NBR Matrix Research Articles

Enhanced dielectric constant of acrylonitrile–butadiene rubber/barium titanate composites with mechanical reinforcement by nanosilica

Acrylonitrile–butadiene rubber (NBR), a synthetic rubber having C≡N dipoles, was chosen as a polymer matrix with a higher dielectric constant than other non-polar rubber like silicone rubber or ethylene–propylene–diene monomer. Barium titanate (BaTiO3), as a ferroelectric material, with a high dielectric constant and low dielectric loss was selected as a main filler to further enhance the dielectric constant of NBR. An effective silane coupling agent (KH845-4), selected from five types of silane coupling agents with different characteristic functional groups, was used to modify the surface of BaTiO3 particles to enhance its interfacial adhesion to the matrix. Fourier transform infrared spectroscopy (FTIR) was used to verify the successful modification. The addition of BaTiO3 obviously enhanced the dielectric constants. In particular, an uncommon pattern of dielectric loss has been displayed and analyzed in this paper. Nevertheless, the reinforcing effect of mechanical strength of the NBR/treated BaTiO3 composites is limited. On this basis, the addition of nanosilica (SiO2), replacing part of NBR, improved the mechanical strength. Confirmed by scanning electron microscopy (SEM), the SiO2 and treated BaTiO3 particles were dispersed well in the NBR matrix. The tensile strength was increased from 4.33 to 6.12 MPa when SiO2 accounted for 4%. Moreover, the curing characterizations, crosslinking density, resistivity, and oil resistance were evaluated. This composite material can be used in manufacturing electronic devices, which are subjected to oily environments for a long time.

Improvement in mechanical properties of NBR/LiClO4/POSS nanocomposites by constructing a novel network structure

The mechanical properties and the possible micro-structure of nitrile-butadiene rubber/lithium perchlorate/polyhedral oligomeric silsesquioxane (NBR/LiClO4/POSS) nanocomposites have been investigated thoroughly. The interactions among Li+ cations, CN groups and COC groups bring in a novel network structure consisting of several kinds of effective crosslinks, causing an increase in the glass transition temperature of POSS, as well as in the crosslink contribution (Gc) and the constraint contribution (Ge), which facilitates strong interface cohesion between POSS and NBR matrix and a well dispersion of POSS. The addition of POSS not only increases the crosslinking density of NBR/LiClO4/POSS nanocomposites, but also improves the 300% modulus and tensile strength greatly. Therefore, a possible micro-structure has been proposed to express the experimental observation.

Properties of acrylonitrile butadiene rubber (NBR)/poly(lactic acid) (PLA) blends and their foams

Thermoplastic elastomers and their foams were prepared by blending elastomeric acrylonitrile butadiene rubber (NBR) and rigid poly(lactic acid) (PLA) with various PLA compositions ranging between 0 and 40%. The thermal and mechanical properties and the morphologies of the blends with various PLA contents were investigated through universal testing machine, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscope analysis. The rheological properties during gel formation were in situ monitored through the evolution of torque with curing time. Furthermore, the microcellular structures and physical properties of the NBR/PLA foams prepared using organic blowing agents were studied. The NBR/PLA blends showed a two-phase morphology made of a continuous NBR matrix and micron or submicron nodules and the tensile strength and modulus; also, hardness of the NBR/PLA blends increased with the increase of the added PLA content. While the foamed samples exhibited a similar cell structure and foaming ratio to that of the pure NBR, the cell formation was considerably reduced as the added PLA content exceeded 30%. We conclude that the mechanical properties of NBR thermoplastic elastomer as well as its foams can be controlled by a judicious introduction of rigid and biodegradable PLA.

Electromagnetic shielding properties of graphene/acrylonitrile butadiene rubber nanocomposites for portable and flexible electronic devices

The modern advances in portable and flexible electronic devices require integration of flexibility into future electromagnetic interference shielding nanocomposites. Lightweight and flexible acrylonitrile butadiene rubber/graphene nanosheets (NBR/GN) nanocomposites were fabricated using conventional rubber – roll milling technique. The surface morphology of as prepared GN and NBR/GN nanocomposites were examined by scanning and high resolution electron microscopy. The incorporation of GN nanosheets into NBR matrix has significantly enhanced the mechanical properties and electrical conductivity of nanocomposites. The dielectric properties of (NBR/GN) in the frequency range from 1 GHz to 12 GHz were studied. The electromagnetic interference shielding effectiveness (SE) of conducting NBR/GN nanocomposites was studied as a function of GN content, frequency and thickness of absorber and their interrelation was explored. We found an excellent agreement among theoretically predicted shielding effectiveness and the experimental data. The obtained results revealed that NBR/GN nanocomposites can be used as very effective, lightweight microwave shielding materials for spacecraft, aircraft, microelectronic and structural applications.

Preparation and properties of acrylonitrile–butadiene rubber–graphene nanocomposites

ABSTRACTThe graphene oxide (GO) was prepared by sonication‐induced exfoliation from graphite oxide, which was produced by oxidation from graphite flakes with a modified Hummer's method. The GO was then treated by hydrazine to obtain reduced graphene oxide (rGO). On the basis of the characterization results, the GO was successfully reduced to rGO. Acrylonitrile–butadiene rubber (NBR)–GO and NBR–rGO composites were prepared via a solution‐mixing method, and their various physical properties were investigated. The NBR–rGO nanocomposite demonstrated a higher curing efficiency and a change in torque compared to the gum and NBR–GO compounds. This agreed well with the crosslinking density measured by swelling. The results manifested in the high hardness (Shore A) and high tensile modulus of the NBR–rGO compounds. For instance, the tensile modulus at a 0.1‐phr rGO loading greatly increased above 83, 114, and 116% at strain levels of 50, 100, and 200%, respectively, compared to the 0.1‐phr GO loaded sample. The observed enhancement was highly attributed to a homogeneous dispersion of rGO within the NBR matrix; this was confirmed by scanning electron microscopy and transmission electron microscopy analysis. However, in view of the high ultimate tensile strength, the NBR–GO compounds exhibited an advantage; this was presumably due to strong hydrogen bonding or polar–polar interactions between the NBR and GO sheets. This interfacial interaction between GO and NBR was supported by the marginal increase in the glass‐transition temperatures of the NBR compounds containing fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42457.

Highly stretchable dielectric elastomer material based on acrylonitrile butadiene rubber

This study presents a highly stretchable dielectric elastomer material for transducers based on acrylonitrile butadiene rubber (NBR). The material has advantages in that its mechanical and electrical properties can be modified according to the requirements of applications by changing the content of additives such as carbon black (CB), multi-walled carbon nanotubes (MWCNT), and graphite (GP) in the NBR matrix. First, the changes of dielectric permittivity depending on the additives are discussed. Moreover, the electrical resistance is examined in detail by changing the compositions of the additives, and the applicability of the material to the electrodes of transducers is investigated. Finally, the optimal contents of additives for actuators or sensors are discussed.

Influence of the Surfactant on the Hydrotalcite Dispersion in NBR/LDH Composites Produced by Coagulation

SummaryDispersions of 10% wt hydrotalcite were prepared by mixing using an ultrasound probe and then incorporated into NBR latex for the purpose of evaluating the influence of the surfactant presence and dispersion stability of the hydrotalcite, both in water and in latex. The surfactant used was Pluronic F‐127 and its influence was determined on the size of the agglomerates, the degree of sedimentation and the viscosity of water/LDH dispersions and latex/LDH suspensions. Preliminary results showed the efficiency of the surfactant in promoting dispersion of water/LDH, presenting lower agglomerate diameter values and increased stability of the dispersion. For the latex/LDH suspension, the viscosity of the system containing surfactant was significantly greater due to a better dispersion of LDH. After coagulation, the systems were examined in detail using X‐ray diffraction (XRD) and the results did not show differences in the degree of intercalation, but XRD pattern of LDH was not observed, indicating the breakdown of crystallinity and ordering of the clay crystallites. The ash content showed that the presence of surfactant was an important factor to optimize the incorporation of the clay during coagulation. The estimation of Payne effect from shear modulus indicated a better filler dispersion in NBR matrix when using Pluronic F‐127, this behavior was also confirmed by FESEM micrographs.

The Structure and Properties of NBR / Recycled Polytetrafluoroethylene (R-PTFE) Composites

The structure and properties of NBR and its composites coupled with different particle size of recycled polytetrafluoetylene (R-PTFE) are investigated. The results show that R-PTFE has a positive effect on NBR enhancing the curing properties of materials, mechanical properties, solvent resistance of NBR when the particle size of R-PTFE less than 200 mesh. However, when it is 200 mesh, R-PTFE is not easily dispersed in the NBR matrix, resulting in decreasing the properties of NBR/R-PTFE composites.

Electrical and mechanical properties of manganese dioxide–magnetite-filled acrylonitrile butadiene rubber blends

Different concentrations of fillers such as manganese dioxide (MnO2) and magnetite (Fe3O4) were incorporated into acrylonitrile butadiene rubber (NBR)-interlinked composites. The prepared composite systems were irradiated by electrons at a constant dose of 50 kGy to induce radiation cross-linking under atmospheric conditions. The effect of different contents of fillers and temperature variations on direct current (DC) electrical conductivity, σDC, in NBR/MnO2 and NBR/Fe3O4 mixture systems was investigated. The calculated activation energy, Δ EDC, from σDC was found to be highly affected by both the type and concentration of the fillers, while the dielectric properties namely dielectric constant, dielectric loss, and the alternating current (AC) electrical conductivity ( σAC), were measured as functions of frequency and temperature and for different filler concentrations of MnO2 and Fe3O4. The σAC value was calculated from dielectric measurements and by employing a simple relationship. The analysis of the σAC results shows that the conductivity increases up to a temperature of about 330 K. Further increase of temperature reduces the conductivity of Fe3O4 samples, while the conductivity of MnO2 samples tends to show almost constant values after this temperature. Mechanical properties, tensile strength (TS), tensile modulus at 100% elongation, and hardness were established as a function of different concentrations of fillers MnO2 and Fe3O4. It was found that filler incorporation into the NBR matrix is one of the major factors that enhance the TS as well as hardness resistance, while the elongation at break shows an adverse behavior by increasing the content of MnO2 and Fe3O4 fillers.

A new approach with prepregs for reinforcing nitrile rubber with phenolic and benzoxazine resins

Acrylonitrile-co-butadiene rubbers (NBR) reinforced with phenolic and benzoxazine resins (NBR–Ph and NBR–Bz respectively) are prepared by a novel method using co-curing. The relative effect of these resin reinforcements with NBR in comparison to the non-reinforced NBR rubber compound NBR–S under the same conditions has been investigated. It was found that these resins exist in the form of a localized, interpenetrating network structure in the NBR matrix. For both NBR–Ph and NBR–Bz composites, the tensile strength, tear strength and elongation at break increases compared to NBR–S. The tensile strength in particular was increased by about 91% for NBR–Ph and by about 109% for NBR–Bz. Thermogravimetric analysis (TGA) provides evidence for the superior thermal stability for NBR composites over NBR–S. A decrease in the swelling values are observed in the NBR composites and the retained tensile strength, elongation at break and modulus from thermal aging studies are found to be superior than NBR–S. These results have shown that both the phenolic and benzoxazine resins are effective reinforcements for NBR materials.

Aluminum silicate fibers impregnated acrylonitrile butadiene rubber composites: Ablation, thermal transport/stability, and mechanical inspection

ABSTRACTVariant concentrations of ceramic fibers (CerFs) were incorporated into acrylonitrile butadiene rubber (NBR) to fabricate elastomeric ablative composites for ultrahigh temperature applications. The CerFs introduction into the polymer matrix has enhanced the ablation resistance up to 59% and successfully reduced the backface temperature of the polymer composite up to 110oC during the ultrahigh temperature ablation investigation. Thermal decomposition of the polymer composites was diminished up to 10% with increasing fiber concentration in the rubber matrix. Thermal conductivity was reduced equal to 63% while thermal impedance was enhanced up to 84% with the utmost fiber incorporation into the NBR matrix. The CerFs have adversely affected the mechanical properties of NBR matrix due to their brittle/inert nature and weak interface bonding with the host matrix. Scanning electron microscopy along with the energy dispersive x‐ray spectroscopy was used to examine the ablated specimens and the fiber dispersion within the host matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4392–4400, 2013

Effect of halloysite nanotubes on curing behavior, mechanical, and microstructural properties of acrylonitrile–butadiene rubber nanocomposites

Halloysite nanotubes (HNTs) have been used as a new type of filler for acrylonitrile–butadiene rubber (NBR) matrix. The NBR/HNT nanocomposites were prepared using a two-roll mill by adding 0–7 parts per hundred rubber (phr) HNTs, and the effect of the loading of HNTs on the curing behavior, mechanical, and microstructural properties were also investigated in this study. The cure characteristics showed that the cure time ( t90) and scorch time ( ts2) decreased, whereas the maximum torque ( MH) exhibited an increasing trend from 0 to 7 phr. The tensile properties improved until optimum loading of HNTs (5 phr) and thermal stability increased with increasing HNT loading. The morphological study revealed the HNTs homogeneously dispersed inside the NBR matrix and good interaction occurred between HNTs and NBR.

Preparation, structure and properties of dynamically vulcanized polypropylene/acrylonitrile butadiene rubber/zinc dimethacrylate ternary blend composites containing maleic anhydride grafted polypropylene

This work demonstrated an approach to compatibilization between polypropylene (PP) and acrylonitrile butadiene rubber (NBR) by using maleic anhydride grafted polypropylene (MA-g-PP) as a compatibilizer in the presence of zinc dimethacrylate (ZDMA). It was observed that ZDMA increased the interfacial bonding between NBR and PP matrix. Incorporation of MA-g-PP further increased the mechanical properties of the resultant blends. The morphology analysis, dynamic mechanical analysis (DMA) and crystallization behavior study indicated that incorporation of MA-g-PP would change the polarity of the PP phase, facilitating more ZDMA diffusing from NBR into the PP phase during melt mixing. As a result, the possible creation resulted from polymerization of ZDMA combined with MA-g-PP increased the interface adhesion and compatibility between PP and NBR phases, which contributed to the considerable improvement in mechanical properties of the resultant blends. Moreover, we found that MA-g-PP did not influence the size of the crosslinked NBR phase, but significantly improved the viscosity of the resultant materials.

Thermogravimetric, differential scanning calorimetric and experimental thermal transport study of MWCNT/NBR nanocomposites

Pristine multiwalled carbon nanotubes (MWCNTs) were impregnated in acrylonitrile butadiene rubber (NBR) using internal dispersion kneader and two roller mixing mill to investigate the effects of various nanotubes concentrations on the thermal transport/stability of rubber nanocomposites. Thermal conductivity (λN) and thermal impedance (R) measurement experimental setups were established according to ASTM E1225-99 and D5470-03. The 1 mass % addition of MWCNTs in the polymer matrix has enhanced R up to 44 % and reduced λN of the rubber nanocomposite up to 40 % compare to the base composite formulation. Thermal decomposition and differential thermal analyses of the fabricated composite specimens simulate that the thermal stability and endothermic capability are augmented with increasing the nanotubes contents in the host matrix. The progressive incorporations of carbon nanotubes into the rubber matrix have efficiently influenced the composite specimens regarding glass transition, crystallization, and melting temperatures including their specific enthalpies. Scanning electron microscopy along with the energy dispersive spectroscopy was used to analyze MWCNTs dispersion in NBR matrix, compositional analysis of the nanocomposite, and impregnated nanotubes.

Fabrication and characterization of NBR/MWCNT composites by latex technology

AbstractTo develop a rubber composite with excellent electrical properties, a sort of synthetic rubber, acrylonitrile butadiene rubber (NBR) with CN dipoles as matrix, multi‐walled carbon nanotubes (MWCNTs) as filler, was synthesized. NBR composites reinforced with 0.5, 1.5, 3, 10, and 20 phr MWCNT contents were fabricated by latex technology. The electrical conductivity, dielectric characteristics, and electromagnetic interference (EMI) shielding effectiveness at room temperature of NBR/MWCNT composites were investigated. MWCNTs were found well dispersed into NBR matrix even for 20 phr content by FESEM observation. The electrical conductivity increased with an increment of MWCNT content. The dielectric constant was over 104 at 103 Hz frequency for 10 and 20 phr MWCNTs‐reinforced NBR composites. It was attributed to the increased electrons and interface polarization. The improved conductivity and dielectric permittivity resulted in an enhanced EMI shielding effectiveness. The EMI shielding effectiveness reached 26 dB at 16.7 GHz frequency for NBR/20 phr MWCNT composite with 1.0 mm thickness. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Influence of Fluorination of Silica Surfaces on Interfacial Mechanical Properties of Acrylonitrile-Butadiene Rubber-Based Composites

In this study, the surface of silica was modified by direct fluorination treatment at different temperatures.The effect of fluorinated silica (F/Si) on the interfacial mechanical properties and thermal stability of acrylonitrile-butadiene rubber (NBR) composites was investigated. The surface properties of the silica were determined by infrared spectroscopy, X-ray photoelectron spectroscopy, and solid NMR measurements.The resultant interfacial mechanical properties and thermal stability of the composites were characterized by tearing energy (G IIIC) and decomposition activation energy, respectively. It was found that the number of fluorine groups introduced onto the silica surfaces increased with increasing temperature of fluorination,resulting in more uniform dispersion of silica in the NBR matrix. As a result, the G IIIC of the F/Si-NBR composites significantly increased compared to the non-treated silica/NBR composite and the highest value was found to be 65% higher. These results could be attributed to the strong intermolecular interactions between F/Si and NBR matrix in composites.

The Formation Mechanism of CH<sub>4</sub> on Nitrile Butadience Rubber in Transformer Oil

Abstract. The thermal aging experiments on nitrile rubber and rubber additives were carried out for different time in 25# transformer oil at 70°C. The amount of CH4 released from non-rubber group, nitrile rubber group and rubber additives group were measured by Gas Chromatography (GC). The molecular structure of NBR matrix and liquid extracted from NBR were analyzed with fourier transform infrared analysis (FTIR), respectively. At last, the formation mechanism of CH4 in nitrile rubber were investigated. The results illustrated that the rubber additive RD released methyl radicals and hydrogen radicals, and generated CH4 by reacted with each other.

Good dispersion of hydrophilic nanoscale calcium carbonate particles in nitrile butadiene rubber matrix

Using the industrial technologies of rubber latex irradiation, hydrophilic nanoscale calcium carbonate (HNCC) slurry preparing and spray drying, we have prepared a novel ultrafine full-vulcanized powder nitrile butadiene rubber (UFPNBR)/HNCC nanocompound, in which the UFPNBR particles and HNCC particles are isolated and adhered to each other. When the UFPNBR/HNCC nanocompound powder is mixed with crude NBR, UFPNBR particles are easily dispersed well in NBR matrix because of their good compatibility, thus the HNCC particles are also dispersed in NBR matrix because of the carrier aidance of UFPNBR particles in 7 phr HNCC loading range, then the novel NBR/UFPNBR/HNCC ternary nanocomposites is fabricated. Compared with NBR/organic reagent-treated HNCC (ONCC) binary composites, the NBR/UFPNBR/HNCC ternary nanocomposites has shorter vulcanization time and better properties of abrasive resistance, oil resistance, dynamic compression properties and flame retardancy in fire.

Mechanical properties of rubber composites with cup-stacked carbon nanotubes

Cup-stacked carbon nanotubes (Cup-CNTs) consist of truncated conical graphene layers which exhibit open edges on the tube outer surface. Therefore, when used as filler, Cup-CNTs are expected to have many contact points with the matrix. Acrylonitrile butadiene rubber (NBR) composites containing Cup-CNTs were prepared by mixing the chloroform solutions of Cup-CNTs and NBR polymer followed by the evaporation of the solvent. Using this method Cup-CNTs were dispersed homogeneously in the NBR matrix. Cup-CNTs with different lengths (short- and middle-types) were used and the dependences of the mechanical properties on the length were investigated. The middle-type Cup-CNTs showed better reinforcing effects in terms of tensile strength, Young's modulus and hardness.

Preparation and luminescence properties of Sm(TTA) 3phen/NBR composites

In the present study, we examined the luminescent properties of uncured and cured samarium tris-(2-thenoyltrifluoroacetone)-1,10-phenanthroline/nitrile rubber composites (Sm(TTA) 3phen/NBR, i.e. Sm-complex/NBR). The formula of Sm-complex was determined by infrared spectroscopy (IR) and elementary analysis. The composites were investigated and characterized by photoluminescent (PL) spectroscopy, scanning electron microscopy (SEM) and X-rays diffraction (XRD). The characteristic emission fluorescent intensities of the Sm 3+ in both uncured and cured composites increase with the increase of Sm-complex content. For the nitrile rubber composites with the same content of Sm(TTA) 3phen, the uncured composites are found to have lower luminescent intensity than that of cured composites. To explain this result, we propose that the cross-linking network structure can help to stabilize the coordination environment of the Sm 3+ ion and improve the energy transfer efficiency from the outside energy to the central Sm 3+ ion. In our study, the rare earth organic complexes were dispersed homogeneously into the NBR matrix. The fluorescent intensity of the composites was high and no fluorescent quenching had been observed until the complexes concentration was up to 14.3%.