NMP at 125°C). Treatment of the data by the method of Inagaki et al. indicates that the steric factor, σ, is 1,89, 1,65 and 1,60 in DMA, DMF, and NMP respectively. It is found that the root-mean-square radius of gyration of the chain measured by light scattering is in good agreement with the root-mean-square radius of gyration of the chain calculated by using the viscosity theory of Inagaki et al. The relations between the root-mean-square radius of gyration of the chain in the three solvents and the molecular weight obtained were as follows: 〈S̄2〉 = 2,95·10−1 M̄ (in DMA); 〈S̄2〉 = 8,13·10−2 M̄ (in DMF) and 〈S̄2〉 = 2,82·10−1 M̄ (in NMP). From the estimation of the second viral coefficient, A2, and the values of B (cf. Eq. (6)) obtained from viscosity data, it is concluded that the polymer chains are more extended in DMA than in DMF and NMP.
Article
The weight-average molecular weights of a series of fractions from two structurally different types of perfluoropolyether fluids were determined by low-angle laser light scattering. The limiting viscosity numbers of both sets of fractions were measured in Freon TF® and related to molecular weights. By using established polymer solution theory, the coil dimensions of the molecules were calculated. Samples from both sets of fractions were subjected to analysis by gel permeation chromatography and the coil dimensions were derived by using the principle of universal calibration. Results from both methods agree well. Bulk viscosities and molecular weights were correlated.
Article
Copolymers of methyl-2,3,3-trifluoroacrylate with isobutylene, propylene, ethylene, and n-alkyl vinyl ethers, (the alkyl being ethyl, propyl, butyl) glycidyl vinyl ether, and 2-methoxyethylvinyl ether were prepared by radical solution polymerization using di(isopropoxycarbonyl) peroxide as the initiator. Their structure was that of the alternating order of methyltrifluoroacrylate and the respective vinyl monomer units. The rate of copolymerization and molecular weights of the copolymers were determined by the ratio of both monomers and by the character of the vinyl comonomer. By means of the alkaline hydrolysis of trifluoroacrylate units, the corresponding copolymers of trifluoroacrylic acid were prepared. Their degree of dissociation was characterized by pK values. The rate of alkaline hydrolysis was considerably affected by the copolymer structure. The polymeric materials prepared in this study possessed good thermal stability, and their thermal decomposition did not occur below 300°C.Durch eine mit Diisopropoxycarbonylperoxid initiierte radikalische Lösungspolymerisation wurden Copolymere von Methyl-2,3,3-trifluoracrylat mit Isobutylen, Propylen, Ethylen und n-Alkylvinylethern (wobei Alkyl Ethyl, Propyl oder Butyl bedeutete) hergestellt. Die Struktur der Copolymeren entspricht einer alternierenden Zusammensetzung der Methyltrifluoracrylat- und Comonomer-Einheiten. Die Polymerisationsgeschwindigkeit und die Molekulargewichte sind durch das Verhältnis der beiden Monomeren und durch die Art des Vinylmonomeren bedingt. Die alkalische Hydrolyse der Trifluoracrylateinheiten liefert Copolymere der Trifluoracrylsäure. Der Dissoziierungsgrad der Copolymeren wird durch den pK-Wert charakterisiert. Die Hydrolysegeschwindigkeit ist stark von der Struktur des Copolymeren abhängig. Die Polymeren sind gut beständig gegen höhere Temperaturen, und eine thermische Zersetzung erfolgt erst bei über 300°C.