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Tire wear particles (TWPs) are generated by driving vehicles and found in the environment. Model TWPs of styrene-butadiene rubber (SBR) vulcanizates with different filler systems, namely, carbon black (SBR-C), carbon black/silica (SBR-M), and silica (SBR-S), were prepared using an indoor abrasion tester, and their pyrolysis behavior was investigated in terms of particle size and filler system. Abundances of the major pyrolysis products, namely, butadiene, 4-vinylcyclohexene (4-VCH), styrene, 2-phenylpropene (2-PP), and 3-phenylcyclopentene (3-PCP), were compared. The 4-VCH/butadiene and 4-VCH/styrene ratios of vulcanized SBR were lower than those of raw SBR, whereas the 2-PP/styrene and 3-PCP/styrene ratios of vulcanizates were higher than those of raw SBR. The abundance ratios of major pyrolysis products of the vulcanized samples showed different trends, although the three vulcanizates had the same compound formulation except for the filler system. The abundance ratio decreased in the order of SBR-C > SBR-M > SBR-S, which can be explained by the sulfur crosslinks and states of the bound rubber. The 4-VCH/styrene, 2-PP/styrene, and 3-PCP/styrene ratios of TWPs increased notably with increasing the TWP size up to 200 μm and then increased slightly or almost remained constant. The pyrolysis behavior of TWPs was influenced by the filler system and particle size. Our study suggests that the differences in the pyrolysis behavior depending on the filler system and particle size should be considered for the quantification of TWPs in environmental samples. • Pyrolysis behavior of TWP made of SBR varied with the size and filler system. • 4-VCH/styrene ratio of raw SBR was greater than those of vulcanized SBR. • 2-PP/styrene and 3-PCP/styrene ratios of raw SBR was lower than those of vulcanized SBR. • The abundance ratios of TWP increased with increasing the particle size. • The abundance ratio decreased in the order of SBR-C > SBR-M > SBR-S. [ABSTRACT FROM AUTHOR]

The crystallinity of rubbers which are amenable to crystallisation upon stretching is classically measured using X-ray diffraction (XRD) techniques. Recently, an alternative method for evaluating the crystallinity in unfilled natural rubber (NR) during stretching was proposed. This method is based on surface calorimetry principles (Le Cam, 2018) and was validated by XRD measurements in Le Cam et al. (2018). For reinforced rubber composites, the calorimetric response is not only due to the elastic couplings and the crystallisation/melting process, but also due to the intrinsic dissipation and additional viscoelastic dissipation resulting from the presence of fillers. This makes estimating the crystallinity of carbon black (CB) reinforced rubber compounds from calorimetric techniques typically more challenging. In this paper, however, the calorimetric approach for measuring crystallinity for CB reinforced rubber compounds was investigated. Crystallinity measurements were performed using both an unfilled and three CB reinforced NR compounds. A comparative study was performed using the XRD technique on the same four compounds. The results confirmed the appropriateness of the calorimetric technique for determining the crystallinity in the unfilled NR. The combination of the XRD and the calorimetric techniques allowed the different heat sources under strain to be identified and therefore, the thermal energy associated with crystallisation to be determined. This was done initially using one of the CB reinforced NR compounds and validated using the two other CB reinforced NR compounds. The results show reasonable correlation between the crystallinity measured using the novel calorimetric technique and the classical XRD technique for CB reinforced NR compounds. The development of this methodology has potentially significant impact. The calorimetric approach does not require the measurement of the mechanical response during testing. This is useful for measuring crystallinity gradients from infrared thermography coupled with full kinematic field measurements, typically at crack tips, where estimating the local mechanical response is very difficult or inaccurate. • Thermography technique to estimate crystallinity is extended to filled elastomers. • Temperature variation upon stretching is measured and used to calculate heat source. • The energy from elastic couplings and crystallinity are decoupled. • The crystallinity energy is used to obtain the crystallinity level while stretching. • Thermography technique shows good correlation with XRD crystallinity measurements. [ABSTRACT FROM AUTHOR]

Thermoplastic materials are gaining popularity, because of their anti-fouling and chemically inert properties, for use in industrial applications that involve heating and cooling of highly reactive fluids. The current work studies the effect of adhesive reinforcement and radial clearance (RC) on developing friction stir welding (FSW)-based thermoplastic tube-to-tubesheet hybrid joints (TTHJs), which has applications in the thermoplastic heat exchanger and piping industries. The workpieces (sheets and tubes) made of carbon black reinforced high-density polyethylene were used. First, the effect of FSW parameters on the tube pull-out behavior was studied. The fractographic investigations (macroscopic and SEM) suggest that the FSW joints can fail in a brittle, ductile, or mixed manner, depending on the FSW conditions used. The FSW technique provides better load bearing capacity (326 N (0.0 RC), 517 N (0.5 mm RC)) compared to adhesive joints (226 N (0.0 RC), 206 N (0.5 mm RC)). For 0.0 RC, the adhesive reinforcement increased the load bearing capacity by 15.6 %. On the contrary, for 0.5 mm RC, the adhesive reinforcement negatively impacted the load bearing capacity and reduced it by 40.6 %. The FSW technique with 0.5 mm RC provides a higher leak path of 77 % remaining tubesheet thickness (> tube thickness) compared to that of 46.6 % (< tube thickness) achieved at 0.0 RC. However, the adhesive reinforcement can enhance the leak path of 0.0 RC FSW joints to around 100 % remaining tubesheet thickness (> tube thickness) by introducing the adhesive material at the tube-sheet interface. • Proposed a novel framework for thermoplastic tube-to-tubesheet hybrid joints. • For 0.0 radial clearance, hybrid joints performed better than FSW joints. • For 0.5 mm radial clearance, FSW joints performed better than hybrid joints. • For 0.0 radial clearance, hybrid joints can improve leak path of FSW joints. [ABSTRACT FROM AUTHOR]

Natural rubber (NR) is major rubber component of tire tread compounds. Tire wear particles (TWPs) are found in the environment, and their quantification has been performed using a pyrolysis technique. Isoprene and dipentene are principal pyrolysis products of NR. In the present work, model TWPs with different sizes and carbon black contents were prepared using tire tread compounds made of NR and an abrasion tester. The carbon black contents were 35, 55, and 75 phr (sample codes: C33, C55, and C75, respectively). The TWPs of 1.0 × 104–4.0 × 106 μm [2], corresponding to the NR weight of 1–1094 μg, were pyrolyzed, and influence of the particle size and carbon black content on the pyrolysis behavior of NR was investigated. The abundances of isoprene and dipentene produced by the TWPs were lower than those produced by the pure NR sample of the same weight. The production rate of dipentene in the C35 sample was lower than those in the other samples. The isoprene/dipentene ratios of the TWPs were lower than those of the pure NR with the same weight. By decreasing the TWP size, the isoprene/dipentene ratios slightly increased until the TWP size was approximately 1.0 × 105 μm [2] and then exponentially increased. The factors influencing the pyrolysis behavior of the TWPs were the adsorption of the pyrolysis products by carbon black, the relatively more significant production rate of isoprene in the sulfur-crosslinked region, and the pyrolysis behavior in the bound rubber region similar to that of pure NR. Because the pyrolysis behaviors of the TWPs differed depending on the size and carbon black content, it should be considered to quantify the TWP content in environmental samples. • Pyrolysis behavior of TWP varied with the size and carbon black content • Production rates of pyrolysis products of TWP were lower than those of pure rubber • Pyrolysis products were adsorbed by carbon black • Isoprene/dipentene ratio of TWP increased notably by decreasing the size • Sulfur crosslinks reduced the formation of dipentene [ABSTRACT FROM AUTHOR]

This study presents an analysis of plasticizers and other additives in elastomers using several techniques to obtain relevant information for aging investigations. Thermogravimetric quantification of polymeric matrix, polymeric matrix char, carbon black, inorganic substances, plasticizers and other additives is commonly used. However, the thermogravimetric weight loss attributed to plasticizers and other additives contains additional components whose contribution to the weight loss has not been considered. Unreported components include water and carbonyl sulfide, which develop over long-term elastomer aging, and should be separately accounted for. This study employed Karl-Fischer oven techniques for calculating water content and linked thermogravimetric analysis with Fourier-transform infrared spectroscopy to measure carbonyl sulfide. Chromatoprobe-GC/MS was used to determine the ratio between rubber-related substances and JP-8 fuel and its additives, which can diffuse into rubbers. In fuel bladders, this occurrence is frequently observed, and the ratio consistently decreases over time. • Calculation of plasticizer content in rubber samples for aging studies. • Analysis of acrylonitrile-butadiene rubber (NBR) by TGA-FTIR. • Analysis of up to 27-year-old NBR-based fuel bladders. • A new approach is proposed as a research tool for aging studies. [ABSTRACT FROM AUTHOR]

Abstract The tensile behavior of uncured carbon black filled rubber is investigated under different loading scenarios and strain rates. A non-contact optical measurement technique, Automated Grid Method, is applied to the tensile tests to capture the full-field large deformation of uncured rubber samples, and then their accurate stress-strain curves are obtained. Based on the test results, the deformation mechanisms of elastic, inelastic, hysteresis and softening behaviors at different strain rates are revealed and discussed. On the other hand, a three parallel network model comprising a hyperelastic part and two elastic-viscoplastic parts is proposed to characterize the constitutive mechanics behavior of uncured rubber. By using this new proposed model, the distinct characteristics of the cyclic tests can be captured well at four different strain rates. Moreover, the model predictions for the multistep tensile relaxation process are found to be consistent with the experimental observations, which provide a physical framework to describe the underlying deformation mechanisms of uncured rubber. Highlights • The tensile mechanical properties of uncured rubber were investigated by Automated Grid Method. • The deformation mechanisms of elastic, inelastic, hysteresis and softening behaviors were researched. • The effect of strain rate on the stress-strain curves was investigated. • A three mechanism model was proposed to capture the constitutive behavior of uncured rubber. • The model predictions were shown to be consistent with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract As the industrial utilization of polymeric materials is increasing owing to recent improvements in material durability and functionality, product safety becomes an important issue. Therefore, various inspection methods for polymeric materials are being developed. In this work, the rapid and non-destructive inspection of the averaged internal orientation of conductive carbon black fillers in rubber composites is demonstrated using a handmade high-speed terahertz polarization spectroscopy system that employs reflection geometry. From the birefringent information obtained from the black rubber sample (with arbitrary stretching condition), the internal orientation of the conductive fillers, which plays an essential role in the properties of the rubber composite, was determined. In addition, since data acquisition with the reflection method is fast, the spatially resolved measurement of the filler orientation could also be performed. The information of the internal orientation of the carbon black fillers allows verification of the condition of the rubber product. Highlights • A novel methodology to reveal the internal filler condition of the black rubber with terahertz polarization reflection spectroscopy is provided. • The internal filler orientation is clearly determined through the birefringent properties. • By comparing the experiments with the model calculation, the validity of our inspection method is confirmed. • A developed high speed spectroscopy system enables to easily obtain the image. • Our novel method can measure most practical rubber products in-situ, nondestructively. [ABSTRACT FROM AUTHOR]

Abstract Ethylene vinyl acetate (EVA) composites, including two different carbonaceous conductive fillers, carbon black (CB) and commercially available graphene (G), were fabricated by solvent-casting and melt compounding methods. The effect of additives and process conditions on electrical and thermal properties of composites was investigated. The dielectric responses of EVA composites were characterized by a percolation threshold of 15 wt % for EVA/G prepared by solvent-casting. However, as the EVA/G15% was also subsequently extruded, the applied shear stress induced by extrusion caused deterioration of the electrical network and reduced the composite's electrical conductivity. A percolating network was found for the EVA composites containing CB at around 5–7 wt % with 10 orders of magnitude increase in electrical conductivity with respect to the neat EVA. The thermal conductivity of EVA/CB7% and EVA/G15% increased 16 and 22% respectively, in comparison to the neat EVA. Both additives increased the electrical and thermal conductivity of composites to be appropriate as jackets for high-voltage cables. Highlights • Electrical and thermal conductivity of EVA composites with two conductive additives were investigated. • A percolation threshold was characterized by broadband spectroscopy for EVA/G at 15% filler content. • EVA composites with CB filler was found to be conductive at 7 wt% CB filler content. • Addition of graphene and carbon black enhanced the thermal conductivity and dynamic mechanical properties of the composite. [ABSTRACT FROM AUTHOR]

Abstract The covalently crosslinking structure between rubber matrix and carbon black (CB) fillers present a significant challenge to analyze the structure and properties of bound rubber in vulcanizate. This work provides a layered exfoliation method to destruct cross-linked network and separate bound rubber encapsulated CB particles out of vulcanizate. A layer of loosely bound rubber was observed by using transmission electron microscopy (TEM), and the existence of tightly bound rubber layer was proved by thermogravimetric analyzer (TGA), atomic force microscopic (AFM) and dispersion experiment. The chemical components of studied layers were further analyzed by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), where the detection of S, N and Zn elements indicated the vulcanization reaction occurred in it, and the content of polysulfide and disulfide bonds was higher than that of monosulfide. The existence of oxygenic groups is resulted from the occurrence of oxidative scission reaction. Highlights • Layered exfoliation of bound rubber encapsulated CB from the vulcanizate was realized. • Layer-by-layer separation was achieved by controlling the degradation degree of the vulcanizate. • Mild oxidation facilitates the chain scission of the vulcanizate. • Loosely and tightly bound rubber on the surface of CB was analyzed. • The content of polysulfide and disulfide bonds was higher than that of monosulfide in the bound rubber. [ABSTRACT FROM AUTHOR]

Abstract Cavitation is a damage process often observed during or after pressure release in polymers exposed to high-pressure diffusive gases. Only a few characterizations of the phenomenon have been reported in the literature, all of them being based on 2D pictures of the sample taken after removal from the pressure chamber or, more recently, inside the chamber during pressure release. This study displays the first time-resolved 3D imaging of decompression failure in high-pressure gas exposed polymers, obtained from in-situ X-ray computed tomography. New data were provided about the out-of-plane shape and volume distribution of cavities. It allowed rigorous estimation of a Morphological Representative Volume Element for the cavity field. The bias resulting from the former 2D-projection methods could be discussed. Highlights • Time-resolved 3D views of decompression failure in rubbers are reported for the first time. • An EPDM, exposed to high-pressure hydrogen, was tracked by in-situ computed tomography. • Novel and quantitative data were provided about the out-of-plane morphology and volume distribution of cavities. • Some bias, induced by 2D projection in the former visible light transmission methods, were discussed. • The experiment opens new routes for a better understanding and accurate quantification of decompression failure. [ABSTRACT FROM AUTHOR]

Abstract In this work, a new approach was developed for the determination of the parameters of a complex constitutive model for a highly filled rubber compound. A SSBR sulfur-vulcanized rubber sheet reinforced by carbon black was prepared. Three test specimens in the form of two rubber strips and dumbbell were cut from it. The Arruda-Boyce equation was selected to describe the hyperelastic behavior of the rubber. A parallel rheological framework (PRF) model and a new equation using a sigmoid function were selected to describe the nonlinear viscoelastic and stress softening effects. The model parameters were determined via a novel methodology based on the solution of the inverse problem comprising of the finite element models of the tests. Two multi-objective optimization loops based on the Nelder–Mead simplex method were designed. The accuracy of the predicted parameters was checked via the comparison of the model predictions with their corresponding data obtained from uniaxial and stress relaxation tests. A thorough analysis was made on the predicted results. Highlights • A multiplicative constitutive equation was proposed for highly filled rubber compounds. • A new model for the Mullins effect in rubbers was proposed and implemented in Abaqus. • The parameters of the constitutive equations were determined using a novel technique. • An optimization loop in Isight was designed for the solution of the inverse problem. [ABSTRACT FROM AUTHOR]

Rubber is a typical viscoelastic polymer and has a low thermal conductivity. The main consequence is heat generation and leads to a temperature rise called heat build-up of the rubber material when subjected to cyclic deformation. Cylindrical carbon black (CB) filled rubber specimens were sinusoidally compressed with a Gabo Eplexor 500N dynamic mechanical analyzer, under various frequencies (10, 30, 50, 70 and 90 Hz) and dynamic strain amplitudes (1%, 2%, 3%, 4% and 5%). A ThermaCAM SC3000 infrared camera was used to capture the surface temperatures of the specimens. To predict the influence of two main influent factors (loading strain amplitude and frequency) on the heat build-up (HBU), relations of the dynamic properties with the strain and frequency were constructed based on the Kraus and General Maxwell model, respectively. And effect of rising temperature on the loss modulus was investigated. Combine with the heat equation, an analytical method for calculating the HBU was established. The comparison between calculated results and experimental data shows that the proposed analysis method provides a satisfactory way to predict HBU for rubber compounds. [ABSTRACT FROM AUTHOR]

High-density polyethylene (HDPE) composites containing propylene-ethylene random copolymers (PEC) elastomer and carbon black (CB) were prepared by melt blending in an effort to obtain excellent balance of properties. HDPE matrix and PEC elastomer were immiscible, and CB fillers were selectively located in HDPE matrix. The introduction of CB fillers into the HDPE/PEC blend significantly improved the viscoelasticity of the composite melts. Percolation network of CB particles was formed at CB content of 5 wt%, which consequently largely improved the conductivity of composites, and the surface resistance decreased to 106 Ω (square)−1, equal to the antistatic range. DSC results suggested that CB with a content more than 5 wt% showed nucleation effect, improving the degree of crystallinity of HDPE. Moreover, the incorporation of CB improved stiffness of composites, and decreased ductility compare with HDPE/PEC blend. The combination of adjustable conductivity and mechanical properties, as well as improved melt viscoelasticity wold further broaden the application fields of HDPE based composites. • HDPE/PEC/CB composites with balance of properties were prepared by melt blending. • CB particles were selectively located in HDPE matrix. • The composites melt showed the improved viscoelasticity. • The addition of CB improved the conductivity of HDPE/PEC blends. • The addition of CB increased the stiffness of HDPE/PEC blends. [ABSTRACT FROM AUTHOR]

Strain induced crystallization is essential to the physicochemical properties of polymer materials, but is difficult to investigate, as it usually requires X-ray sources in combination with stretching machines. We improve and validate a recently developed method which allows the calculation of the crystallinity index using easily available thermography and stress-strain data. For natural rubber, the method is shown to be reproducible and delivers results quantitatively comparable to spectroscopic methods such as wide angle X-ray scattering. The incorporation of different amounts of carbon black is shown to increase the level of crystallization and to change the shape of the strain-crystallization curves. Additionally, crystallinity during partial retraction is investigated and reveals that crystallization characteristics change at sufficiently high strain. [ABSTRACT FROM AUTHOR]

Elastomers are usually mechanically reinforced with high loadings of carbon black (CB) to achieve the properties demanded; high amounts of mineral flame retardants are used to fulfill fire safety requirements. In this study, multilayer graphene (MLG), a nanoparticle made of only 10 graphene sheets, is applied in low loadings, 3 parts per hundred rubber (phr) to reduce the total amount of filler or boost performance in hydrogenated acrylonitrile-butadiene rubber (HNBR). In the HNBR/MLG nanocomposites, 3 phr MLG replaced 15 phr CB, 3 phr aluminum trihydroxide (ATH), or 15 phr CB + 3 phr ATH. The nanocomposites were prepared via master batch by ultrasonically assisted solution mixing and subsequent conventional two-roll milling. A comprehensive study is presented, illustrating the impact of MLG on curing and mechanical properties; e.g. replacing 2.5 phr ATH with 3 phr MLG increased the Young's modulus by over 60% and hardness by 10%, while improving flame retardancy, and reducing the total heat evolved by 10%. MLG is a multifunctional filler, as demonstrated by various enhancements in terms of the mechanical and flame retardancy properties of the rubber composites. [ABSTRACT FROM AUTHOR]

The aims of this paper are three-fold. The first is to determine the reinforcement of high performance short aramid fiber in two representative rubber matrices, namely natural rubber and acrylonitrile rubber. The second is to ascertain the effect of rubber polarity on the reinforcement. The third is to establish a pattern of reinforcement for use with less studied fibers. The rubbers were reinforced either with only aramid fiber or with a hybrid of aramid fiber and carbon black. The fiber contents were varied at 0, 2, 5 and 10 parts (by weight) per hundred rubber (phr) while those of carbon black were 0, 10, 20 and 30 phr. Conventional sulfur vulcanization was used. It was found that aramid fiber can reinforce both rubbers in the low strain region effectively, although to a significantly different degree. The hybrid carbon black provides additional reinforcement at low to medium strains and allows high strain stress upturn to occur in both rubber matrices. The findings enable the preparation of rubber composites having a wide, controllable range of mechanical behavior for specific high-performance engineering applications. Significantly, they also serve as a benchmark for developing reinforced systems from alternative fibers, particularly those from natural sources. [ABSTRACT FROM AUTHOR]

To better understand the effect of rectorite and carbon black (CB) on the aging performance of styrene-butadiene rubber (SBR), SBR/CB, SBR/CB/rectorite and SBR/rectorite nanocomposites with the same total filler loading were prepared. The microstructure of the three SBR nanocomposites was characterized by XRD, TEM and SEM. After thermal aging, oxygen-containing molecules were found to be formed in the SBR nanocomposites, as verified by FTIR analysis. The SBR/rectorite nanocomposite showed the highest aging coefficient and the lowest change rate of tensile strength and stress at 100% strain among the three SBR nanocomposites, indicating that the introduction of nano-dispersed rectorite layers can enhance the thermal aging resistance of the nanocomposites. For the SBR/CB/rectorite nanocomposite, the addition of CB helped to improve the interfacial compatibility between the filler and matrix, resulting in the best crack resistance as the aged SBR/CB/rectorite nanocomposite always demonstrated the least cracks on the surface during either stretching or bending experiments. [ABSTRACT FROM AUTHOR]

A new methodology based on a Neural Network approach is developed for three-dimensional reconstruction of pseudo-hemispherical geometry of a hyperelastic specimen during a creep bulge test. On the basis of this procedure, the inflated membrane stress and strain states are established to determine the material mechanical properties. A new and economic experimental apparatus, used to conduct the bulge test, is provided with a sliding crossbar for the dome image acquisition in order to detect its strain state. A pressure regulator is used to ensure constant pressure, essential for creep. The artificial neural network was trained by using the position (x, y, z) of the membrane points at different values of the pressure measured in the bulge test chamber. The main characteristics of the system, which consist of the experimental apparatus and the neural post-processing, are accurate characterization of the materials and the ability to analyze materials with moderate anisotropy. This method has been verified on carbon black-reinforced SBR. The hyperelastic parameters that were obtained are in agreement with the values reported in scientific literature. [ABSTRACT FROM AUTHOR]

Two different types of thermodynamically induced self-assembled hierarchical structures were formed in carbon black (CB)-filled POM/SAN/TPU and POM/SAN/PA6 ternary polymer blends when the minor third polymer components TPU and PA6, which have the highest affinity to CB among the three polymer components, were individually incorporated into CB-filled POM/SAN binary blend: TPU with imbedded CB forms the interphase, while PA6 with imbedded CB forms droplets inside the SAN phase. The efficiencies of the two types of conductive networks formed by these hierarchical structures are compared in terms of electrical percolation threshold. The percolation threshold of CB in POM/SAN (70/30) blend decreases by 59% and 54% when only 5 wt% of POM is replaced by TPU and PA6, respectively. The mechanisms of conductive network formation are different in the two cases and related to their blend morphology, one is double percolation in a tri-continuous blend and the other is triple percolation in a cocontinuous blend. [ABSTRACT FROM AUTHOR]

The dimensions of reinforcing filler is a key factor in influencing the fracture and fatigue of rubbers. Here, the fracture and fatigue resistance of natural rubber (NR) filled with different dimensional carbon-based fillers including zero-dimensional spherical carbon black (CB), one-dimensional fibrous carbon nanotubes (CNTs) and two-dimensional planar graphene oxide (GO) were explored. To obtain equal hardness, a control indicator in the rubber industry, the amounts of CB, CNTs, and GO were 10.7 vol%, 1.2 vol%, and 1.6 vol%, respectively. J -integral and dynamic fatigue tests revealed that NR filled with CB exhibited the best quasi-static fracture resistance and dynamic crack growth resistance. The much higher hysteresis loss of NR filled with CNTs weakened its fatigue resistance. The planar GO played a limited role in preventing crack growth. Furthermore, digital image correlation revealed that NR filled with CB had the highest strain amplification level and area at the crack tip, which dissipated the most local input energy and then improved the fracture and fatigue performance. [ABSTRACT FROM AUTHOR]

Findings of a study of stress relaxation behaviour of hydrogenated nitrile butadiene rubber (HNBR) at nominal compressive strains up to 0.4 and temperatures above and below the glass transition temperature T g are reported. Two formulations of a model HNBR with 36% acrylonitrile content and carbon black (CB) loading of 0 and 50 phr were investigated. The relaxation function of HNBR is found to be independent of strain at temperatures right above the T g or at times longer than 10 −3 s for the deformations employed. CB imparts higher long-term stiffness and also larger relaxation strength at times longer than 10 −4 s to the HNBR, but it does not affect the relaxation behaviour of the rubber in the time span from 10 −3 – 10 4 s. In addition, the relationship between the strain energy function of HNBR and temperature is demonstrated to have a complex concave-downward shape which is affected by two competing contributions of entropy elasticity and the stress relaxation. [ABSTRACT FROM AUTHOR]

The present study explores the feasibility of using a mathematical enhancement, such as the second order derivative of FTIR-ATR spectra, for compositional analyses of natural rubber (NR), chloroprene rubber (CR) and their blends in carbon black-filled vulcanizates. The infrared spectra of natural rubber, polychoroprene rubber and their respective carbon black-filled vulcanizates were recorded by using FTIR-ATR on a germanium crystal. Subsequently, the second order derivative of the spectra was obtained for analysis. The important infrared bands for the identification of these materials were assigned, and compositional analyses of the blends were carried out by using the second order derivative spectra. [ABSTRACT FROM AUTHOR]

The influence of heat treatment on the electrical conductive behavior of carbon black (CB) filled high density polyethylene (HDPE) composites was investigated. The results showed that the effects of annealing temperature on the resistivity and the PTC intensity of the HDPE/CB composites were significant; the resistivity and the PTC intensity of the composites varied with increasing number of thermal cycles; while the variation became small after the third thermal cycle. Furthermore, the variation of the resistivity was 1.7 times higher than that of the composites without annealing, and the variation of the PTC intensity of the composites was 0.22, which were smaller than those of the specimens without heat treatment. A suitable annealing heat treatment could reduce the resistivity and enhance the PTC intensity of the composites; it was also helpful to improve the stability of the properties of the composites and the repeatability of the PTC effect. [ABSTRACT FROM AUTHOR]

Frequency-sweep tests at various temperatures were conducted to study the asymmetric dynamic response of carbon black (CB) filled rubber. The master curves of storage modulus were constructed by use of time-temperature superposition (TTS), and the dynamic response of the material over a wide range of frequencies covering about 20 decades exhibits asymmetry. Based on the experimental results, the fractional Zener model and Prony series are verified to be unsuitable to reproduce the dynamicviscoelastic behavior. Therefore, a modified model by adding a spring-pot into the fractional Zener model is presented. The applicability of the modified model in describing the dynamic behavior of the CB-filled rubber is validated by the experimental results. [ABSTRACT FROM AUTHOR]

To evaluate the performance of pyrolytic carbon black (pCB), we filled styrene-butadiene rubber (SBR) with pCB and N330 industrial carbon black (CB). We used two ratios of pCB and N330: 1/9 and 1/1. N330 was selected because its specific surface area was close to that of pCB. The overall CB content in the mixes was 0, 30, 45 and 60 part per hundred rubber (phr). We studied the effects of types and amounts of CB on the dispersion, cure behavior, dynamic mechanical thermal behavior, tensile mechanical and fracture mechanical properties of the filled rubbers. Dispersion of pCB was poorer than that of N330 CB. With respect to tensile mechanical properties – except tear strength – N330 outperformed pCB. The tear strength and fracture mechanics characteristics (J-integral at crack tip opening, and trouser tear strength) of SBR were higher with pCB than with N330. This can be attributed to the broader dispersion of pCB than N330. The combined use of N330 and pCB resulted in intermediate values, reflecting the actual N330/pCB ratio for all measured parameters. We wanted to correlate the mechanical performance with the apparent molecular weight between crosslinks (M c ), and found reasonable correlations for the Payne effect, tensile strength and critical J-integral. On the other hand, we only found a tendency for tear characteristics; this was ascribed to additional effects of (p)CB dispersion. [ABSTRACT FROM AUTHOR]

The aim of this work is to improve the performance of natural rubber reinforced with a hybrid of pineapple leaf fiber with carbon black. When there are multiple components to be mixed into a rubber matrix, mixing can be carried out in more than one way. Thus, in this study, the effects of preparation method and the resulting carbon black distribution on the mechanical properties of the hybrid composite were evaluated. Pineapple leaf fiber (PALF) and carbon black contents were fixed at 10 parts (by weight) and 30 parts (by weight) per hundred parts of rubber (phr), respectively. In order to improve the dispersion, PALF with rubber was prepared as a masterbatch. Carbon black was added to the compound either as a single portion or as two separate portions, one in the PALF masterbatch and the other in the main mixing step. It was found that, despite using the same final compound formulation, the mixing scheme significantly affected the medium strain region of the vulcanizate stress-strain curve. No stress drop in this strain region was observed for the two-step mixing scheme. Models for composites with different preparation methods are proposed and discussed. [ABSTRACT FROM AUTHOR]

Synergistic processes in hybrid composites have frequently been described in the literature over the past few years, opening doors to new studies and applications for this type of material. In this study, three-phase composites were obtained using polyurethane (PU) as the matrix, lead zirconate titanate (PZT) as the ferroelectric ceramic and carbon black (CB) as the conductive phase. The discussion is primarily focused on a comparison of the electrical, thermal and dielectric properties of three-phase composites with those of PU_CB and PU_PZT biphasic composites. The study describes a synergistic effect between the PU/PZT/CB phases involved in the generation of charges between the particles, implying better homogeneity of the composites as well as influence over the PU crystallization. The PU_CB conductivity profile showed a phenomenon of multi-step percolation thresholds attributed to the molecular structure and repulsive surface charge of CB particles. The surface charge phenomenon restricted the percolation curve analysis of the three-phase composites by means of classic percolation theory, shown by distortion of the critical exponents. The dielectric constant three-phase composites increased gradually as a function of CB in accordance with the percolation profile. [ABSTRACT FROM AUTHOR]

Carbon black commonly found in elastomeric composites is the main precursor of smoke formed during thermal decomposition and combustion of these materials. It has been proven that soot particles suspended in the air, absorbing carcinogenic, mutagenic and teratogenic, organic compounds from the groups of dioxins, furans and polyaromatic hydrocarbons, penetrating into living organisms through the respiratory tract, pose a serious threat to human health and life. Therefore, it has been proved in this paper, that partial replacement of carbon black with a natural lignocellulosic filler, also in synergetic system with non-halogen flame retardants, not only reduces the flammability of the obtained composites, but also significantly reduces their smoke formation, PCDD/Fs and PAHs emissions, as well as the toxicity of gaseous inorganic decomposition products expressed by a toxicometric index taking into account the emissions of CO, CO 2 , SO 2 , NO 2 , HCl and HCN. In addition, the use of natural fillers in elastomeric composites perfectly fits the European regulations regarding the development of reusable or recyclable materials and reducing the cost of their production through the use of cheap renewable raw materials. Flammability and smoke density of studied composites were determined in accordance with European standards with the use of cone calorimeter and smoke density chamber. PCDD/F and PAH were determined with the use of GC-MS-MS technique. Toxicometric index was determined with the use of FB-FTIR technique (fluidised bed reactor and the infrared spectrum analysis). • Styrene-butadiene rubber, carbon black, lignocellulose filler, flammability, optical smoke density, polychlorinated dibenzo-p-dioxins and furans, benzo(a)pirene, toxicometric index, optical smoke density. [ABSTRACT FROM AUTHOR]

The paper reveals the influence of different methods of carbon black (CB) incorporation in the compatible blend of 50/50 (wt %) Ethylene vinyl acetate (EVA) and Acrylonitrile butadiene elastomer (NBR) on different properties of vulcanized blend compounds. The partitioning of two types of CB in two different phases of the blend was estimated from dynamic mechanical analysis (DMA). The distribution of CBs due to preferential addition in different phases of the blend affects property variations in different degrees. From the analysis of SEM, TEM, AFM and electrical property measurements, it is found that mixing method significantly affects the electrical properties, morphology, and surface topography. The variation in AC conductivity and surface resistance study confirms the formation of different conductive network of CB with variation in mixing technique and it is supported by morphology analysis. The DMA have shown that CB has higher affinity towards less viscous EVA phase. This is further corroborated by the surface energy measurement, which in turn controls the electrical conductivity behaviour as well as mechanical properties of the blends. [ABSTRACT FROM AUTHOR]

Observations are reported on a carbon black–reinforced thermoplastic elastomer in multistep uniaxial tensile cyclic tests with a mixed deformation program (oscillations between maximum elongation ratios k max and various minimum stresses σ min with k max monotonically increasing with number of cycles n). Fading memory of deformation history is demonstrated: when specimens are subjected to two loading programs that differ along the first n −1 cycles of deformation and coincide afterwards, their stress–strain diagrams become identical starting from the n th cycle. A constitutive model is developed in cyclic viscoplasticity with finite deformations, and its adjustable parameters are found by fitting the observations. Ability of the stress–strain relations to describe the fading memory phenomenon and to predict the mechanical response of polymer composites in multi-step cyclic tests with large strains is confirmed by numerical simulation. [ABSTRACT FROM AUTHOR]

The effect of adding gilsonite micrometric particles on the properties of N330 carbon black (CB) reinforced natural rubber (NR) compounds was investigated. Formulations with 30/0, 22.5/7.5, 15/15, 7.5/22.5 and 0/30 parts per hundred of rubber (phr) of CB/gilsonite were used, comparing the effect of conventional and efficient vulcanization systems. Gilsonite was characterized by X-ray fluorescence (XRF), thermogravimetric analysis (TGA), elemental analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Tension, uniaxial compression, compression-set, abrasion resistance and dielectric strength tests were carried out on specimens that were moulded using the optimal curing time measured by oscillating disc rheometry (ODR). Abrasion wear resistance, and mechanical and rheometric properties varied with the CB/gilsonite content and on the vulcanization system. It was found that gilsonite facilitated the incorporation of carbon black during mixing, diminished the reversion during rheometric tests of compounds with efficient vulcanization cure systems and increased the dielectric strength. Some gilsonite/CB/NR compounds showed similar rheometric properties, compressive modulus and wear resistance to CB/NR compounds, which evidenced the use of gilsonite as an available filler for NR-based materials. [ABSTRACT FROM AUTHOR]

The aim of this paper is to demonstrate that the stress–strain behavior of natural rubber reinforced with short pineapple leaf fiber (PALF) can easily be manipulated by changing the cross-link density and the amount of carbon black (CB) primary filler. This gives more manageable control of mechanical properties than is possible with conventional particulate fillers alone. This type of hybrid rubber composite displays a very sharp rise in stress at very low strains, and then the stress levels off at medium strains before turning up again at the highest strains. The composites studied here contain a fixed amount of PALF at 10 part (by weight) per hundred rubber (phr) and varying carbon black contents from 0 to 30 phr. To change the cross-link density, the amount of sulfur was varied from 2 to 4 phr. Swelling ratio results indicate that composites prepared with greater amounts of sulfur and carbon black have greater cross-link densities. Consequently, this affects the stress–strain behavior of the composites. The greater the cross-link density, the less is the strain at which the stress upturn occurs. Variations in the rate of stress increase (although not the stress itself) in the very low strain region, while dependent on fillers, are not dependent on the crosslink density. The effect of changes in crosslinking is most obvious in the high strain region. Here, the rate of stress increase becomes larger with increasing cross-link density. Hence, we demonstrate that the use of PALF filler, along with the usual carbon primary filler, provides a convenient method for the manipulation of the stress–strain relationships of the reinforced rubber. Such composites can be prepared with a controllable, wide range of mechanical behavior for specific high performance engineering applications. [ABSTRACT FROM AUTHOR]

Hydrogenated acrylonitrile butadiene rubber (HNBR) was chosen to develop peroxide cured and carbon black N220 (CB) reinforced high modulus vulcanizates with possible applications in packers for oil exploration. HNBR vulcanizates are investigated by Rubber Processing Analyzer RPA 2000 and stress-strain tests conducted both in elongation and compression mode. All the mechanicals properties were tested both at room temperature (RT) and 150 °C in order to reflect application of packers. The results show that the modulus of CB filled HNBR vulcanizates increases with the increase of CB loadings in shear, tensile and compression mode. The physical interactions resulting from CB reinforcements show a stronger temperature-dependence than chemical crosslinks formed by curing agent. So the addition of reinforcing carbon black will have limited benefit for producing packer compounds with high enough modulus at high temperature, but more amount of curing agent will contribute to a stable high enough modulus. It is testified the filler-filler interaction is more temperature dependent than filler-rubber interaction and more chemical crosslinks increase the filler-rubber bonding and slightly decrease the filler-filler interaction, which is confirmed by the reinforcement factors. Compression tests show a strong dependence on the geometry of the samples and the compressive Payne Effect is examined by the multiple compression cycles. It gets stronger as the CB loading is increased. [ABSTRACT FROM AUTHOR]

Ethylene Propylene Diene Monomer (EPDM) rubber emerges as a dominant elastomer for major engineering applications like automobiles, constructions, electric and electronic industries and many more. The major engineering properties of EPDM are its outstanding heat, ozone and weather resistance ability. The resistance to polar substances and steam is also good. EPDM rubber has a common use as seals in automobiles. In the present work friction and sliding wear behaviors of ethylene propylene diene monomer rubbers (EPDM) of different hardness have been studied against steel counterpart under dry working condition. Different hardness of EPDM have been achieved by adding different proportion (parts per hundred) of carbon black (CB) content with the main ingredients of EPDM. Tribo-testing has been carried out in a multi tribo-tester (Ducom, India). EPDM rubber of different hardness like 55 Å, 70 Å and 85 Å has been slid against EN-8 stainless steel roller of the tester. Experiments have been conducted with different rotational speeds of the wheel at a constant load of 25N for a constant duration of 900 s. The coefficient of friction (COF), mass loss and wear of EPDM rubbers have been determined from the test data. The worn surface morphology has also been studied using scanning electron microscope (SEM) and concluded accordingly. Present experimental work attempts to highlight some important tribo-characteristics of an indigenous EPDM rubber as well as to shed light on various possible areas of further research works. [ABSTRACT FROM AUTHOR]

The stretchable conductive polymers were fabricated by adding conductive activated carbon fillers to the silicon elastomers and subsequently silver electroplating was performed. To solve the ecological and economical footprint issues the waste of Kevlar fibers were converted into activated carbon particles. The microstructure and porous activated carbon particles were prepared by chemical and physical activation process. The conductive elastomers were prepared into two steps. At first prepared carbon particles were mixed in polymeric silicon elastomer to make it conductive. Hence, the absorbance/adherence of carbon particles was confirmed into elastomer to develop the continuous network to facilitate the electrical conduction. Secondly, further electroplating of silver was performed to make the compact layer on carbon filled polymer. The surface morphology, element analysis and size of activated particles, carbon filled silicon elastomer and electroplated silicon elastomer was observed by SEM, EDX and Zeta size analysis. The FIR analysis was done to analyse the functional groups after the activation of Kevlar web before and after carbonization. Furthermore, the existence of carbon and silver was confirmed by XRD. The electrical resistivity and EMI shielding of elastomer samples was evaluated at different stages (after carbon filling, after silver plating, at stretching state and multiple stretching cycles). The minimum resistivity (12 Ω mm) and maximum EMI shielding (74 dB) was recorded at 0% stretch. While resistivity was increased up to 156 Ω mm at 60% stretch. Furthermore, the thermal stability of develop elastomeric sensors was checked through TGA and Ohmic heating process. At the end, the durability against moisture regain and mechanical action (tensile and hardness) was checked. The prepared elastomers can be used in number of applications including sensors (thermal, humidity control, insulation and electrical conduction). They can also be used as a flexible electrode adjusted with medical devices EMG, ECG and TENs machine. • Carbon particles were prepared from the Kevlar waste. • The prepared conductive activated carbon fillers were added to the silicon elastomers to develop conductive polymers. • Silver electroplating was performed to make the compact layer on carbon filled polymer. • The developed novel silver/carbon conducting polymer elastomers revealed significant electrical conductivity. [ABSTRACT FROM AUTHOR]

In this study, the influence of the ambient temperature in the range of 20–60 °C on the die swell behavior of rubber compound were studied by a capillary rheometer with new designed external heating device. The results demonstrated that the die swell ratio (B) increased rapidly in the initial phase and reached a stable value after a certain time. The time dependence of B was then calculated based on the experimental data using Burger's model. In addition, it can be found that B was proportional to the ambient temperature of the extrudate, since the relaxation time decreased obviously with increasing ambient temperature. At the constant time of 130 min, B in the range of 20–60 °C were 1.393, 1.405, 1.420, 1.425 and 1.438 mm, respectively. Furthermore, an equation was established to describe the relationship among the B, test time and ambient temperature. The calculated value was consistent with experimental data, which was 1.447 and 1.449 mm, respectively. While the equation was not applicable when the ambient temperature lay above 70 °C due to the decreased interaction between rubber and carbon black. It was also found that the contraction effect played a significant role on the behavior of die swell. B of the extrudate under 60 °C and 70 °C was reduced by 1.5% and 1.2%, respectively. • The die swell behavior of the rubber compound at different ambient temperature was monitored by online method. • With increasing test time, die swell ratio of the extrudate increased rapidly in the initial phase and then kept stable. • An equation was established to describe the relationship among the die swell ratio, test time and ambient temperature. [ABSTRACT FROM AUTHOR]

A comprehensive set of guidelines on the use of the torsion pendulum for the viscoelastic characterisation of carbon black reinforced rubber is presented, including the set up selection, the post processing steps and the final evaluation of the method using temperature sweep results at small strains. The torsion pendulum is based on the free vibration principle, in which the sample is instantaneously perturbed to initiate a torsional movement and then left to freely vibrate. From the frequency and damping of this impulse response function, the properties of the material can be obtained against temperature and time. However, despite the extensive use for many years of the torsion pendulum, the difficulty of activating only the desired torsional mode hinders the acquisition of accurate results. The method presented aims to improve the torsion pendulum performance and can be divided in two stages. The pre-testing phase covers the influence of the test set up and sample geometry on the measured response. The test set up will determine the frequency at which the dynamic properties are obtained, while the sample geometry will influence the torsional strain and bending deflection. The post-testing phase includes the steps to post-process the curve and the criteria to identify and select the most reliable data sets from all of the measured data. The quality of the curve is assessed in the frequency domain by evaluating the frequency components of its Fast Fourier Transform and in the time domain by evaluating its fit to an ideal exponentially decreasing sinusoidal curve. The final selection of the response functions that can be used to measure the viscoelastic properties of the rubber samples is made based on the maximum strain level and the minimum variation of the dynamic properties within one curve. The validity of the method is then tested by comparing temperature sweep results before and after the application of the presented guidelines, where a clear decrease on the results deviation can be observed. Finally, the results obtained with this method are compared to Dynamic Mechanical Analysis results over the same temperature range, where a good fit is obtained. Thus, this investigation presents a comprehensive method, useful to all torsional pendulum users aiming to measure and characterise the mechanical behaviour of viscoelastic materials. • The torsion pendulum is used for the viscoelastic characterisation of filled rubber. • A new method is presented to improve the performance of the torsion pendulum. • After application of the method, temperature sweep results are greatly improved. • The torsion pendulum results compare very well with DMA data. [ABSTRACT FROM AUTHOR]

As the essential mixing equipment, long hours of work can cause wear and tear on the end face of the compactor. The wear of the end faces leads to an increase in the gap between the chamber and the end faces, which leads to leakage, reduces the mixing effect, and ultimately affects the rubber properties. Therefore, it is necessary to study the end face metal wear during the mixing process. Thermally cracked carbon black, as recycled material for scrap rubber, can be used as a substitute for other carbon blacks in some fields, vastly reducing the production cost and promoting the reuse of scrap rubber. In this paper, thermally cracked carbon black (CBp) was mixed with multi-walled carbon nanotubes (MWCNTs) and added rubber by mechanical blending to obtain CBp/MWCNTs composites. The synergistic mechanism of CBp and MWCNTs was investigated to analyze the effect of CBp/MWCNTs ratios on the frictional wear of metal on the end face of the compactor. The results showed that MWCNTs cooperated with CBp particles to form a three-dimensional "grape bunch" network structure. On the one hand, the three-dimensional "grape bunch" network structure can adsorb CBp particles to promote the dispersion of CBp particles. On the other hand, the three-dimensional "grape bunch" network structure can also hinder the overflow of aromatic oil and affect oil film formation. At the same time, the three-dimensional "grape bunch" network structure can also form a physical isolation layer between the rubber and the metal. This significantly influences the degree of CBp particle dispersion, friction coefficient, metal surface roughness, and metal wear. It seems that the synergistic effect between MWCNTs and CBp particles is maximized when the content of MWCNTs in CBp/MWCNTs composites is 4 phr, the area of CBp/MWCNTs three-dimensional mesh is maximized, the dispersion of CBp particles is the best, and the wear of CBp/MWCNTs composites on metal is the lowest. • As the essential mixing equipment, long hours of work can cause wear and tear on the end face of the compactor. • The effect of the synergistic effect of CBp and MWCNTs on the friction and wear of end-face metal was analyzed. • The results showed that MWCNTs cooperated with CBp particles to form a three-dimensional "grape bunch" network structure. [ABSTRACT FROM AUTHOR]

The properties of carbon black (CB)-filled natural rubber (SMR-L) compounds, with and without the addition of Alkanolamide (ALK), based on various curing systems such as efficient, semi-efficient and conventional vulcanisation systems were investigated. The ALK loading was fixed at 5.0 phr. It was found that ALK gave improvements to the cure rate, torque difference, crosslink density, filler dispersion, rubber–filler interaction and reinforcing efficiency of CB. ALK also enhanced the tensile modulus, hardness, resilience, tensile strength and elongation at break of CB-filled SMR-L vulcanisates for each curing system. The degree of improvement of cure characteristics and mechanical properties depended on the level of sulphur and the ratio of accelerator to sulphur in each system. Scanning electron microscopy (SEM) proved that the CB-filled SMR-L vulcanisates with ALK for each curing system displayed a greater matrix tearing line and surface roughness due to greater rubber–filler interaction. [ABSTRACT FROM AUTHOR]

Non-isothermal crystallization kinetics of poly(3-hydoxybutyrate) (PHB) filled with different amounts of carbon black (CB) was investigated by differential scanning calorimetry for both, the cold and melt crystallization process. The Friedman method was applied to describe the crystallization kinetics and to determine the conversion dependent apparent activation energies. It was found that carbon black acts as a nucleating agent, reducing the apparent activation energy for the crystallization onset significantly, and thus greatly facilitating the phase transformation. Considering PHB-CB compounds with CB content ≥5%, the kinetic data can only be interpreted assuming a complex multi-step crystallization mechanism, where the exact role of CB is unclear. [ABSTRACT FROM AUTHOR]

A thermally triggered shape memory polymer (SMP) was prepared by blending electrically conductive carbon black (CB) into the resin prior to curing. The CB filled composite can then be activated through resistive heating. With the aim of using such SMPs in reconfigurable structures and/or actuators, the effect of strain on the conductive nature of the SMP composite was investigated. The study has specifically focused on changes to conductivity in, i) the transverse direction during tensile elongation to assess the impact of the Poisson effect, and ii) in samples deformed in compression. The dynamic response characteristics of the electrically activated SMP were also tested to assess the feasibility of using the composite in tunable vibration damping applications. Findings have shown that the pattern of changes in the transverse conductivity, which is marked by an increase-decrease-increase sequence, resembles that seen in the axial direction. SEM imaging of the samples was performed along the axial and transverse axes of deformation and shows no anisotropy in the CB filler distribution. To demonstrate potential uses of a conductive SMP in the sub- T g temperature range, a discussion of a vibration damping application has been included. [ABSTRACT FROM AUTHOR]

The effect of TiB 2 nano-powder content on the electrical conductivity and positron annihilation characteristics of ternary silicone rubber/CB/TiB 2 nanocomposites was studied. The endothermic enthalpy of melting (ΔH m ) and melting temperature of the composites (T m ) were determined by differential scanning calorimetery (DSC). The addition of 12 phr TiB 2 leads to a maximum shift in T m toward higher temperature. Also, χ c values of the investigated composites were found to decrease with increasing TiB 2 content. The dc conductivity has reached maxima in the region of 12 phr TiB 2 followed by a decrease with increasing TiB 2 content. The temperature dependence of the conductivity showed peaks at certain temperatures and shifted to higher temperature with increasing TiB 2 content up to 12 phr. Two types of free volume cavities were detected by positron annihilation lifetime, ranging from V 1 (8.77–18.18 Å 3 ) and V 2 (270.68–274.48 Å 3 ). A correlation between positron annihilation parameters was also used to discuss the properties of the investigated composites. [ABSTRACT FROM AUTHOR]

A typical carbon black reinforced hydrogenated nitrile butadiene rubber (HNBR) was exposed to a mix of hydrocarbons (toluene, heptane and cyclohexane) at elevated temperatures and pressure in order to chemically age the material. The effect of this exposure on the mechanical properties is reported; the most significant change is a dramatic increase in tensile stiffness for specimens exposed at 160 °C for 12 weeks. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) revealed changes in the glass transition behaviour of this material, with a general reduction in the magnitude of the glass transition with increasing ageing time. In addition, gravimetric studies of the swollen specimens after removal from the hydrocarbon mix showed that the more aged specimens underwent significantly slower drying rates compared to less aged specimens. These results may be explained by an increase in crosslink density in the materials being the main mechanism occurring during chemical ageing of these HNBR compounds. [ABSTRACT FROM AUTHOR]

Rubber composites with very high moduli at low elongation, high elongation at break and high ultimate breaking strength have been developed. The matrix was acrylonitrile butadiene rubber (NBR) and the hybrid (fibrous and particulate) reinforcements were short, fine pineapple leaf fiber (PALF) and carbon black. The amount of PALF was fixed at 10 parts (by weight) per hundred of rubber (phr) while that of carbon black was varied from 0 to 30 phr. Uniaxial NBR composites were prepared. Tensile strength, elongation at break, modulus and tear strength of the hybrid composites were characterized in both longitudinal (parallel to the fiber axis) and transverse (perpendicular to the fiber axis) directions. The addition of carbon black causes the slope of the early part of the stress–strain curve to increase and also extends breaking to greater strains. At carbon black contents of 20 phr and above, the stress–strain relation displays an upturn at high elongations, providing greater ultimate strength. Comparison with the usual carbon black filled rubber shows that the composite behavior at low strains is determined by the PALF, and at high strains by the carbon black. This high performance PALF-carbon black reinforced NBR shows great promise for engineering applications. [ABSTRACT FROM AUTHOR]

The effect of Alkanolamide (ALK) loading on properties on three different types of carbon black (CB)-filled rubbers (SMR-L, ENR-25, and SBR) was investigated. The ALK loadings were 1.0, 3.0, 5.0 and 7.0 phr. It was found that ALK gave cure enhancement, better filler dispersion and greater rubber–filler interaction. ALK also enhanced modulus, hardness, resilience and tensile strength, especially up to 5.0 phr of loading in SMR-L and SBR compounds, and at 1.0 phr in ENR-25 compound. Scanning electron microscopy (SEM) proved that each optimum ALK loading exhibited the greatest matrix tearing line and surface roughness due to better rubber - filler interaction. [ABSTRACT FROM AUTHOR]

Various amounts of predispersed multi-wall carbon nanotubes (MWCNT) were mixed with natural rubber (NR), with and without carbon black (CB), for preparing MWCNT-filled NR (NC) and MWCNT/CB-filled NR (NH) vulcanizates. All NH vulcanizates contained 30 phr CB and the amount of MWCNT for both NC and NH was varied from 0 to 8 phr. Helium ion microscopy (HIM) and FE-SEM images showed that MWCNT in the NH was dispersed much better than in the NC. Additionally, the well dispersed CB and MWCNT in the NH functioned synergistically in promoting an increase in longitudinal crack growth, leading to enhancement of edge-cut tensile strength (CTS) with increasing MWCNT loading. In contrast, all NC specimens ruptured in a simple lateral direction relating to their lower CTS. Results also revealed that abrasion resistance of the NH was not significantly changed with increasing MWCNT, whereas that of the NC increased. Nevertheless, abrasion resistance of both vulcanizates showed good correlation with the average value of ridge spacing on their abraded surfaces. It was also found that tensile strength of the NH was almost unchanged when the MWCNT loading was increased because the reinforcement by CB predominates over the MWCNT. However, 100% modulus and hardness of both NC and NH increased with increasing MWCNT content. [ABSTRACT FROM AUTHOR]

Although the magnitudes of inelastic and viscoelastic effects in filled rubbers are small relative to that of the elastic response, these effects are nevertheless critical in applications such as gaskets, seals and dampers. This study investigates the role of deformation history on relaxation of rubber through time-dependent experiments following a range of deformation histories. Two grades of carbon-black filled EPDM were subjected to uniaxial tensile deformation followed by stress-relaxation or stress memory at fixed deformation. Stress relaxation was found to be highly dependent on strain levels following a single loading. When an additional load-unload cycle was added to the history, the rubbers relaxed an approximately constant fraction of stress after a given time, provided that the strain at stress relaxation was smaller than the historical maximum. This fraction was independent of both the applied strain and of the maximum strain, and suggests that the relaxation process is independent of scragging procedures used to control the modulus. Stress memory observed following load-unload cycles was also approximately independent of strain history. [ABSTRACT FROM AUTHOR]

J-integral theory and fatigue testing were adopted to investigate the fracture and fatigue properties of silica/carbon black (CB)/natural rubber composites with total filler content of 50 phr. Critical J-value JIC and tearing modulus TR, were obtained. JIC, as an indicator of crack initiation resistance, was dependent on the pre-cut length. TR was related to the crack propagation of the composite. With increasing the silica/CB ratio, both JIC and TR were enhanced, indicating that the resistance to crack initiation and propagation were improved. The strain energy density at a fixed strain decreased with an increase in the silica/CB ratio. Fatigue testing under constant tensile strain conditions demonstrated that the composite with higher silica/CB ratio exhibited lower cyclic crack growth rate and longer fatigue life. This was in accordance with the results of TR, JIC and strain energy density of the composite, hence TR, JIC and strain energy density of the composite can be used to predict its fatigue properties. [ABSTRACT FROM AUTHOR]

Electrically conductive polymer composites (ECPCs) based on porous polymeric matrices of PEBA 4033 incorporating different types of graphene platelets were prepared and tested. PEBA 4033 polymer was mixed with different graphene platelets: grade H5, grade MX and grade C-750. Porous morphology was obtained for the ECPCs prepared with graphene platelets grade MX and H5, while for the grade C-750 only a dense ECPCs was obtained. The porous ECPC loaded with 15 vol.% of graphene M5 exhibited a linear piezoresistive response oin a log-log plot. Some limitations were detected for this ECPC, namely hysteresis and drift due to the poor mechanical properties. The porous ECPC loaded with 15 vol.% M5 was further crosslinked, which improved its mechanical properties but the piezoresistive effect became negligible. The incorporation of carbon black in this ECPC formulation was shown to be much more efficient than crosslinking to improve mechanical properties, but the piezoresistive response became poor. [ABSTRACT FROM AUTHOR]