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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]

Non-linear rheological behaviours of high fluorine content fluoroelastomer (HF-FKM) mixtures with varied carbon black (CB) filling amounts were investigated. Non-linear viscoelastic characteristics of HF-FKM mixture are characterised by large amplitude oscillatory shear (LAOS) tests, correlations between rheological behaviour and CB content were then discussed. Each non-linear viscoelastic parameter of HF-FKM mixture presents a three-stage characteristic with increasing CB content, corresponding to ranges of 0–20 phr, 25–30 phr, and 35–45 phr. Three stages of viscoelasticity characteristics for HF-FKM mixtures were considered to depend on the alteration of CB-elastomer network structure with increasing CB content, corresponding to the states where continuous phase of gum, CB-elastomer mesophase and excessive CB agglomerates predominate in mixture compound, respectively. After vulcanisation, samples with 30 phr CB content show the best resilience performance against thermal ageing, contributing to the existence of CB-elastomer mesophase. Samples with 25 phr CB content possess the second lowest compression sets at 225 and 250 °C ageing conditions but perform no better than those with 35 phr at 275 °C. The reason is presumed to be that the presence of excessive CB agglomerates in HF-FKM vulcanisate reduced irreversible deformation of the CB-elastomer network under compression at elevated temperatures. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) nanoparticles have been used at different concentrations (1–5 wt%) to prepare fluoroelastomer (FKM) nanocomposites. The physico-mechanical features of FKM nanocomposites exhibit an increase in tensile strength, modulus, hardness and elongation at break decrease with increasing concentration of GO nanoparticles. This is due to the good distribution of GO in FKM rubber. The effect of GO concentration on dielectric performances which includes dielectric loss tangent (tan δ), real impedance, imaginary impedance and electrical conductivity were studied as a function of frequency range 10−2 –105 Hz. The intensity of tan δ peak of FKM nanocomposites has a gradual decrease with frequency as well as their peaks also shifts toward lower frequency region. Variation in spectra of real impedance reveal decreasing behavior with frequency and imaginary impedance characterizes the properties like diminished peak intensity for GO/FKM nanocomposites. The Nyquist plots show good semicircles that exhibit polarity with a single relaxation time. The extent of the GO concentration has a significant impact on the dielectric permittivity of the nanocomposites. Using the percolation theory, it has been determined how frequency affects electrical conductivity. The percolation phenomenon has been discussed using electrical conductivity of GO/FKM nanocomposites and found at 4 wt% GO concentration. [ABSTRACT FROM AUTHOR]

Due to their excellent chemical stability, fluoroelastomers have been widely used in various severe circumstances since birth. At present, carbon blacks and inorganic fillers are the two most prominent reinforcing agents in fluoroelastomers. However, despite the rise of silica in the rubber industry, it is still difficult to apply this non‐carbon filler alone as a reinforcing agent in fluoroelastomer. Research on the interaction between silica and fluoroelastomer is even less and not systematical. Based on the above, we analyzed the interaction between silica and fluoroelastomer under different conditions through x‐ray photoelectron spectroscopy (XPS), Fourier‐transform infrared spectroscopy, bound rubber (BR) content analysis and rheological properties, and so forth. The interaction between fluoroelastomer and silica can be characterized by the binding energy variation at different temperatures (especially 260°C the new peak at about 685 eV) and wavenumber shift of Si–OH and Si–O–Si in XPS and infrared (IR) analysis, respectively. The BR content varied with loading, temperature, and atmosphere, reflecting the strength of the interaction from a macro perspective. The evolution of the rheological curves of different recipes and test conditions correlate closely with the results of XPS, IR, and BR content analysis, which also shows the sensitive response of polymer‐filler interaction to temperature and load. The observation results of transmission electron microscopy (TEM) directly demonstrate the differences in the dispersion of fillers at different temperatures. The proposed mechanism of fluoroelastomer–silica interaction mode will provide us with novel approaches to the applications of silica in the fluorine industry. Highlights: X‐ray photoelectron spectroscopy analysis indicates new fluorine species on the interfaces.Infrared and bound rubber tests verify the fluoroelastomer–silica interactions.Rheological curves reflect the interaction strength. [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]

Polymers for implantable devices are desirable for biomedical engineering applications. This study introduces a water-resistant, self-healing fluoroelastomer (SHFE) as an encapsulation material for antennas. The SHFE exhibits a tissue-like modulus (approximately 0.4 MPa), stretchability (at least 450%, even after self-healing in an underwater environment), self-healability, and water resistance (WVTR result: 17.8610 g m−2 day−1). Further, the SHFE is self-healing in underwater environments via dipole–dipole interactions, such that devices can be protected from the penetration of biofluids and withstand external damage. With the combination of the SHFE and antennas designed to operate inside the body, we fabricated implantable, wireless antennas that can transmit information from inside the body to a reader coil that is outside. For antennas designed considering the dielectric constant, the uniformity of the encapsulation layer is crucial. A uniform and homogeneous interface is formed by simply overlapping two films. This study demonstrated the possibility of wireless communication in vivo through experiments on rodents for 4 weeks, maintaining the maximum communication distance (15 mm) without chemical or physical deformation in the SHFE layer. This study illustrates the applicability of fluoroelastomers in vivo and is expected to contribute to realizing the stable operation of high-performance implantable devices. [ABSTRACT FROM AUTHOR]

Fluoroelastomer nanocomposites have been prepared using different concentrations (1-5 wt%) of graphene oxide (GO) nanoparticles through mechanical mixing and compression molding. The surface morphology of prepared fluoroelastomer/GO nanocomposites has been studied by scanning electron microscopy (SEM). The mechanical properties of fluoroelastomer nanocomposites show increase in hardness, tensile strength, modulus, toughness and decrease in elongation at break with the increasing of GO's concentration. This can be attributed towards excellent distribution of GO nanoparticles in the fluoroelastomer matrix. The effect of GO nanoparticle concentration on rheological properties of fluoroelastomer nanocomposites like: loss factor, storage modulus, loss modulus and complex viscosity have been studied as a function of temperature (5-100°C) and at different frequency 1, 10, and 100 Hz. The non-linear relationship between storage and loss moduli have been observed through Cole-Cole plots of fluoroelastomer/GO nanocomposites. The linear relationship of loss factor and storage modulus plots was explained on the basis of fluoroelastomer/GO interactions. The visco-elastic properties show increase in loss modulus, storage modulus, complex viscosity and decrease in loss factor with GO concentration, which can be attributed towards better fluoroelastomer-nanoparticle interactions. [ABSTRACT FROM AUTHOR]

The molecular transport of a series of industrial solvent mixtures into O-rings of Viton fluoropolymers was studied. Sorption, diffusion, and permeation of the individual liquids toluene, cyclohexane, and methanol, and their binary and ternary mixtures, were evaluated from the solvent uptake using a gravimetric method. From the sorption results, the diffusion coefficients were calculated using Fick's equation. A numerical method was employed to calculate the liquid concentration profiles in cylinder-shaped polymers. The desorption mechanism was also evaluated. The composition dependence of sorption, diffusion, and permeation was assessed, and the results were analysed in terms of potential interactions between polymer and penetrant molecules. Observed sorption of methanol and methanol mixtures by the polymer was very high, in some cases higher than for pure liquids. In general, the amount of methanol present in the mixture determined its diffusion coefficient. Methanol showed the smallest solubility coefficient within the polymer, but due to its high mobility and permeability, it was shown to be the liquid that flows faster through Viton fluoropolymers. Flows of toluene and cyclohexane are still considerable, notwithstanding that this fluoropolymer is usually indicated as hydrocarbon resistant. This is an important fact to keep in mind when choosing sealings for applications with a mix of solvent media. [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]

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. [ABSTRACT FROM AUTHOR]

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The melt viscosity of ultra-high molecular weight polyethylene (UHMWPE) is extremely high, rendering its processing exteremely difficult; thus, flow modification is required to improve its flow properties. In this study, calcium stearate (CaSt) and a fluoroelastomer (FP) were used as flow modifiers to improve the flow properties of UHMWPE. The experimental results revealed that both lubricants improved the flowability of UHMWPE: CaSt improved the melt flow index of UHMWPE, while the FP had no significant effect on the melt flow index but significantly reduced the torque. The underlying mechanisms for the above effects were investigated in terms of the structure–property relationships. Rheological and dynamic mechanical analyses revealed that CaSt acted as an internal lubricant, reducing the degree of entanglement among HMWPE molecular chains. Torque rheological measurements revealed that the FP primarily acted as an external lubricant, precipitating to form an external lubricant layer during extrusion, which reduced the torque and die pressure. [ABSTRACT FROM AUTHOR]

Fluoroelastomers are suitable materials for several applications at high temperature. The present paper presents the modifications of material stability of fluoroelastomer Tecnoflon FOR 80 HS under hard operation conditions: thermal and radiation degradation. The sequence of aging stages influences the oxidation state of polymer, which loses its thermal characteristics in the close relation with scission degrees. The chemiluminescence investigation and mechanical testing are the selected procedures for the evaluation of sustained degradation asked for the qualification of O-rings, buffers and gaskets destined to nuclear power plants. The contributions of the two kinds of degrading energies: heat and ionizing radiation are discussed by means of the values of activation energies, which may describe the modification in the oxidation strength. The high temperatures applied in the assessment of material stability (170, 195 and 220 °C) as well as the descendant shape dependencies of the CL intensity vs time indicate the damage tendency with respect to the progress of oxidation in polymer matrix. The large differences between the evolutions of oxidation in the nonisothermal CL spectra of Tecnoflon material depict the existence of different local concentrations of radicals. Their decay takes place over about 100 °C, after which various routes of degradation are followed. [ABSTRACT FROM AUTHOR]

This paper addresses physical and chemical resistance evaluation of tactile sensors. We have developed cantilevertype MEMS tactile sensors embedded in the elastomer. In this work, we used a combination of silicone elastomer with excellent mechanical properties and fluoroelastomer with excellent chemical resistance. As a new embedding method for the sensor, we devised a method of embedding with PDMS with low creep and coating with a fluoroelastomer for surface protection. We further performed three evaluations to demonstrate the physical and chemical resistance of sensors. Consequently, using the devised method, we have demonstrated that the sensor with both physical and chemical resistance are feasible. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study presents the preparation of acrylamide grafted fluoroelastomer (FKM‐g‐acrylamide) by melt mixing process and its evaluation as a reactive compatibilizer for fluoroelastomer (FKM) and methyl vinyl silicone rubber (MVQ) blend system (at different compositions) in terms of mechanical properties, thermal stability, aging behavior, and morphological aspects. Mechanical properties investigation discloses almost 20% increment in tensile strength after the incorporation of 3 parts per hundred rubber of FKM‐g‐acrylamide into the FKM/MVQ blend. The shifting of the Tgs of both the rubber phases toward each other along with the decrease of the heat capacity value (Cp) attest the effective compatibilization role of the compatibilizer. However, no significant changes in the thermal stability of the blends are observed after incorporation of the prepared compatibilizer. The heat and oil aging behavior shows remarkable percentage retention of the mechanical properties for the compatibilized blend system compared to the uncompatibilized one. The morphological study indicates the abrupt reduction of the FKM domain size (2000–180 nm) in the MVQ matrix for the compatibilized blend. [ABSTRACT FROM AUTHOR]

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. [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]

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]

Fluoroelastomer (FKM) composite embedded with natural graphite (NG) was prepared and its thermal, mechanical, dielectric, and solvent transport properties were explored as a function of NG loading. The morphology of the composites was done by AFM, SEM, and TEM analysis, and XRD provides the structural analysis. The composite with 20 phr of NG content showed the highest tensile properties and thermal stability and was supported by fracture surface SEM analysis. Enhancement in polymer‐filler interaction in the composite was further confirmed by the increase in Tg value obtained from DSC analysis. The dielectric permittivity value showed tremendous increment by 30 phr of NG addition with decreased dielectric loss. The resistance to solvent uptake with increase in NG loading by the formation of tortuous pathway is also a clear evidence for the exfoliation of the graphite flakes in the FKM matrix. Better inclusion of NG in FKM matrix efficiently enhanced the thermal, mechanical, dielectric and the transport properties of the composites. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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]

Nanocomposites were prepared using carbon nanotubes (CNTs) in the formulations of fluoroelastomer (FE). Thermogravimetric analysis (TGA) results revealed that CNT improved the thermal properties of FE, resulting in higher amount of FE and char remaining within the temperature range of 520–900 °C, relative to unfilled FE and carbon black (CB)-filled FE. The same results also revealed that more percentage of FE was undegraded or less degraded especially near CNT. Energy dispersive X-ray (EDX) results indicated that the percentage of carbon and fluorine in the residue of TGA scans up to 560 °C of CNT-filled FE (CNT/FE) were higher compared to the CB-filled FE (CB/FE), and CB/FE was higher than FE. EDX results of TGA residue (run up to 900 °C) showed that most of the undegraded FE which was not degraded at temperatures below 560 °C was degraded from 560 °C to 900 °C in both CNT/FE and CB/FE, with the char in CNT/FE being more than that in CB/FE. Residue of samples after TGA scans up to 900 °C indicated that, Zn did not undergo any reaction with CNT in the CNT/FE. In CB/FE, some percentage of ZnO reacted with carbon. EDX analysis of thermal aged specimens under air showed that with increasing aging time, more percentage of C, O, and F were lost from the surface of filler/FE and FE. The order of element loss is: CNT/FE < FE < CB/FE. [ABSTRACT FROM PUBLISHER]

Fluoroelastomer (FKM) composites, reinforced with multiwalled carbon nanotubes (MWNTs), were prepared by conventional method to determine the possibility of using MWNTs to develop an antistatic composite in automotive fuel systems. The results obtained from the composite containing 0-9 phr of MWNTs were compared. A 5 points increase in hardness was achieved with the addition of only 1 phr of MWNTs and 9 phr added FKM composite was increased 6.4MPa in tensile strength compared to the MWNTs unfilled FKM composite. In addition, electrical conductivity increased from 0 to 1.039 Scm with increase in the MWNTs concentration, and the dynamic damping property was increased in the rubbery state region accordingly. These phenomena can be explained by the MWNTs networks formed in FKM matrix. This research will therefore be useful in the development of an antistatic rubber composite for fuel system components, which are deformed or vibrated while in operation. [ABSTRACT FROM AUTHOR]

Distinct melt viscoelastic properties of novel polyamide 6 (PA6)/fluoroelastomer (FKM) thermoplastic elastomeric blends have been reported with special reference to the micro- and nano-structures. In the entire frequency regime (0.0628-628 rad/s), nanostructured blend (the average dimension of the dispersed rubber phase, D ~ 90 nm) exhibited higher complex viscosity than the microstructured blend (D ~ 0.35 µm). The values of various interfacial parameters such as specific interfacial area per unit volume, interfacial tension, interaction parameter, interfacial thickness and infrared spectroscopic analysis confirmed the existence of more contact surface area between the blend components in nanostructured blend which increased intermolecular interaction. Due to the existence of greater restriction of mobility of the polymer chains, the relaxation time for the nanostructured blend was higher than that of the microstructured blend. The etched extrudate surface morphology was studied using field emission scanning electron microscopy and correlated with viscoelastic response of the blends. [ABSTRACT FROM AUTHOR]

The dynamics of water-vapor dissolution in Viton O-rings is measured with a gravimetric method using a precise mass comparator. A sample gasket was degassed in high vacuum for a sufficiently long period to remove more than 99 % of the dissolved water vapor. After that, it was exposed to the ambient atmosphere with a controlled temperature, and relative humidity and water-vapor uptake curves were measured gravimetrically with a precise balance. The dynamics of a water-vapor release into vacuum from another sample that was previously saturated with water vapor at room temperature was determined. The sample was placed in a vacuum outgassing rate measurement apparatus. The time dependence of the evolved water vapor was calculated by integrating the measured outgassing rate. The physical process of water absorption can be described by the diffusion equation. The geometry of the samples required solving the diffusion equation in cylindrical coordinates. This was done numerically using a finite-difference method. As a result of the modeling, room temperature values of the diffusion constant $$D$$ , the solubility $$s$$ , and the permeability $$K = D\times s$$ of water vapor in the sample material (Viton A-401C) were obtained. For sample 1, we obtained $$D = 8.0 \times 10 ^{-8}$$ cm $$^{2}\,\,{\cdot }\,\,$$ s $$^{-1}$$ and $$s = 6.5 \times 10^{-7}$$ g $$\,{\cdot }\,$$ cm $$^{-3}\,{\cdot }\,$$ Pa $$^{-1}$$ , while for sample 2, $$D = 3.0 \times 10^{-7}$$ cm $$^{2}\,{\cdot }\,$$ s $$^{-1}$$ and $$s = 3.5 \times 10^{-7}$$ g $$\,{\cdot }\,$$ cm $$^{-3}\,{\cdot }\,$$ Pa $$^{-1}$$ . [ABSTRACT FROM AUTHOR]

The bisphenol AF/benzyltriphenylphosphonium chloride (BPP) vulcanization system is the most commonly used fluoroelastomer (FPM) vulcanization system. In this article, polyphenol hydroxy acrylic rubber (PHACM) was prepared through a two-step reaction: grafting polymerization and condensation. The properties of FPM/PHACM/acrylic rubber (ACM) blends including vulcanization properties, mechanical properties, aging properties, oil resistance and thermal properties were studied. The results of vulcanization properties show that under the bisphenol AF/BPP vulcanization system, the FPM can achieve covulcanization with PHACM without adding bisphenol AF and get longer scorch time than that of FPM with the same level of bisphenol AF, which means that FPM/PHACM/ACM blends have better processability and curing security. Furthermore, the blends show better mechanical properties and thermal stability. The results of differential scanning calorimeteric analysis show that the FPM and PHACM achieve co-cross-linking and have good compatibility. The glass transition temperature (Tg) of the blends has been reduced to −18.57°C, which is 8.33°C lower than that of pure FPM, when the content of blends is equal to 100/100. The scanning electron microscopy shows that PHACM can improve interfacial adhesion between the FPM and ACM. [ABSTRACT FROM PUBLISHER]

The fluoroelastomer rubber (FR) was successfully incorporated in natural rubber (NR) matrix composites using a colloid stabilization-destabilization methodology in the spherical shape of a few-micrometer size, where the electrostatic surface charge of the FR and NR colloidal drops were controlled to give either stable or unstable colloid mixtures. Measuring the zeta potential of the drops with respect to pH, the stabilized colloid mixture ensured the FR to be incorporated up to 25 phr in the NR matrix as a well-dispersed ocean-island composite structure with the FR size of 0.5∼10 μm. The NR/FR composites including various additive fillers showed a good interfacial bonding and enhanced thermal stability with substantially increased mechanical properties of strength as well as elongation- at-break values. This novel technique provided a unique and highly loaded composite structure composed of FR spherical particles well dispersed in the NR matrix, which can hardly be achieved by the conventional shear-mixing techniques because of the high viscosity and viscoelastic characteristics of elastomers. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The influence of several kinds of fillers including nano-calcium carbonate particle, ZnO whisker and hollow glass bead on the vulcanizing performances and mechanical properties of fluoroelastomer (FKM) was studied. The results showed that ZnO whisker is the most helpful to lower the viscosity of the compound and improve processing flowability, and then the glass bead, while the nano-calcium carbonate can improve the mechanical property of the FKM compounds. The comprehensive properties of ZnO whisker filled FKM compound are better than those of the other two fillers. [ABSTRACT FROM AUTHOR]

The present work deals with the synthesis of specialty elastomer [fluoroelastomer and poly (styrene- b-ethylene-co-butylene-b-styrene (SEBS)]-clay nanocomposites and their structure-property relationship as elucidated from morphology studies by atomic force microscopy, transmission electron microscopy and X-ray diffraction and physico-mechanical properties. Due to polarity match, hydrophilic unmodified montmorillonite clay showed enhanced properties in resulting fluoroelastomer nanocomposites, while hydrophobic organo-clay showed best results in SEBS nanocomposites. [ABSTRACT FROM AUTHOR]

Interpenetrating polymer networks (IPNs) based on fluoroelastomer/ butadiene-acrylonitrile rubber (FKM/NBR) by molten blending at a high temperature and chemical cross-linking of two components were prepared. The influence of the two networks component on the mechanical properties and thermostabilities was studied. The experimental results show that the mechanical properties of the IPNs are superior to those of the individual FKM and NBR networks due to forming the case of interpenetrating and intercross-linking between the two networks, the mechanical properties and thermal resistance exhibit higher values when 80/20 (w/w) FKM and NBR is blended and respectively cured simultaneously. The co-continuous morphology of the IPNs in the blends of 80/20 (w/w) FKM/NBR is found by transmission electron microscopy (TEM), the differential scanning calorimetry (DSC) determination shows that the blends of 80/20 (w/w) FKM/NBR have better compatibility, and the glass transition temperature of the elastomer is −21.5 °C. [ABSTRACT FROM AUTHOR]

The viscoelastic behaviour of three different low Tg fluoroelastomer materials belonging to the class of Fluorosilicones (FVMQ), Perfluoropolyether-hydrosilanes (Sifel™) and Perfluoropolyether-polyurethanes (FEU) was investigated. Materials considered were high hardness rubbers and were characterized by dynamic-mechanical analysis (DMA), thermo-mechanical analysis (TMA), and swelling tests in Fuel C and other solvent mixtures. DMA spectra in dynamic scan allowed the determination of Tg and other minor intensity relaxation phenomena. Thermo-mechanical analysis was used to measure the thermal expansion coefficient α L and the low temperature retraction curve R e( T) in creep and recovery experiments with different test conditions. Highly diversified behaviours were observed, apparently related to polymer Tg and damping in the rubbery plateau. Swelling measurements showed a better performance for the two perfluoropolyether samples than for fluorosilicones. [ABSTRACT FROM AUTHOR]

The variations of the flow induced phase morphology of fluoroelastomer/polycarbonate (FL/PC) extruded blends and their mechanical properties were investigated in this paper. The phase morphology and mechanical property of extruded blends under the capillary die were examined by scanning electron microscope (SEM) and tensile machine, respectively. From SEM observation, the dispersed phases in the longitudinal direction for these extruded blends were categorized as sphere, ellipsoid, rod, and fiber. Furthermore, the processing window for the deformation of phase morphology in the longitudinal direction for FL/PC 10/90 w/w and 25/75 w/w extruded blends at 235 and 260 °C was studied. As shear stress was smaller than 7.0 × 104 Pa, the spherical phase almost did not deform. The transformation from the sphere to the fiber form occurred in the range of shear stress 7.0 × 104 Pa and 15.8 × 104 Pa. In particular, as shear stress was larger than 15.8 × 104 Pa, the fiber broke up into a series of small droplets. Finally, it was concluded that the morphology with the mixture of fiber-like and spherical structures in the longitudinal direction could enhance the FL/PC blends with longer break elongation and higher Young’s modulus. [ABSTRACT FROM AUTHOR]

Organs-on-chips are microfluidic devices typically fabricated from polydimethylsiloxane (PDMS). Since PDMS has many attractive properties including high optical clarity and compliance, PDMS is very useful for cell culture applications; however, PDMS possesses a significant drawback in that small hydrophobic molecules are strongly absorbed. This drawback hinders widespread use of PDMS-based devices for drug discovery and development. Here, we describe a microfluidic cell culture system made of a tetrafluoroethylene-propylene (FEPM) elastomer. We demonstrated that FEPM does not absorb small hydrophobic compounds including rhodamine B and three types of drugs, nifedipine, coumarin, and Bay K8644, whereas PDMS absorbs them strongly. The device consists of two FEPM layers of microchannels separated by a thin collagen vitrigel membrane. Since FEPM is flexible and biocompatible, this microfluidic device can be used to culture cells while applying mechanical strain. When human umbilical vein endothelial cells (HUVECs) were subjected to cyclic strain (~10%) for 4 h in this device, HUVECs reoriented and aligned perpendicularly in response to the cyclic stretch. Moreover, we demonstrated that this device can be used to replicate the epithelial–endothelial interface as well as to provide physiological mechanical strain and fluid flow. This method offers a robust platform to produce organs-on-chips for drug discovery and development. [ABSTRACT FROM AUTHOR]

Fluoroelastomer (FKM) rubber containing different weight percentage of in-situ generated nanosilica particles have been prepared by sol-gel method using tetraethoxysilane (TEOS) as precursor and n-butyl amine as catalyst. FKM rubber with precipitated silica particles have also been prepared to compare the effect of in-situ generated nanosilica particles and precipitated silica particles on the physico-mechanical properties of FKM rubber. It is interesting to note that the FKM rubber containing in-situ generated nanosilica particles display excellent tensile stress-strain properties, rheological properties and thermal properties in comparison to the FKM rubber containing precipitated silica particles. The better performance of the in-situ generated nanosilica particles has been attributed to the good dispersion of in-situ generated nanosilica particles in FKM rubber matrix when compared to the precipitated silica particles. The fourier transform infrared (FTIR) spectroscopy clearly confirms the existence of chemical interaction between the FKM rubber chains and the in-situ generated nanosilica particles which leads to the good dispersion of the nanosilica particles in the rubber matrix. Strain sweep studies confirm the presence of more rubber-filler interaction in FKM rubber filled with in-situ generated nanosilica particles. On the other hand, strain sweep studies confirm the presence of more filler-filler aggregation in FKM rubber filled with precipitated silica particles. The dispersion of the in-situ generated nanosilica particles and precipitated silica particles in the surface and bulk of FKM rubber has been studied by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Selected samples have been cured to understand the effect of curing on the efficiency of in-situ generated nanosilica particles and precipitated silica particles on the physico-mechanical properties of FKM rubber. [ABSTRACT FROM AUTHOR]