Variation of the Payne Effect in Natural Rubber Reinforced by Graft-Modified Carbon Black

Carbon black (CB) was modified by liquid grafting and used for natural rubber (NR) reinforcement. Payne effects during NR reinforcement by the graft-modified carbon black (GCB) were analyzed in this paper. The results showed a proportional relationship between filler content and the Payne effect. Rubber compounds with GCB presented weaker Payne effects than their non-modified counterparts. Qualitative analysis of the correlation between filler network structure and filler content was conducted according to the relationship between bound rubber of a rubber compound and shear modulus. The impact of the storage period on the Payne effect was further studied, and the results demonstrated that the longer the storage period of the rubber compound, the stronger the Payne effect tended to be. The mechanisms by which the Payne effects were manifested differed according to the content of the filler in the rubber.     

Effect of Dispersion of Carbon Black on Electrical and Thermal Properties of Poly(Ethylene Terephthalate)/Carbon Black Composites

A type of grafted carbon black (GCB), prepared with a low molecular weight antioxidant compound by in-situ reaction, was dispersed in poly(ethylene terephthalate) (PET) by a melt-blending process. Dispersion of fillers, volume resistivity, and thermal properties were investigated using scanning electron microscopy, a high-resistance meter, differential scanning calorimetry, and thermogravimetric analysis, respectively. The results show that, compared with carbon black (CB) particles, GCB particles dispersed better in the PET matrix, whereas the conductivity percolation threshold of PET/GCB was higher than that of PET/CB. The addition of GCB or CB elevated the cold crystallization temperature of PET, reflecting the effectiveness of carbon fillers as nucleating agents. But carbon fillers decreased the crystallization enthalpy of PET during both heating and cooling process. Both CB and GCB elevated the starting temperature of thermal degradation of PET and increased the amount of residues for the composites over that of neat PET.     

The Nucleation Effect of Grafted Carbon Black on Crystallization of Poly(Ethylene Terephthalate)/Grafted Carbon Black Composite

Poly(ethylene terephthalate)/grafted carbon black (PET/GCB) and poly(ethylene terephthalate)/carbon black (PET/CB) composites were prepared by melt blending. The nucleating effect of CB and GCB were investigated using differential scanning calorimetry (DSC) analysis. The morphologies of the spherulites in PET, PET/CB and PET/GCB composites were observed by means of scanning electron microscopy (SEM). All results showed that GCB had higher nucleating activity than CB in PET and PET/GCB composite had higher rate of nucleation and crystallization. The melting behaviors of neat PET, PET/CB and PET/GCB composites after non‐isothermal crystallization were investigated as well. It was evident that the melting behavior of PET is greatly influenced by addition of CB and GCB.     

Molecular dynamics simulation on surface modification of carbon black with polyvinyl alcohol

A novel and reasonable model of carbon black (CB) was built to investigate the surface encapsulation modification of CB particles with polyvinyl alcohol (PVA) by molecular dynamic simulation. The modification process of PVA on CB surface was intuitively exhibited, which indicated that the encapsulation films were formed by stacking PVA molecules layer by layer on the surface of CB. The dispersion stability of unmodified and modified CB particles was compared both by simulation and by scanning electron microscope graphs. The simulation results indicated that surface modification had great effect on reducing the interaction energy of CB/water interface so as to alleviate agglomeration phenomenon significantly. Moreover, the influences of PVA amount on the morphology and the compatibility of PVA/CB interface were also investigated. The amount of PVA would neither influence the arrangement of single PVA molecule nor change the orientation of the single PVA layer but only decide the thickness of the modification film. Besides, the energy analysis results indicated that a suitable thickness of PVA coating could improve the dispersion stability of CB particles.     

Carbon Black–Filled Styrene Butadiene Rubber Masterbatch Based on Simple Mixing of Latex and Carbon Black Suspension: Preparation and Mechanical Properties

An improved process was developed for the production of carbon black (CB)–filled styrene butadiene rubber masterbatch (SBR-CB-MB) using a simple latex/CB mixing technology; the improvement comprised processing the CB as an emulsifier-free aqueous suspension by high-rate shearing. Tensile and tear strength, dynamic compression behaviors, the Payne effect, equilibrium swelling and bound rubber of the SBR-CB-MB and dry mixing CB filled SBR (SBR-CB-DM), covering a wide range of CB loading (45–70 phr), were investigated and compared. It was found that the tensile and tear strength, heat buildup and compression set, abrasion volume loss, and the Payne effect of the SBR-CB-MB were lower than those of the SBR-CB-DM, while the bound rubber content were higher, indicating good CB/rubber interaction in the SBR-CB-MB. SEM analysis showed that no free CB could be found on the surface or inside of the granular SBR-CB-MB particles, indicating good CB dispersion in the rubber matrix.     

Carbon Black Filled Powdered Natural Rubber

Carbon black (CB) filled powdered natural rubber [P(NR/N234)] was prepared using a patented method of latex/CB coagulation technology. The influence of curing recipes and CB contents on the curing, mechanical, and dynamic properties were studied in depth, and the results were compared with that of NR/N234 compounds based on traditional dry mixing of bale NR and CB. The results showed that, compared with NR/N234, P(NR/N234) showed higher tensile strength, tear strength, rebound elasticity and flexibilities, and the antiabrasion properties were similar, while the dynamic temperature-build-up and dynamic compression permanent set were about 50% of that of NR/N234. The analysis based on scanning electron micrographs (SEM) and the Payne effect showed that the fine dispersion of CB in the rubber and the enhanced interaction between CB and rubber contributed to the excellent properties of P(NR/N234), sufficient that they make P(NR/N234) a potential material for the tread compounds of heavy-duty all-steel cord radial tires.     

Preparation and Characterization of Acrylic Resin/Hindered Phenolic Antioxidant (AO80)-modified Carbon Black Nanocomposite

To improve the dispersion stability of carbon black (CB) in an acrylic resin coating, a hindered phenolic antioxidant (AO80) was chosen to modify the CB by a solid state method based on the blending of CB and AO80 in an internal mixer. The modified CB (m-CB) was directly introduced into the acrylic resin with 50% solid content in butyl acetate by ball milling without any other treatment. That the majority of the m-CB particles were nanosized in ethanol was proven by a particle size analyzer. Transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM) micrographs indicated that the m-CB particles were also dispersed in the acrylic resin as nanoscale particles. Compared with the unmodified CB, the modification of CB can decrease the viscosity of the acrylic resin/m-CB nanocomposite and improve its flow property. The adhesion and gloss of the acrylic resin/m-CB nanocomposite were also improved. More importantly, the UV shielding and stability of the acrylic resin/m-CB nanocomposite were enhanced.     

Dynamic Fatigue Behavior of Natural Rubber Reinforced with Nanoclay and Carbon Black

The dynamic fatigue behaviors of natural rubber (NR) filled with carbon black (CB) and both nanoclay (NC) and CB at same hardness was evaluated using the stepwise increasing strain test (SIST) and long-term testing. Compared with NR/CB composites, NR/CB/NC nanocomposites exhibited higher fatigue-limited strain, stronger dynamic stress relaxation, and longer compression fatigue life. By examining the fracture morphologies, nonlinear viscoelastic behavior, and hysteresis loss of filled NR, it was found that NR, synergisticly reinforced by NC and CB, exhibited improved anti-fatigue ability than NR filled with CB due to stronger filler–filler interactions between NC and CB (a local filler network) and the high aspect ratio and typical lamellar structure of NC.     

Influence of Carbon Black on Crosslink Density of Natural Rubber

Vulcanization and reinforcement are two important factors contributing to the properties of vulcanized rubber. In order to investigate the influence of carbon black (CB) on chemical crosslinking, three groups of samples with different crosslink densities were prepared. In each group with the same crosslink density, different amounts of CB were introduced. Data fitting showed that delta torque (ΔM = M _H–M _L, the difference between the highest and lowest torques during curing) in the cure curves of each group had a good linear relationship with CB load and extrapolation of the fitting lines almost intercepted the x coordinate at the same value, which indicated that CB had no influence on the chemical crosslinking of the rubber. To verify the above result, a series of nonfilled natural rubber (NR) vulcanizates with different crosslink densities were studied using equilibrium swelling and the swelling ratios were compared with those of corresponding CB filled rubbers with the same sulfur and accelerator amount. The results of both the equilibrium swelling and NMR relaxation parameter measurements showed that CB filled vulcanizates had higher apparent crosslink densities than those of unfilled ones due to the strong interaction between rubber molecules and the surface of the CB particles. The swelling ratios of filled rubbers had a parallel relationship with those of the unfilled ones which indicated that CB had little influence on chemical crosslink density introduced by chemical vulcanization.     

Crystallization Behavior of Poly(Lactic Acid) Filled with Modified Carbon Black

A novel method was employed to modify the surface of carbon black (CB) by an organic small molecule in a Haake Rheomix mixer. The modified carbon black (MCB) was dispersed uniformly in poly(lactic acid; PLA). The crystallization behaviors of PLA, PLA/CB and PLA/MCB composites were investigated by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and polarizing optical microscopy. It is found that the addition of CB or MCB can influence the crystallization behavior of PLA. PLA/MCB has a faster crystallization rate and higher crystallization peak temperature than PLA/CB. For non-isothermal studies, Jeziorny and Mo equations were employed. The Mo equation can well describe the non-isothermal crystallization of the three samples. For PLA/CB and PLA/MCB composites containing 3wt% fillers, the nucleating activity for CB is about 0.32, and about 0.16 for MCB. All these results show that MCB is an effective nucleating agent. PLA/MCB has a higher nucleation rate than PLA/CB because of the finer dispersed particles size and improved interaction between MCB and PLA.     

Study of stress-strain characteristics of SBR and blended NR/SBR rubber

The effect of temperature and carbon black (CB) on the mechanical characteristics of styrene-butadine rubber (SBR) and natural rubber (NR) was studied at various temperatures. The relation obtained between true stress and true strain for both types of rubber showed three regions at room temperature and two regions at high temperature. The optimum CB concentration was found to be 95 phr for the unblended samples as it increases the stiffness of the SBR rubber materials at a maximum value. It was also found that the addition of NR to SBR increases the elasticity in the plastic region. The activation energy at the fracture of SBR samples decreased from about 2.7×10^–20 to 1.8×10^–20 J while for the blended samples NR/SBR it increased from 8×10^–20 to 10.1×10^–20 J with increasing CB concentration.     

Effect of the Super Network on Rubber Reinforcement

The influence of carbon black (CB) on rubber reinforcement was studied. A new reinforcement model, the super network structure model, was proposed. The super network is composed of irreversible chemical crosslinks and reversible physical crosslinks due to CB–rubber interaction. The two crosslink systems are not isolated but interlaced with each other. With increased interaction strength of the reversible physical crosslinks, the CB reinforcement became more effective.     

Improved Dispersion of Carbon Nanoparticles Modified by Poly(Sodium 4-Styrenesulfonate) and Its Influence on the Properties of Natural Rubber Latex

A novel strategy of radical polymerization of sodium 4-styrenesulfonate on the surface of carbon black (CB) in the solid state was developed to prepare hydrophilic carbon nanoparticles (PNASS-CB). A high performance natural rubber latex (NRL)/PNASS-CB composite was produced by the latex compounding technique. Scanning electron microscope shows considerable improvement in the dispersion of PNASS-CB in rubber matrix. The lower degree of filler–filler networks and the stronger filler–rubber interaction of PNASS-CB in rubber matrix were confirmed by dynamic mechanical thermal analysis. Rheometric properties of NRL/PNASS-CB, like scorch time and optimum cure time, decreased. Tensile strength, tear strength, and elongation at break increased due to stronger interaction between the PNASS-CB and rubber matrix. Dynamic mechanical properties of the modified carbon nanoparticles further corroborated a significant contribution from the better dispersion and efficient load transfer of PNASS-CB on the static and dynamic mechanical properties of composites.     

Raman study of oxidation-reduction dispersion of silver

We have examined the process of redox dispersion of silver, using a solution simultaneously containing an oxidizing agent (potassium ferricyanide) and a reducing agent (sodium borohydride). We have studied the changes over time in the Raman spectra of the indicated solution when no silver particles are present and when such particles are added to the solution. We have established that the silver particles have a catalytic effect on the reaction between potassium ferricyanide and sodium borohydride, kinetically slowed down in alkaline medium. The original silver particles (1–20 μm) undergo redox dispersion as a result, and Ag particles are formed with sizes 1–10 nm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 182–186, March–April, 2006.     

Synthesis of carbon black/polystyrene conductive nanocomposite. Pickering emulsion effect characterized by TEM

In this study, carbon black/polystyrene electrically conductive composites were obtained by suspension polymerization technique. The composite was characterized using transmission electron microscopy, which indicated two outstanding features concerning to the carbon black; first, that the carbon particles were adsorbed onto the surface of the polystyrene particles, similarly as in the Pickering emulsion phenomenon and second, that the primary aggregate structure of the carbon black was significantly affected by the dispersion process. On the other hand, the composite resistivity was in the order of 200 Ωcm, which was attributed to the direct contact of primary carbon black particles (percolation) and not to the tunneling effect. The obtained composite was evaluated as the electrically conductive element in SBR matrix.     

Comparative Properties of Styrene-Butadiene Rubbers (SBR) Containing Pyrolytic Carbon Black,Conventional Carbon Black,and Organoclay

To evaluate the reinforcing potential of pyrolytic carbon black, styrene-butadiene rubber (SBR) was filled with pelletized pyrolytic carbon black (pCB_p), N660 industrial CB, their blend in a 1/1 ratio, and the latter also in the absence and presence of additional organoclay (OC). The Shore A hardness of the filled SBR gums was 65 ± 2°. Effects of the compositions on the filler dispersion, cure behavior, dynamic mechanical thermal parameters (including the Payne effect), tensile mechanical (including the Mullins effect), and fracture mechanical (making use of the J-integral concept) properties were studied and discussed. Though pCB_p had a higher specific surface weight than CB, the latter proved to be a more active filler with respect to the tensile strength. The opposite tendency was found for the tear strength and fracture mechanics characteristics (J-integral at crack tip opening, tearing modulus, and trouser tear strength). This was traced to an enlargement in the crack tip damage zone supported by the dispersion characteristics of the pCB_p. The performance of pCB_p was similar to that of CB with respect to some other properties. OC supported the filler networking which positively affected the resistance to crack initiation.     

Reinforcing mechanism of a novel hydrophilic nano-carbon black in natural rubber latex

Novel water-dispersible carbon nanoparticles (PNASS-CBs) were produced by radical polymerization of sodium 4-styrenesulfonate (NASS) on the surface of carbon black (CB) in the solid state. Scanning electron microscopy (SEM) and the Payne effect results showed that the modified CBs were less likely to form particle networks and thus dispersed better in the natural rubber (NR) matrix, with an average size of 90 nm that was much less than that of the aggregated pristine CBs. We propose that the appropriate modification of CBs mitigates filler-filler interaction and enhances the filler-rubber interaction, which can also be proved by the higher bound rubber contents of the NRL/PNASS-CB composites. When a NRL/PNASS-CB composite is subjected to an outside force, e.g. tensile, more physically absorbed rubber chains (bound rubber) slip and self-adjust their absorbed spots on the CBs’ surface (stress redistribution) in order to jointly share the applied stress. This has a positive effect on the resistance to damage of the rubber molecular chains. Therefore, the addition of the hydrophilic CBs in NR latex leads to significant improvements in the mechanical properties of the NRL/PNASS-CB composites.     

Synthesis and Characterization of ZnO Nanoparticles and Their Natural Rubber Composites

Abstract

Nanoparticles of zinc oxide were synthesized by a solution combustion method. The average size of these particles was analyzed by using X-ray diffraction. Composites of natural rubber and the ZnO nanoparticles were prepared by a latex blending method. The matrix phase was cured by using the crosslinking agent, pentane-1,5-diylidenediamine. Effects of crosslinking and incorporation of nanoparticles on the tensile and solvent transport properties of the natural rubber were studied in detail. The nature of the dispersion of the nanoparticles was analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). It was observed from the tensile studies that the addition of the curing agent and the ZnO nanoparticles increased the stability considerably. Incorporation of the nanoparticles also considerably increased the solvent resistance of the cured natural rubber. We suggest the addition of ZnO nanoparticles at a low loading level provided better properties compared to other reinforcements, such as carbon black and nano-clay.     

On-the-fly green generation and dispersion of AgI nanoparticles for cloud seeding nuclei

This study reports on an on-the-fly green synthesis/dispersion of silver iodide (AgI) nanoparticles from the combustion of AgIO₃/carbon black (CB)/nitrocellulose (NC) composites, which could be used as a candidate for a cloud-seeding pyrotechnic. Films were formed by direct electrospray deposition of a mixture of synthesized silver iodate with CB and NC. The decomposition pathways of AgIO₃/CB and AgIO₃/CB/NC were evaluated by temperature jump time of flight mass spectrometry (T-jump TOFMS) and XRD, showing that AgI particles and CO₂ are released from the reaction between AgIO₃ and CB without other toxic residuals. The flame propagation velocity of AgIO₃/CB/NC films increases with the increasing of particle mass loading of AgIO₃ and CB and peaks at 40 wt%, which is much higher than that of an AgI/AP/NC film. The mean diameter of the resultant AgI nanoparticles is from 51 to 97 nm. The mass loading of AgIO₃ and CB was found to play a major role in size control of the AgI nanoparticles.     

Properties of Natural Rubber Vulcanizates/Nanosilica Composites Prepared Based on the Method of In-situ Generation and Coagulation

Using the characteristics of silica sol dispersing well in water and easy formation of silica gel when the silica sol is heated, by mixing a system of concentrated natural rubber latex and silica sol, the silica sol can in-situ generate SiO₂ particles when heated. After coagulation of the mixed system, natural rubber/nanosilica composites C(NR/nSiO₂) were obtained. The composites C(NR/nSiO₂) and their vulcanizates were studied using a rubber processing analyzer (RPA), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The influence of silica contents on the C(NR/nSiO₂) vulcanizates mechanical properties, cross-linking degree, Payne effect, dissipation factor (tanδ), and the particle size and dispersion of SiO₂ in NR were investigated. The results obtained were compared with the NR/SiO₂ composites based on traditional dry mixing of bale natural rubber and precipitated silica (white carbon black). The results showed that when using a sulfur curing system with a silica coupling agent (Si69) in C(NR/nSiO₂), the vulcanizate had better mechanical properties, higher wet resistance, and lower rolling resistance than those without Si69. In the composites C(NR/nSiO₂) and their vulcanizates, the SiO₂ particles’ average grain diameter was 60 nm, and the good-dispersion of the in-situ generated SiO₂ in the rubber matrix were a significant contribution to the satisfactory properties of C(NR/nSiO₂) composites and their vulcanizates.