Carbon Black-filled Natural Rubber Research Articles

Utilization of palm oil as an alternative processing oil in carbon black-filled natural rubber compounds

Due to the toxicity of distillate aromatic extract (DAE), palm oil (PO) being environmental friendliness, renewability, and sustainability, was used as an alternative processing oil in this study. The properties of carbon black-filled natural rubber compounds containing PO were investigated and compared with the DAE-added rubber compound. The results revealed that the presence of PO in the rubber compound gave the same degree of filler–filler interactions but higher filler-rubber interactions compared with the one with DAE. Payne effect as referred to filler-filler interactions of the rubber compounds with DAE and PO was 191 and 189 kPa, respectively. In addition, the presence of PO not only accelerated the vulcanization reaction but also reduced the crosslink density within the rubber matrix. The crosslinking type of PO-added rubber compounds consisted only of polysulfidic linkages, whereas the DAE-added rubber compound contained various crosslinking types, i.e., mono-, di-, and polysulfidic linkages. On the other hand, the presence of PO in rubber compounds promoted a positive effect on elastic properties, as indicated by the temperature scanning stress relaxation (TSSR) index and tan δ at 60 °C. The TSSR index of rubber compounds with DAE and PO was 0.69 and 0.71, respectively. Given the low tan δ at 60 °C of the PO-added rubber compounds, PO promoted a low rolling resistance when applied in tire applications, providing tires with safe energy.

Sustainable plasticizer from agroindustrial waste for natural rubber compounds: Influence on the curing system and compound properties

The industry has pursued efforts to minimize the use of fossil fuel-based processing oils in favor of naturally occurring nontoxic oils from renewable sources, such as vegetable oils. In this study, the feasibility of replacing naphthenic oil (NAPH)-based plasticizers in natural rubber (NR) compounds with oil originating from cashew nut shells was evaluated. Cardanol oil (Cdn), which is derived from decarboxylated cashew nut shell liquid, a byproduct of cashew nut production, was chemically modified by acetylation and named Cdn-A. The successful acetylation of Cdn with acetic anhydride was confirmed. The effects of Cdn and Cdn-A as plasticizers on the curing characteristics, thermal aging, and physical, mechanical, and dynamic properties of carbon black-filled NR compounds were then evaluated. Cdn acted as a co-activator for rubber vulcanization; by contrast, Cdn-A showed negligible effects on this process. Vulcanized Cdn- and Cdn-A-containing NR compounds exhibited improved abrasion and tear resistance compared with the reference compound containing NAPH, as well as antioxidant activity. The Cdn-added NR compound also demonstrated high elongation at break and toughness. The results collectively suggest that NR compounds containing Cdn exhibit properties suitable for tire tread applications requiring high grip characteristics.

Competition between Strain-Induced Crystallization and Cavitation at the Crack Tip of Unfilled and Carbon Black-Filled Natural Rubber

Competition between Strain-Induced Crystallization and Cavitation at the Crack Tip of Unfilled and Carbon Black-Filled Natural Rubber

Effects of the Diamine Chain End Functionalized Liquid Butadiene Rubber as a Processing Aid on the Properties of Carbon-Black-Filled Rubber Compounds.

The implementation of vehicle electrification and autonomous driving technologies has recently emphasized the importance of abrasion resistance and fuel efficiency of truck bus radial (TBR) tire treads that undergo high loads and long driving times. In this study, a functionalized liquid butadiene rubber (F-LqBR) was introduced to replace the treated distillate aromatic extracted (TDAE) oil as a way to improve abrasion resistance and fuel efficiency in the TBR tire tread compound and to solve the oil migration. First, radical polymerization was used to synthesize nonfunctionalized LqBR (N-LqBR) and amino-LqBR with an amine group at the chain ends. The synthesized LqBRs were then substituted in place of TDAE oil to manufacture carbon-black-filled natural rubber (NR) compounds and to evaluate their physical properties. The results show that LqBRs improved the migration resistance and enhanced the abrasion resistance by lowering the glass transition temperature (Tg) of the compound. In particular, amino-LqBR improved carbon black dispersion in the rubber matrix through a chemical bond between the functional group of the carbon black surface and the base rubber. In conclusion, amino-LqBR successfully served as a processing aid in a carbon black-filled NR compound while simultaneously enhancing its fuel efficiency and abrasion resistance.

Improving hysteresis of a typical carbon black-filled natural rubber tread compound by using a novel coupling agent

Potential of Sumilink-200 was investigated in a typical natural rubber-based tread compound in connection with its ability to act as a coupling agent for carbon black to reduce hysteresis loss of the compound. Optimum physical properties were obtained at 2 phr loading of Sumilink-200. At this loading, tensile modulus at 300% elongation improved by 9.6% with a reduction in visco-elastic energy dissipation (loss tangent) at 60°C by 8.3% over the control compound. The abrasion resistance properties of the compounds found to remain unaffected with the introduction of Sumilink-200.

Mixing time influence on fatigue crack growth in a carbon black-filled natural rubber vulcanizate

Various processing parameters affect the dispersion of carbon black (CB) in a rubber matrix, of which mixing time plays a major role. The physical properties of a green compound namely bound rubber and Mooney viscosity along with mechanical and fatigue crack growth (FCG) are affected by the dispersion of filler particles. To determine the effect of mastication on dispersion, the mixing time was varied from 120 s to 600 s where it was gauged that an optimum range of mixing times display better dispersion. The difference in dispersion between the green and the cured compounds was also stark due to the flocculation mechanism. Longer mixing times do not show much decrease in agglomerate size on curing, that is, approximately 2%, whereas shorter time has led to a decrease of 20%. The FCG properties were studied using a tear and fatigue analyser, where the FCG rate displays a similar trend with the dispersion of CB.

Multiple Structural Changes Found around Crack Tip of Carbon Black-filled Natural Rubber Vulcanizate

Multiple Structural Changes Found around Crack Tip of Carbon Black-filled Natural Rubber Vulcanizate

Cure characteristics, swelling behaviour and tensile properties of carbon black-filled Natural Rubber (NR)/Chloroprene Rubber (CR) blends in the presence of alkanolamide

The cure characteristics, swelling behaviour and tensile properties of carbon black (CB)-filled natural rubber (NR)/chloroprene rubber (CR) blends in the presence of alkanolamide (ALK) were investigated. The NR/CR blends were prepared at 50/50 blend ratio. The ALK was prepared from Refined Bleached Deodorized Palm Stearin (RBDPS) and diethanolamine and added into the CB-filled NR/CR blends as a rubber additive. The ALK loadings were 0.0, 1.0, 3.0, 5.0 and 7.0 phr. It was found that the ALK exhibited shorter scorch and cure times and higher elongation at break of the CB-filled NR/CR blends. The ALK also exhibited higher torque differences, tensile modulus and tensile strength up to 5.0 phr of ALK and then decreased with further increases in the ALK loading. The swelling test proved that the 5.0 phr loading of ALK caused the highest degree in crosslink density of the CB-filled NR/CR blends.

Viscoelastic Behaviors of Carbon Black Gel Extracted from Highly Filled Natural Rubber Compounds: Insights into the Payne Effect

Carbon black filled natural rubber (CB/NR) is a paradigm of nanocomposite materials with high performances. However, the mechanism for the nonlinear Payne effect is still not fully clear. CB gel (CBG) network embedded in the entanglement rubber matrix is supposed to be crucial for the reinforcement and viscoelastic nonlinearity. In this paper, we report for the first time the preparation of bulk CBGs by extracting the highly filled compounds in toluene and the systematic study of their viscoelastic behaviors. The CBG obtained from highly filled compounds with CB loadings from 40 to 70 phr has almost identical microstructure and composition, containing 40 wt % inextractable rubber fractions, among which ∼12 wt % is glassy. Dynamic rheological studies show that the Payne effect of the CBG network is frequency-independent and highly resilient, exhibiting an unjamming characteristic. On the other hand, the Payne effect of highly filled compounds is determined by the coupling between the breakdown of CBG network and the frequency-dependent chain disentanglement of extractable rubber fractions. This work provides new insights into the Payne effect of CB filled NR and should merit designing other rubbery nanocomposites with high performances and functions.

The effect of the addition of alkanolamide on properties of carbon black-filled natural rubber (SMR-L) compounds cured using various curing systems

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.

Traction and wear of an elastomer in combined rolling and sliding

Under combined rolling and sliding materials can experience millions of cycles as well as complex loading and slip conditions, which can dramatically affect their friction and wear behaviour. It was shown that for a carbon black-filled natural rubber compound in combined rolling and sliding contact with a smooth alumina coated disk, the traction coefficient, as a function of slip percent, was dependent upon the normal load and independent of rolling velocity. The wear rate of this material pair was found to be independent of slip percentage as well as rolling velocity but dependent upon sliding distance. The wear rate was found to be approximately the same for all tested cases (K ~ 1 × 10−4 mm3·Nm−1). The worn profiles of the ball specimens showed that this wear occurred preferentially on the left side (inner radius) of the contacting area. Copyright © 2015 John Wiley & Sons, Ltd.

The effect of alkanolamide loading on properties of carbon black-filled natural rubber (SMR-L), epoxidised natural rubber (ENR), and styrene-butadiene rubber (SBR) compounds

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.

Flocculation and Viscoelastic Behaviour in Carbon Black-Filled Natural Rubber

The process of particulate flocculation in natural rubber melts and subsequently crosslinked samples is investigated using carbon blacks of varying surface free energy, surface area and morphology. The surface free energies are varied via thermal treatment of the carbon blacks (graphitization). Reduction in surface free energy of the particulates accelerates the flocculation processes in the melt as measured by rheological experiments and reduces the percolation volume fraction threshold as determined by D/C conductivity measurements. The consequent effects on amplification of the small strain storage moduli of the crosslinked compounds are dramatic. Reduced polymer–filler interactions result in both an increased small strain modulus versus the unmodified carbon black-filled materials and an increased mechanical fragility of the fractal networks. Examination of the dynamic elastic moduli of crosslinked carbon black-filled samples loaded at volume fractions below the onset of network development reveal a significant temperature dependence isolated at the filler–rubber interface.

COMPARATIVE PROPERTIES OF SILICA- AND CARBON BLACK-REINFORCED NATURAL RUBBER IN THE PRESENCE OF EPOXIDIZED LOW MOLECULAR WEIGHT POLYMER

ABSTRACT This work investigates the effect of epoxidized low molecular weight natural rubber (ELMWNR) in silica- and carbon black-filled natural rubber (NR) compounds on processing and mechanical and dynamic mechanical properties. The ELMWNRs with different mol% epoxide content were prepared from depolymerization of epoxidized NR using periodic acid in latex state to have a molecular weight in a range of 50 000–60 000 g/mol. Their chemical structures and actual mol% of epoxide were analyzed by 1H NMR. The ELMWNRs were added to the filled NR compounds as compatibilizers at varying loadings from 0 to 15 phr. The addition of ELMWNR decreases compound viscosity and the Payne effect, that is, filler–filler interaction, of the silica-filled compound. In the silica–silane compound and the compound with 28 mol% epoxide (ELMWNR-28), the compound viscosities are comparable. The optimal mechanical properties of silica-filled vulcanizates are obtained at the ELMWNR-28 loading of 10 phr. In contrast, the addition of ELMWNR to a carbon black-filled compound shows only a plasticizing effect. The incorporation of ELMWNR into NR compounds introduces a second glass transition temperature and affects their dynamic mechanical properties. Higher epoxide contents lead to higher loss tangent values of the rubber vulcanizates in the range of the normal service temperature of a tire.

CHARACTERISTICS OF STRAIN-INDUCED CRYSTALLIZATION IN NATURAL RUBBER DURING FATIGUE TESTING: IN SITU WIDE-ANGLE X-RAY DIFFRACTION MEASUREMENTS USING SYNCHROTRON RADIATION

ABSTRACTStrain-induced crystallization of carbon black-filled natural rubber is investigated by wide-angle X-ray diffraction (WAXD) during in situ fatigue tests using synchrotron radiation. Thanks to an original experimental method, we measure the evolution with the number of cycles of: (i) the index of crystallinity, both (ii) size and (iii) orientation of the crystallites, and finally (iv) the lattice parameters. It is shown that when the minimum stretch ratio of the fatigue test is lower than the onset of melting of the crystallites, then the index of crystallinity and the size of the crystallites decrease, whereas they increase when the minimum stretch ratio is higher than the onset of melting. For all the fatigue tests, the misorientation of the crystallites slightly decreases and the lattice parameters remain constant with the number of cycles.

Synergism of novel thiuram disulfide and dibenzothiazyl disulfide in the vulcanization of natural rubber: curing, mechanical and aging resistance properties

Various combinations of synthesized thiuram disulfides (TD), namely Bis (N-phenyl piperazine) thiuram disulfide (PPTD) and Bis (N-ethyl piperazine) thiuram disulfide (EPTD) with mercapto benzothiazole disulfide (MBTS) are studied in natural rubber (NR) vulcanization. At the same time, we also revised the TD-MBTS binary accelerator on the carbon black-filled NR system. An evaluation is prepared between the synthesized safe thiuram disulfides with the unsafe tetra methyl thiuram disulfide (TMTD) in the light of mechanical and aging resistance behavior to introduce non-carcinogenic rubber additives to vulcanization of rubber. Synthesized safe amine-based thiuram disulfides in combination with MBTS display strong synergism in the gum vulcanization. Higher concentration of thiuram disulfide in presence of MBTS (6:3 mM ratio) shows better results with respect to cure and physical properties. In the specific concentration of 9 mM per hundred gram of rubber (6:3 mM ratio of TD to MBTS), however, PPTD-MBTS accelerated filled vulcanizates show utmost aging resistance behavior, but EPTD-MBTS accelerated filled stock spectacles show superior aging as well as mechanical properties as compared to that of TMTD-MBTS accelerated system.

Strain-induced crystallization of carbon black-filled natural rubber during fatigue measured by in situ synchrotron X-ray diffraction

Natural rubber (NR) exhibits great fatigue properties which are usually explained by its ability to crystallize under strain. Nevertheless, strain-induced crystallization of NR in fatigue has never been investigated. We perform original in situ fatigue tests during which the degree of crystallinity, and the number and volume of crystallites are measured by synchrotron wide angle X-ray diffraction. For all loading conditions, the number of crystallites is constant. The evolution of their volume depends on the minimum stretch ratio achieved at each cycle. The results show that cyclic loading conditions modify the macromolecular structure of the material, in particular of its amorphous phase.

Influence of filler and cure systems on thermal aging resistance of natural rubber vulcanizates under strained condition

Aging and decomposition of polymer based articles are influenced by various environmental factors. Hence, it is important to research the various factors precisely to interpret the aging mechanism. This study deals with the tensile set properties of natural rubber (NR) vulcanizates with different reinforcing and cure systems after thermal aging. The tensile set increased with increasing both the aging temperature and aging period. Thermal aging resistance and tension set was enhanced by increasing the cure accelerator content in the sample. The carbon black-filled NR vulcanizates showed better thermal aging resistance than the silica-filled ones. It was found that silane coupling agent enhanced the thermal aging resistance of the silica-filled NR vulcanizates. The experimental results could be explained by the cross-link density change and also from the consumption of the antidegradants due to thermal aging. The permanent tension set and cross-link density were increased as the aging temperature and aging time were increased. The filler and cure systems were found to influence on the surface morphologies of the thermally aged samples. The cross-link density change was a key factor of the changes of tension set. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synergy in carbon black-filled natural rubber nanocomposites. Part I: Mechanical, dynamic mechanical properties, and morphology

Natural rubber (NR)/nanoclay and NR/carbon nanofiber (CNF) nanocomposites were consolidated with different loadings and grades of carbon blacks (CBs) to obtain ternary nanocomposites. It was observed that the mechanical and dynamic mechanical properties of these nanocomposites were much better compared with those of either NR/clay or NR/CNF nanocomposites or the NR/black control microcomposite. Thus, not only the grueling and at times conflicting property requirements of modern day applications were met, but also the tendency of saturation of property enhancements at high loadings could be mitigated. These nanocomposites exhibited 18% increment in tear strength, 40% in modulus at 300% elongation, and 326% in room temperature storage modulus, over the control microcomposite. Viscous loss properties were influenced favorably, as well. This indicated the presence of a much sought after synergy between CB and nanofillers. Transmission electron micrographs of the nanocomposites showed that CB formed “nano-blocks” of reinforcement—close association of nanofiller and black—driven by zeta potential differences between the black and the nanofillers. This unique ternary architectural base, with the space between nanofillers (clay/fiber) occupied by small CB aggregates forming networks or “nano-channels”, accounted for the synergistic improvements.

Description of fatigue damage in carbon black filled natural rubber

ABSTRACTThe present paper describes macroscopic fatigue damage in carbon black‐filled natural rubber (CB‐NR) under uniaxial loading conditions. Uniaxial tension‐compression, fully relaxing uniaxial tension and non‐relaxing uniaxial tension loading conditions were applied until sample failure. Results, summarized in a Haigh‐like diagram, show that only one type of fatigue damage is observed for uniaxial tension‐compression and fully relaxing uniaxial tension loading conditions, and that several different types of fatigue damage take place in non‐relaxing uniaxial tension loading conditions. The different damage types observed under non‐relaxing uniaxial tension, loading conditions are closely related to the improvement of rubber fatigue life. Therefore, as fatigue life improvement is classically supposed to be due to strain‐induced crystallization (SIC), a similar conclusion can be drawn for the occurrence of different types of fatigue damage.