Nitrile Butadiene Rubber Matrix Research Articles

γ-Aminopropyl triethoxysilane functionalized graphene oxide for composites with high dielectric constant and low dielectric loss

A facile and efficient approach was developed to simultaneously functionalize and tune the reduction state of graphene oxide (GO) with γ-aminopropyl triethoxysilane (APTES) aided by NH3 solution. X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy indicated that many surface groups of GO sheets were removed, and APTES were successfully functionalized onto GO sheets. The APTES-functionalized GO sheets (GO-APTES) were dispersed in water and further incorporated into nitrile butadiene rubber (NBR) by latex co-coagulation to form GO-APTES/NBR composites. These composites featured high degrees of exfoliation and intercalation of GO-APTES sheets throughout the NBR matrix. More significantly, the GO-APTES/NBR composites exhibited a relatively high dielectric constant (∼30.8) and a small loss factor (<0.04) at 1.0kHz, combining with a good insulating property. The unique dielectric responses of GO-APTES/NBR composites open up the potential applications of these materials in resistive and capacitive field grading materials.

Reactive Blending of Nitrile Butadiene Rubber and In situ Synthesized Thermoplastic Polyurethane‐Urea: Novel Preparation Method and Characterization

AbstractBlends of nitrile butadiene rubber (NBR) and in‐situ synthesized thermoplastic polyurethane‐urea (PUU) are prepared by a reactive blending method. The PUU is synthesized in‐situ from the polyaddition of 4,4′‐diphenylmethane diisocyanate‐terminated prepolymer with Bisaniline‐M during blending with NBR in an internal mixer. The 1H NMR spectroscopic analysis shows up to 93% conversion of Bisaniline‐M to PUU in NBR/PUU blends. The incorporation of PUU improves the tensile characteristic, tear and abrasion resistance however a temperature dependent softening of amorphous PUU phase diminishes the dynamic‐mechanical behavior of blend vulcanizates. Improvement in physical properties of blends is attributed to good interfacial adhesion between dispersed PUU domains and continuous NBR matrix as seen by TEM.

Flexible microwave absorbers based on barium hexaferrite, carbon black, and nitrile rubber for 2–12 GHz applications

Flexile single layer electromagnetic wave absorbers were designed by incorporating appropriate amounts of carbon black in a nitrile butadiene rubber matrix along with an optimized amount of magnetic counterpart, namely, barium hexaferrite for applications in S, C, and X-bands. Effective dielectric permittivity and magnetic permeability were measured using cavity perturbation method in the frequency range of 2–12 GHz. The microwave absorbing characteristics of the composites were studied in the S, C, and X-bands employing a model in which an electromagnetic wave is incident normally on a metal terminated single layer. Reflection loss exceeding −20 dB is obtained for all the samples in a wide frequency range of 2–12 GHz when an appropriate absorber thickness between 5 and 9 mm is chosen. The impact of carbon black is clearly observed in the optimized composites on the mechanical strength, thickness, band width of absorption, dielectric properties, and absorptivity.

Lignosulfonate as dispersant for layered double hydroxide in nitrile–butadiene rubber composites

Nitrile–butadiene rubber (NBR) based layered double hydroxide (LDHs) composites have been prepared through melt-compounding method using sodium lignosulfonate modified LDH (SLS–LDH) as a filler obtained by in-situ synthesis method. The composites were characterized in terms of LDH particles dispersion, mechanical properties and thermal properties. Both X-ray diffraction and scanning electron microscopy analysis data of the composites showed that layered SLS–LDH particles were obtained and SLS improved the dispersion of LDH particles in the NBR matrix. Experimental results indicated that both pristine LDH and SLS–LDH improved the mechanical properties of NBR composites while SLS–LDH showed a more obvious reinforcing ability compared with pristine LDH. The thermal stability of composites containing SLS–LDH was remarkably improved when 50% weight loss was selected as a point of comparison in thermogravimetric analysis. Differential scanning calorimetry analysis data showed that the glass transition temperature of the SLS–LDH/NBR composites increased when compared with LDH/NBR composites indicating the enhancement of interactions between NBR chains and LDH particles in the presence of SLS.

Self-polymerization of Eu(TTA)3AA in rubber and their fluorescence effect

A simple europium complex, Eu(TTA)3AA (TTA=4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, AA=acrylic acid) was synthesized by a simple solution method. Then, two kinds of rubber matrix, nitrile-butadiene rubber (NBR) and silicone rubber (SiR) were used as the substrate for Eu(TTA)3AA to prepare fluorescence composites. The neat Eu(TTA)3AA complex showed the ability of self-polymerization when it was heated at 145 °C. It was found that the fluorescence intensity of the neat Eu(TTA)3AA decreased over 70% when the polymerization time was over 25 min at 145 °C. The results also revealed that the polymerizated Eu(TTA)3AA could be dispersed in nano-scale in two matrices and the luminescent intensities decreased 52% in NBR matrix, and 95% in SiR matrix compared with two relative compounds without crosslinking. To optimize the luminescence intensity of the composites, the Eu(TTA)3AA polymerization kinetic process in matrix was investigated in detail by controlling the temperature, the crosslinking agent, etc. The results showed that the peroxide could accelerate Eu(TTA)3AA self-polymerization in the rubber matrix, and therefore improved the dispersion, but not be helpful for the luminescence intensity enhancement. In addition, the relatively higher luminescence intensity in Eu(TTA)3AA/NBR in comparison to that of Eu(TTA)3AA/SiR might contribute to the interaction between nitrile group (–CN) in NBR and Eu-complexes, suggesting that the luminescence intensity of the composites also depended on the matrix characteristics.

Flexible electromagnetic interference shields made of silver flakes, carbon nanotubes and nitrile butadiene rubber

The recent advances in portable and flexible electronic devices demand integration of flexibility into future electromagnetic interference shielding materials. Here we synthesized flexible adhesive shields made of microscale silver flakes (Ag flakes), multi-walled carbon nanotubes decorated with nanoscale silver particles (nAg-MWNTs), and nitrile butadiene rubber (NBR). The addition of nAg-MWNTs into the Ag flake–NBR mixture significantly enhanced both conductivity and shielding effectiveness. Long nanotubes electrically linked microscale Ag flakes embedded in the NBR matrix, and nanoscale silver particles further improved the contact interface. There was a logarithmic relationship between the conductivity and shielding effectiveness. The dominant mechanism of electromagnetic interference shielding was reflection. The achieved maximum shielding effectiveness was about ∼75dB at 1GHz. The flexible adhesive shield printed on a polyimide film was wrapped around a cylindrical rod with a radius of 4mm. The shielding effectiveness decreased about 20% after 100 wrapping cycles. The conductivity and shielding effectiveness could be adjusted by changing the Ag flake concentration. There was an excellent agreement between the theoretically predicted shielding effectiveness and the experimental data.

Preparation and characterization of nitrile butadiene rubber-nanoclay composites with maleic acid anhydride as compatibilizer. Part I

Nitrile butadiene rubber (NBR)-nanoclay composites have been prepared. Maleic acid anhydride-treated organoclay (MOC) was synthesized and utilized as a compatibilizer. The prepared clay structures were analyzed by Fourier transform infrared (FTIR) spectroscopy. Furthermore, the FTIR investigation confirmed the incorporation of (MOC) in the NBR matrix, X-ray diffraction analysis indicated that an exfoliated structure was obtained, and scanning electron microscope images displayed the good interaction between the MOC and the rubber matrix. The influence of the MOC content (i.e. 1, 3, 5, 10, 20 phr) relative to the micrometer clay (i.e. 10, 20 phr) on the NBR compounds was analyzed through rheometric and swelling characteristics. The rheometric study demonstrated an increase in minimum and maximum torques, delayed scorch time and optimum cure time for the MOC (3 phr)-incorporated NBR compound compared to pure NBR. The cure rate index followed the same trend. In addition, these particular compounds showed decreased equilibrium swelling in toluene solvent, increased crosslinking density, a greater volume fraction and bound rubber content compared to the corresponding rubber filled with micrometer clay.

Mechanochemical preparation of devulcanized ground fluoroelastomers for the enhancement of the thermal stability of nitrile–butadiene rubber vulcanizates

AbstractMechanochemically devulcanized ground fluoroelastomer (FKM) was used as a low‐cost functional additive for the enhancement of the thermal stability of nitrile–butadiene rubber (NBR) vulcanizates. Without the use of any chemicals, the stress‐induced mechanochemical devulcanization of ground FKM was achieved through solid‐state mechanochemical milling at ambient temperature. The sol fraction of the ground FKM was increased from its original 1.4 to 19.8% after milling; this confirmed the realization of the mechanochemical devulcanization of FKM. Moreover, the oxygen‐containing polar groups on the surface of the mechanochemically milled FKM benefitted its interfacial adhesion with the polar NBR matrix. The curing characteristics and mechanical properties of the devulcanized, FKM‐filled NBR vulcanizates were investigated and compared with those of the untreated FKM‐filled NBR vulcanizates. The results show that the mechanical properties of the devulcanized FKM‐filled NBR vulcanizates were much better than those of the untreated FKM‐filled NBR vulcanizates. The presence of the reclaimed FKM significantly increased the onset degradation temperature of the NBR vulcanizates as a result of the improved polymer–filler interaction, uniform dispersion, and high thermal stability of the reclaimed FKM. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Microwave absorbing properties of a thermally reduced graphene oxide/nitrile butadiene rubber composite

Reduced graphene oxide (RGO) with a layered and porous structure was synthesized by thermal exfoliation of graphite oxide. Synthesized RGO is very light weight and flaky. The formation of RGO was studied using Fourier transform infrared and Raman spectroscopies, X-ray diffraction and scanning electron microscopy. Composites were prepared by dispersing 2%, 4% and 10% by weight of the synthesized RGO into nitrile butadiene rubber (NBR) matrix. Microwave absorption properties of RGO/NBR composites were investigated by measuring their complex permittivity and permeability by using waveguide method. Simulation studies show that 10wt.% of graphene oxide in NBR matrix exhibits high values of reflection loss (>10dB) over a wide frequency range 7.5–12GHz and maximum loss is 57dB at 9.6GHz at a thickness of 3mm.

Structure and dynamic properties of nitrile‐butadiene rubber/hindered phenol composites

AbstractCrosslinked nitrile‐butadiene rubber (NBR)/hindered phenol composites were successfully prepared by mixing tetrakis [methylene‐3‐(3‐5‐ditert‐butyl‐4‐hydroxy phenyl) propionyloxy] methane (AO‐60) into NBR with 35% acrylonitrile mass fraction. The structural and mechanical properties of the NBR/AO‐60 composites were systematically investigated by using differential scanning calorimeter, XRD, Fourier transform infrared, scanning electronic microscope, dynamic mechanical analyzer, and tensile testing. The results indicated that the AO‐60 changed from crystalline form into amorphous form, and most of the AO‐60 molecules could be uniformly dispersed in the NBR matrix. The glass transition temperature (Tg) of NBR/AO‐60 composites increased gradually with increasing content of AO‐60. The increase in Tg could be attributed to the formation of a strong hydrogen bonding network between the AO‐60 molecules and the NBR matrix. Unlike the pure NBR, the NBR/AO‐60 rubber composites had only one transition with a high loss factor. With increasing content of AO‐60, the loss peak shifted to the high temperature region, the loss factor increased from 1.45 to 1.91, and the area under the tan δ versus temperature curve (TA) also showed a significant increase. All these results were ascribed to the good compatibility and strong intermolecular interactions between NBR and AO‐60. Furthermore, all NBR/AO‐60 composites exhibited higher glass transition temperatures and tensile strength than NBR, and they had other desirable mechanical properties. They have excellent prospects in damping material applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Electropolymerization of 3,4-ethylenedioxythiophene within an insulating nitrile butadiene rubber network: Application to electroreflective surfaces and devices

Innovative designs based on semi-interpenetrating polymers networks (semi-IPN), where an electronic conductive polymer (ECP) is formed within – but on each side – a film of a polymer network chosen both for their mechanical properties and ionic conductivity lead to devices with battery-like architecture. Usually, the route to introduce the ECP is an oxidative chemical polymerization leading to conducting semi-IPN with mixed conductivities (electronic and ionic). We will present the fabrication of such semi-IPN using an electrochemical route to form the ECP. This strategy is interesting since it allows the choice of the electrolytic medium and therefore the nature of the doping ion. This process implies the electropolymerization of the conjugated monomer – 3,4-ethylenedioxythiophene (EDOT) – within a flexible insulating matrix, which is a Nitrile Butadiene Rubber (NBR) network or a flexible IPN made of NBR and a branched polyethylene oxide (PEO) network. In the first part, scanning electron microscopy experiments show that the two-phases composition of the semi-IPN NBR/PEDOT obtained notably the localization of PEDOT inside the NBR matrix. The electropolymerization process is discussed and electrochemical characterization by cyclic voltamograms demonstrates the accessibility of the PEDOT inside the matrix. In the second part, we present first the reflective properties of the NBR/PEDOT semi-IPN. Upon chemical oxidation/reduction processes, it is possible to observe a 25% reflection contrast in the Near Infrared (NIR) at 2.5μm. Then, we described the device's fabrication requiring the dual combination of two semi-IPNs. In order to favor the adhesion between them, we chose a whole system based on an NBR/PEO/PEDOT semi-IPN in which the EDOT is polymerized under the same conditions as previously. The junction was ensured by the PEO partner serving as binder between the two semi-IPNs.Then, after the addition of an electrolyte (LiClO4 0.1M/PC) to complete the device elaboration, it was possible to electrochemically switch the system and to observe NIR optical modulation with a promising contrast up to Δ%R=14% at 2.5μm. The optical properties were also measured in the middle infrared region: the contrasts were Δ%R3–5μm=18% and Δ%R8–12μm=17% in the integrated bands II (3–5μm) and III (8–12μm), respectively.

Study on Magnetic and Physical Mechanical Properties of NBR Composites Filled with Nano-Sro.6Fe2O3

In this study, we used nano-SrO.6Fe2O3 particles as modified filler to prepare nitrile butadiene rubber/SrO.6Fe2O 3 composites. Surface microstructure of the composites was observed using scanning electron microscope, the distribution of nano-SrO.6Fe 2O3 particles was measured by energy-dispersive X-ray spectrometer, and magnetic properties of the composites were tested by a U5-10 magnetizer. The results showed that nano-SrO.6Fe2O3 particles were closely inosculated with nitrile butadiene rubber and well distributed in the nitrile butadiene rubber matrix. With adding different mass fractions of nano-SrO.6Fe2O3, stress at 300% definite elongation, maximum elongation, and tensile strength of the composites were slightly decreased, but shore A hardness of the composites was markedly improved. Magnetic properties of the composites were uncorrelated to the degree of scatter of nano-SrO.6Fe2O3 particles, and relied only on mass fraction of nano-SrO.6Fe2O3 particles. The nitrile butadiene rubber/SrO.6Fe2O3 composites have good soft magnetism performance, which laid the foundation for further application of the composites.

Migration of novel epoxidized neem oil as plasticizer from PVC: Experimental design approach

AbstractMigration behavior of epoxidized neem oil (ENO) from poly(vinyl chloride) (PVC) plasticized with ENO to acrylo nitrile butadiene rubber (NBR) was investigated. Central composite rotatable design (CCRD) for three variables at five levels was chosen as the experimental design. Concentration of Neem oil in PVC matrix, acrylo nitrile (ACN%) content in NBR matrix, and peroxide content used in NBR formulation were selected as three independent variables. Other parameters pertinent to migration phenomena such as partition coefficient, activation energies, rate constants, and diffusion coefficients were evaluated and these properties were fitted to a distinctive response equation generated by CCRD. Proposed response equations for most parameters were considered as having sufficient explanatory power and “good fit” in the statistical sense. Partitioning of ENO as a plasticizer between PVC and NBR follows first order equilibrium kinetics, and the forward reaction is found to be endothermic. The percentage migration of plasticizer at 296 K at equilibrium is well below 25% for the majority of cases irrespective of other pertinent factors. Parameters such as forward, backward, and overall rate constants and their respective activation energies and enthalpy change related to the partitioning phenomenon are influenced to different degrees by plasticizer concentration in PVC, ACN% in NBR and crosslink density of NBR. The influence caused by plasticizer concentration and ACN% was found to be the most significant. Diffusion of plasticizer through PVC matrix is the rate determining step for the overall migration process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Design and preparation of cross-linked α-methylstyrene-acrylonitrile copolymer nano-particles for elastomer reinforcement

Crosslinked α-methylstyrene and acrylonitrile (MStAN) copolymer particles in a latex form were synthesized by free radical emulsion polymerization. The particles took a spherical shape with an average size of 53.1 nm in a narrow distribution. When filled into styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), and natural rubber (NR), the MStAN nano-particles exhibited excellent reinforcing capabilities and the best in NBR. By the employment of heat treatment, mechanical properties of the MStAN-filled SBR composites had got remarkable further improvements. But mechanical properties, together with the morphology, of the MStAN-filled NBR composites, varied little after heat treatment, which, however, divulged the naturally good compatibility between the MStAN particles and the NBR matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The Effects of Coupling Agents on the Mechanical Properties of NBR-Clay Nanocomposites and its Conventional Composites

Organoclay, precisely montmorillonite, is modified with octadecylamine and then its surface is individually treated by silane coupling agents, DB550, DB580, and DB619. The nitrile butadiene rubber (NBR) is mechanically mixed with organophilic clay via melt blending method. Characterizations of prepared hybrids based on NBR-organoclay treated by silane coupling agents are investigated on such aspects as X-ray diffraction (XRD), scanning electron microscopy, infrared spectra, mechanical properties, and dynamic mechanical analysis (DMA). The XRD result shows that layered silicates are intercalated by polymer chains. The nanocomposites with coupling agent DB580 or DB619 have superior mechanical properties in comparison with conventional composites and ordinary nanocomposites. Apart from a limited increase in tensile stress at small strains, the ultimate stress at rupture of the nanocomposites is much higher than that of microcomposites. It is presumed that these enhancements are attributed not only to the more uniform dispersion of nanoparticles of organoclay into the polymer matrix but also to the coupling agent bond or micro-adhesion between the NBR matrix and the organoclay.

Development of nitrile butadiene rubber–nanoclay composites with epoxidized natural rubber as compatibilizer

The most important factor, which indicates the improvement of properties in rubber by nanoclay, is the distribution in the rubber matrix. The simple mixing of rubber and nanoclay will not exfoliate the filler in the rubbery matrix. Hence, some sort of compatibilizer like epoxidized natural rubber (ENR) can be utilized safely in exfoliating the nanoclay in the matrix polymer. Epoxidized natural rubber and organically modified nanoclay composites (EC) were prepared by solution mixing. The nanoclay employed in this study was Cloisite 20A. The obtained nanocomposites were incorporated in nitrile butadiene rubber (NBR) with sulphur as a curing agent. The morphological study showed the intercalation of nanoclay in ENR and further incorporation of EC in NBR matrix leads to exfoliation of nanoclay. Curing study demonstrated faster scorch time, cure time and increase in maximum torque for the EC incorporated NBR compounds compared to pure NBR. Dynamic mechanical thermal analysis showed increase in storage modulus and lesser damping characteristics for the compounds containing EC loading in NBR matrix. In addition, these particular compounds showed enhancement in overall mechanical properties, higher swelling resistance in oil and solvent and decrease in compression set due to higher reinforcing efficiency of nanoclay in the NBR matrix.

Exfoliated sodium-montmorillonite in nitrile butadiene rubber nanocomposites with good properties

We prepared and utilized a novel ultrafine fully-vulcanized powder nitrile butadiene rubber (UFPNBR)/sodium montmorillonite (Na-MMT) nanocompound powder, in which nanoscale UFPNBR particles and nanoscale platelets of Na-MMT were isolated and stuck each other. When the UFPNBR/Na-MMT nanocompoud powder was mixed with crude nitrile butadiene rubber (NBR), UFPNBR particles could be easily dispersed in NBR matrix because of good compatibility, and nanoscale Na-MMT was also dispersed well in NBR matrix due to the carrier aidance of UFPNBR particle, thus the NBR/UFPNBR/Na-MMT ternary nanocomposites adapting to industry was fabricated. X-ray diffraction test and scanning electron microscopy (SEM) observation indicated that nanoscale Na-MMT was dispersed well in NBR matrix. Compared with NBR/Na-MMT binary composites, NBR/UFPNBR/Na-MMT ternary nanocomposites have shorter vulcanization time and higher flame retardancy due to the exfoliated Na-MMT in NBR matrix.

Preparation and properties of nanocomposites based on different polarities of nitrile–butadiene rubber with clay

AbstractNanocomposites were prepared with different grades of nitrile–butadiene rubber (NBR) [with nitrile (CN) contents of 26, 35, and 42%] with organoclay (OC) by a melt‐compounding process. The rubber/clay nanocomposites were examined by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). An increase in the polarity of NBR affected the XRD results significantly. The dispersion level of the nanofiller in the nanocomposites was determined by a function of the polarity of the rubber, the structure of the clay, and their mutual interaction. The intercalated structure and unintercalated structure coexisted in the lower polar of NBR. In addition, a relatively uniformly dispersed state corresponded to a more intercalated structure, which existed in the higher polar of NBR matrix. Furthermore, high‐pressure vulcanization changed the extent of intercalation. The mechanical properties and gas barrier properties were studied for all of the compositions. As a result, an improvement in the mechanical properties was observed along with the higher polarity of NBR. This improvement was attributed to a strong interaction of hydrogen bonding between the CN of NBR and the OH of the clay. Changes in the gas barrier properties, together with changes in the polarity of the rubbers, were explained with the help of the XRD and TEM results. The higher the CN content of the rubber was, the more easily the OC approached to the nanoscale, and the higher the gas barrier properties were. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

New Strategy and Easy Fabrication of Solid-State Supercapacitor Based on Polypyrrole and Nitrile Rubber

Solid state redox supercapacitors were fabricated using a solid polymer electrolyte, nitrile butadiene rubber (NBR)-KCI and chemically deposited polypyrrole (PPy) as the conducting polymer electrodes on both surfaces of a NBR film. The optimal conditions for the preparation of the PPy/NBR electrode were confirmed as functions of the uptake of pyrrole monomer into the NBR matrix as well as the immersion time in an oxidant solution. The morphology of the PPy-NBR-KCI capacitor was observed using scanning electron microscopy. The performance of the capacitors was characterized using a galvanostatic charge-discharge technique.

Novel Europium‐Complex/Nitrile‐ Butadiene Rubber Composites

AbstractThe novel europium complex acrylato(1,10‐phenanthroline)bis(2‐thenoyltrifluoroacetonato)europium(III) [Eu(tta)2(aa)(phen)] [Eu‐AAPhen; Htta = 4,4,4‐trifluoro‐1‐(2‐thienyl)‐1,3‐butanedione, Haa = acrylic acid, phen = 1,10‐phenanthroline], which combines the excellent fluorescence properties of [Eu(tta)3(phen)] and the reactivity of acrylic acid with radicals, has been synthesized. Various amounts of this complex (powder) are mixed with nitrile‐butadiene rubber (NBR) and peroxide to form uncured composites. These composites are vulcanized to obtain cured Eu‐AAPhen/NBR composites. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that the dispersion dimension for the cured composites is far finer than that for the uncured composites. Wide‐angle X‐ray diffraction (WAXD) experiments show that the crystallinity of Eu‐AAPhen in the composite decreases dramatically after the crosslinking process, implying that in‐situ reactions (including polymerization and grafting) of Eu‐AAPhen initiated by peroxide radicals should take place during the crosslinking of the NBR matrix with peroxide. The dispersion phase of the cured Eu‐AAPhen/NBR composite should be composed of nearly nanometer‐sized aggregates of poly(Eu‐AAPhen) and residual Eu‐AAPhen particles with reduced dimensions. The fluorescence properties of the cured composite are much better than those of the uncured one.