Enhancing silica dispersion and interfacial interaction in styrene butadiene/silica rubber composites by using epoxidized styrene butadiene rubber as interfacial compatibilizer

It is usually desired but often challenging to improve the wet traction, and reduce the abrasion and rolling resistance simultaneously in tread rubber, which is referred to as “magic triangle” in tire industry. To fulfill this goal, the filler dispersion and interfacial interaction required to be improved, as they are two essential factors to concurrently govern the ultimate properties of rubber composites. Herein, we synthesized the epoxidized solution polymerized styrene butadiene rubber (ESSBR) with different epoxy level, and used them as interfacial compatibilizer to promote the silica dispersion and silica/rubber interfacial interaction. The epoxy of ESSBR would react with silanol on silica surface and co-crosslink with SSBR simultaneously, therefore build a strong bridge between rubber matrix and filler. By incorporation of 20 phr of ESSBR-15% (15% of double bonds on main chain was epoxidized), the wet grip was improved by 40%, and DIN abrasion and rolling resistance were reduced by 38% and 21%, respectively with hardly sacrifice the mechanical properties. We envisage that this study provides an approach for the fabrication of rubber composites with improved silica dispersion and strengthened interfacial interaction.     

Thiol‐containing ionic liquid for the modification of styrene–butadiene rubber/silica composites

To introduce thiol–ene chemistry in the modification of composites by ionic liquid (IL), a novel functional IL, 1‐methylimidazolium mercaptopropionate (MimMP), was synthesized and investigated as a modifier for styrene–butadiene rubber/silica composites. MimMP could be hydrogen‐bonded with silica and react with the double bonds of rubber chains via thiol–ene chemistry. The filler networking, curing behavior, filler dispersion, crosslink density, and mechanical performance were fully studied. The filler networking in the uncured rubber compounds was effectively restrained. The vulcanization was largely accelerated by MimMP. The interfacial interaction was quantitatively evaluated and found to consistently increase with increasing MimMP. The mechanical performance and abrasion resistance of the modified vulcanizates improved considerably. The remarkable improvements were mainly ascribed to the improved interfacial structure comprised of MimMP–silica hydrogen bonding and MimMP–rubber covalent bonds via thiol–ene chemistry. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Silica nanoparticles reinforced natural rubber latex composites: The effects of silica dimension and polydispersity on performance

The nano-size autonomous monodisperse silica (AS) particles were prepared by hydrolysis and condensation of tetraethoxysilane using l -lysine as catalyst. The silica/natural rubber (NR) masterbatches were then produced via latex compounding, in which NR latex was mixed with the above AS dispersion. The commercial precipitated silica (PS) was introduced as a control. The effects of both AS and PS particles on the interfacial and mechanical properties of composites were systematically examined. It was found that the AS formed bead-like morphology wherein the clear particle edges can be distinguished in rubber matrix. Compared with PS/NR, the AS/NR composites were proved to possess more bound rubber and weaker filler–filler interaction resulting in higher tensile strength, abrasive resistance, and resilience. Meanwhile, the efficiency of premodified AS and PS surfaces using bis-(3-triethoxysilylpropyl) tetrasulfide on reinforcing the properties of silica/NR composites was studied. The results presented that the overall properties of modified silica/NR vulcanizates were improved significantly. In special, the values of heating building-up and compression set showed an evident decline which was of great significance for tire tread or other rubber products. For the dynamic properties, the magic angle spinning/NR composites had lower rolling resistance. In short, AS may be applied as an ideal substitution of PS in rubber. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47449.     

Effect of silane integrated sol–gel derived in situ silica on the properties of nitrile rubber

Nitrile rubber/silica composites are prepared by a sol–gel process using tetraethoxysilane as precursor in the presence of γ‐mercaptopropyltrimethoxysilane as a silane coupling agent. Here, we follow a novel processing route where the silica particles are generated inside the rubber matrix before compounding with vulcanizing ingredients. The effect of in situ generated silanized silica on the properties of the rubber composite has been evaluated by studying curing characteristics, morphology, mechanical and dynamic mechanical properties. Enhanced rubber–filler interaction of these composites is revealed from stress–strain studies and dynamic mechanical analysis. Excessive use of silane shows an adverse effect on mechanical properties of the composites. Due to finer dispersed state of the in situ silica and enhanced rubber–filler interaction, the mechanical properties and thermal stability of the composites are improved compared to corresponding ex situ processed composite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40054.     

Crack growth of natural rubber filled with functionalized silica particles

In the present work, functionalized liquid isoprene rubber (FLIR) was used to improve the filler dispersion and filler–rubber interaction in the silica filled natural rubber system. By the infrared spectra and scanning electron microscopy, it was proved that the FLIR was successfully grafted on the silica and the functionalized silica was dispersed in the NR matrix homogeneously. Based on the real‐time crack tip morphology monitoring method, the influence of FLIR on the crack growth behavior of NR filled with silica was analyzed. By the adding of FLIR, the crack resistance of the natural rubber embedded with functionalized silica is remarkably increased. When the weight ratio of FLIR to silica is 3:10, the NR composite has the best crack resistance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42972.     

The behavior of natural rubber–epoxidized natural rubber–silica composites based on wet masterbatch technique

Natural rubber–epoxidized natural rubber–silica composites were prepared by the wet masterbatch technique and the traditional dry mixing method. Performances of the composites based on different preparation methods were investigated with a moving die rheometer, an electronic universal testing machine, a dynamic mechanical analyzer, a nuclear magnetic resonance crosslink density analyzer, a rubber processing analyzer (RPA), a scanning electron microscope (SEM), and a transmission electron microscope (TEM). The RPA, SEM, and TEM analyses indicated that silica has better dispersion, lower filler–filler interaction, and better filler–rubber interaction in compounds based on the wet masterbatch technique, leading to improvements in mechanical strength and the dynamic mechanical and compression properties of the composites. It also indicates that composites prepared by the wet masterbatch technique have shorter scorch time, faster curing velocity, and higher crosslink density. The composites prepared by the wet materbatch technique also have lower rolling resistance, which is an important property for their use as a green material for the tire industry. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43571.     

Properties of natural rubber composites reinforced with silica or carbon black: influence of cure accelerator content and filler dispersion

Filler dispersion is a critical factor in determining the properties of filled rubber composites. Silica has a high density of silanol groups on the surface, which lead to strong filler–filler interactions and a poor filler dispersions. A cure accelerator, N‐tert‐butyl‐2‐benzothiazole sulfenamide (TBBS), was found to improve filler dispersion in silica‐filled natural rubber (NR) compounds. For the silica‐filled NR compounds without the silane coupling agent, the reversion ratio generally increased with increase in TBBS content, whereas those of the silica‐filled NR compounds containing the silane coupling agent and carbon black‐filled NR compounds decreased linearly. The tensile strength of the silica‐filled NR vulcanizate without the silane coupling agent increased as the TBBS content increased, whereas carbon black‐filled samples did not show a specific trend. The experimental results were explained by TBBS adsorption on the silica surface and the improvement of silica dispersion with the aid of TBBS. Copyright © 2003 Society of Chemical Industry     

Thermal and mechanical enhancement of styrene–butadiene rubber by filling with modified anthracite coal

Anthracite is the highest rank of coal with a layered structure similar to that of graphite. Here, styrene–butadiene rubber/modified anthracite (MA) composites were prepared and analyzed. The microstructure and dispersion of the anthracite were improved by ball milling with the modifier bis-(γ-triethoxysilylpropyl)-tetrasulfide (KH-Si69). The particle size of the modified coal was decreased significantly to ~3 μm, while surface interactions with the modifier yielded enhanced lamellar morphology and hydrophobic surfaces. The anthracite lamellae were well dispersed in the rubber matrix, providing good reinforcement; the tensile strength of the composite exceeded that of a composite with carbon black (CB) N660 filler (16.65 vs. 14.68 MPa). Moreover, low-level CB or silica compositing further promoted the dispersion of coal particles in the rubber, effectively enhancing the mechanical reinforcement behavior of the coal particles as well as the thermal stability of the rubber composite. Notably, it led to a 10.63% improvement in tensile strength and a 9.96 °C increase in the 5% mass loss temperature compared to the composite with a single MA filler. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48203.     

Cure retardation of peroxide‐cured silica filled natural rubber influenced by organosilane

The influence of silane coupling agent on properties of silica‐filled compounds under peroxide curing was investigated. bis (triethoxysilylpropyl) tetrasulfide (TESPT) was selected in this study and its content was varied from 0 to 12% w/w of silica. It is found that with increasing TESPT content, bound rubber content, tensile strength, elongation at break and tear strength are enhanced. By contrast, magnitude of Payne's effect, modulus at 100% elongation (M₁₀₀) and heat build‐up are decreased. The changes of such properties are attributed to the reduction of crosslink density in conjunction with the improvements of both rubber–filler interaction and degree of filler dispersion with increasing TESPT content in the peroxide curing system. POLYM. ENG. SCI., 59:42–48, 2019. © 2018 Society of Plastics Engineers     

Preparation of dispersible nanosilica surface-capped by hexamethyl disilazane via an in situ surface-modification method and investigation of its effects on the mechanical properties of styrene–butadiene/butadiene rubber

Silica has been established as one of the most promising materials in green tires. The filler–rubber interactions can increase the comprehensive performance of rubber composites. In this study, sodium silicate was used as the silicon source and hexamethyl disilazane (HMDS; molecular formula: C₆H₁₉NSi₂) was used as a modifier to synthesize dispersible silica (DNS) via an in situ surface-modification method. The effects of the HMDS-capped silica on the properties of rubber–matrix composites made of styrene–butadiene rubber (SBR) and high-cis-polybutadiene rubber (BR9000 or BR) were investigated with Zeosil 1165MP (Z1165-MP; a commercial highly dispersible silica produced by Rhodia for the production of green tires in the rubber industry) as a reference. The results show that the SBR–BR–DNS composite was before the SBR–BR–Z1165-MP composite in increasing the tear strength and elongation at break and reducing the compression heat buildup. On the basis of the resulting properties, the reinforcing behaviors in the rubber–matrix composites were analyzed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47763.     

Interfacial interactions and properties of natural rubber–silica composites with liquid natural rubber as a compatibilizer and prepared by a wet‐compounding method

Natural rubber–silica [W(NR–SiO₂)] composites were prepared by wet‐compounding technology with liquid natural rubber (LNR) as a compatibilizer. The effects of the LNR content and wet‐compounding technology on the filler dispersion, Payne effect, curing characteristics, mechanical properties, and interfacial interactions were investigated. The results show that the incorporation of LNR promoted vulcanization and decreased the Payne effect of the W(NR–SiO₂) composites. With the addition of 5 phr LNR, the remarkable improvements in the mechanical properties of the W(NR–SiO₂) vulcanizates were correlated with the improved silica dispersion and strengthened interfacial bonding. Furthermore, the W(NR–SiO₂) vulcanizates containing LNR exhibited improvements in both the wet‐skid resistance and rolling‐resistance performance. The interfacial interactions, quantitatively evaluated by the Mooney–Rivlin equation and Lorenz–Park equation on the basis of the rubber elasticity and reinforcement theory, were strengthened in the presence of LNR. Accordingly, an interfacial structural model was proposed to illustrate the improvements in the mechanical properties of the W(NR–SiO₂) composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46457.     

Improved dispersion and physico-mechanical properties of rubber/silica composites through new silane grafting

3-Octanoylthio-1-propyltriethoxysilane (a new silane) grafted styrene butadiene rubber/ silica composites were prepared in the present work, where grafting weight percentage of the base rubber (0%, 2%, 4%, and 6%) and filler content of the composites (0, 5, 15, 35, and 50 phr) were varied to investigate dispersion of the filler in the rubber. A detailed quantitative study of morphology-physical property relationship of the composites using dispersion degree parameter was carried out. Pronounced improvement of dispersion was observed with increasing grafting weight percentage of the base rubber. A mechanism of polymer to filler interaction was shown by Fourier transform infrared spectroscopy. The dispersion rate constant from the torque-time curve increased with the grafting percentage. Bound rubber content and Payne effect measurement indicated improved rubber-filler interaction for the grafted rubber compound. A relation between low strain modulus of the composites and grafting percentage was proposed. The nanoindentation studies gave further insight into the results. Other physico-mechanical properties at different grafting weight percentages at particular filler loading (50 phr) and at different filler loadings at a particular grafting weight percentage (4%) were evaluated. The improved mechanical and dynamic mechanical properties with increasing grafting weight percentage are an indication that this methodology could be used in green tire application.     

Reinforced chloroprene rubber by in situ generated silica particles: Evidence of bound rubber on the silica surface

Nano silica is generated in situ inside the uncrosslinked chloroprene rubber (CR) by the sol‐gel reaction of tetraethoxysilane (TEOS). This results in appreciable improvement in mechanical properties of the CR composites at relatively low filler content. Furthermore, exploitation of reactive organosilanes, γ‐aminopropyltrimethoxysilane (γ‐APS) in particular, in the silica synthesis process facilitates growing of spherical silica particles with a size distribution in the range of 20‐50 nm. The silica particles are found to be uniformly dispersed and they do not suffer from filler‐filler interaction. Additionally, it is observed that the silica particles are coated by silane and rubber chains together which are popularly known as bound rubber. The existence of the bound rubber on silica surface has been supported by the detailed investigations with transmission electron microscopy (TEM), energy filtered transmission electron microscopy (EFTEM) and energy dispersive X‐ray spectroscopy (EDAX). The interaction between rubber and silica, via bi‐functionality of the γ‐APS, has been explored by detailed FTIR studies. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43717.     

Reinforcement of maleated natural rubber by precipitated silica

Graft copolymers of maleic anhydride and natural rubber or so‐called maleated natural rubbers (MNRs) were prepared in a molten state with varying maleic anhydride contents from 4 to 10 phr. In this work, the filler–filler and filler–rubber interactions of the MNR and precipitated silica were investigated. The MNR compounds containing 40 phr of silica both with and without 9 wt % of silane coupling agent were prepared. By increasing the maleic anhydride contents, the Mooney viscosity and cure times were increased, but the torque differences and cure rate indices were decreased. Bound rubber was increased with increasing maleic anhydride content, indicating an increase of filler–rubber interaction. In case of the compounds without silane, the MNR with 6 phr of maleic anhydride showed the lowest filler–filler interaction as indicated by a decrease of storage modulus upon an increase of strain in the filled compound i.e., Payne effect. This MNR compound also yielded the optimum mechanical properties. It has been demonstrated that a use of MNR with appropriate maleic anhydride content can reduce filler–filler interaction dramatically and hence improve a silica dispersion, as confirmed by SEM micrographs, resulting in an enhancement of the mechanical and dynamical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

叶腊石/白炭黑/NBR复合材料的结构与性能研究

利用机械共混法制备了叶腊石/白炭黑/NBR复合材料,采用RPA2000、SEM、DMA等实验方法研究改性剂的种类、增塑剂DOP用量对复合材料性能的影响。结果表明,偶联剂Si-69不仅可以改善复合填料的分散性,而且可以提高复合填料与NBR之间的相互作用,其改性效果最佳。增塑剂DOP可以改善NBR胶料的加工性能,提高NBR复合材料的耐溶剂性能、回弹性及耐低温性能,对NBR复合材料的补强及耐热空气老化性能不利,但可以降低胶料成本。     

Promoting the dispersibility of silica and interfacial strength of rubber/silica composites prepared by latex compounding

The dispersibility of precipitated silica and its interfacial interaction with rubber matrix can affect the performances of tires which is a difficult problem to be solved. A well-dispersed silica dispersion was obtained through ball milling and modification process followed by heat treatment to enhance the properties of NR composites prepared by latex compounding. Benefiting from the modifier Si-747, the well-dispersed silica/NR composite (Silica-MSH-C) shows excellent tensile strength of 30.8 ± 0.5 MPa, which is 17.6 ± 3.8% higher than latex compounding pure silica/NR composite (Silica-C) and 21.7 ± 4.3% higher than traditional mechanical blending pure silica/NR composite (T-Silica-C). The tan delta values indicate that Silica-MSH-C has better dynamic properties and also has stronger interface strength according to swelling tests, heat capacity curves and Mooney-Rivlin equation. The molecular dynamics (MD) simulation further shows the binding energy between NR and Si-747 modified SiO₂ is 58.88 Kcal/mol larger than the value of NR and pure silica.     

The aggregation structure regulation of lignin by chemical modification and its effect on the property of lignin/styrene–butadiene rubber composites

The aggregation structure of lignin in aqueous solution had an important effect on the dispersion of lignin and the properties of lignin/styrene–butadiene rubber (SBR) composites. This article revealed the relationship between aggregation structure and chemical structure of modified lignin. Unmodified lignin was amorphous; however, our results showed that aldehyde‐modified lignin was transformed into spherical aggregates, while propylene‐oxide‐modified lignin self‐aggregated into supramolecular domains. The relationships between aggregation structure, filler dispersion, filler–rubber interaction, and performance were also studied by investigating the microstructure, viscoelastic behavior, and mechanical properties of lignin/SBR composites. Meanwhile, a solution to improve the coprecipitation efficiency of lignin and SBR latex was proposed. In this article, epoxidized natural rubber (ENR) was also used as compatibilizer to improve the interfacial adhesion between polar lignin and nonpolar SBR. The results showed better lignin dispersion for the ENR‐containing rubber composites, as well as superior wet skid resistance and lower rolling resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45759.     

Comparative role of Interface in reinforcing mechanisms of Nano silica modified by Silanes and liquid rubber in SBR composites

The objective of the present study is to discuss the role of silica-rubber interfacial interactions on vulcanization kinetics, morphology, mechanical and viscoelastic behavior of silica filled styrene butadiene rubber (SBR) composites. Three types of modifiers, namely mono- and bi-functional silanes as well as hydroxyl-terminated poly butadiene (HTPB) liquid rubber were grafted to silica surface, and composites prepared by these fillers were characterized. Results showed that modified silica, especially grafted by bi-functional silane and liquid rubber, accelerated vulcanization reactions, while pristine silica slowed down vulcanization kinetics of SBR. Morphological studies indicated that all modifications improved dispersion of silica, but HTPB-grafted silica was dispersed to a greater extent in SBR. The observed differences in mechanical and dynamic-mechanical properties of vulcanizates were correlated to the significant differences in silica-rubber and silica-silica interactions. Type of interfacial interactions, i.e. rigid covalent bonds in the bi-functional silane, flexible polymeric bonds in the liquid rubber, and weak energetic bonds in the mono-functional silane, could explain the observed differences. Although all modifications reduced filler networking, rigid covalent bonding by bi-functional silane significantly improved mechanical properties and stabilized the filler network. The mono-functional silane lacks these mechanisms. The soft and flexible interphase of HTPB could create bonds and transfer stresses between the rubber matrix and silica to some extent, however it could not improve the mechanical properties and reduce the Payne effect as much as the bi-functional silane did.     

Effect of ultrasonic extrusion of star styrene-butadiene rubber on properties of carbon black- and silica-filled compounds and vulcanizates

Extrusion of star styrene-butadiene rubber (SBR) without and with ultrasonic treatment at amplitudes 3.5, 5, 7.5, and 10 μm was carried out. The molecular structure of untreated and treated star SBR was determined. Significant reduction of die pressure was observed during ultrasonic treatment due to the thixotropic and degradation effects. Ultrasonic treatment of star SBR at 3.5 μm created molecules of higher molecular weight via long-chain branching without gel formation. Ultrasonic treatment of star SBR at 5 μm created a small amount of gel. At high ultrasonic amplitudes more gel was generated hindering mixing of star SBR with silica. Extruded star SBR was compounded with carbon black and precipitated silica, with and without silane. It was found that the long-chain branching induced by ultrasonic treatment improved the rubber–filler interaction in precipitated silica without silane, as confirmed by the increase of bound rubber content. The filler–filler interaction was reduced in silica compounds without silane, as indicated by study of Payne effect. The significantly improved rubber–filler interaction and reduced filler–filler interaction led to an increase of the modulus at 100% elongation and tensile strength of SBR/silica vulcanizates. Extensive comparisons were made with earlier study on ultrasonic treatment of linear SBR. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47451.     

硅藻土/白炭黑复合填料的补强性研究

为拓展硅藻土在高分子复合材料中的应用,将硅藻土/白炭黑填充到天然橡胶/丁苯橡胶/顺丁橡胶中制备了复合材料。通过RPA2000和扫描电镜分析了复合填料的Payne效应和分散性,考察了硅藻土用量对复合材料工艺性能、力学性能、耐磨耗性能影响。结果表明:少量硅藻土的加入有利于白炭黑在橡胶中的分散,能降低复合材料的门尼粘度和Payne效应,提高复合材料的硫化速度,缩短硫化时间,复合填料的补强效果较好;随着硅藻土用量的增加,复合填料容易聚集,其力学性能呈下降趋势,而磨耗性能变化不大;当硅藻土用量10~20份时,复合材料的综合性能最好。