Using synchrotron‐radiation X‐rays for nanoscale computed tomography (X‐ray nano‐CT), the structure and corresponding reinforcement effects of carbon black (CB) filler at various amounts in natural rubber (NR) are studied during cyclic loading. All structural parameters of the CB filler, which are extracted from X‐ray images—such as the destruction and reconstruction ratios of the aggregates and the network connectivity, show a transition point with the CB content at around 30 phr (phr = parts by weight per hundred parts of rubber). When the CB content is above the transition point, the effective volume fraction exceeds the percolation threshold, and a stress‐bearing filler network can form; this network can effectively transmit the external stress to the entire sample and abruptly enhance the reinforcement factor. Below the percolation threshold, the CB filler is mainly disconnected aggregates, where its reinforcement of the rubber matrix can be mainly described by the volume‐filling effect. Using the dynamic cluster–cluster aggregation (CCA) model, calculations of the mechanical properties related to the CB content suggest that the network structure plays a major role in the reinforcement of the NR.
The properties of hybrid multiwall carbon nanotube (MWCNT) and carbon black (CB) in natural rubber nanocomposites were studied. The results show that the scorch and cure time decreased as the MWCNT loading increased in CB/MWCNT hybrid loading ratio but for the maximum torque, the result shown otherwise. As the MWCNT loading increased in CB/MWCNT hybrid loading ratio, the tensile strength, elongation at break and fatigue life are decrease, however the tensile modulus and rubber filler-interaction (Qf/Qg) value increased. The SEM results show a dispersion of CB and MWCNT in natural rubber matrix. Furthermore, the thermal stability for the hybrid nanocomposites is enhanced. 相似文献
Abstract The dynamic mechanical properties of ethylene vinyl acetate (EVA) rubber filled with different loadings of carbon black and at different degrees of crosslinking were studied over a wide range of temperatures (-150° to +200°C). The loss tangent (tan δ) versus temperature plots indicated presence of different transitions. The α-transition (or the glass-rubber transition) corresponding to the maximum in tan δ value, occurred at ?17°C, which is the principal glass-transition temperature (abbreviated as Tg) of EVA rubber. The γ-transition occurred in the temperature region of ?125° to ?135°C, while the β-transition appeared as a shoulder in the temperature region of ?65° to ?75°C. Besides, there was also a high tempeature transition around +62°C which is known as liquid to liquid transition (T1.1). Incorporation of carbon black filler did not cause any shift of Tg, while the tan δ peak values at Tg decreased sequentially with increase in filler loading. The γ- and β-relaxations were found to be insensitive to filler loading. The T1.1 transition, however, was found to be suppressed by incorporation of carbon black filler particularly at high loading. Extent of crosslinking did not influence the Tg But, the T1.1 transition, which was prominent with the lightly crosslinked system was found to be suppressed at high level of crosslinking. Strain dependent dynamic mechanical properties under isothermal conditions showed that the secondary structure breakdown of carbon black filler under the effect of strain amplitude is influenced by the degree of crosslinking of EVA rubber. 相似文献
The properties of acrylonitrile-butadiene rubber (NBR) composites were studied at five different compositions of NBR/HNTs/Silica or NBR/HNTs/CB (i.e., 100/5/0, 100/4/1, 100/3/2, 100/2/3, 100/0/5 parts per hundred rubber (phr)). The tensile strength and modulus (M100) of both composites decreased, whereas elongation at break increased and maximum torque with increasing the silica or carbon black content. However, both composites show opposite trends for cure time and scorch time, where NBR/HNTs/Silica composite exhibited an increasing trend, while NBR/HNTs/CB composite shows the decreasing trend. The rubber-filler interaction studies showed that carbon black is a more reinforcing filler than silica. 相似文献
Hybrid fillers have been prepared of conductive carbon black/magnetite at various ratios of the phases: 90:10, 70:30, and 50:50. The fillers have been characterized and their effect on the curing, mechanical, electric, and dynamic properties of natural rubber–based vulcanizates has been also investigated. The macrohomogeneity of the composites has been evaluated by ohmic resistivity measurements and correlation analysis. It has been established that all properties studied are dependent on the ratio between the filler’s phases. Viewing their composition, we conclude that the hybrid fillers are expected to exhibit both high dielectric and magnetic losses and may find application in the manufacturing of microwave absorbers. 相似文献
Mixing torque, morphology, tensile properties and swelling studies of natural rubber/ethylene vinyl acetate copolymer blends were studied. Two series of unvulcanized blends, natural rubber/ethylene vinyl acetate (SMRL/EVA) copolymer blend and epoxidized natural rubber (50% epoxidation)/ethylene vinyl acetate (ENR-50/EVA) copolymer blend were prepared. Blends were prepared using a laboratory internal mixer, Haake Rheomix polydrive with rotor speed of 50 rpm at 120°C. Results indicated that mixing torque value and stabilization torque value in ENR-50 blends are lower than SMRL blends. The process efficiency of ENR-50/EVA blends is better due to less viscous nature of the blend compared to SMRL/EVA blends as indicated in stabilization torque graph. Tensile properties like tensile strength, M100 (modulus at 100% elongation) and Eb (elongation at break) increase with increasing EVA fraction in the blend. At the similar blend composition, ENR-50 blend shows better tensile properties than SMRL blends. In oil resistance test, swelling percentage increased with immersion time and rubber composition. At a similar immersion time, ENR-50 blends exhibit better oil resistance compared to SMRL blends. Scanning electron microscopy (SEM) of tensile fractured surface indicated that EVA/ENR-50 blends need higher energy to cause catastrophic failure compared to EVA/SMRL blends. In etched cryogenically fractured surface, size and distribution of holes due to extraction of rubber phase by methyl ethyl ketone (MEK) were studied and holes became bigger as rubber composition increased due to coalescence of rubber particle. 相似文献
Summary: Pyrolytic carbon black (CBp) has been prepared by rubber crumb pyrolysis under nitrogen flow at 700 °C. The CBp obtained by this process had an average surface area of 81 m2 · g?1 and was obtained in 43% yield over the starting rubber crumb. Although the CBp surface area can be increased up to 109 m2 · g?1 by washing away the Zn‐ and Si‐based ashes with HF treatment, the CBp was tested in a standard NR/SBR‐based formulation without any purification and ash extraction. CBp was tested at increasing loading levels as partial or full replacement of a standard N339 furnace carbon black. CBp depresses the physical properties of the rubber compound in a way which is directly proportional to the amount added. The reason of this result and the limited reinforcing effect is discussed in terms of low surface area and low structure in comparison to N339 carbon black as well as in terms of low surface activity, the interference of the ashes and the poor dispersion. Ideas of further development works are outlined.
Abstract Commercial graphite flakes and carbon black grade N234 have been subjected to γ-radiation treatment to a total dose of IMGy. The resulting radiation-damaged materials were studied by Raman spectroscopy. Raman spectra have revealed that graphite underwent substantial changes in its structure with formation of hexagonal diamond sites as well as onion-like and amorphous carbon domains. Changes also in the Raman spectra of irradiated carbon black have been observed which could be interpreted in the light of the results on irradiated graphite. A compound evaluation of γ-treated carbon black has been performed in comparison to a pristine sample. The results show a spectacular increase in the reinforcing effect as measured by the 200% and 300% modulus, hence an increase of the filler-to-polymer interaction, a reduction of the Payne effect and of the hysteresis (measured by tand at 70[ddot]C). 相似文献
Styrene-based deproteinized natural rubber (SNR) latex was synthesized by in situ polymerization. Three pre-vulcanization systems [conventional-cured (CV), semi-efficient-cured (Semi-EV), and efficient-cured (EV)] were studied in terms of tensile and adhesion properties. Good tensile properties were observed for CV and EV SNR. The Semi-EV SNR showed the best adhesion properties based on the good anchorage performance in all substrate pairings (polystyrene–polystyrene, polystyrene–rubber, and rubber–rubber). The pH modification on SNR latex via KOH addition has beneficial effects of removing protein layers, resulting in more styrene grafting sites in the rubber molecules. Consequently, the tensile and adhesion properties of the SNR are improved as more styrene polymers are grafted onto the rubber matrix. Semi-EV SNR with pH 12 has superior adhesive performance; hence, it is suitable for use as a pressure-sensitive adhesive. 相似文献