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Ethanol is considered as a potential biofuel for blending with gasoline and, in India, it is planned to increase the ethanol content to 20 percent in gasoline by year 2025 from present allowable limit of maximum 10 percent. It is important to evaluate the impact of E20 fuel on the materials used in fuel-system components. An evaluation of 8 metals, 6 elastomers and 4 plastics used in various fuel-system components was conducted through systematic exercise of laboratory immersion following standard methods like SAE J1747 and SAE J 1748 with all the quality and quality assurance measures. The study was conducted with E20 as test fuel and commercial gasoline (BS IV) as a baseline fuel for comparative assessment. Impact of E20 on metals was evaluated through calculation of corrosion rates in mm/year based on data obtained for change in mass post-immersion in above fuels. Similarly, impact of elastomers and plastics was evaluated through observed changes in properties like mass, volume, tensile strength, elongation, impact strength and hardness. Impact of E20 on metals tested was found to be insignificant based on the corrosion rates. Polychloroprene, SBR, HNBR and Fluoroelastomer were found to perform similar or better in most of the properties with E20. Impact of E20 on NBR-PVC and Epichlorohydrin was more as compared to commercial gasoline. Similar changes in properties of PA12, PBT and Acetal were observed in both the fuels. Impact of E20 on tensile strength and volume change properties of PA66 was found to be more than commercial gasoline. The vital information generated can be utilised by design engineers for selection, modification of materials for various components of fuel-system of vehicles

Fluoroelastomer has received increasing attention for energetic materials application due to its high fluorine contents. Different contents (0 wt%–30 wt%) of poly(VDF-ter-HFP-ter-TFE) terpolymer are added into Al/MnO2 nanothermite. The peak exothermic temperature of thermite reaction for Al/MnO2 system is about 554°C with 1070 Jg−1 heat release. After adding terpolymer, it mainly exists in the gap among Al nanoparticles and MnO2 nanorods, and react with Al and MnO2 at the range of 350 to 540°C before the occurrence of the thermite reaction. 10 wt% terpolymer has relatively little effect on the thermite reaction, but for the samples with higher terpolymer content, more nanothermite components react with terpolymer at an early stage. Ignition and combustion performance show terpolymer can reduce ignition current threshold by up to 9.82% and increase combustion duration time at least several times. The potential reasons for the above results are analyzed. This work can shed light on the application of fluoroelastomer in energetic-materials. Published version This work was supported by China Scholarship Council (No. 201903170086), the Natural Science Foundation of Shaanxi Province, China (Grant no. 2020JC-50).

We introduce a volumetric analysis technique to characterize the solubility of hydrogen dissolved in polymers and its diffusion coefficient by electrical capacitance measurement electrodes to determine the water level in graduated cylinders. This new and simple technique measures the volume of hydrogen released from rubber inside a graduated cylinder after a sample is exposed to high-pressure hydrogen and subsequent decompression. A diffusion analysis program is utilized to determine the total uptake (C0) and diffusivity (D) of hydrogen, which are used to calculate the solubility (S) and permeability (P). This method is applied to spherical rubber samples of nitrile butadiene rubber (NBR), ethylene propylene diene monomer (EPDM), and fluoroelastomer (FKM), which are potential sealing materials for H2 energy infrastructures. C0 follows Henry's law for all samples. No sample size and pressure dependence is observed for S, whereas an appreciable size dependence for the three rubbers is detected for D. The uncertainty is evaluated by considering uncertainty factors that affect the measurement. The correlation between D and density of rubber is found. The developed method can be utilized as a standard test for the transport properties versus pressure of various polymer membranes regardless of the sample shapes and size.

Carbon nanotube (CNT)-, surface-modified CNT: acid (–COOH) modified (MCNT) or base (–OH) modified (OHCNT), carbon black (CB)-filled fluoroelastomer (FE) and unfilled FE were prepared (CNT/FE, MCNT/FE, OHCNT/FE, CB/FE and FE). The thermal properties of the composites were assessed by TGA-GCMS and TGA and compared for all samples. TGA-GCMS results show that degradation products that obtained due to breakage of the CF2-CH2 bond (group A) and CF2-CF2 bond (group B) in base FE, obtained in lower temperatures and higher temperatures of TGA scan respectively, therefore CF2-CF2 bond is more thermally stable than CF2-CH2. For degradation products of group A and group B, the relative abundance decreased in the following orders respectively for all samples: CB/FE, CNT/FE, OHCNT/FE, FE, MCNT/FE; and MCNT/FE, OHCNT/FE, FE, CNT/FE, CB/FE. Therefore nanofillers and particularly surface-modified nanofillers produce less amount of group A degradation products and more amount of group B degradation products and therefore increase the thermal stability of the base FE. For all samples, the volatile degradation products that have the highest intensity are: (C6F7H2)•+, C4H6F+ and C6F11+ and the volatile degradation products are similar except for OHCNT/FE and MCNT/FE. TGA results also show that thermal stability reduced in the following orders in the lower temperature range and higher temperature range respectively: OHCNT/FE, FE, CB/FE, CNT/FE, MCNT/FE; and CB/FE, MCNT/FE, CNT/FE, FE, OHCNT/FE. Totally the results show that OHCNT/FE, MCNT/FE and CNT/FE can be used at high temperatures for making O-rings for very deep oil and gas drilling.

A novel fluorinated soft thermoplastic elastomer (sTPE) for microfluidics is presented. It allows the rapid fabrication of microfluidic devices through a 30‐second hot embossing cycle at 220°C followed by self‐sealing through simple conformal contact at room temperature, or with baking. The material shows high chemical resistance, particularly in comparison to polydimethylsiloxane (PDMS), to many common organic solvents and can be rapidly micropatterned with high fidelity using a variety of microfluidic master molds thanks to its low mechanical stiffness. Self‐sealing of the material is reversible and withstands pressures of up to 2.8 bar with room temperature sealing and four bar with baking at 185°C for 2 hours. The elastomeric, transparent sTPE exhibits material characteristics that make it suited for use as a microreactor, such as low absorption, surface roughness and oxygen permeability, while also allowing a facile and scalable fabrication process. Modular microfluidic devices, leveraging the fast and reversible room temperature self‐sealing, are demonstrated for the generation of water droplets in a toluene continuous phase using T‐junctions of variable size. The sTPE offers an alternative to common microfluidic materials, overcoming some of their key drawbacks, and giving scope for low‐cost and high‐throughput devices for flow chemistry applications.

The aging behaviors and mechanism of fluoroelastomer (FKM) under lubricating oil (FKM-O) and air (FKM-A, as a comparison) at elevated temperatures were studied from both physical and chemical viewpoints. The obvious changes of mechanical and swelling performances indicate that the coupling effect of lubricating oil and temperature causes more serious deterioration of FKM-O compared to that of FKM-A. Meanwhile, much stronger temperature dependence of both bulk properties and micro-structures for FKM-O is found. Three-stage physical diffusion process is defined in FKM-O due to the competition between oil diffusion and elastic retraction of network. FTIR results reveal that the dehydrofluorination reaction causes the fracture of C-F bonds and produces a large number of C-C bonds in the backbone. The coupling effect of oil medium and high temperature could accelerate the scission of C-C bonds and generate a series of fragments with different molecular sizes. The TGA results, crosslinking density Ve, and glass transition temperature Tg derived from different measurements coherently demonstrate the network destruction in the initial stage and the simultaneous reconstruction occurring at the final stage. The newly formed local network induced by reconstruction cannot compensate the break of the original rubber network and thus only provides lower tensile strength and thermal stability.

Multi-walled carbon nanotubes (MWCNTs) modified with silane coupling agent A-1120 (MWCNTs-A1120) were prepared. Compared with the raw MWCNTs, acidified MWCNTs (MWCNTs-COOH), and MWCNTs grafted with EDA (MWCNTs-NH2), MWCNTs-A1120 have the best dispersion in fluoroelastomer at the same doping ratio. Therefore, fluoroelastomer/MWCNTs-A1120 composite has the best mechanical properties with tensile strength of 13.92 MPa and elongation at break of 111.78%. Then, the effects of doping amount of MWCNTs-A1120 on the electrical properties of the composites were investigated. The dielectric constant of the composite increases with the increase of MWCNTs-A1120, and the dielectric loss does not change much at the low doping amount such as 0.5 wt%. When the doping amount of MWCNTs-A1120 is 5 wt%, the dielectric constant and the dielectric loss value are greatly increased, and the volume resistivity is greatly decreased, which proves that the conductive network is formed in the composite, so the filling amount of 5 wt% is the percolation threshold. The tensile deformation of the sample also affects the electrical properties of the composites. As the tensile deformation increases, the dielectric constant and dielectric loss of the composite decrease. For the composite with 5 wt% MWCNTs-A1120, excessive tensile deformation will destroy the conductive network structure of the composite, so the composite will change from conductive material to dielectric material. Therefore, such composite is a good candidate for flexible conductive material or flexible dielectric material used in harsh environments such as high temperatures and various aggressive solvents.

The concentrations of triallyl isocyanurate (TAIC) in a peroxide-curable fluoroelastomer terpolymer containing 67 wt% of fluorine were varied to generate compounds of differing crosslink densities. Experimental analysis was undertaken using rheometry, hardness, stress–strain (Mooney–Rivlin), equilibrium solvent swell, and low-field nuclear magnetic resonance (NMR) using the double quantum (DQ) technique. Increasing the TAIC concentration caused a systematic rise in rheometry elastic torque, hardness, and tensile strength, whereas both elongation at break and swelling levels decreased. These results are concurrent with an enhanced overall level of crosslinking, which was confirmed by the steady increase of the Mooney–Rivlin C1 values. DQ NMR analysis using hydrogen and fluorine probes and subsequent application of fast Tikhonov regularization to the corrected intensity data were particularly useful in discerning the inhomogeneous nature of the compound morphology. The spatial distribution of the crosslink density suggests that the compound consists of small, highly crosslinked/entangled polymerized TAIC domains embedded within the elastic crosslinked matrix. A concentration of 3 phr of TAIC is optimal according to compression set testing.

The dielectric permittivity in polymers, fluoroelastomers and ethylene propylene diene monomers was measured as a function of both frequency and temperature. Several relaxation processes were revealed and analyzed through a developed algorithm to analyze the relaxation. The β and the α relaxations were observed and occurred in that order as the temperature was increased. Maxwell-Wagner-Sillars contributions, including conduction, were present at high temperatures and low frequencies. The molecular chains responsible for the relaxation processes were assigned by using molecular modeling with the dipole moment included. The activation energy, Vogel-Fulcher temperature and glass transition temperature were also obtained.

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.

Commercial fluororubber SKF 32, fluoroplastic F-32L, fluoroelastomer Kel-F, fluoroplastic FK 800 (labeled as SKF 32, F-32L, Kel-F and FK 800) and an in-house prepared poly(vinylidene fluori...

Copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) make up the largest volume of fluoroelastomers sales. Within this family, Viton A (VDF/HFP 60/40 wt%, 66% fluorine) is most important commercially. Determination of thermomechanical properties of such fluorinated polymers is still limited to experimentation or empirical models, while computational prediction of their physical properties is still at its infancy. Considerable efforts have been made to develop molecular force fields for the prediction of properties of various crystalline as well as amorphous fluorinated substances. These force fields were parametrized based on small molecules or oligomers, hence their transferability to longer and more complex (i.e. copolymer) chain architectures must be tested. In this work, thermodynamic, structural, and mechanical properties of the Viton A fluoroelastomer are evaluated using atomistic molecular dynamics (MD) simulations for several force fields and compared with available experimental data. Differences in molecular structure of the chains modeled by different force fields are shown to substantially influence thermodynamic and mechanical behavior. OPLS-derived force fields give rise to extended chains that are more mobile and result in softer material that lack in molecular structure. Other force fields rely on strong nonbonded interactions that interfere with chain dynamics and mechanics. PCFF is shown to most satisfactorily predict structural properties and thermal volumetric behavior around Tg, demonstrating relatively successful transferability to long linear polymer chains.

A novel dielectric material of fluoroelastomer/MWCNTs-COOH (acidified MWCNTs) composite that can be applied in the harsh conditions was prepared by a simple solution blending method. Thermogravimetic analysis was applied to evaluate the thermal stability of the fluoroelastomer/MWCNTs-COOH composite. It shows that the thermal decomposition temperature is greater than 400 °C. Besides, the thermal decomposition mechanism and service life of the composites were determined by various thermal decomposition kinetics methods. The results show that the thermal decomposition mechanism of the composite belongs to the first-order reaction, and the limit temperature of 2 years of use is 227.8 °C. Due to the excellent electrical properties of MWCNTs, the dielectric constant of the composite increases by 28.2% with only 1.5 wt% fillers loading. Most importantly, the composite shows excellent corrosion resistance. There are few changes in dielectric properties of the composite after soaked in acid for 9 days. The dielectric constant does not change more than 1.5, and the dielectric loss is basically unchanged. Therefore, such composite is a good candidate for high performance dielectric material used at elevated temperature or acid environment.

In this paper, a femtosecond laser manufacturing process is effectively employed to produce a pattern of micro dimples on a fluoroelastomer. To quantify the microtexture tribological performance, two configurations are implemented: non-conformal and conformal contacts are tested on a pin-on-disk tribometer. Due to the reduced number of dimples engaged in the contact region, no significant friction enhancement is obtained in the non-conformal configuration. On the contrary, in the case of conformal contacts, outstanding outcomes in terms of friction reduction - up to 60% - can be achieved by a properly designed micro-texture. Such a result is obtained by improving the wear debris entrapment and the cavitation respectively at low and high speed, without increasing significantly the occurrence of flow eddies.

The present work was focused on studying the effects of different CB loadings on the rheological, thermal, tensile, dynamic mechanical, and electrical properties of polyvinylidene fluoride and FKM composites. To these ends, dynamic mechanical thermal analysis (DMTA) was conducted, and the CB grade and method chosen for compound preparation were CB (N330) by melt mixing with different shear effects were examined, respectively. The composites were melt-blended with CB at 190 °C in an internal mixer, after which the properties of filled and unfilled composites were compared. The DMTA analysis revealed that the area under the loss tangent (tanδ) peak decreased and that the tanδ temperature of the rubber phase increased with CB loading. The presence of CB improved the mechanical properties, such as the Young’s modulus and tensile strength, of the composites and increased thermal stability given the high thermal stability of CB and the interaction between the CB particles and the polymer matrices. The increase in the electrical conductivities of the composites under different CB loadings was also examined with different shear effects because of the different dispersion states of CB. The percolation threshold of conductive thermoplastic vulcanizate composite based on conductive CB was observed and the experimental data could be well fitted to the general equation model.

Elastomer seals are essential for zonal isolation in vertical and deviated wells. They are often used either as O-rings (static seals) or as energized seals (packers). For elastomers to perform their functions effectively over an extended period, it is essential that the elastomer withstand the deleterious effects of pressure, prolonged loading effects, severe temperature, corrosive fluids, and acidic gases. As such it is imperative to understand the various elastomer degradation mechanisms and develop methods to reduce the degradation. The objectives of this study are: to investigate if elastomers are “fit for service” for well construction applications and to evaluate elastomer performances under downhole corrosive conditions. To achieve this goal, some dynamic wellbore conditions which close-to-real field conditions are were simulated in a controlled laboratory setup. The following properties were investigated: elastomer hardness, elastomer compression, and elastomer volumetric swelling. In the experimental setup, four frequently used elastomers in the oil and gas industry were studied: Nitrile butadiene rubber (NBR), Ethylene propylene diene monomer (EPDM), Fluoroelastomer (FKM) commonly known as Viton, and Polytetrafluoroethylene (PTFE). The results indicate that NBR exhibited the most significant deterioration. Viton showed the least amount of deterioration but has poor decompression resistance. The aging condition that proved to be the most damaging is CO2. Analysis of Variance (ANOVA) was also performed on the data from the samples as a statistical analysis indicator. Some other observations and conclusions are that the degree of chain growth and chain rupture depends on the temperature and the degree of chemical exposure.

The present work was focused on studying the effects of different CB loadings on the rheological, thermal, tensile, dynamic mechanical and electrical properties of polyvinylidenefluoride (PVDF) and FKM composites. To these ends, the CB grade and method chosen for compound preparation were CB (N330) and melt mixing, respectively. The composites were melt blended with CB at 190 °C in an internal mixer, after which the properties of filled and unfilled composites were compared. The presence of CB improved the mechanical properties, such as the Young's modulus and tensile strength, and increased thermal stability given the high thermal stability of CB and the interaction between the CB particles and the polymer matrices. The dynamic mechanical thermal analysis (DMTA) showed the glass transition temperatures of the composites. The analysis also revealed that the area under the loss tangent (tan δ) peak decreased and that the tan δ temperature of the rubber phase increased with CB loading. The increase in the electrical conductivity of the composites under different CB loadings was also examined, and the percolation threshold of conductive thermoplastic vulcanizate composite based on conductive CB was observed. The effect of CB and its content on rheological behavior of the PVDF/FKM blends was studied and the experimental data was correlated by a physical model named General Equation Model (GEM). A relation between rheology and conductivity of the blends with filler percolation was found.

We study the temperature and velocity dependency of rolling friction. Steel and PMMA cylinders are rolled on sheets of nitrile butadiene rubber (NBR), with and without filler, and fluoroelastomer (FKM) with filler. Measurements of the rolling friction are performed for temperatures between −40 °C and 20 °C, and for velocities between 5 μm s−1 and 0.5 cm s−1. For the unfilled NBR, a smooth rolling friction master curve is obtained using the bulk viscoelastic frequency–temperature shift factor aT. For the filled rubber compounds, a small deviation from the bulk viscoelastic shift factor is observed at low temperatures. The experimental data are analyzed using an analytical theory of rolling friction. For the filled compounds, good agreement with theory is obtained when strain softening is included, which increases the rolling friction by a factor ∼2 for the filled FKM and ∼3 for the filled NBR compounds. For the unfilled NBR, the maximum of the rolling friction occurs at higher sliding speeds than predicted by the theory. We discuss the role of the adhesive (crack-opening) contribution to the rolling friction, and the role of frozen-in elastic deformations as the rubber is cooled down below the rubber glass transition temperature.

This study examines the influence of various electrical parameters on the volume resistivity of the Viton fluoroelastomer. The transient current, the temperature dependence of volume resistivity, the voltage dependence of resistivity, and the surface morphology of Viton insulators are investigated for new and aged specimens. An accelerated aging process has been employed in order to simulate the natural aging of insulators in service. A detailed comparison between the new and aged samples is presented. The transient effect, which is a challenge to the resistivity measurement of insulators, has been investigated. The first 60 s of the resistivity measurement test showed a significant influence from the transient effect and should be excluded from the data. The volume resistivity of both new and aged samples decreased when the temperature increased. However, the resistivity of the aged sample was lower than the new one at all tested temperatures. When the temperature increased from 35 to 190 °C, resistivity decreased from 4.77 × 1010 to 6.99 × 108 Ω-cm for the new sample and from 2.6 × 1010 to 6.68 × 108 Ω-cm for the aged sample under 500 V. Additionally, the results from this study showed that the volume resistivity is inversely proportional to the applied voltage. Finally, scanning electron microscope (SEM) micrographs/images allowed us to closely examine the surface morphology of new and aged Viton samples. The surface of aged samples has been recognized with higher surface roughness and more significant surface cracks leading to poor performance under high voltage applications.

The resistance to failure through tearing is a crucial mechanical property for the application of different elastomers . In this work, graphene nanoplatelets (GNPs) were introduced into a fluoroelastomer (FKM) matrix with the aim of improving its tear resistance. The fracture energy through tearing was evaluated using the pure shear test. It was found that the tearing energy increased linearly with the volume fraction of the GNPs. At the maximum GNP content, the tearing resistance was 3 times higher, suggesting efficient toughening from the GNPs. Theoretical analysis of the micromechanics was conducted by considering debonding and pull-out of the nanoplatelets as possible toughening mechanisms. It was determined quantitatively that the main toughening mechanism was debonding of the interface rather than pull-out. The formation of cavities at flake ends during the deformation, as confirmed by scanning electron microscopy, was found to contribute to the remarkably high interfacial debonding energy (~1 kJ/m 2).

Fluoroelastomer and silicone rubber lie in the two different poles of elastomer family in terms of polarity. Hence, combining them in a single material and making it as at least technologically compatible substance is a great challenge. In this article, the compatibilization effect of fluorosilicone rubber (block copolymer) (trifluoropropylpolydimethylsiloxane) with various loading of modified silica filler on the novel advanced polymer architecture based fluoroelastomer (copolymer of hexafluoropropylene, vinylidene fluoride, and tetrafluoroethylene) and silicone rubber (poly methylvinylsiloxane) blends has been studied in details. The mechanical properties show significant improvement at room temperature (13%) and remarkably more at high temperature (54%) for the compatibilized system. Tan delta peak shifting in DMA study indicates better compatibilization for 2.5 phr loading of fluorosilicone and 15 phr loading of silica at 50/50 blend ratio. The reduction in domain size (from ⁓3 μm to ⁓200 nm) of the fluorocarbon phase by the synergistic effect of silica and fluorosilicone proves the decrease in interfacial tension and better compatibilization. This blend can be judiciously applicable in the sealing system as oil and fuel resistant O-rings and gaskets for a very wide range of temperature.

Nanocomposites with multifunctional properties are of great interest as they meet the needs of the developing industrial and engineering fields. The present study focus on the development of multifunctional elastomeric nanocomposites with exfoliated graphite (EG) as the reinforcing content and the speciality material fluoroelastomer as the polymer matrix. Morphological analysis of the nanocomposites in terms of TEM, AFM and SEM were done to look at the polymer-filler interactions which in turn lead to the property enhancement. The dispersion of the EG in the nanoscale which resulted in the property enhancement is clear from the TEM images. Nanocomposites exhibited improved thermal stability and higher mechanical strength by the addition of 12 phr of EG nanofiller. Moreover the dielectric performance of the nanocomposites was also enhanced by the addition of conductive EG nanofiller and the nanocomposites showed higher dielectric constant value and AC conductivity with lower dielectric loss. In addition to this the solvent transport features of the nanocomposites were also analyzed to reveal the reinforcement effect of the nanofiller and the effective polymer-filler interactions.

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.

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.

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.

Carboxylic functionalized multi-walled carbon nanotubes (MWCNTs-COOH) were modified by using ethylenediamine (EDA) to prepare amino-functionalized multi-walled carbon nanotubes (MWCNTs-A). MWCNTs-A were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Fluoroelastomer (FKM) was reinforced by incorporation of MWCNTs-COOH and MWCNTs-A, respectively. The thermal, electrical and mechanical properties of the FKM/MWCNT composites were studied. The results indicated that a more homogeneous dispersion of nanotubes and a stronger interfacial interaction in FKM/MWCNTs-A composites were achieved than in FKM/MWCNTs-COOH ones. As a result, the thermal, electrical and mechanical properties of the FKM/MWCNTs-A composites were higher than that of the FKM/MWCNTs-COOH composites due to the participation of MWCNTs-A in the crosslinking process to form dual crosslinking networks in the FKM matrix.

This study evaluates the dehydrofluorination of fluoroelastomer (poly(VDF-co-HFP) copolymer) which was dissolved by organic solvent and reacted with different concentrations of KOH and different amount of phase transfer catalyst (PTC) at 20–60 °C.The structures, sequence types and contents of double bonds of samples were analyzed and investigated by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy(ATR-FTIR), 1H nuclear magnetic resonance (NMR), 19F NMR spectroscopy and chemical titration method. The results revealed that dehydrofluorination of the studied fluoroelastromers could be carried out at room temperature in alkaline environments, wherein the temperature and alkali concentration were the great factors. And the dehydrofluorination of poly(VDF-co-HFP) copolymer conformed mainly to Zaitsev's rule and partially to Hofmann's rule. The double bonds (–C=C–) would generate in five positions of molecular chains and contents could be controlled. With increase of alkali concentration or reaction temperature, there would be dehydrofluorination accompanied with oxidation reaction whereby some –C=C– converted to hydroxyl groups. Finally, the mechanism of reaction was also deduced.

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.

Carbon nanotube (CNT)-, carbon black (CB)-filled fluoroelastomer (FE) and unfilled FE compounds were prepared (CNT/FE, CB/FE and FE). The oil-based drilling mud (OBD) aging resistance of these elastomers were assessed by tests of atomic force microscopy (AFM), optical microscopy and X-ray diffractometry (XRD). Weight gain, swelling and hardness were also determined. The whole conclusion is that CNT/FE can be used as O-rings in OBD drilling while FE and CB/FE can not.

To further facilitate commercialization of automotive fuel cells, durability concerns need to be addressed. Currently the addition of a mechanical support in the membrane is able to adequately solve issues of mechanical degradation, but chemical degradation via oxygenated radical attack remains an unsolved challenge. Typical mitigation strategies use cerium or manganese species to serve as radical scavengers, but these ions are able to migrate in the membrane and even leach out of the system. The approach used in this study is to covalently link and immobilize a heteropoly acid (HPA), more specifically 11-silicotungstic acid (HSiW11), a lacunary HPA of the Keggin structure to a fluoroelastomer, serving as both a radical decomposition catalyst and the proton conducting acid. This dual functionality allows for both high content of radical scavenging species and high ion-exchange capacity. An efficient three step, high yield (77%), commercially viable synthesis for this polymer is reported. The synthesis route for making this new heteropoly acid functionalized polymer is confirmed using infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis (TGA). The material exhibits clustering of the HSiW11 moieties, resulting in a poorly connected proton conducting phase when dry, but excellent conductivity is achieved at elevated humidities (0.298 S cm−1 at 80 °C and 95% RH). The proton conductivity shows an enhancement above 60 °C due to a softening of the polymer, as shown by DSC. Under an aggressive chemical accelerated stress test (AST), 90 °C, 30% RH, zero current, and pure O2, the PolyHPA losses only 0.05 V of open circuit voltage (OCV) after 500 h, greatly out performing any other material reported in the literature. For comparison, the Nafion® N211 fuel cell drops below 0.8 V after only 76 h under the same conditions. In fuel cell testing the PolyHPAs have outstanding chemical stability and also possess very low in situ high frequency resistance (HFR) leading to high performance (1.14 W cm−2 at 2 A cm−2), compared to 1.11 W cm−2 for the Nafion® N211 fuel cell at the same current. At 75 wt% HSiW11 loading, the fuel cell HFR showed a 22% decrease over N211.

The introduction of new fuels to power internal combustion engines requires testing the compatibility of such fuels with materials commonly used in fuel supply systems. This paper investigates the influence of alternative fuels on the acrylonitrile-butadiene rubber and fluoroelastomer used in the automotive industry. In the study, conventional diesel fuel, its blend with 7% of fatty acid methyl esters and paraffinic diesel fuel produced with the Fisher Tropsch synthesis from natural gas were interacted with the elastomers. The immersion tests were carried out at room temperature (20 °C) for 168 h. The effect was evaluated based on changes in the selected rubber’s volume, mass and hardness. It has been confirmed that the synthetic component without aromatic hydrocarbons had a different effect on the tested rubber than did conventional fuel. In follow-up work, the selected rubbers were also subjected to microscopic observation. The most frequently observed effect was the washing out of the seal protective layer.

We report our study of stress relaxation of Viton™ A hexafluoropropylene-vinylidene fluoride co-polymer fluoroelastomer compressed 25% and irradiated at room temperature in air to nominal absorbed doses of 10 – 106 Gy with 1.17 and 1.33 MeV gammas from a cobalt-60 source. Our data show that the true stresses at room temperature in ring samples of Viton™ A fluoroelastomer compressed 25% decline slightly from 1014±93 kPa at zero dose to 996±115 kPa at a dose of 103 Gy, decrease to 967±98 kPa at 104 Gy and then drop sharply to 640±116 kPa at 105 Gy and 157±32 kPa at 106 Gy. We briefly discuss the implications of this data for the integrity of seals in high-radiation environments.

In this research, the novel nano-filled fluoroelastomer (FKM) composites with excellent thermal and mechanical properties were prepared using the Siligraphene (graphene-like SiC), g-C3N4, and Siligraphene/g-C3N4 composites to improve the thermal and mechanical stability of FKM. The nanocomposites were exposed to heat aging test and characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), dynamic mechanical analysis (DMA), and tensile test. Results show that Siligraphene, g-C3N4, and Siligraphene/g-C3N4 improved the tensile properties of FKM before and after exposure to the aging test. Si and N dopants in the graphenic structure of Siligraphene and g-C3N4 nanofillers are the effective parameter to reinforce the properties of nanocomposites. In general, these nanofillers provided better adhesion with FKM matrix. It can be justified by a better distribution of filler and higher interaction between filler and FKM which form the cellulation structure that can improve the mechanical properties and prevent the rubber decomposition at high temperatures by resisting molecular mobility.

Vegetable oils are potential alternative lubricants for the twofold purpose of achieving good tribological properties while protecting the environment. However, any intended use of bio-lubricants in machinery requires of a previous study of their compatibility with the involved sealing materials. In particular, Jatropha oil (JO) is inexpensive and easy to obtain, which make it a good candidate to be used as bio-lubricant in machinery. In this work, a compatibility study of four commercial sealing elastomers, namely, fluoroelastomer (FKM), silicone rubber (VMQ), neoprene/chloroprene (CR), and ethylene-propylene-diene monomer (EPDM) with JO, engine mineral oil (EMO) and a blend of EMO and JO (80-20%) (B20), for the purpose of comparison, was conducted. The analyses include the basic measurements comprised in the ASTM-D471 and ASTM-D7216 methods, namely, changes in mass, volume, tensile and tear resistance and hardness. In addition, non-standard measurements of creep compliance, surface morphology and topography, and chemical composition were performed to achieve a deeper evaluation of the interaction of JO with the elastomers. In general, good compatibility was found regarding the standard methods for the four elastomers with JO, VMQ being the most compatible sealing material. However, FKM, CR and EPDM showed changes in the creep compliance modulus and surface morphology when in contact with the three lubricants, which may considerably affect their sealing performance and decrease their useful life. Overall, pure JO generated much less physical changes on the elastomers than EMO and B20, which can be ascribed to the concentrations of free fatty acids contained in JO.

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), 1H nuclear magnetic resonance (NMR), 19F-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.

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.

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.

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.

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.

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.

The energy storage system (ESS) is widely investigated because it can solve various energy-related problems without additional power plants. Among the ESSs, a vanadium redox flow battery (VRFB) is one of the most promising technologies due to its scalability without explosiveness. The bipolar plate is a multifunctional component that provides an electrical path and separates cells. A bipolar plate should simultaneously have low electrical resistance, high mechanical properties and chemical durability. In this study, a nano carbon/fluoroelastomer composite bipolar plate was developed to substitute for the conventional thick graphite bipolar plate. The ‘soft-layer method’ was adopted to expose the carbon fibers on the surface of the composite to increase its electrical conductivity. The solution casting method was applied to fabricate the high fiber volume fraction composite structure with a dispersion of carbon black. The performance of the carbon/fluoroelastomer composite bipolar plate was evaluated by testing the permeability, mechanical properties, and electrical properties. Finally, unit-cell charge/discharge tests were conducted to verify the performance of the composite bipolar plate.

In the CO2 injection process, the CO2 in the supercritical state and the H2S gas produced in the well have strong corrosion ability to the rubber material in the tool, therefore, it is necessary to study the rubber material suitable for the supercritical CO2 injection process. According to the H2S concentration in a CO2 injection block of Yushulin oil field in Daqing, Select six kinds of rubber materials for common underground tools to carry out CO2, H2S corrosion test, and heat resistance test. According to the experimental results, choose the rubber with the best performance. And then, characterize the molecular structure of the selected rubber samples to verify the corrosion resistance of CO2 and H2S. The results show that supercritical CO2 gas has strong solubility in perfluoroether rubber, type-A fluoroelastomer, and tetrapropyl fluoroelastomer; nitrile-butadiene rubber and ethylene-propylene-diene misch-polymere have poor heat-resistant-aging property; hydrogenated butadiene-acrylonitrile rubber and ethylene-propylene-diene misch-polymere have good resistance to high temperature; nitrile-butadiene rubber has the worst resistance to high temperature; hydrogenated butadiene-acrylonitrile rubber has high mechanical properties before and after aging and strong supercritical CO2 corrosion resistance. So, hydrogenated NBR is the best rubber material suitable for supercritical CO2 injection process. The changes in performance parameters of six common rubber materials before and after corrosion are obtained under high temperature and high pressure CO2 and H2S gas environment. It provides a reference for rubber materials of downhole tool selection in supercritical CO2 injection process.

In this study, a novel hybrid stretchable sensor is developed with a combination of carbon nanotubes (CNTs) and long silver nanowires (AgNWs) in fluoroelastomer (FKM) via melt-mixing method. An electrically conductive hybrid structure is created which provides a wider detection range of strain, i.e. from 23% strain sensing for single filler to more than 135% strain sensing for the hybrid CNT/AgNW fillers. Very long silver nanowires (AgNWs) are synthesized using an optimized polyol method producing high-aspect-ratio AgNWs with 75-100µm in length and 150nm in diameter. This comprehensive report includes a scalable fabrication process, morphology characterization, electrical properties and route to improve the strain sensing performance. The overall properties of hybrid FKM nanocomposite with 80/20 volume ratio of CNT/AgNW meet the requirements for many applications for flexible and stretchable electronics.

Fluoroelastomers (FKM) are vital sealing materials in acidic environment and their failure can cause severe safety problems. Therefore, investigation of the degradation behavior and mechanism of FKM materials is of great significant. Herein, we investigate a diffusion model of an acidic solution into an FKM composite and its degradation behavior upon immersion in hot nitric acid solution. The results indicate that the diffusion process of the HNO3 solution into the FKM composite conforms to the Fick diffusion model at a low concentration of nitric acid solution. Besides, the concentration of HNO3 solution affects the diffusion process of solvent molecules and the dissolution process of the filler particles to some extent. SEM showed that the surface topography of the FKM was significantly altered after it was immersed in HNO3 solution. The structural and chemical changes of the FKM were studied using ATR-FTIR, SEM-EDS and MAS NMR, which demonstrated the occurrence of decrosslinking via hydrolysis of the crosslinks and backbone cleavage by dehydrofluorination. This was also manifested by the decrease in crosslinking degree and mechanical properties. The present study is helpful for revealing the chemical changes in FKM in hot HNO3 solution.