Functional thiol ionic liquids as novel interfacial modifiers in SBR/HNTs composites

Two kinds of thiol ionic liquids (ILs), 1-methylimidazolium mercaptopropionate (MimMP) and bis (1-methylimidazolium) mercaptosuccinate (BMimMS), were investigated as novel interfacial modifiers for styrene butadiene rubber/halloysite nanotubes (SBR/HNTs) composites. According to model compounds, it was found that their affinities toward HNTs were originated from hydrogen bonding and that they could be grafted onto SBR chains via thiol-ene reactions. The ILs addition could promote vulcanization and effectively facilitate HNTs dispersion in rubber matrix. The interfacial interaction, quantitatively evaluated by a proposed equation based on rubber elasticity and reinforcement theory, was consistently increased. Mechanical properties of SBR/HNTs vulcanizates were largely improved and better than those of the 3-mercaptopropyl trimethoxysilane modified system. The BMimMS’s efficiency on modifying SBR/HNTs vulcanizates was higher than the other for its Gemini structure. Significantly mechanical improvements and lowered mechanical loss in the range of 50-80 °C were correlated to the improved HNTs dispersion and strengthened interfacial interactions.     

Effect of a coupling agent on the properties of hemp‐hurd‐powder‐filled styrene–butadiene rubber

Styrene–butadiene rubber (SBR) composites filled with hemp hurd powder (HP) were prepared with bis(3‐triethoxysilylpropyl) tetrasulfide (Si69) as a coupling agent. The effects of the filler content and coupling agent on the curing characteristics and dynamic mechanical properties of the composites were studied. The results indicate that with increasing filler loading, the torque values increased and the curing time decreased. The mechanical properties improved with increasing filled HP content up to 60 phr. Usually, long fibers led to a sharp decrease in the toughness of the composites, whereas short fibers, such as HP, had a positive effect on the elongation at break within the loading range studied. The extent of the filler–matrix interaction and the scanning electron micrographs of the fractured surfaces confirmed that the addition of Si69 improved the interfacial interaction between HP and the SBR matrix, which led to an increase in the maximum torque and the mechanical properties. Moreover, the coupling agent was helpful in dispersing the filler in the rubber matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

Promoted dispersion of silica and interfacial strength in rubber/silica composites by grafting with oniums

The dispersion of filler and interfacial interaction are crucial in determining the properties of rubber composites. Aiming to improve the dispersion and filler–rubber interaction, we introduce rubber graft bearing oniums in a rubber/silica composite. To fulfill this goal, the graft, which is prepared via thio-ene click reaction between 1-methylimidazolium mercaptopropionate (MMP) and the pendent vinyl groups of a solution-polymerized styrene-butadiene rubber (SSBR), is introduced into the silica-filled styrene-butadiene rubber (SBR) composite. The dispersion of silica and interfacial interaction are improved via hydrogen bonding interaction. Moreover, the graft exhibits catalytic effect toward the silanization, which can improve interfacial interaction in the composites with bis [3-(triethoxysilyl) propyl] tetrasulfide. With 2 phr of the graft, the tensile modulus (stress at 300% strain) is increased by 18% and the abrasion loss is decreased by 31%. This study opens a new attempt to improve the filler dispersion and filler–rubber interaction in the composites with onium-bearing polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48243.     

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.     

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.     

Grafting hydroxy‐terminated polybutadiene onto nanosilica surface for styrene butadiene rubber compounds

Hydroxy teminated polybutadiene (HTPB) was grafted onto the surface of nanosilica particles via toluene di‐isocyanate (TDI) bridging to reduce filler–filler interactions and improve dispersion of nanosilica in rubber. Also, this prepolymer as modifier contains double bonds which participate in sulfur curing of styrene butadiene rubber (SBR) matrix to enhance filler/polymer interaction and reinforcement effects of silica. The reactions were characterized by titration and Fourier transforms infrared spectroscopy. Thermogravimetric analysis was utilized to evaluate the weight percentage of grafted TDI and HTPB. About 60% of the hydroxyl sites of silica were reacted with excess TDI in the first reaction. In the second reaction, HTPB as desired reactive coating was grafted on the functionalized nanosilica to constitute about 24 wt % of the final modified silica. The sedimentation experiments showed good suspension stability for the modified nanosilica in the organic media. Scanning electron microscopy revealed nanoscale dispersion of modified silica aggregates in the SBR matrix at concentration of about 14 phr. Also, vulcanization characteristics and mechanical properties of compounds demonstrated that HTPB grafting improved dispersion of nanosilica as well as its interaction to the rubber matrix as an efficient reinforcement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Contribution of hydrogen and/or covalent bonds on reinforcement of natural rubber latex films with surface modified silica

A macromolecular coupling agent containing hydrophilic and hydrophobic groups is made to react with precipitated silica. Interfacial interactions between  OH groups of silica and  COOH groups of macromolecule are found to be created through either hydrogen bonds alone or through hydrogen bonds and covalent bonds. Aqueous dispersions of unmodified and modified silica are prepared and the colloidal stability and particle size distribution of the dispersions are observed. The dispersions at neutral pH are incorporated into vulcanized/unvulcanized natural rubber latex. The formation of hydrogen bonds and/or covalent bonds is studied via FTIR spectroscopy and their contribution in encouraging filler‐rubber interactions is emphasized through mechanical and swelling properties. Uniform distribution and dispersion of modified filler particles throughout the rubber matrix is confirmed by the microstructures of the latex films cast from filler added natural rubber latex. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40380.     

Hybridized reinforcement of natural rubber with silane‐modified short cellulose fibers and silica

Natural‐rubber‐based hybrid composites were prepared by the mixture of short cellulose fibers and silica of different relative contents with a 20‐phr filler loading with a laboratory two‐roll mill. The processability and tensile properties of the hybrid composites were analyzed. The tensile modulus improved, but the tensile strength and elongation at break decreased with increasing cellulose fiber content. The scorch safety improved with the addition of 5‐phr cellulose fiber in the composites. The Mooney viscosity significantly decreased with increasing cellulose fiber content. To modify the surface properties of the cellulose fiber and silica fillers, a silane coupling agent [bis(triethoxysilylpropyl)tetrasulfide, or Si69] was used. The effects of Si69 treatment on the processing and tensile properties of the hybrid composites were assessed. We found that the silane treatment of both fillers had significant benefits on the processability but little benefit on the rubber reinforcement. The strength of the treated hybrid composite was comparable to that of silica‐reinforced natural rubber. Furthermore, to investigate the filler surface modification and to determine the mixing effects, infrared spectroscopic and various microscopic techniques, respectively, were used. From these results, we concluded that the fillers were better dispersed in the composites, and the compatibility of the fillers and natural rubber increased with silane treatment. In conclusion, the hybridized use of short cellulose fibers from a renewable resource and silica with Si69 presented in this article offers practical benefits for the production of rubber‐based composites having greater processability and more environmental compatibility than conventional silica‐filler‐reinforced rubber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of nano‐zinc oxide/EPDM composites with both good thermal conductivity and mechanical properties

In this article, nano‐zinc oxide (ZnO) filled ethylene propylene diene monomer (EPDM) composites are prepared, and the mechanical (static and dynamic) properties and thermal conductivity are investigated respectively, which are further compared with the traditional reinforcing fillers, such as carbon black and nano‐silica. Furthermore, influence of in‐situ modification (mixing operation assisted by silane at high temperature for a certain time) with the silane‐coupling agent Bis‐(3‐thiethoxy silylpropyl)‐tetrasufide (Si69) on the nano‐ZnO filled composites is as well investigated. The results indicate that this novel reinforcing filler nano‐ZnO can not only perform well in reinforcing EPDM but can also improve the thermal conductivity significantly. In‐situ modification with Si69 can enhance the interfacial interaction between nano‐ZnO particles and rubber matrix remarkably, and therefore contribute to the better dispersion of filler. As a result, the mechanical properties and the dynamic heat build‐up of the nano‐ZnO filled composites are improved obviously by in‐situ modification, without influencing the thermal conductivity. In comparison with traditioanl reinforcing fillers, in‐situ modified nano‐ZnO filled composites exhibit the excellent performance in both mechanical (static and dynamic) properties and better thermal conductivity. In general, our work indicates that nano‐ZnO, as the novel thermal conductive reinforcing filler, is suitable to prepare elastomer products serving in dynamic conditions, with the longer expected service life. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Self‐crosslinkable epoxidized natural rubber–silica hybrids

Epoxidized natural rubber (ENR)–silica hybrids without any other additives were prepared by an open‐mill mixing method at room temperature. The curing characteristics, crosslinking density, mechanical properties, and dynamical mechanical properties were investigated. The results indicate that the ENR–silica hybrid materials could be cured with silica as a crosslinking and reinforcing agent. Attenuated total reflection–Fourier transform infrared spectroscopy and solid‐state ¹³C‐NMR spectroscopy exposed the characteristics of the interfacial interaction in the hybrids and confirmed the existence of chemical bonds and hydrogen bonds between the epoxy group and Si? OH. Scanning electron microscopy illustrated a good dispersion of silica in the ENR matrix. Meanwhile, the modulus at 100% elongation of the hybrid reached 9.64 MPa when 100‐phr silica was loaded; a similar trend was observed for the hardness. Finally, our findings might extend the concept of rubber curing and open a new space for making an environmentally friendly rubber composite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44605.     

Effects of palm ash loading and maleated natural rubber as a coupling agent on the properties of palm‐ash‐filled natural rubber composites

Natural rubber composites were prepared by the incorporation of palm ash at different loadings into a natural rubber matrix with a laboratory‐size two‐roll mill (160 × 320 mm²) maintained at 70 ± 5°C in accordance with the method described by ASTM D 3184–89. A coupling agent, maleated natural rubber (MANR), was used to improve the mechanical properties of the natural rubber composites. The results indicated that the scorch time and cure time decreased with increasing filler loading, whereas the maximum torque exhibited an increasing trend. Increasing the palm ash loading increased the tensile modulus, but the tensile strength, fatigue life, and elongation at break decreased. The rubber–filler interactions of the composites decreased with increasing filler loading. Scanning electron microscopy of the tensile fracture surfaces of the composites and rubber–filler interaction studies showed that the presence of MANR enhanced the interfacial interaction of the palm ash filler and natural rubber matrix. The presence of MANR also enhanced the tensile properties and fatigue life of palm‐ash‐filled natural rubber composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Silica and diatomite fillers modified fluorine rubber composites treated by silane‐coupling agents

The fluorine rubber nanocomposites were prepared by using the silane‐coupling agents treated silica and diatomite, in which 3‐amino propyltriethoxysilane (KH550), 3‐mercapto‐propyl trimethoxysilane (KH590), and bis‐(γ‐triethoxysilylpropyl)‐tetrasulfide (Si69) of the coupling agent were used as the filler modifiers to increase the compatibility between filler and fluorine rubber. The structure and morphology of the composites were investigated by Fourier transform infrared spectroscopy and scanning electron microscopy. The T_g and thermal stability of the composites were investigated by dynamic mechanical analysis and thermogravimetric analysis. The results showed that the best coupling agent was KH550 and 2 phr (parts per hundred rubber). The KH550‐modified compound filler was crosslinked with fluorine rubber, and the compatibility between filler and fluorine rubber was improved and further confirmed to improve the thermal properties of fluorine rubber with the KH550‐modified filler. J. VINYL ADDIT. TECHNOL., 26:55–61, 2020. © 2019 Society of Plastics Engineers     

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.     

High‐performance natural rubber latex composites developed by a green approach using ionic liquid‐modified multiwalled carbon nanotubes

The effect of multiwalled carbon nanotubes (MWCNTs) modified by a hydrophilic ionic liquids (ILs), including 1‐ethyl‐3‐methylimidazolium bromide and 1‐hexyl‐3‐methylimidazolium bromide, was studied. The obtained water‐suspensible carbon nanotubes (CNTs) were still homogeneously distributed in water a month after sonication. The microstructural development of filler networks and the uniform dispersion of MWCNTs in the presence of IL were analyzed by TEM. The apparent physical (cation–π/π–π) interaction between the MWCNTs and the IL was characterized by Raman spectroscopy, DSC, and TGA. Furthermore, high‐performance composites of natural rubber latex (NRL) and CNTs modified with IL were obtained by the liquid latex blending method. The CNTs were homogeneously distributed in the matrix and CNT–ILs improved the fatigue resistance and mechanical properties of the NRL/CNT–IL composites. This study demonstrates a simple and eco‐friendly approach to develop multifunctional advanced materials based on IL‐modified MWCNT elastomer composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46588.     

Enhancement of the mechanical and tribological properties of carboxylated acrylonitrile butadiene rubber filled with cryptocrystalline graphite by different preparation methods

As a cost-effective and environmentally friendly natural mineral, cryptocrystalline graphite (CG) is applied in rubber materials and its performance has been evaluated. In this work, the filler dispersion and mechanical and tribological properties of carboxylated acrylonitrile butadiene rubber (XNBR)/CG composites by different preparation methods were studied. XNBR/CG composites prepared by latex blending (XNBR/CG-L) exhibited better mechanical and tribological performance, higher toughness, and lower heat build-up than those prepared by mechanical blending (XNBR/CG-M). These differences were ascribed to the filler dispersion degree, filler amount and dispersed size, and also filler–rubber interfacial interaction. Adding CG was conducive to improving the stability of the friction coefficient and reduced the wear rate via the formation of graphite lubricant and transfer films. The tribological performance of XNBR/CG-L was superior to that of XNBR/CG-M because of the improved tensile strength, tear resistance, and toughness as well as lower temperature rise. Scanning electron microscopy (SEM) and optical microscope observation showed a smoother worn surface, less and smaller wear debris of XNBR/CG-L, and a more uniform transfer film on the steel counterpart surface. The relevant results provided new insight into the performance and structural design of CG/rubber composites.     

碳包覆白炭黑的研究及在橡胶中的应用

以葡萄糖为碳源物质制备出碳包覆白炭黑填料,通过改变葡萄糖在碳包覆白炭黑填料中的占比,研究不同碳含量对碳包覆填料/橡胶纳米复合材料性能的影响。研究表明,碳包覆白炭黑填料在橡胶中的分散性能及其填充胶加工性能都大幅提升,以葡萄糖为碳源的碳包覆填料硫化胶的耐磨性能相比纯白炭黑硫化胶提升 30%时的碳包覆白炭黑填料填充胶的物理机械性能最为优异。本文通过对碳包覆填料/橡胶纳米复合材料的性能分析及填料自身的微观表征,对填料中碳源物质与白炭黑的作用机理及对橡胶性能的影响进行了总结探讨。     

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.     

Novel technique for crosslinking and reinforcing high‐cis polybutadiene rubber using a silanized silica nanofiller

A large amount of a precipitated amorphous white silica nanofiller was mixed with a high‐cis polybutadiene rubber. The silica surfaces were pretreated with bis(3‐triethoxysilylpropyl)tetrasulfide (TESPT). TESPT is a sulfur‐containing bifunctional organosilane that chemically adheres silica to rubber. The rubber was cured primarily with sulfur in TESPT, and the cure was optimized by the addition of a sulfenamide accelerator, which helped to form sulfur chemical bonds between the rubber and the filler. The hardness, tensile properties, tear strength, abrasion resistance, modulus, and cyclic fatigue life of the cured rubber improved substantially when the filler was added. Interestingly, this new technique produced a rubber with good mechanical properties, and only one accelerator was needed to optimize the chemical bonding between the rubber and the filler and fully cure the rubber. As a result, a substantial reduction in the use of the curing chemicals was achieved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Silica‐modified SBR/BR blends

The purpose of this article is that the silica‐modified SBR/BR blend replaces natural rubber (NR) in some application fields. The styrene‐butadiene rubber (SBR) and cis‐butadiene rubber (BR) blend was modified, in which silica filler was treated with the r‐Aminopropyltriethoxysilane (KH‐550) as a coupling agent, to improve mechanical and thermal properties, and compatibilities. The optimum formula and cure condition were determined by testing the properties of SBR/BR blend. The properties of NR and the silica‐modified SBR/BR blend were compared. The results show that the optimum formulawas 80/20 SBR/BR, 2.5 phr dicumyl peroxide (DCP), 45 phr silica and 2.5 mL KH‐550. The best cure condition was at 150°C for 25 min under 10 MPa. The mechanical and thermal properties of SBR/BR blend were obviously modified, in which the silica filler treated with KH‐550. The compatibility of SBR/BR blend with DCP was better than those with benzoyl peroxide (BPO) and DCP/BPO. The crosslinking bonds between modified silica and rubbers were proved by Fourier transform infrared analysis, and the compatibility of SBR and BR was proved by polarized light microscopy (PLM) analysis. The silica‐modified SBR/BR blend can substitute for NR in the specific application fields. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.