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Fluoroelastomers (FKM) are used to manufacture seals and other rubber devices that can withstand harsh operating conditions, including aggressive media and extreme low and high temperatures. Even though nuclear magnetic resonance, Fourier-transform infrared spectroscopy (FTIR), and chromatographic techniques have been extensively used in the characterization of raw FKM molecules, the identification of cured compounds entails a characterization method that is able to overcome the complexity related to this kind of structure. In this sense, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy can outperform other characterization techniques because it does not require solubilization or any special preparation of the sample. In this study, 10 FKM compounds were produced in this study utilizing four commercial types of FKM and the fillers carbon black, barium sulfate, and iron oxide. All unfilled-FKM (as received) and their compounds were analyzed by ATR-FTIR with germanium crystal. Between 15 and 25 analyses were performed for all each FKM type sample and their respective compounds. All spectra were analyzed, and the bands were assigned. Findings regarding the interference of the fillers in the spectra were also reported. From relationships between the height of the spectral zones and the bands at 1397 and 1428 cm−1, it was possible to distinguish all sample compositions of FKM types 1, 2, 3, and 5. This study demonstrates that ATR-FTIR has the potential to be utilized as a technique to detect the type of FKM compounds, an important rubber used in harsh industrial applications. Replacing carbon with BaSO4 reduces the tensile at 50% strain of FKM types 1 and 2 composites. FKM types 3 and 5 composites filled with 30 phr of carbon black have a higher tensile at 50% strain than those of FKM type 1. [ABSTRACT FROM AUTHOR]

The combination of fluoropolymer and nano‐thermite has been a research focus in the field of materials in the field of energy and storage in recent years, but it faces the problem of uneven mixing of fluoropolymer and nano‐aluminum powder (nAl). Therefore, it is of great significance to obtain a fluorine/aluminum uniform composite by a solid/solid phase mixing method. In this paper, Pickering emulsions effectively blend difficult‐to‐mix powders of nAl and solid bulk fluoroelastomers on the micro‐ and nanoscale. The emulsion was prepared by Pickering emulsion with an ethyl acetate solution of fluororubber as the oil phase and perfluorocarboxylic acid‐modified nano‐aluminum powder as a surfactant. The effects of oil/water ratio, fluororubber/aluminum ratio, and standing time on the stability of the emulsion were studied. The nano‐aluminum powder/fluororubber composite microspheres were prepared and their morphology, thermal decomposition, and combustion properties were characterized. The results showed that the emulsion prepared with the oil/water ratio of 1:8 and m(fluororubber):m(modified nano‐aluminum powder) of 5:1 had good stability and dispersion. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) results showed that the complex was observed to be regular spherical and the size was about 10 µm, and the composite microspheres prepared by the Pickering emulsion had good. The TG‐DSC results showed that the decomposition of the composite microspheres started at about 450 °C and finished at 519 °C. The composite microspheres prepared in this paper are stable and rapid in exotherm, with a combustion rate of 33 cm s−1 and excellent combustion performance. The Pickering emulsion introduces a new idea for the preparation of thermite by mixing the solid reactants at the micro‐nano level without introducing substances that reduce the energy of the system. [ABSTRACT FROM AUTHOR]

Liquid‐metal embedded elastomers (LMEEs) have been demonstrated to show a variety of excellent properties, including high toughness, dielectric constant, and thermal conductivity, with applications across soft electronics and robotics. However, within this scope of use cases, operation in extreme environments – such as high‐temperature conditions – may lead to material degradation. While prior works highlight the functionality of LMEEs, there is limited insight on the thermal stability of these soft materials and how the effects of liquid metal (LM) inclusions depend on temperature. Here, the effects on thermal stability, including mechanical and electrical properties, of LMEEs are introduced. Effects are characterized for both fluoroelastomer and other elastomer‐based composites at temperature exposures up to 325 °C, where it is shown that embedding LM can offer improvements in thermo‐mechanical stability. Compared to elastomer like silicone rubber that has been previously used for LMEEs, a fluoroelastomer matrix offers a higher dielectric constant and significant improvement in thermo‐mechanical stability without sacrificing room temperature properties, such as thermal conductivity and modulus. Fluoroelastomer‐LM composites offer a promising soft, multi‐functional material for high‐temperature applications, which is demonstrated here with a printed, soft heat sink and an endoscopic sensor capable of wireless sensing of high temperatures. [ABSTRACT FROM AUTHOR]

Layered double hydroxide/graphene oxide (GLDH) composites (SGLDH) modified by 7‐octenyltrimethoxysilane (7‐OTOS) were prepared by co‐precipitation method. The structure and morphology of SGLDH were characterized using x‐ray diffraction, Fourier‐transform infrared spectroscopy (FTIR), x‐ray photoelectron spectroscopy, scanning electron microscopy (SEM), high‐resolution transmission electron microscopy, energy‐dispersive x‐ray spectroscopy, and thermogravimetric analysis. According to the obtained results, 7‐OTOS was successfully grafted onto graphene oxide (GO) and layered double hydroxide (LDH) surfaces. 7‐OTOS was grafted on both GO and LDH surfaces, which is why the amount of LDH loaded on the SGLDH surface was significantly increased compared with that on the GLDH composite. The filler‐matrix interfacial interactions of the SGLDH‐filled fluoroelastomer composites were characterized using contact angle analysis, dynamic mechanical analysis, RPA analysis, FTIR, SEM, and cross‐linking density tests. It was indicated that the interfacial interactions between the SGLDH and matrix were significantly improved, and the SGLDH was well dispersed in the fluoroelastomer composites. In addition, the gas barrier properties and mechanical properties of the fluoroelastomer composites were tested. The carbon dioxide permeability coefficients of the fluoroelastomer composites filled with 10‐phr SGLDH increased by about 32.1% and 20.3%, and the tensile strengths increased by about 47.6% and 27.7%, respectively, compared with those of the fluoroelastomer composites filled with 10‐phr LDH and GLDH. Highlights: SLDH nanocomposites are based on silyl ether linkages to increase LDH loading.Elastomer nanocomposites exhibited interfacial cross‐linking mechanism.Interfacial interactions were exhibited between FKM and SGLDH.FKM/SGLDH exhibited enhanced gas barrier properties (+32%) compared to FKM.FKM/SGLDH exhibited enhanced mechanical properties (+47%) compared to FKM. [ABSTRACT FROM AUTHOR]

The mineralization of fluoroelastomers (FKMs) in superheated water in the presence of potassium hydroxide (KOH) was investigated with the aim of developing a methodology for recycling the fluorine element. Two FKMs—an "uncrosslinked FKM", representing a poly(vinylidene fluoride-co-hexafluoropropylene) (poly(VDF-co-HFP)) copolymer with a VDF/HFP molar ratio of 78/22 and a "crosslinked FKM" consisting of this copolymer (cured by peroxide) and carbon black—were treated. The fluorine content of these FKMs was efficiently transformed into F− ions in the reaction solution using low KOH concentrations (0.10–0.50 M) at 200–250 °C. When the uncrosslinked or crosslinked FKMs reacted with aqueous KOH (0.20 M) at a rather low temperature (200 °C) for 18 h, the fluorine content of these FKMs was completely mineralized (both F− yields were 100%). Although the crosslinked FKM contained carbon black, the fluorine mineralization of the FKM was not inhibited. The addition of Ca(OH)2 to the reaction solutions after the superheated water treatment at 250 °C for 6 h with aqueous KOH (0.50 M) led to the production of pure CaF2, identified using X-ray spectroscopy, with 100% and 93% yields for the uncrosslinked and crosslinked FKMs, respectively. [ABSTRACT FROM AUTHOR]

This work aimed to investigate the CO2 gas barrier and mechanical properties of fluorine rubber nanocomposites filled with Ca/Al layered hydroxide (graphene oxide [GO]/LDH-Ca2Al) modified by GO. GO/LDH-Ca2Al nanocomposite fillers were prepared by depositing Ca/Al layered hydroxide (LDH-Ca2Al) into the surface of alkalized GO (Al-GO). The prepared GO/LDH-Ca2Al nanocomposite fillers and complexes were characterized by Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) for structural and micromorphological characterization. The results showed that GO/LDH-Ca2Al was successfully prepared with strong interactions between Al-GO and LDH, and the compatibility of GO/LDH-Ca2Al nanocomposite fillers with the polymer was significantly improved compared with that of LDH-Ca2Al. Consequently, both the fracture strength (σb) and strain (εb) of GO/LDH-Ca2Al nanocomplexes remarkably increased, and they exhibited excellent mechanical properties. Differential scanning calorimetry and thermogravimetric analysis were used to characterize the thermal stability of GO/LDH-Ca2Al nanocomposite fillers, and GO/LDH-Ca2Al nanocomposite fillers have better thermal stability than LDH-Ca2Al. The reaction products (S-LDH-Ca2Al and S-GO-Ca2Al) of LDH-Ca2Al and GO/LDH-Ca2Al with CO2 were characterized using XRD and TGA, respectively, and the results show that LDH-Ca2Al reacts readily and chemically with CO2, resulting in a lower diffusion coefficient of CO2 in the LDH-Ca2Al nanocomplexes than that of the GO/LDH-Ca2Al nanocomplexes and leading to the destruction of the laminar structure of LDH-Ca2Al, while GO/LDH-Ca2Al has better CO2 resistance stability. GO/LDH-Ca2Al nanocomplexes exhibited a reduced content of hydroxyl groups with pro-CO2 nature exposed on the surface of LDH-Ca2Al, improving the interfacial interaction between the nanofillers and the rubber matrix and enhancing the dispersion of GO/LDH-Ca2Al in the polymers. Moreover, CO2 in the soluble GO/LDH-Ca2Al nanocomposites was significantly reduced, while the diffusion properties demonstrated weak temperature dependence on solubility. The mechanism of the CO2 gas barrier of polymers filled with GO/LDH-Ca2Al was proposed on the basis of the Arrhenius equation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

It has been shown that defect-free Stone–Wales (SW) free few-layer graphene (FLG) can be obtained by carbonizing lignin under conditions of self-propagating high-temperature synthesis (SHS). The obtained few-layer graphene was used as a modifying additive for pyrotechnic compositions. It was found that the addition of 2.5 mass % of few-layer graphene synthesized from lignin to a pyrotechnic complex based on porous silicon and fluoropolymer leads to a significant increase in the combustion intensity of pyrotechnic compositions. [ABSTRACT FROM AUTHOR]

Fluoropolymers are a distinct class of per‐ and polyfluoroalkyl substances (PFAS), high molecular weight (MW) polymers with fluorine attached to their carbon‐only backbone. Fluoropolymers possess a unique combination of properties and unmatched functional performance critical to the products and manufacturing processes they enable and are irreplaceable in many uses. Fluoropolymers have documented safety profiles; are thermally, biologically, and chemically stable, negligibly soluble in water, nonmobile, nonbioavailable, nonbioaccumulative, and nontoxic. Although fluoropolymers fit the PFAS structural definition, they have very different physical, chemical, environmental, and toxicological properties when compared with other PFAS. This study describes the composition, uses, performance properties, and functionalities of 14 fluoropolymers, including fluoroplastics and fluoroelastomers, and presents data to demonstrate that they satisfy the widely accepted polymer hazard assessment criteria to be considered polymers of low concern (PLC). The PLC criteria include physicochemical properties, such as molecular weight, which determine bioavailability and warn of potential hazard. Fluoropolymers are insoluble (e.g., water, octanol) solids too large to migrate into the cell membrane making them nonbioavailable, and therefore, of low concern from a human and environmental health standpoint. Further, the study results demonstrate that fluoropolymers are a distinct and different group of PFAS and should not be grouped with other PFAS for hazard assessment or regulatory purposes. When combined with an earlier publication by Henry et al., this study demonstrates that commercial fluoropolymers are available from the seven participating companies that meet the criteria to be considered PLC, which represent approximately 96% of the global commercial fluoropolymer market. Integr Environ Assess Manag 2023;19:326–354. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Key Points: Fluoropolymers have well‐established safety profiles are thermally, biologically, and chemically stable, negligibly soluble in water, nonmobile, nonbioavailable, nonbioaccumulative, and nontoxic.This study describes 14 fluoropolymers, including fluoroplastics and fluoroelastomers, and presents data to demonstrate that they satisfy the widely accepted polymer hazard assessment criteria to be considered polymers of low concern (PLC).This study, combined with a prior 2018 study of four fluoropolymers, demonstrates that 18 commercial fluoropolymers are available that meet the PLC criteria representative of approximately 96% of the global commercial fluoropolymer market.The study results demonstrate that fluoropolymers are clearly a distinct and different group of per‐ and polyfluoroalkyl substances (PFAS) and should not be grouped with other PFAS for hazard assessment or regulatory purposes. [ABSTRACT FROM AUTHOR]

• In-depth analysis of properties of FKM elastomers before and after aging at long times, high temperatures, and high pressures in water and aggressive fluid. • Holistic investigation approach by concurrently examining mechanical, thermal, and chemical properties alongside swelling behavior. • Investigation of practical environmental effects in water and hydraulic fluid, on degradation of field FKM sample. • Proposed degradation scheme outlining the intricate degradation pathways and integrating findings from mechanical, thermal, and chemical analyses. Fluoroelastomer compositions are used in extreme environments, such as high pressure and high temperature (HPHT), in a wide range of applications in the oil and gas industry. As hydrocarbon production is expanded to deeper formations, and operating temperature and pressure become higher, the material performance of these elastomers becomes more important. Hence, fluoroelastomers face new challenges and require further understanding when these undergo aging. In this study, a practical fluoroelastomer (FKM) composition was aged in deionized water and an alkaline hydraulic fluid up to 31 MPa, 225 °C and 168 hrs. High pressure, high temperature and aging time have deleterious effects on the physical and mechanical properties of FKMs in both the fluids. Spectroscopically, under these conditions, two hydrocarbon-related bands at 2917 and 2850 cm−1 and three fluorocarbon bands at 886, 1158 and 1396 cm−1 in the Fourier Transform Infrared spectra decreased in intensity after aging. The temperature, at which the rate of degradation was maximum, measured through thermogravimetry also decreased under HPHT conditions. It was further observed that the filler particles bound to the rubber leached out during the aging experiment to cause a color change of the fluid. The tensile sheet was delaminated with cracks on the surface under extreme conditions due to rapid changes in the properties of the surface compared to the bulk. Based on the characterization of the aged rubber vulcanizate and the particles leached out into the aging fluid, a mechanism of HPHT aging of FKM vulcanizate is proposed, which would be helpful in designing fluorocarbon compositions in extreme environments. [Display omitted] [ABSTRACT FROM AUTHOR]

The possibility of using fluoroperoxides derived from polyfluorinated di- and tetracarbonyl compounds as vulcanizing agents for SKF-32 and SKF-260 fluororubbers was examined. The vulcanizates obtained are characterized by the tensile strength of up to 5.1 MPa and relative elongation at break of up to 130%. The resistance of the vulcanizates to H2SO4 and H2SO4–HNO3 mixture increases by a factor of approximately 1.5–2, and the resistance to toluene and acetic acid, by 20–30% relative to the vulcanizates obtained from the same rubbers using benzoyl peroxide or Peroxymon F40 as a vulcanizing agent. [ABSTRACT FROM AUTHOR]

Nitrile rubber (NBR) and polysulfides are two classes of polymers known for their resistance against swelling when in direct contact with hydrocarbon-based oils and non-polar solvents. In this study nitrile rubber (NBR) and a cyclic tetrasulfide (CTS) are combined with a goal of achieving a rubber blend that has superior properties than of each component. The role of CTS in the blend is discussed, as it presents several functions. This study represents a fundamental analysis of NBR-CTS blends, starting with polymeric phase analysis by Scanning Electron Microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX). Thermodynamic compatibility studies are deployed in this study to illustrate the materials' compatibility. Mechanical properties with an emphasis on Payne effect were also studied for blends of NBR-CTS. The synergistic effect found between NBR and CTS can be further expanded in a practical application of rapid gas decompression test as a side-by-side comparison for NBR and NBR-CTS blend compounds. This type of polymer blend represents a potential replacement of fluoroelastomers. • Rubber compound based on a polymer blend of ethylene nitrile rubber (NBR) and cyclic tetrasulfide (CTS). • CTS is a reactive low molecular weight polymer, which can act as a sulfur donor and coagent. • Polymer blend represents as a potential replacement of fluoroelastomers. • Rapid gas decompression compound. • Improvement of Payne effect. [ABSTRACT FROM AUTHOR]

The molecular polarizability and dipole moments of the fragments of copolymer fluoroelastomers was evaluated by the quantum chemical method. It was shown that the polarity of fluororubbers is provided by the presence of vinylidene fluoride units. The dynamic mechanical analysis method was used to obtain the frequency and temperature dependencies of the storage modulus E′ and the mechanical loss tangent tan δ of fluororubbers and vulcanizates on their basis. The characteristic features of the influence of the rubbers composition and vulcanization on the mechanical and thermophysical characteristics of elastomers were established. The values of tensile strength and elongation at break were obtained for vulcanizates of the studied fluoroelastomers, as well as the Mooney viscosity and the compression set values. The crucial influence of the rubber polarity and the vulcanization network parameters on the specified parameters was identified. The swelling kinetics of rubbers and vulcanizates on their basis in 1,2-dichloroethane at 50°С was studied. The sorption limitation degree of the solvent at the appearance of the vulcanization network and its parameters were evaluated. It was found that with regard to the reduction in their equilibrium degree and swelling rate in dichloroethane, elastomers go in the following order: SKF-26 > Elaftor 3061R > Elaftor 7075 > Elaftor 1000R, symbatically to the decrease in their polarity. [ABSTRACT FROM AUTHOR]

The preparation of liquid fluoroelastomers that are liquid with excellent mechanical properties remains a challenge. Here, we show a very straightforward method to produce liquid fluoroelastomers by introducing carborane. Carborane-terminated liquid fluoropolymer was synthesized by Steglich reaction of carboxyl-terminated liquid fluoropolymer and 1,7-bis (hydroxy)-carborane. The product is brown, viscous at room temperature and in the semi-solid state. On this basis, HDI Trimer was used as a curing agent to cure liquid fluoroelastomer. Thermogravimetric analysis of the cured products was carried out. The carbon residue rate of the cured product increased from 35% to 58% of the cured product. The results show that the addition of carborane structure can effectively improve the carbon residue rate of liquid fluoroelastomer. The tensile strength, elongation and shore hardness of the cured product were also examined, and the results show that the tensile strength of carborane modified liquid fluorine increased by 463% compared with that before modification, but the elongation at break was reduced by 42%, which was mainly due to the introduction of rigid structure of carborane. At the same time, the solvent resistance test results show that the introduction of carborane structure has little effect on the aviation kerosene resistance and organic solvent resistance of fluororubber, but it can improve its alkali resistance. [ABSTRACT FROM AUTHOR]

Permeation properties of hydrogen gas (H2) into nitrile butadiene rubber (NBR), ethylene propylene diene monomer (EPDM), and fluoroelastomer (FKM) which are the strong candidates for sealing material in H2 energy infrastructures, was quantified using a thermal desorption analysis gas chromatography (TDA GC) and a self-developed diffusion-analysis program. The samples were charged with H2 in a high-pressure chamber for 24 h then decompressed into atmosphere, and the mass of H2 released from the sample was measured as a function of elapsed time after decompression. The developed program calculated the total charging amount C0 and diffusivity D, which were then used to calculate the H2 solubility S and permeability P for variation of pressure. The samples were polymerized with and without carbon black (CB) filler in cylindrical shapes with different diameters. There was no appreciable pressure up to 12 MPa or diameter dependence investigated in this study on D, S and P. NBR and EPDM showed dual hydrogen diffusion with fast and slow diffusion behaviors caused by CB, whereas FKM showed a single diffusion behavior. The determined D are Dfast, NBR = (1.55 ± 0.28) × 10–10 m2/s, Dslow, NBR = (3.1 ± 0.5) × 10–11 m2/s, Dfast, EPDM = (3.65 ± 0.66) × 10–10 m2/s, Dslow, EPDM = (3.3 ± 0.5) × 10–11 m2/s, DFKM = (7.7 ± 0.8) × 10–11 m2/s. It appeared that the filler contributes to increase S and decrease D. The uncertainty analysis against the evaluated data was carried out, too, in order that the method could be applicable as a standard test for the permeation properties of various polymer membranes. [ABSTRACT FROM AUTHOR]

Fluoroelastomers are commonly used as seal, gasket or membrane materials in many industrial applications. The temperature- and environment-dependent material property of rubbers will result in degradation and creep. In this study, the effects of both temperature and concentration of hydrochloric acid solution on mechanical properties and creep behavior of fluoroelastomer are investigated. The tensile test results demonstrate that the mechanical properties of rubber after acid treatment show a continual decrease as temperature or concentration increased. This degradation is attributed to the combination of both the swelling of rubber for the matrix which is penetrated by a number of acid solution molecules and the damage of chain networks where the acid–rubber reactions are generated inside. The tensile creep of the acid-treated rubbers is examined under controlled acidic environmental conditions. The creep rate and creep strain are both increased with increasing temperature or concentration. The creep curves are correctly fitted at long times by standard four-element model to evaluate the contributions from separate creep components. From fitting results, the change of viscoelastic strain component and viscous strain component suggests there are structural rearrangements within rubber chains and deformation of rubber matrix. [ABSTRACT FROM AUTHOR]

Our objective is to develop a versatile and facile method that allows the synthesis of novel primary fluorinated co‐oligomers as precursors of photo‐crosslinkable networks. Transparent carboxyl‐terminated fluorinated co‐oligomers with molecular weights ranging between 2000 and 10 400 g mol−1 were synthesized via facile degradation. The structural changes of fluorinated backbone were investigated using various analysis techniques. Then two major approaches, namely esterification and ring opening, were applied to obtain photochemical diacrylates (HEMA‐ and GMA‐IEM‐terminated co‐oligomers). These two precursors can be cured in 60 s under UV radiation without high temperature, high pressure or toxic solvent. The glass transition temperatures of HEMA‐ and GMA‐IEM‐terminated fluoropolymers at about −20 °C, assessed from differential scanning calorimetry, showed an increase after crosslinking, and the glass transitions at 20 °C were no longer observed. These two crosslinked films were found to have higher decomposition temperatures, when compared to starting precursors. The contact angles on the surface of the two elastomer materials were only about 74° and 78°, which increased to 105° and 110° after UV irradiation. The tensile strength of the two cured fluoroelastomers can still reach 1.3 MPa at 200 °C. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel functionalized CF grafted with PEI and F17 was constructed by combining chemical grafting with oxidation method. • The PEI and F17 grafting could form a strong interface mechanical interlocking and covalent bonding between CF and FKM. • The interface connection and mechanical properties of FKM/FCF was remarkably enhanced. • Compared with FKM, the tensile strength and Young's modulus of FKM/FCF increased by 173% and 117%, respectively. • The thermal and electrical properties were improved. A novel functionalized carbon fiber (CF) grafted with polyelectrolyte polyethyleneimine (PEI) and trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (F 17) was constructed by combining chemical grafting with oxidation method. The desized CF was first oxidized in concentrated acid and then grafted with PEI and F 17. The effect of CF modification on the mechanical, thermal and electrical properties of fluoroelastomers (FKM) were systematically investigated. The results showed that the PEI and F 17 grafted CF shows the highest mechanical properties' enhancement function. Compared with blank FKM, the tensile strength, Young's modulus, modulus at 100 % strain and hardness achieved a 173 %, 117 %, 310 % and 30 % increment, respectively. The compression set sharply reduced to 20.61 % and exhibiting excellent anti-compression properties. In addition, the thermal and electrical properties were also improved. Such a high-performance functionalized CF exhibits excellent mechanical, thermal and electrical properties enhancement function and own great potential in industry. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT)-, carbon black (CB)-filled fluoroelastomer (FE) and unfilled-FE compounds were prepared (CNT/FE, CB/FE and FE). The compounds were subjected to heat air aging and characterized by tensile test and X-Ray Diffraction (XRD) analysis. Results show that CNT improved tensile properties of FE before and after aging. All samples show stress induced crystallization (SIC) during tension. XRD results show that under all conditions, the crystals were in the form of γ-phase. For both aged and un-aged specimens, the degree of crystallinity (Xc) is low. After tensile stretching, Xc of un-aged specimens increases tremendously, with larger crystal size. Under the same conditions, the order of elongation at break (EL) was FE > CB/FE > CNT/FE. Normal modulus (NM) and tangent modulus (TM) at the same conditions was in the order of CNT/FE > CB/FE > FE. Tensile strength had the order of CNT/FE > CB/FE > FE.

Fluoroelastomer (FE) reinforced with carbon nanofiber (CNF) (1 and 2 phr) was prepared using an instrumented batch mixer. A property–structure relationship was compared with the compounds containing carbon black (30 phr), neat FE, and hybrid sample (nanofiber + carbon black, 2 phr + 30 phr, respectively). Nanofiber did not improve the mechanical behavior while swelling characteristic was improved as well the initial weight loss by thermogravimetry. The compounds achieve conductive characteristic using only 1 phr. The thermal decomposition of the compounds was carried out using different kinetic approaches in order to establish consistent parameters. It has been shown that the approaches using consistent kinetic parameters can be combined in such a way as to enhance the reliability and quality of each other and consequently the overall kinetic analysis. The limited dispersion with agglomerations seems to be the crucial factor for all analyses evaluated. Finally, the synergism between nanofiber and carbon black for hybrid compound make CNFs very attractive to be used as an additive in the elastomeric composition. POLYM. ENG. SCI., 59:1223–1232 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Fluoroelastomer (FKM)/reduced graphene oxide (RGO) composites were prepared by fast evaporation mixing and traditional mechanical mixing, respectively. RGO was characterized by Fourier transform infrared and Raman spectroscopy. The transparency of FKM/RGO compounds was characterized by UV‐Vis spectra. The effect of different processing methods on the mechanical, dynamic and electrical properties of FKM/RGO composites was investigated. The reinforcement efficiency of RGO to FKM matrix was calculated. Pristine RGO and FKM/RGO composites were characterized by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and thermogravimetric analysis. The results showed that the tensile strength of FKM/RGO nanocomposites prepared by fast evaporation mixing is 3.8 MPa higher than that by traditional mechanical mixing. The electrical resistivity decreases by about an order of magnitude and the thermal stability is improved with the addition of 0.05 phr RGO. Ultra‐high reinforcement efficiency is achieved with the value of 380 and the electrical conductivity is improved because of good dispersion of RGO in FKM matrix via fast evaporation mixing. POLYM. COMPOS., 40:E1495–E1503, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • IL modified rGO inclusion in FKM matrix with enhanced dispersion was developed. • Simultaneous increment in dielectric, mechanical and viscoelastic properties. • Cation-pi interaction between rGO and IL leads to better dispersion in FKM matrix. • Improved FKM/ILrGO interaction is revealed by increase in both Tg and Χ im values. Abstract Utilization of Ionic Liquids (IL) as suitable candidate for nanofiller modification is of considerable interest in the current scenario owing to its peculiar properties. In the present study reduced graphene oxide (rGO) is modified with varying amount of IL to improve the dispersability and interaction with fluoroelastomer (FKM) matrix. The surface modification of rGO using IL, its dispersion and incorporation into the FKM matrix was confirmed by FTIR, Raman, XRD, and AFM surface roughness analysis. The prepared nanocomposites achieved better static and dynamic mechanical properties by the addition of 2 phr of IL to rGO. Moreover the nanocomposites showed an increase in glass transition temperature from DSC (−18.82 for FIL 0 to −14 for FIL 2) analysis that supports the enhanced interaction between FKM and modified filler. Dynamic mechanical analysis of the nanocomposites proved the reinforcing ability and the effectiveness of ILrGO to enhance the properties as a whole. The dielectric study of the nanocomposites showed improved AC conductivity, dielectric constant value (60 with 2 phr of IL content) and a decrease in dielectric heating coefficient value with increase in ILrGO content. These property combinations make the nanocomposites a multifunctional material. [ABSTRACT FROM AUTHOR]

Straight vegetable oils (SVO's) are currently used as renewable sources of fuel in diesel engines for electricity production, transport or agricultural mechanization. Despite various environmental benefits, the use of SVO's may result in shortcomings for the engine operation, in particular, degradation of seals and polymeric components. Thus, deterioration of seals into contact with SVO's in engines must be analyzed to make a safe use of these alternative fuels. In this work, the deterioration of silicone rubber (VMQ), fluoroelastomer/Viton ® (FKM), ethylene-propylene-diene monomer (EPDM) and neoprene/chloroprene rubber (CR), upon exposure to straight Jatropha oil (SJO), diesel, and a blend 80% diesel-20% SJO (B20), respectively, was analyzed by immersion tests with measurements of changes in mass, volume, tensile and tear strengths, and hardness. Complementary measurements of changes in viscoelasticity, surface morphology, topography, and chemical composition provided further insight into the understanding of deterioration of the elastomers. Overall, the four elastomers exhibited negligible deterioration with SJO while only FKM exhibited minimal deterioration with diesel and B20. VMQ and FKM were the less deteriorated elastomers by SJO and diesel, respectively. These experimental results were found to be in good agreement with predictions of compatibility based on the use of the Hansen solubility theory. [ABSTRACT FROM AUTHOR]

The conservation of historical buildings and outdoor cultural assets is of great value for the humankind. In this context, consolidation treatments represent a fundamental procedure to assure the survival of deteriorated cultural artefacts. For porous materials characterized by a wide distribution of pore sizes, adequate consolidation treatments require a product with a sufficient penetration depth and homogeneous distribution inside the unconsolidated substrate. Since water is one of the main deterioration agents of stone, the wettability of rock should also be minimized. A non-invasive and non-destructive technique, able to localize the consolidation agent and the water uptake, is needed to evaluate the efficiency of the treatments. NMR techniques are good candidates to satisfy this requirement. The present study aims at investigating the efficiency of two commercial consolidants, i.e. ethyl silicate and nano-silica, and a new formulated mixture of a fluoroelastomer and nano-silica by NMR relaxometry and MRI. The tested compounds showed adequate characteristics to be used as consolidating agents for highly porous carbonate rocks like limestone. All the products, in fact, penetrated uniformly and homogeneously into the porous structure, and preserved the connectivity of the stone matrix, as demonstrated by T 2 - T 2 relaxation exchange experiments. Moreover, the hydrophilic behavior of commercial consolidants could be reduced, when the newly formulated agent was used. This study shows how the combination of different NMR techniques, applied in the time domain and with spatial resolution, is a powerful approach for evaluating the consolidation efficiency. [ABSTRACT FROM AUTHOR]

ABSTRACT: Lubricating oils for gasoline and diesel engines are formulated to include amphiphilic dispersants for soot particle stabilization and prevention of particle aggregation. Primary and secondary amines used within the polar group of traditional dispersants provide basic nitrogen, which is able to neutralize acidic by‐products from combustion and does not contribute to sulfated ash. However, these active‐hydrogen‐containing amines present significant problems for fluoroelastomer seals and metals in terms of degradation and corrosion. Polyisobutylene (PIB)‐based dispersants containing only tertiary amines, intended to remediate these problems, were synthesized from primary‐bromide‐terminated PIB, 1‐(2‐aminoethyl)piperazine, and an anhydride such as phthalic anhydride. Intermediates and final dispersant molecules were characterized by NMR, GPC, TGA, and MALDI‐TOF MS. Using Langmuir adsorption studies with carbon black as a surrogate for soot, a direct dependence on the affinity for adsorption of the dispersant with respect to the number of phenyl rings present was identified. Performance testing revealed increased compatibility of the dispersants, including limited degradation of seals and corrosion of metals, while retaining total base number. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1657–1675 [ABSTRACT FROM AUTHOR]

Electron-induced reactive processing (EIReP) is a sustainable and energy effective processing technology to modify polymeric materials in the molten state by its spatial and temporal precise energy input. In the present research, the influence of EIReP on nano-mechanical properties of polyamide 6 (PA6)/fluoroelastomer (FKM) blends (50/50 w/w) was successfully explored using advanced PeakForce quantitative nano-mechanical mapping (PF QNM) atomic force microscopy (AFM) technique. In addition, the influence of EIReP on long period of PA6 lamellae and its crystallinity in the blends was studied using small- and wide-angle X-ray scattering (SAXS and WAXS). The AFM based DMT (Derjaguin-Muller-Toporov) moduli of the matrix phase (PA6) and the dispersed phase (FKM) were found to increase, whereas, adhesion force, dissipation energy and deformation of both phases decreased with increasing dose (12.5–25 kGy). Besides of the different crystallinity of PA6 in blends compared to pure PA6, WAXS experiments have demonstrated that the unit cell dimension c-axis of PA6 was sensitive to the melt blending and EIReP. SAXS provided information about the lamellar morphology of the blend component PA6. Variations in the long period of the PA6 lamellae could be assigned to parameters of melt blending and EIReP (dose) and were correlated with the interaction parameter of the phase components and the crystallinity of the blends. PF QNM AFM and X-ray scattering studies established the relationship between the nanoscale phase structure and properties of EIReP modified rubber-plastic blends. [ABSTRACT FROM AUTHOR]

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Acid surface–modified carbon nanotube (ACNT)-, carbon nanotube (CNT)-filled fluoroelastomer (FE), and unfilled-FE compounds were prepared (ACNT/FE, CNT/FE, and FE). The oil-based drilling (OBD) mud aging resistances of these elastomers were assessed by tests of weight gain, swelling, atomic force microscopy (AFM), and optical microscopy. The results show that for ACNT/FE-OBD (OBD mud tested ACNT/FE) and CNT/FE-OBD, there are no blisters, cracks, swellings, and deformed or uneven surfaces; however, for FE-OBD surfaces, these defects exist. ACNT/FE-OBD and CNT/FE-OBD have very low swelling, while for FE-OBD, the swelling is negative which indicates OBD chemical degradation of FE-OBD. All samples under study show low weight gain. AFM results show that roughness and average height of FE-OBD surface decreased considerably compared to that of FE. However, the changes in AFM results of ACNT/FE-OBD and CNT/FE-OBD compared to ACNT/FE and CNT/FE, respectively, are minor. ACNT/FE-OBD has a rougher surface with more average height and height variations compared to CNT/FE-OBD. Optical microscopy images show that the surface of FE-OBD is full of cracks but those of ACNT/FE-OBD and CNT/FE-OBD have no cracks. This study indicates that FE is not resistant to OBD, while ACNT/FE and CNT/FE are resistant to OBD. [ABSTRACT FROM AUTHOR]

Previous observation of EPDM and FEPM materials aged in thermo-oxidative and thermo-oxidative plus hydrolytic environments revealed an unusual trend: the degradation and disintegration of these polymers in the former case but the ability to maintain mechanical performance and shape in the latter [1]. No abnormalities were observed in the chemical (oxidation rates, FTIR spectra, solvent uptake, gel content, and weight loss vs. temperature) or physical (modulus profile) measurements that could explain these empirically observed aging differences. A second controlled aging test was conducted to verify this trend using only EPDM. Once again it was shown that thermo-oxidative conditions appear to cause more degradative damage (enhanced embrittlement) than observed for the combined thermo-oxidative plus hydrolytic environments. From these data we conclude that water may favorably interfere with normal thermo-oxidative degradation processes. This interference may occur via some combination of chemical and physical property changes in the presence of steam such as: oxidation rate and O 2 permeability changes, additional sensitivity to hydrolytic damage, and/or mechanistic changes in relation to pH and hydroperoxide formation. [ABSTRACT FROM AUTHOR]

They are also used for reinforcing fluorine-containing polymers, in particular, the copolymer of tetrafluoroethylene with ethylene (ETFE) [[2]]. However, the features of the effect of radiation modification on the mechanical characteristics of carbon fiber-filled ETFE-matrix composites have not been fully studied. Effect of Radiation Crosslinking on the Yield Strength of a Carbon Fiber Reinforced Tetrafluoroethylene-Ethylene Copolymer. [Extracted from the article]

Materials and components employed in the presence of intense neutron and gamma fields are expected to absorb high dose levels that may induce deep modifications of their physical and mechanical properties, possibly causing loss of their function. A protocol for irradiating elastomeric materials in reactor mixed neutron and gamma fields and for testing the evolution of their main mechanical and physical properties with absorbed dose has been developed. Four elastomeric compounds used for vacuum O-rings, one fluoroelastomer polymer (FPM) based and three ethylene propylene diene monomer rubber (EPDM) based, presently available on the market have been selected for the test. One EPDM is rated as radiation resistant in gamma fields, while the other elastomers are general purpose products. Particular care has been devoted to dosimetry calculations, since absorbed dose in neutron fields, unlike pure gamma fields, is strongly dependent on the material composition and, in particular, on the hydrogen content. The products have been tested up to about 2 MGy absorbed dose. The FPM based elastomer, in spite of its lower dose absorption in fast neutron fields, features the largest variations of properties, with a dramatic increase in stiffness and brittleness. Out of the three EPDM based compounds, one shows large and rapid changes in the main mechanical properties, whereas the other two feature more stable behaviors. The performance of the EPDM rated as radiation resistant in pure gamma fields does not appear significantly better than that of the standard product. The predictive capability of the accelerated irradiation tests performed as well as the applicable concepts of threshold of radiation damage is discussed in view of the use of the examined products in the selective production of exotic species facility, now under construction at the Legnaro National Laboratories of the Italian Istituto Nazionale di Fisica Nucleare. It results that a careful account of dose rate effects and oxygen penetration in the material, both during test irradiations and in operating conditions, is needed to obtain reliable predictions. [ABSTRACT FROM AUTHOR]

Parafilm is a soft, solvent-proof and self-sealant thermoplastic material obtained by blending paraffin wax and polyolefin and that displays irreversible elongational thinning as the material is stretched. In this paper a lamination process was used to transfer graphene nanoplatelets (GNPs) on self-adherent Parafilm substrate and we show that a high-strain state of such conductive Parafilm/GNPs film is reversible when the film is transferred by lamination to a fluoroelastomer (FKM) substrate. The stretching of GNP network stuck on viscoelastic Parafilm gave rise to regions of high and low GNP concentrations with increasing the electrical resistance upon stretching. Upon relaxation from a high-strain state, the composite film on FKM substrate maintain the initial electrical conductive state. Finally it was shown the reduction of the ethanol corrosion action in terms of swelling and mechanical performance of the neat FKM when the Parafilm/GNPs film is used for its packaging. In view of the low cost thermoplastic polymer used for the transferring and the lamination method proposed, these findings represent a facile and an industrial scalable approach to realize novel multifunctional elastomer composites. [ABSTRACT FROM AUTHOR]

OH-functionalized carbon nanotube (BCNT)-, carbon nanotube (CNT)-filled fluoroelastomer (FE) and unfilled-FE compounds were prepared (BCNT/FE, CNT/FE and FE). The oil based drilling mud (OBD mud) aging resistances of these elastomers were assessed by tests of AFM, weight gain, swelling and optical microscopy and EDX elemental analysis (to determine the elements of C, O, F, Si and Ca). The following results were obtained when the above mentioned test results for FE-OBD (OBD mud tested FE) were compared to those of FE: The roughness and average height of surface decreased considerably (approximately −42% and −37%, respectively). Defects appeared on the surface. The swelling was negative and significant (nearly −15.7%). The surface was full of cracks. A considerable amount of fluorine was lost from the surface (Wt%: 32.0%). The following results were obtained when the before mentioned test results for BCNT/FE-OBD and CNT/FE-OBD compared to those of BCNT/FE and CNT/FE respectively: The changes in AFM results were minor. There were no defects on the surfaces. The swelling was low (approximately 5.7% and 4.1%, respectively). There were no cracks on the surfaces. Nanocomposites did not lose fluorine from the surface (Wt%: roughly 10.3% and 7.3%, respectively). Therefore, BCNT/FE and CNT/FE are resistant to OBD mud and can be used as sealing rubbers (for example o-rings) in OBD drilling for oil and gas. In contrast the original FE compound cannot be used. [ABSTRACT FROM AUTHOR]

This study evaluates the dehydrofluorination mechanism, structure and thermal stability of pure fluoroelastomer which was dissolved by organic solvent and reacted with different concentrations of KOH at 20 ∼ 60 °C. The sequence types and contents of double bonds and other oxygen-containing groups of samples were analyzed and investigated by Attenuated total reflectance/Fourier transform infrared (ATR-FTIR), 1 H nuclear magnetic resonance (NMR), 19 F-NMR spectroscopy and chemical titration method; thermal decomposition temperatures of samples were analyzed by thermogravimetric analysis (TGA). The results revealed that dehydrofluorination of fluoroelastomer would accompain with oxidation reaction whereby some double bonds conforming to Hofmann’s rule had been converted to hydroxyl groups, wherein the temperature and alkali concentration were the important factors. The double bonds generated in seven positions of molecular chains, sequence types were mainly conformed to Hofmann’s rule and Zaitsev’s rule supplemented. With the increase of reaction temperature and concentration of KOH, the thermal stability of fluoroelastomer decreased obviously since hydroxyl groups had a greater effect on it. Finally, the mechanism of reaction was also deduced. [ABSTRACT FROM AUTHOR]

Decomposition of poly(vinylidene fluoride- ter -hexafluoropropylene- ter -tetrafluoroethylene) terpolymer, a typical fluoroelastomer with high flexibility and high resistance to permeation of oil and excellent adhesive ability to other materials, in subcritical water (SubCW) was studied as a first example of the decomposition of the terpolymer with the aim of developing a technique to recover the fluorine element. Compared to the common fluoropolymers such as poly(vinylidene fluoride), the terpolymer was considerably stable in SubCW. 19 F NMR spectral analysis of the decomposition products obtained from the reaction at 300 °C was carried out to better understand the decomposition mechanism. When the reaction was performed in SubCW at 300 °C for 6 h under argon, only a negligible amount of F − ions (1%) was released. Addition of H 2 O 2 into the reaction system accelerated the mineralization of the terpolymer to form F − and CO 2 . Apart from these major products, small amounts of malonic acid and CF 3 H were detected. When this polymer was heated in SubCW at 350 °C with 4.0 M H 2 O 2 , both the yields of F − and CO 2 reached up to 95%. These features indicate a quasi-complete mineralization of the terpolymer. Furthermore, the reaction in the presence of 4.0 M H 2 O 2 and stoichiometric amount of Ca(OH) 2 at 350 °C for 18 h resulted in the formation of pure CaF 2 , a raw material for hydrofluoric acid, in 84% yield. [ABSTRACT FROM AUTHOR]

Graphene is one of the most promising fillers for functional nanocomposites due to its high strength, high conductivity and high specific surface area, etc. However, its poor interfacial compatibility makes it difficult to simultaneously satisfy high strength and low gas permeability of nanocomposites. Herein, we proposed a novel strategy to regulate interfacial adhesion by fluorine-hydrogen (F-H) polar interaction in the FKM composites. The F-H polar interactions effectively induce the graphene oxide (GO) interact with the chain of fluoroelastomer (FKM) in spatial arrangements on molecular-level, promoting the construction of interconnected GO network. Specifically, a 10-fold increase in tensile strength of FKM/GO-5 with the incorporation of 5 phr GO is realized compared with pure FKM, and the oxygen permeability of FKM/GO-5 decreases by 79%. At the same filler contents, FKM/GO-5 composites exhibit higher mechanical property and lower gas permeability compared with FKM/rGO composites. Such enhanced performances make FKM/GO composites with an interconnected network very competitive for potential applications as multi-functional structural materials. The proposed strategy provides a novel effective approach for developing and designing the high-performances fluorine-based polymer nanocomposites. [ABSTRACT FROM AUTHOR]

Due to sufficient polymer chain mobility and molecular diffusion, most of the present intrinsic self-healing polymers that heal damage by utilizing reversible bonds are soft or gel. However, a tough self-healing polymer is needed as they can be used as strong and light weight material for engineering applications. Based on the high versitility of polyurethanes, herein we report the development of a disulfide-containing poly(urea-urethane) (PUU) network, where aromatic disulfide diamine is used to establish linkages for tri-functional homopolymer of hexamethylene diisocyanates (tri-HDI) as well as aliphatic prepolymer chains, resulting in the readily conversion between a well cross-linked network and an un-crosslinked structure. With this linkage, the network is able to balance the two seemly contradictory forces, exhibiting simultaneously superior mechanical performances and high self-healing efficiencies in the absence of any catalyst or external intervention. In addition, these materials are capable of repairing themselves repeatedly thus possessing a high potential for industrial applications with further investigation. [ABSTRACT FROM AUTHOR]

This study aims to investigate the one-component permeation of carbon dioxide through two commercial perfluoroelastomers, Kalrez 6375 and Kalrez 7090, in long-duration tests (more than 30 days). The permeation rate in the cells filled with supercritical CO 2 (SC-CO 2 ) at the initial pressure of about p in = 41 MPa has been analyzed by measuring the pressure decrease over time at the constant temperature of about 334 K. These measurements have revealed two distinct regimes of permeation which are separated by a local maximum at p ∼ 12.5 MPa. In the lower pressure regime, the molar flux of the permeant linearly slows down with the pressure decrease. The high-pressure regime is characterized by a pressure independent molar flux of SC-CO 2 through the elastomer. Considering the solution-diffusion model of permeation, we have developed a theoretical model describing the mass transport of CO 2 through the elastomer at three different time scales. Its comparison with experimental observations provides insight into the fundamental aspects determining the membrane transport properties (diffusion, sorption, permeability). Application of the results for the plane sheet model to the realistic geometry of the sealing rings is discussed. [ABSTRACT FROM AUTHOR]

The authors describe the preparation of carbon nanofibers (CNFs) with a three-dimensional network structure by one-step carbonization of bacterial cellulose at 800 °C. The 3D CNFs wrapped with Nafion polymer were cast on a glassy carbon electrode (GCE) which then enables sensitive detection of Cd(II) and Pb(II). Under optimized conditions and at typical stripping peaks of around −0.80 and −0.55 V (vs Ag/AgCl), the electrode exhibits high sensitivity and a wide analytical range of 2-100 μg·L for both Cd(II) and Pb(II). The detection limits are 0.38 μg·L for Cd(II) and 0.33 μg·L for Pb(II), respectively. The modified GCE was successfully employed to the determination of trace amounts of Cd(II) and Pb(II) in both tap water and waste water. [ABSTRACT FROM AUTHOR]

This communication describes a glove capable of wirelessly translating the American Sign Language (ASL) alphabet into text displayable on a computer or smartphone. The key components of the device are strain sensors comprising a piezoresistive composite of carbon particles embedded in a fluoroelastomer. These sensors are integrated with a wearable electronic module consisting of digitizers, a microcontroller, and a Bluetooth radio. Finite-element analysis predicts a peak strain on the sensors of 5% when the knuckles are fully bent. Fatigue studies suggest that the sensors successfully detect the articulation of the knuckles even when bent to their maximal degree 1,000 times. In concert with an accelerometer and pressure sensors, the glove is able to translate all 26 letters of the ASL alphabet. Lastly, data taken from the glove are used to control a virtual hand; this application suggests new ways in which stretchable and wearable electronics can enable humans to interface with virtual environments. Critically, this system was constructed of components costing less than $100 and did not require chemical synthesis or access to a cleanroom. It can thus be used as a test bed for materials scientists to evaluate the performance of new materials and flexible and stretchable hybrid electronics. [ABSTRACT FROM AUTHOR]

The mechanical response of fluoroelastomer F2314 under uniaxial extension and its relation with strain-induced structural change are investigated by mechanical analysis, in-situ small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS). Yielding of samples followed by strain hardening is found without necking. Meanwhile, the strain range of strain softening is short, which is 0.77 at 25 °C and 0.3 at 60 °C. Microscopically, solution-cast F2314 shows microphase separation and low crystallinity. Results of WAXS and SAXS indicate strain-induced formation of fibrillar crystal during strain hardening. Based on these findings, it is supposed that the fast relay between destruction of microphase separated domains and formation of fibrillar crystal is the origin of the unique mechanical response. [ABSTRACT FROM AUTHOR]

A failure analysis of a forged and machined pull rod made of a quenched and tempered high strength steel – namely DIN 34CrNiMo6 – is presented in this paper. The pull rod under study is one of the three rods that connect the three existing hydraulic cylinders to the roller mill and it is used to exert grinding pressure on the roller in an ATOX raw mill. The study of the failure involved the mechanical system's simulation, as well as the fatigue damage assessment based on the application of the Rainflow Method and Fracture Mechanics principles. The pull rod's stress state was determined from in situ strain gages rosettes measurements, and system's simulation showed that the pull rod was designed to support axial loadings only. To ensure this stress state, a proper functioning of the plain bearings and a good condition of the elastomers of the horizontal rod buffer are required. According to the stress-life approach given in the FKM guideline, the current design solution should provide a useful life of 50 years to the pull rod. However, fatigue crack growth calculations made with the strain spectra registered demonstrated that the presence of an initial surface crack is extremely harsh to the lifespan of the rod, which will reach a critical value in a much shorter period of time. Surface finish, corrosion protection and maintenance actions to ensure the correct functioning of the plain bearings, could be important to ensure the desired longevity of the pull rod. [ABSTRACT FROM AUTHOR]

A new pulse sequence for obtaining 19F detected DOSY (diffusion ordered spectroscopy) spectra of fluorinated molecules is presented and used to study fluoropolymers based on vinylidene fluoride and chlorotrifluoroethylene. The performance of 19F DOSY NMRexperiments (and in general any type of NMR experiment) on fluoropolymers creates someunique complications that very often prevent detection of important signals. Factors that create these complications include: (1) the presence of many scalar couplings among 1H, 19F and13C; (2) the largemagnitudes of many 19F homonuclear couplings (especially 2JFF); (3) the large 19F chemical shift range; and (4) the low solubility of these materials (which requires that experiments be performed at high temperatures). A systematic study of the various methods for collecting DOSY NMR data, and the adaptation of these methods to obtain 19F detected DOSY data, has been performed using a mixture of low molecular weight, fluorinated model compounds. The best pulse sequences and optimal experimental conditions have been determined for obtaining 19F DOSY spectra. The optimum pulse sequences for acquiring 19F DOSY NMR data have been determined for various circumstances taking into account the spectral dispersion, number and magnitude of couplings present, and experimental temperature. Pulse sequences and experimental parameters for optimizing these experiments for the study of fluoropolymers have been studied. [ABSTRACT FROM AUTHOR]

In this study, a facile method to enhance the ductility of conjugated polymer thin films by using elastomeric substrates with a self‐wrinkled structure is demonstrated. A brittle polymer of poly(selenophene‐alt‐3,6‐dithophene‐2‐yl‐2,5‐bis‐(2‐octyldodecyl)‐2,5‐dihydro‐pyrrolo[3,4‐c]pyrrole‐1,4‐dione) (PSeDPP) is transferred onto a poly(vinylidene fluoride‐hexafluoropropylene) (PVDF‐HFP) substrate, which has a wrinkled structure formed during thermal curing. The ductility of the PSeDPP thin film on the fluoroelastomer substrate is significantly improved compared to that on poly(dimethyl siloxane) (PDMS). When the fluoroelastomer is employed in a fully stretchable transistor as the substrate as well as the dielectric layer, the device exhibits ideal transfer characteristics and excellent mechanical robustness. The transistor device with high electrical performance (≈1.51 (cm2 V−1 s−1) mobility, 104 on–off current ratio) can be stretched up to 30% over 2000 cycles and maintain device performance with 7.32 × 10−1 (cm2 V−1 s−1) and ≈104 on–off current ratio. To demonstrate the compatibility of this method with other semiconducting materials, conjugated polymers such as poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) and poly(isoindigo‐bithiophene) (PII2T‐C8C10) are also used as the active layer, and they show similar results to the PSeDPP. Hence, this method demonstrates a general strategy to significantly enhance the ductility of the conjugated polymer thin films, achieving stretchable organic field effect transistors with both high performance and mechanical compliance. [ABSTRACT FROM AUTHOR]

Fluoroelastomer (FKM)/montmorillonite (MMT) nanocomposites were prepared by fast evaporation mixing and melting mixing, respectively. The mechanical properties and curing behaviors of the nanocomposites prepared by the two methods were compared. The nanocomposites were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), rubber processing analysis (RPA), thermal gravity analysis (TGA) and dynamic mechanical analysis (DMA). The results indicate that the nanocomposites that were prepared by fast evaporation mixing show better mechanical properties than those prepared by melting mixing according to the increase of the MMT contents from 0.5 to 2.5 phr. When the MMT content was 2.5 phr, exfoliated MMT platelets were found to disperse uniformly in the FKM matrix and the nanocomposites possessed a higher tanδ max and weaker Payne effect. By contrast, some aggregated MMT appeared in the matrix by melting mixing, which led to a lower tanδ max and stronger Payne effect. Therefore, fast evaporation mixing is an eco-friendly and simple processing technology that can be used to realize a good dispersion of nano-fillers in a rubber matrix. [ABSTRACT FROM AUTHOR]

The degradation of fluoroelastomers (FKM) based on different monomers, additives and curing systems was studied after exposure to rapeseed biodiesel at 100 °C and different oxygen partial pressures. The sorption of fuel in the carbon black-filled FKM terpolymer was promoted by the fuel-driven cavitation in the rubber. The bisphenol-cured rubbers swelled more in biodiesel than the peroxide-cured FKM, presumably due to the chain cleavage caused by the attack of biodiesel on the double bonds formed during the bisphenol curing. With any of the selected types of monomer, the FKM rubbers absorbed biodiesel faster and to a greater extent with increasing oxygen partial pressure due to the increase in concentration of the oxidation products of biodiesel. Water-assisted complexation of biodiesel on magnesium oxide and calcium hydroxide particles led to dehydrofluorination of FKM, resulting in an extensive fuel uptake and a decrease in the strain-at-break and the Young's modulus of the rubbers. An increase in the CH 2 -concentration determined by infrared spectroscopy, and the appearance of biodiesel flakes in scanning electron micrographs of the extracted rubbers, were explained as being due to the presence of insoluble biodiesel grafted onto FKM on the unsaturated sites resulting from dehydrofluorination. The extensibility of the GFLT-type FKM was the least affected on exposure to biodiesel because this rubber contained less unsaturation and metal oxide/hydroxide particles. [ABSTRACT FROM AUTHOR]