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     

Comparing effects of silanized silica nanofiller on the crosslinking and mechanical properties of natural rubber and synthetic polyisoprene

The effect of the same amount of precipitated silica nanofiller on the curing and mechanical properties of natural rubber and synthetic polyisoprene was investigated. The silica surfaces were pretreated with bis(3-triethoxysilylpropyl) tetrasulfide (TESPT) to chemically bond silica to rubber. The rubbers were primarily cured by using sulfur in TESPT, and the cure was optimized by the addition of accelerator and activator, which helped to form sulfur chemical bonds between the rubber and filler. Different amounts of accelerator and activator were needed to fully crosslink the filled rubbers. The hardness, tensile strength, elongation at break, stored energy density at break, tearing energy, and modulus of the vulcanizates improved substantially by the incorporation of the filler in the rubber. This was due to high level of rubber-filler adhesion and formation of chemical bonds between the rubber and TESPT. Interestingly, natural rubber benefited more from the filler than did synthetic polyisoprene. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanistic aspects of silane coupling agents with different functionalities on reinforcement of silica‐filled natural rubber compounds

Silane coupling agents containing different specific functionalities are studied to gain understanding of their roles in silica‐filled natural rubber (NR) compounds. Five different silane coupling agents, that is bis‐(triethoxysilylpropyl) tetrasulfide (TESPT), bis‐(triethoxysilylpropyl) disulfide (TESPD), octyltriethoxysilane, vinyltrimethoxysilane, and bis‐(trimethyl‐silylmethyl) tetrasulfide (TMSMT), are comparatively investigated, by taking the most commonly used TESPT as a reference. The results reveal that alkoxy‐based silanes can effectively reduce the filler–filler interaction and lower compound viscosity owing to the effect of silane‐to‐silica hydrophobation which contributes to better compatibility between silica and NR. The alkoxy‐silanes with a sulfur moiety, that is TESPT and TESPD, show more pronounced improvement in overall properties as a result of filler–rubber interactions. The use of TMSMT which has no alkoxy groups but contains only a sulfur moiety elucidates that there are three reaction mechanisms involved in systems with sulfur‐alkoxy‐based silane. These are as follows: (1) the silane‐to‐silica or silanization/hydrophobation reaction; (2) the silane‐to‐rubber or coupling reaction; and (3) rubber–rubber crosslinking originating from active sulfur released by the polysulfide‐based silane TESPT. These simultaneous reactions are temperature dependent, and show an optimum level at a dump temperature of approximately 140–150°C, as depicted by filler–filler and filler–rubber interactions, as well as mechanical properties of such compounds. POLYM. ENG. SCI., 55:836–842, 2015. © 2014 Society of Plastics Engineers     

Using a sulfur-bearing silane to improve rubber formulations for potential use in industrial rubber articles

The availability of the coupling agent bis (3-triethoxysilylpropyl)-tetrasulfide (TESPT) has provided an opportunity for enhancing the reinforcing capabilities of precipitated amorphous white silica in rubber. Styrene-butadiene rubber, synthetic polyisoprene rubber (IR), acrylonitrile-butadiene rubber, and natural rubber (NR) containing the same loading of a precipitated silica filler were prepared. The silica surface was pretreated with TESPT, which is a sulfur-bearing bifunctional organosilane to chemically bond silica to the rubber. The rubber compounds were subsequently cured by reacting the tetrasulfane groups of TESPT with double bonds in the rubber chains and the cure was optimized by adding sulfenamide accelerator and zinc oxide. The IR and NR needed more accelerators for curing. Surprisingly, there was no obvious correlation between the internal double bond content and the accelerator requirement for the optimum cure of the rubbers. Using the TESPT pretreated silanized silica was a very efficient method for cross-linking and reinforcing the rubbers. It reduced the use of the chemical curatives significantly while maintaining excellent mechanical properties of the cured rubbers. Moreover, it improved health and safety at work-place, reduced cost, and minimized damage to the environment because less chemical curatives were used. Therefore, TESPT was classified as “green silane” for use in rubber formulations.     

Using a silanized silica nanofiller to reduce excessive amount of rubber curatives in styrene‐butadiene rubber

In recent years, the rubber industry has come under pressure to improve health and safety at work, minimize damage to the environment, reduce costs, and increase competitiveness. Rubber compounds contain additives including curing chemicals, which are hazardous and harmful. Reducing their use or eliminating them altogether will be beneficial to rubber compounders and manufacturers of rubber articles. A styrene‐butadiene rubber (SBR) was cured and reinforced with a high loading of precipitated amorphous white silica nanofiller. The silica surfaces were pretreated with bis(3‐triethoxysilylpropyl) tetrasulfide (TESPT), which is a sulfur‐bearing bifunctional organosilane to chemically adhere silica to the rubber. The chemical bonding between the filler and rubber was optimized via the tetrasulfane groups of TESPT by adding accelerator and activator. The rubbers were subsequently cured and their hardness, tensile strength, elongation at break, stored energy density at break, tearing energy, tensile modulus, Young's modulus, and bound rubber content were measured. This study showed that using the filler in combination with a sulfur‐donor accelerator was the most efficient method for curing and reinforcing the rubber. This led to a significant reduction in the use of the curing chemicals, a faster curing cycle, and very good mechanical properties for the rubber vulcanizate. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Use of epoxidized rubber seed oil as a coupling agent and a plasticizer in silica‐filled natural rubber compounds

To obtain good reinforcement by silica filler in nonpolar rubbers, it is almost essential to use coupling agents, such as bis(triethoxy silyl propyl) tetrasulfane (TESPT). Chemicals that can interact with the silanol groups on the silica particles and reduce their network formation are also expected to enhance reinforcement. We made a comparative evaluation of TESPT, epoxidized rubber seed oil (ERSO), and their combination as a coupling agent and a plasticizer in silica‐filled natural rubber compounds. The results indicate that compounds containing ERSO showed physical and mechanical properties between that of TESPT and naphthenic oil. The action of ERSO in the improvement of the properties was expected to be bifunctional and similar to that of TESPT; that is, it caused the hydrophobation of silica, which increased its degree of dispersion and the formation of chemical bonds with the rubber, thereby ensuring strong polymer–filler interactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3531–3536, 2004     

The role of devulcanizing agent for mechanochemical devulcanization of styrene butadiene rubber vulcanizate

More or less universally, bis(3‐triethoxysilyl propyl) tetrasulfide (TESPT) has been used as a coupling agent during dispersion of silica filler in a virgin nonpolar rubber compound. It is for the first time that TESPT has been used as a devulcanizing agent and as‐grown devulcanized rubber facilitates the silica dispersion in nonpolar rubber compound without any coupling agent. Dual functionalities of TESPT have been modeled and validated in this work. Various factors like the role of sol‐gel content, inherent viscosity of sol rubber, crosslink density, and degree of devulcanization were investigated as a function of devulcanization time and amount of TESPT to optimize devulcanization time and TESPT amount. To study the silica reinforcement, revulcanization of devulcanized SBR was carried out with silica filler and the curing characteristics of the material were evaluated. From the mechanical properties and thermogravimetry analysis the optimum time for devulcanization is determined. Further, scanning electron microscopy (SEM) studies were undertaken to check the coherency and homogeneity of the material. POLYM. ENG. SCI., 58:74–85, 2018. © 2017 Society of Plastics Engineers     

The rubber damper reinforced by modified silica fume (mSF) as an alternative reinforcing filler in rubber industry

Silica fume (SF) is a by-product from the production of ferrosilicon alloy which it can be purified. The surface of SF is treated with bis (3-triethoxysilylpropyl) tetrasulphide (TESPT) to obtain modified silica fume (mSF) as reinforcing filler. FTIR and TGA results confirmed that TESPT can successfully treated onto the surface of SF. The effect of surface treatment by TESPT and mSF content on the cure characteristics and rubber mechanical properties are investigated; as compared with SF and unfilled natural rubber. Results reveal that, the mSF affects not only fast cure rate, but also improve rubber mechanical properties. Additionally, the mSF and SF are incorporated into the natural rubber to produce rubber damper and then study the rubber product performance such as static spring rate and durability property. The mSF seems effective in improving the stiffness and crack resistance of rubber damper more than SF which is due to enhancing the degree of crosslink density. It can be proved that mSF as alternative reinforcing filler in rubber industry.     

Effect of silane coupling agent on filler and rubber interaction of silica reinforced solution styrene butadiene rubber

In the present article, the influence of bis‐(triethoxysilylpropyl)‐tetrasulfide (TESPT) content on the viscoelastic behavior of silica filled Solution Styrene Butadiene Rubber (SSBR) was carefully studied in terms of loss tangent spectrum and bound rubber content. The results showed that both relative tan δ area and tan δ_max of filled SSBR with TESPT were detected to present maximum value at 2.5 wt% TESPT(with respect to silica loading). Larger tan δ area and tan δ_max meant more chains participating in the glass transition in the present system, which is reflected by the variation of effective filler volume with TESPT content. The interaction between filler and rubber can be improved remarkably when a little amount of TESPT up to 2.5 wt% was incorporated, whereas as the TESPT content exceeds 2.5 wt% the filler–rubber interaction was weakened, which was also proven by TEM images and Payne effect. The bound rubber content of this SSBR system studied presents the same tendency as tan δ_max. Once TESPT linked with rubber chains, the condensation reaction between silica and SCA is somewhat hindered because of the difficulty in diffusion of large molecules after SCA is chemically bonded with rubber molecules. The network structure of the filled SSBR was analyzed by applying elasticity model. The consecutive increase of crosslink density compensated the reduction of topological tube‐like constrains and thus tensile strength continued to ascend with TESPT content, but sacrificed the ultimate strain. POLYM. COMPOS., 34:1575–1582, 2013. © 2013 Society of Plastics Engineers     

Modulating silica‐rubber interface by a biorenewable urushiol derivative. Synthesis,surface modification,and mechanical and dynamic mechanical properties of vulcanizates therefrom

Hydrogenated urushiol (i.e., 3‐pentadecylcatechol) can be used to directly modify silica particles via surface complexation with silicon. The degree of surface coverage can be varied by experimental conditions. Mooney viscosity and Payne effect studies of uncured rubber compounds show that dispersion of silica filler completely covered by hydrogenated urushiol in the absence of coupling agent bis[3‐(triethoxysilyl)propyl] tetrasulfide (TESPT) is as effective as dispersion of standard unmodified silica in the presence of TESPT under otherwise identical mixing conditions. Low bound rubber content and observation of filler flocculation at the early stage of vulcanization demonstrate that the filler‐rubber interaction is physical in nature as the result of surface modification by hydrogenated urushiol. When silica is partially covered by hydrogenated urushiol, it can be used in conjunction with TESPT. Judicial combination of partially covered silica and TESPT can give optimal properties to the resultant vulcanizate, including reduced Payne effect and improved cut resistance while maintaining other key parameters the same in comparison with a standard silica‐TESPT reinforced rubber. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45937.     

Influence of TESPT content on crosslink types and rheological behaviors of natural rubber compounds reinforced with silica

Rheological behaviors in the rheographs and crosslink types of silica‐filled natural rubber compounds with differing contents of silane coupling agent were investigated. Bis‐(3‐(triethoxysilyl)‐propyl)‐tetrasulfide (TESPT) was used as a silane coupling agent. In the rheographs of the silica‐filled compounds containing TESPT, the local minimum torque regions after the maximum torque were observed, and the time to reach the local minimum torque was found to become faster with increase of the TESPT content. The reversion ratio, on the whole, was decreased by increasing the TESPT content. By increasing the TESPT content, the crosslink densities of the mono‐, di‐, and polysulfides were increased. Ratio of the polysulfides of the total crosslink density increased, while those of the mono‐ and disulfides decreased with increase of the TESPT content. Changes of the crosslink densities after thermal aging were also investigated. The experimental results were explained with the reduction of curatives adsorbed on the silica, increase of sulfur content, and crosslink formation between the silica and rubber by adding TESPT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical and dynamic mechanical properties of natural rubber blended with waste rubber powder modified by both microwave and sol–gel method

Waste rubber powder (WRP) was modified by microwave, sol–gel method, and both microwave and sol–gel method, respectively. The mechanical and dynamic mechanical properties of natural rubber (NR)/modified WRP composite were investigated. The influence of bis‐(3‐(triethoxysilyl)‐propyl)‐tetrasulfide (TESPT) content on curing characteristics and mechanical properties of vulcanizate was also studied. The results showed that NR/WRP modified by both microwave and sol–gel method composite owned the best mechanical properties. Rubber processing analyzer was used to characterize the interaction between silica and rubber chains and the dispersion of silica. With increase of TESPT content, the Payne effect decreased. Scanning electron microscopy indicated the coherency and homogeneity of in situ generated silica filled vulcanizate. Dynamic mechanical analyzer showed that NR/WRP modified by both microwave and sol–gel method composite with 5 phr TESPT exhibited the lower tan δ at temperature range of 50–80°C, compared with composite without TESPT and the higher tan δ at temperature of 0°C, compared with the conventional modification of WRP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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     

Effect of vulcanization technique on the physical properties of silica‐filled EPDM rubber

The present study aims to enhance EPDM rubber–silica interaction by employing a special technique called Two‐Stage Vulcanization, with the help of a multifunctional rubber additive, bis diisopropyl thiophosphoryl disulfide (DIPDIS). In this process EPDM rubber was heated along with rubber additives up to the time just before the commencement of cure and then filler was incorporated to the preheated rubber to get the final mix. The efficiency of this novel technique is evaluated by the enhancement of physical properties of the silica‐filled vulcanizates. This novel technique is also employed to investigate the effect of a silane‐coupling agent, viz., bis (3‐triethoxy silyl propyl) tetrasulphide (TESPT), in addition to DIPDIS, on the rubber–filler interaction. The positive role of this technique in enhancing the rubber–filler interaction is evidenced by the dynamic mechanical analysis and scanning electron microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1132–1139, 2006     

不同种类低共熔溶剂对白炭黑填充丁苯橡胶物理机械性能的影响

以低共熔溶剂（DES）为白炭黑的改性剂,通过与双[3-（三乙氧基硅）丙基]四硫化物（TESPT）并用进行原位反应改善白炭黑在丁苯橡胶中的分散性,研究了不同种类DES对白炭黑/丁苯橡胶复合材料硫化特性、加工性能、物理机械性能和微观形貌的影响。结果表明,氯化胆碱/尿素与TESPT并用可以明显改善白炭黑在丁苯橡胶中的分散性,使Payne效应减弱,并提升白炭黑/丁苯橡胶硫化胶的力学性能和压缩疲劳性能;氯化胆碱/乙二酸与TESPT并用对提高白炭黑与丁苯橡胶界面结合力效果显著,所得白炭黑/丁苯橡胶复合材料的耐磨性能优异;而当DES用量较大时改性效果不佳。     

Two advanced styrene‐butadiene/polybutadiene rubber blends filled with a silanized silica nanofiller for potential use in passenger car tire tread compound

Styrene‐butadiene rubber (SBR) and polybutadiene rubber (BR) were mixed together (75:25 by mass) to produce two SBR/BR blends. The blends were reinforced with a precipitated amorphous white silica nanofiller the surfaces of which were pretreated with bis(3‐triethoxysilylpropyl)‐tetrasulfide (TESPT). TESPT is a sulfur‐bearing bifunctional organosilane that chemically bonds silica to rubber. The rubbers were primarily cured by using sulfur in TESPT and the cure was optimized by adding non‐sulfur donor and sulfur donor accelerators and zinc oxide. The hardness, Young's modulus, modulus at different strain amplitudes, tensile strength, elongation at break, stored energy density at break, tear strength, cyclic fatigue life, heat build‐up, abrasion resistance, glass transition temperature, bound rubber and tan δ of the cured blends were measured. The blend which was cured with the non‐sulfur donor accelerator and zinc oxide had superior tensile strength, elongation at break, stored energy density at break and modulus at different strain amplitudes. It also possessed a lower heat build‐up, a higher abrasion resistance and a higher tan δ at low temperatures to obtain high‐skid resistance and ice and wet‐grip. Optimizing the chemical bonding between the rubber and filler reduced the amount of the chemical curatives by approximately 58% by weight for passenger car tire tread. This helped to improve health and safety at work and reduce damage to the environment. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

填料对双组分缩合型室温硫化硅橡胶性能的影响

考察了多种补强填料和半补强(或增量)填料如硅藻土、碳酸钙和氧化铝等对室温硫化(RTV)硅橡胶的机械性能和介电性能的影响。结果表明,采用经六甲基二硅氮烷处理的气相法白炭黑或沉淀法白炭黑作填料时,RTV硅橡胶多方面的性能都有所提高;采用补强填料和半补强填料并用的RTV硅橡胶的性能优于使用单一补强填料的RTV硅橡胶;随着填料用量的增加,RTV硅橡胶的机械性能、相对介电常数和介质损耗因数都有一定程度的提高,但体积电阻率有所降低。     

Application of rice husk ash as fillers in the natural rubber industry

Rice husk ash (RHA) obtained from agricultural waste, by using rice husk as a power source, is mainly composed of silica and carbon black. A two‐stage conventional mixing procedure was used to incorporate rice husk ash into natural rubber. For comparison purposes, two commercial reinforcing fillers, silica and carbon black, were also used. The effect of these fillers on cure characteristics and mechanical properties of natural rubber materials at various loadings, ranging from 0 to 40 phr, was investigated. The results indicated that RHA filler resulted in lower Mooney viscosity and shorter cure time of the natural rubber materials. The incorporation of RHA into natural rubber improved hardness but decreased tensile strength and tear strength. Other properties, such as Young's modulus and abrasion loss, show no significant change. However, RHA is characterized by a better resilience property than that of silica and carbon black. Scanning electron micrographs revealed that the dispersion of RHA filler in the rubber matrix is discontinuous, which in turn generates a weak structure compared with that of carbon black and silica. Overall results indicate that RHA can be used as a cheaper filler for natural rubber materials where improved mechanical properties are not critical. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 34–41, 2005     

Reinforcing effect of silica on the properties of styrene butadiene rubber–reclaim rubber blend system

Incorporation of silica into styrene butadiene rubber (SBR)–reclaim rubber (RR) blend system was carried out by sol–gel technique and conventional method. A well known silica coupling agent bis(3‐triethoxysilyl propyl) tetrasulfide was found to affect the curing characteristics and mechanical properties of SBR/RR vulcanizate. Here, the effect of RR on silica reinforcement was studied for different SBR/RR blend system. Silica incorporation by conventional mechanical mixing in absence of TESPT showed a much higher tensile properties than that of silica incorporated by the in situ sol–gel reaction of tetraethoxy silane both in presence and absence of TESPT. Studies of equilibrium swelling in a hydrocarbon solvent were also carried out. ATR study indicates that RR forms bond with silica particles due to the presence of active functional site on RR. The amount of silica incorporated by sol–gel reaction was determined through thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) studies further indicate the coherency and homogeneity in the silica filled SBR/RR vulcanizate. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 957–968, 2006     

Investigation and improvement of the scorch behavior of silica-filled solution styrene-butadiene rubber compound

Effects of different silane coupling agents on scorch time of silica-filled solution styrene-butadiene rubber compounds were studied. The flocculation of silica at high temperature, which was characterized by rubber processing analyzer (RPA) and transmission electron microscope (TEM), has been proved to be an important factor affecting the scorch time of the compounds. In order to prolong the scorch time, the hybrid silane technology, that is, combining different silanes such as bis(triethoxysilypropyl)-tetrasulfide (TESPT) and n-octyltriethoxysilane (OTES) together, was developed to improve silica dispersion and suppress silica flocculation. The results showed that when the content of TESPT is fixed, the increase of OTES can effectively increase the scorch time due to the suppression of silica flocculation while not affecting the polymer crosslinking. This phenomenon is absent for the case where the OTES content is fixed, but the TESPT content is varied because the sulfur atoms in the TESPT molecules will also participate in the vulcanization process, leading to the decrease in scorch time. Through the present study, a connection between silica flocculation and scorch time has been built up, which is important for rubber composite processing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47918.