Investigation of Carbon Black Network in Natural Rubber with Different Bound Rubber Contents

A new method was applied to modify the surface activity of virginal carbon black (VCB). LA‐57, one kind of hindered amine light stabilizer, was adsorbed onto the carbon black surface through a strong shear force induced by the screws of a HAAKE internal mixer. The modified carbon black (MCB) was characterized by FT‐IR and thermogravimetric analysis (TGA). The bound rubber content of the natural rubber (NR) compounded with MCB and VCB varied with the fraction of LA‐57 on the MCB surface. The nonlinear effect at small strains, generally referred as the Payne effect, was investigated in the rubber compounds based on the different bound rubber contents. The NR compound containing the lowest bound rubber content had an obvious Payne effect. Based on the bound rubber content, the types of filler network varied from direct contact mode to the joint rubber shell mechanism.     

Characterization of Filler-rubber Interaction,Filler Network Structure,and Their Effects on Viscoelasticity for Styrene-butadiene Rubber Filled with Different Fillers

For styrene-butadiene rubber (SBR) compounds filled with the same volume fraction of carbon black (CB), precipitated silica and carbon–silica dual phase filler (CSDPF), filler-rubber interactions were investigated thru bound rubber content (BRC) of the compounds and solid-state ¹H low-field nuclear magnetic resonance (NMR) spectroscopy. The results indicated that the BRC of the compound was highly related to the amount of surface area for interaction between filler and rubber, while the solid-state ¹H low-field NMR spectroscopy was an effective method to evaluate the intensity of filler-rubber interaction. The silica-filled compound showed the highest BRC, whereas the CB-filled compound had the strongest filler-rubber interfacial interaction, verified by NMR transverse relaxation. The strain sweep measurements of the compounds were conducted thru a rubber process analyzer; the results showed that the CSDPF-filled compound presented the lowest Payne effect, which is mainly related to the weakened filler network structure in polymer matrix. The temperature sweep measurement, tested by dynamic mechanical thermal analysis, indicated that the glass transition temperature did not change when SBR was filled with different fillers, whereas the storage modulus in rubbery state and the tanδ peak height were greatly affected by the filler network structure of composites.     

Natural Rubber/Graphene Oxide Nanocomposites Prepared by Latex Mixing

Natural rubber/graphene oxide (NR/GO) nanocomposites were prepared by latex mixing. The dispersion state of GO and the mechanical properties of the nanocomposites were studied. It was found that a uniform dispersion of GO in the NR matrix was achieved with the latex mixing method. The well-distributed GO was remarkably effective in improving the tensile strength and storage modulus of NR at very low filler contents, without sacrificing the ultimate strength. The percolation point of GO in the nanocomposites took place at a content of less than 0.1 parts by weight per hundred parts of rubber. The Halpin-Tsai model was used to analyze the reinforcement effect of GO for NR.     

SiO2 Reinforced EVM/TPU Blends: Bound Rubber and Rheology Behavior

Silica is shown to be a more active filler than carbon black for the reinforcement of EVM/TPU blends. The static rheology of EVM/TPU blends is considerably influenced by a tightly bound rubber structure developing between the TPU and silica that was identified by a tetrahydrofuran extraction test and SEM observations. Dynamic rheology behavior corroborated the development of bound rubber and indicated the existence of the Payne effect because of filler-filler networks in the blends. The silica-TPU interaction is thermally unstable at 190°C and mechanically unstable at a shear frequency of 1 Hz.     

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.     

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.     

Dynamic Rebound Behavior of Silica/Natural Rubber Composites: Fly Ash Particles and Precipitated Silica

This article investigated the elastic response of natural rubber (NR) compounds filled with silica from fly ash particles (FASi) and commercial precipitated silica (PSi), through a dynamic rebound test. The effects of silica content and initial drop‐height on the height and number of rebounds, dynamic stiffness, and the energy loss were of interest. The results suggested that the unfilled NR vulcanizates exhibited a greater elastic response than the FASi and PSi‐filled vulcanized composites. For given silica contents, the NR compounds with FASi had better elastic response than those with PSi, where the elastic response decreased with an increase in silica content. The greater the silica contents, the higher the dynamic stiffness of the composites. The initial drop‐height had no effects on the elastic response change for the unfilled NR compound, but resulted in an increase in the energy loss for the silica‐filled NR composites. The differences in the elastic responses for the NR compounds filled with silica from FASi and PSi were associated with the differences in crosslink density and the filler–filler interaction influenced by content of bis(3‐triethoxysilylpropyl) tetrasulfane (designated as Si69) used.     

Influence of In-situ Grafting on the Dispersion of Carbon Black in Solvents and Natural Rubber

In-situ grafting of natural rubber (NR) onto the carbon black (CB) surface by a solid-state method was used to obtain grafted carbon black (GCB). The morphology of the original CB and GCB particles was observed by AFM and TEM. The original CB particles fused together and occurred as large dendritic agglomerates while the GCB particles occurred as small aggregates about 150 nm in diameter. The dispersion and dispersion stability of CB and GCB in toluene and cyclohexene were studied by zeta potential and a spectrophotometer. The results showed that the grafting procedure can improve both dispersion and dispersion stability of CB particles. The dispersion in NR was studied by DMA and observed by SEM. It was shown that GCB has better dispersion than CB in a NR matrix. As expected a weakened filler-filler interaction and enhanced filler-polymer interaction occurred after grafting modification.     

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.     

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.     

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.     

The effect of accelerator contents on the vulcanizate structures of SSBR/silica vulcanizates

Physical properties of rubber compounds are affected by the filler–rubber interaction, filler dispersion in the rubber matrix, and cross-link structure formed during vulcanization. In particular, the cross-link structure is closely related to the physical properties of vulcanizates and has been analyzed using the swelling test and Flory-Rehner equation. However, the relationship between the structure and physical properties of vulcanizates cannot be explained by the cross-link density obtained using these methods. The cross-link density obtained from the swelling test is a complex result of the filler–rubber interaction occurring during the compounding as well as the chemical cross-link structure formed by sulfur during the vulcanization. Moreover, the rubber vulcanizates that use silica need to be separately analyzed for each factor as its physical properties are affected more by the filler–rubber interaction than by carbon black. Therefore, this study determines the factors that contribute to the total cross-link density of vulcanizates into chemical cross-link density and filler–rubber interaction via quantitative analysis using the swelling test results and Flory-Rehner and Kraus equations. The vulcanizates used for the analysis were carbon black-filled and silica-filled non-functionalized SSBR compounds with varying cure accelerator for each filler loading. Their chemical cross-link density was measured and the effect of the filler–rubber interactions on their mechanical and dynamic viscoelastic properties was investigated. Furthermore, the relationship between the structure and physical properties of rubber vulcanizates was elucidated.     

基于傅里叶红外光谱的钢渣代炭黑环保型复合橡胶的补强机理及性能研究

以铁水脱硫渣作为研究对象,利用铁水脱硫渣作为橡胶填料取代部分炭黑与丁苯橡胶进行复合,制备铁水脱硫渣/丁苯橡胶。利用多种方法测试铁水脱硫渣/丁苯橡胶的性能,采用傅里叶变换红外光谱仪测试硫化过程中不同阶段铁水脱硫渣的结构组成。结果表明：利用铁水脱硫渣部分替代炭黑,可达到补强效果与降低补强剂成本的目的。铁水脱硫渣/丁苯橡胶的正硫化时间(t₉₀)为25.08 min,其焦烧期为0~15 min、热硫化期15~25 min和硫化平坦期25~45 min。在焦烧期铁水脱硫渣可以提供碱环境,利于增加丁苯橡胶流动性;在热硫化期与硫化平坦期,铁水脱硫渣中Ca₂SiO₄能够持续加速发生水化反应生成C-S-H凝胶,达到对丁苯橡胶补强的效果。另外,铁水脱硫渣可以避免铁水脱硫渣/丁苯橡胶过硫化期的出现。     

A Comparative Study on the Reinforcing Effect of Aramide and PET Short Fibers in a Natural Rubber-Based Composite

Four types of chopped fibers have been studied as reinforcement additives in a standard natural rubber based, carbon black filled formulation. The fibers studied were aramide (2 types) and polyester (2 types). The chopped fibers were added on top of the carbon black filled rubber compound at 2, 4, and 8 phr levels. The extra reinforcing effect in the modulus, especially at low elongation, the increase in hardness, the anisotropic properties, and the stiffening effects have been studied together with the evaluation of the mechanical hysteresis in strain and in compression. The permanent set of the resulting rubber compounds have been evaluated as well. The best compromise in performances and price was found for a certain type of polyester fiber.     

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.     

基于FTIR与XRD的改性脱硫灰取代部分炭黑 制备复合橡胶的补强机理研究

脱硫灰是半干法脱硫的主要副产品,其利用难度大且成本高,导致大量脱硫灰以直接堆放和填埋的方式处理,不但造成环境污染,而且浪费潜在资源。炭黑(8 000 元·t-1)与白炭黑(6 000 元·t-1)是常用的橡胶补强填料,生产工艺繁杂,消耗大量能源和资源,导致成本较高。面对上述问题,如何利用脱硫灰开发一种价格低廉的无机橡胶补强填料,既是固体废弃物高附加值利用的重要途径之一,也是橡胶企业大幅降低填料成本提高经济效益的重要途径之一。由于脱硫灰属于无机材料,橡胶属于有机材料,为了更好的降低脱硫灰界面与橡胶界面(无机界面/有机界面)的不相容性,需要对脱硫灰进行化学改性处理,以提高脱硫灰代替部分炭黑制备橡胶的力学性能。该研究创新性以硅烷偶联剂Si69、硅烷偶联剂KH550与脱硫灰制备改性脱硫灰,然后以改性脱硫灰取代部分炭黑制备复合橡胶。根据国家与行业标准测试复合橡胶的力学性能,如拉伸强度、撕裂强度和硬度。利用扫描电子显微镜(SEM)对复合橡胶的微观形貌进行测试与分析,傅里叶变换红外光谱仪(FTIR)对改性脱硫灰的组成结构进行测试与分析,X射线衍射仪(XRD)对改性脱硫灰的矿物组成进行测试与分析,以揭示硅烷偶联剂Si69与硅烷偶联剂KH550协同对脱硫灰的改性机理,以及改性脱硫灰对复合橡胶的补强机理。结果表明：采用硅烷偶联剂KH550与硅烷偶联剂Si69协同改性脱硫灰,其取代炭黑的增强效果最佳,即复合橡胶的拉伸强度为20.36 MPa、撕裂强度为45.71 kN·m-1和邵尔A硬度为66;硅烷偶联剂KH550与硅烷偶联剂Si69协同改性脱硫灰,不仅保持脱硫灰依然良好的碱性,有利于对复合橡胶起到增强效果;而且可以改善脱硫灰的表面特性与结构,提高改性脱硫灰与丁苯橡胶的无机界面/有机界面相容性。     

Study on the Reinforcing Effect of Milled Carbon Fibers in a Natural Rubber Based Composite

Milled carbon fibers (MCF) have been tested at 2, 4, and 6 phr in a standard natural rubber compound with 45 phr of N375 carbon black. A dramatic increase in the low elongation moduli was observed even with only 2 phr of MCF. The presence of MCF confers anisotropic properties to the rubber compounds that can be measured by an anisotropic factor σ, defined as the ratio between the modulus parallel to the MCF prevalent direction over the modulus orthogonal to the MCF prevalent direction. It has been shown that the presence of MCF is able to reduce the mechanical hysteresis and also the compression set of the natural rubber compound. However, the tear strength properties are affected negatively. The present study demonstrates the feasibility and the advantages derived by the utilization of the carbon fibers as extra reinforcing filler in rubber compounds.     

炭黑橡胶复合材料导热逾渗行为

研究了导电炭黑40b2填充天然橡胶复合材料的导热性能和力学性能随炭黑体积分数的变化规律,并采用扫描电子显微镜观察了炭黑橡胶体系内部的炭黑分布状况.结果表明,导热性能随炭黑体积分数的变化规律存在类似于导电逾渗现象的导热逾渗现象,逾渗阈值在8.3%～13.63%之间.在逾渗阈值之后,复合材料的拉伸强度下降.炭黑橡胶复合材料...     

Effects of Carbon Black on Chain Mobility and Dynamic Mechanical Properties of Solution Polymerized Styrene-Butadiene Rubber

The structure of the bound rubber, the ¹H NMR (nuclear magnetic resonance) relaxation time, and the crosslink density of the physical network and the glass transition, were studied for solution polymerized styrene-butadiene rubber (SSBR) filled by carbon black, to investigate the effects of carbon black on the chain mobility and dynamic mechanical properties. It was found by ¹H NMR analysis that the rubber chains were adsorbed on the surface of carbon black to form physical crosslinks and restrict the mobility of the chains, especially for some high-mobility units such as chain ends. It was calculated, according to the molecular weight between adjacent crosslinks, that the main motion units of the tightly adsorbed chains appeared to be similar in size to the chain segments. The glass transition temperature (T _g) obtained by differential scanning calorimetry (DSC) could not be used to judge the effect of carbon black on chain mobility, while the appearance and change of the loss-tangent (tan δ) peak at high temperature in dynamic mechanical thermal spectrometry (DMTS) test showed that there were three chain states: free chains, loosely adsorbed chains, and tightly adsorbed chains. The dynamic rheology test showed that the unfilled SSBR compound had the rheological characteristics of entangled chain networks; however the nonlinear viscoelasticities of the filled SSBR were related to the gradual disentanglement of adsorbed chains and free chains. The peaks in tan δ vs. temperature curves implied that the motion unit size decreased with the increase of bound rubber content, and the modulus vs. temperature curve showed an apparently lower mobility of adsorbed chains than that of free chains through the very low dependence of modulus on temperature for the highly filled compounds. The extremely high tensile modulus of the vulcanizate with 63.6% carbon black at room temperature also implied that the adsorbed chains were in the glass state due to their restriction by the carbon black.     

Preparation and Characterization of Grafted Natural Rubber/Graphene Oxide Nanocomposites

Vinyltriethoxysilane (VTES) was grafted onto natural rubber (NR) in latex form, using potassium persulfate (KPS) as initiator. The VTES grafted NR (NR-g-VTES) was then further reinforced with graphene oxide (GO) by a mechanical mixing method with different GO loadings to get the rubber composite (GO/NR-g-VTES). The NR-g-VTES was characterized and confirmed by attenuated total teflectance-Fourier transforms infrared spectroscopy (ATR-FTIR). The effect of GO content on the curing characteristics and resulting mechanical properties of the GO/NR-g-VTES were studied and compared with neat NR filled with GO (NR/GO). The maximum and minimum torque and the tensile and tear strength of the NR-g-VTES/GO composites were higher than that of NR/GO. The samples containing low GO concentration showed maximum torque and tensile and tear strength. Dynamic mechanical analysis showed that the interaction between GO and NR-g-VTES was better than that of the GO-reinforced NR.