Improving Cure Reversion Resistance and Physical Properties of Silica Filled Epoxidised Natural Rubber Compound for Tyre Treads (original) (raw)
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Advances in Materials Science and Engineering
Modern fuel-saving tire treads are commonly reinforced by silica due to the fact that this leads to lower rolling resistance and higher wet grip compared to carbon black-filled alternatives. The introduction of secondary fillers into the silica-reinforced tread compounds, often named hybrid fillers, may have the potential to improve tire performance further. In the present work, two secondary fillers organoclay nanofiller and N134 carbon black were added to silica-based natural rubber compounds at a proportion of silica/secondary filler of 45/10 phr. The compounds were prepared with variable mixing temperatures based on the mixing procedure commonly in use for silica-filled NR systems. The results of Mooney viscosity, Payne effect, cure behavior, and mechanical properties imply that the silica hydrophobation and coupling reaction of the silane coupling agent with silica and elastomer are significantly influenced by organoclay due to an effect of its modifier: an organic ammonium der...
2014
Since the introduction of Green Tyre concept, in the early 90ies, the use of silica as reinforcing fillers has spread and grown worldwide. The general advantages of silica as reinforcing filler over carbon black filler are better rolling resistance by achieving at least equal wet traction while tread wear should not be adversely affected. In general, high filler loading in ENR attributes poor dispersion and lack of adhesion to the rubber matrix which in turn affect the processability and physical properties of the rubber compounds. In this work, effect of dual fillers (silica and carbon black) and coupling agent in ENR/silica compound was studied respectively. The mixing was done in a Banbury® BR 1600 internal mixer and the filler dispersion and physical properties were analysed. The carbon black filler was varied from 5 phr to 20 phr, where the total filler was fixed at 60 phr for truck tyre tread compound. The coupling agent was mixed in the mixing at two different stages which is...
Moisture cure and in-situ silica reinforcement of epoxidized natural rubber
Polymer International, 1995
Epoxidized natural rubber (ENR) was first precured with 3aminopropyltriethoxysilane (APS) by the normal compression molding technique. The resultant sheet was further subjected to moisture cure, via hydrolysis and condensation reactions, by soaking it in water. The moisture-cured sample, when prepared under appropriate reaction conditions, demonstrated partial strain-induced crystallization behavior and moderate tensile strength, as opposed to typical peroxide-cured and sulfur-cured vulcanizates. The suitability of the ENR-APS precured sample for in-situ silica reinforcement by the sol-gel process, using tetraethyl orthosilicate (TEOS) as the silica precursor, was also demonstrated. Silica content as high as 36% by weight could be incorporated into the rubber, and TEOS-to-silica conversion of over 60% was observed. Comparative analysis with a typical peroxide-cured sample that was subjected to the same sol-gel process indicates that the silica in the final ENR-APS sol-gel vulcanizate is chemically bound to the rubber network. K e y words: Epoxidized natural rubber, moisture cure, sol-gel process, in situ silica reinforcement, tensile properties.
Recycling of Waste Tyre into Silica-Rubber Compounds for Green Tyre Application
2021
The prevention of detrimental effects to environment, owing to generation of a huge amount of rubber wastes, is a big challenge across the globe that warrants a thorough investigation of recycling and reuses waste of rubber products. In this spirit a sustainable development of a devulcanization process along with the production of value added devulcanized rubber is a task of hours. The present work describes a simultaneous devulcanization and chemical functionalisation process of waste solution styrene butadiene rubber (S-SBR). This kind of rubber is generally used as the main polymer component in silica filled tread rubber compounds for high-performance passenger car tyres. As-grown ethoxy groups on the functionalized devulcanized styrene butadiene rubber (D-SBR) are exploited for the coupling between silica and the devulcanized rubber chains. We compare the mechanical and dynamic mechanical performance of D-SBR with that of virgin SBR control composites. Covalently bonding interfa...
Rubber Chemistry and Technology, 2017
Achieving high polymer-filler interaction and lowering the energy consumption required to disperse precipitated silica in a rubber matrix have been the main motivations behind the recent interest in silica-coating processes. A simple, low-cost, and environmentally friendly process is available to graft epoxidized liquid polybutadienes onto a silica surface. The polymer-grafted silicas are applied as reinforcing fillers in typical car tire tread compounds. The processability, cure kinetics, and properties of the vulcanizates are greatly affected by the degree of epoxidation, molar mass, and microstructure of the epoxidized polybutadienes used for coating the silica surface. The dynamic-mechanical behavior is superior to that of the reference compound, using bis-[triethoxysilylpropyl] tetrasulfide as a coupling agent, in stiffness and hysteresis at low temperatures, which is indicative of superior performance in wet grip and emergency maneuvers (hard-handling). Thus, the use of this reinforcement system for high-performance car tires, for which safety features should be prioritized, is promising.
Asian Journal of Chemistry, 2013
Silanol groups on a silica surface lead to strong hydrogen bonding between the silica particles and aggregates, resulting in a poor dispersion of silica in rubber compounds. This study improved the compatibility between silica and rubber by coating the silica surface with a polyisoprene film using an admicellar polymerization technique. The modified silica was characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. A comparison of the properties of natural rubber compounds filled with modified silica, silica with silane, carbon black and a mixed filler of silica and carbon black showed that the silicasilane filled compound exhibited the highest mixing torque and Mooney viscosity, whereas the modified silica-filled compound exhibited the lowest values. The silica-silane filled vulcanizates showed a higher modulus, reinforcing index, hardness and abrasion resistance than the vulcanizates containing modified silica. On the other hand, the modified silica-filled vulcanizates exhibited excellent ultimate tensile properties. The loss tangent at 0 ºC and 60 ºC of the vulcanizates filled with different types of fillers as well as filler dispersion are also discussed.
2000
Introduction 1 Chapter 2 Literature overview: reinforcement efficiency of silica-filled rubber with different compatibilizing techniques 7 Chapter 3 Silica-reinforced tire tread compounds compatibilized by using epoxidized natural rubber 45 Chapter 4 Silica-reinforced natural rubber compounds compatibilized by ENR in combination with TESPT and sulfur compensation 73 Chapter 5 Silica-reinforced natural rubber compounds compatibilized by ENR in combination with different silane coupling agent types 97 Chapter 6 Influence of types of silane coupling agents on the reinforcement of silica in natural rubber compounds Chapter 7 Preparation and characterization of silane-grafted natural rubber Chapter 8 Silane-grafted natural rubber as compatibilizer in silicareinforced natural rubber Chapter 9 Compatibilization of silica-filled natural rubber by using silane-grafted-natural rubber with compensation of sulfur Summary Samenvatting Symbols and abbreviations Bibliography Acknowledgements Curriculum vitae colored or transparent articles, e.g., shoe soles. For tire compounds, precipitated silica was first used in small amounts in combination with carbon black to improve adhesion in tire cord-rubber, and to improve cutting and chipping resistances. [8] After a patent of Michelin on the so-called "Green Tire" [9] , silica-silane technology has been increasingly used for passenger car tire treads. Silica is an inorganic filler with hydroxyl, also called silanol groups on its surface that can form hydrogen bonds and thus strong filler-filler interactions to generate silica aggregates and agglomerates. It is therefore difficult to disperse and does not interact with non-polar rubber matrices like natural rubber (NR) and styrene-butadiene rubber (SBR), which are the types of rubbers used in tire compounds. To improve the properties of silica-filled compounds, silane coupling agents are generally added to improve silica-rubber interaction and to decrease the silica-silica interaction. The use of silane coupling agents leads to reduction of compound viscosity, an improvement in cure characteristics and a significant increase of modulus, tensile strength, and abrasion resistance. The first silane coupling agent introduced by Union Carbide, was mercaptopropyl-trimethoxysilane (MPS) under the trade name of A-189. Afterwards, Bis-(triethoxysilylpropyl)tetrasulfide (TESPT) was introduced under the trade name Si-69 by Degussa. [10] The use of the silica/TESPT combination in tire tread compounds improves wet traction and rolling resistance without negative affects on abrasion resistance. Silica technology has been further developed to improve the properties of silica-filled compounds, either in aspects of the silica characteristics or development of new silane coupling agents or compatibilizer systems. 1.2 Background of the thesis Natural rubber (NR) is an important material to produce rubber tires, especially heavy duty truck tires. NR has superior mechanical properties over other synthetic rubbers, due to its high molecular weight, and regular structure of cis-1,4-polyisoprene. NR can crystallize when it is stretched by external force, so called "strain-induced crystallization", which leads to high tensile strength and elongation at break. Despite the good strength of NR, reinforcing fillers such as carbon black and silica are commonly used to enhance the properties of NR further for high performance products such as tires. Due to the strong filler-filler interactions between silica aggregates caused by the large number of silanol groups on the silica surface, the use of silica in NR or other hydrocarbon rubbers requires a silane coupling agent or compatibilizer. The most commonly used silane coupling agent is TESPT, but some drawbacks of the use of this silane in silica-filled compounds have been reported. These are an increase of Mooney viscosity upon storage 1.4 Concept of the thesis This project investigated the use of chemically functionalized natural rubbers as compatibilizers in silica-reinforced natural rubber with emphasis on the improvement of silica-rubber interaction, mechanical properties and tire performance, i.e. wet skid and rolling resistance, in comparison with the use of a conventional silane coupling agent. The thesis is composed of the following chapters; Chapter 1 Introduction: This first chapter shortly reveals the development of tires and filler technology with emphasis on tire compounds. It is then followed by a description of the background and aims of this research. Chapter 2 Literature overview: This part focuses on the use of reinforcing fillers mainly carbon black and silica in rubber compounds. The reinforcing efficiency of silica, factors influencing silica reinforcement and development of silica technology for tire compounds are reviewed. The use of silane coupling agents, some polar materials and chemically modified rubbers to improve silica-rubber interactions and the properties of silica-filled compounds are discussed. This chapter ends by providing motivation and scope of the project. Chapter 3 Silica-reinforced tire tread compounds compatibilized by using epoxidized natural rubber: This chapter first describes the preparation and characterization of epoxidized natural rubber (ENR) with various mole% of epoxide. ENRs with different mole% of epoxide groups are used as compatibilizers to optimize the properties of silica-filled natural rubber compounds compared to compounds with Bis-(triethoxysilylpropyl)tetrasulfide (TESPT) and without compatibilizer. Chapter 4 Silica-reinforced natural rubber compounds compatibilized by ENR in combination with TESPT and sulfur compensation: While a silica-filled natural rubber compound with only ENR as compatibilizer shows overall lower properties than with TESPT silane coupling agent, this section studies the use of an optimized ENR type and content (i.e. 7.5 phr of ENR-51) in combination with TESPT to further enhance the properties of the compounds. The TESPT contents are varied and the effect of extra sulfur to compensate for the sulfur contents in TESPT molecules on the properties of silicareinforced natural rubber is investigated. Chapter 5 Silica-reinforced natural rubber compounds compatibilized by ENR in combination with different silane coupling agent types: The reinforcing CHAPTER 2 Literature Overview: Reinforcement Efficiency of Silica-Filled Rubber with Different Compatibilizing Techniques This Chapter gives an overview of reinforcing fillers which have been used in the rubber industry with particular attention to fillers used in tire compounds, e.g. carbon black and silica. Filler characteristics, such as specific surface area, filler structure and surface activity, that influence the properties of filled rubber are discussed. Filler reinforcement of rubbers in general, and dynamic properties of filled rubber in relation to tire performance are reviewed. Silica-reinforced rubber compounding and its associated difficulties coming from silica-rubber incompatibility are addressed. This leads to the development of silicasilane technology which involves a silanization reaction between alkoxy groups of a silane and silanol groups on the silica surface. Due to the greatly increased interest in silica usage especially for low rolling resistance tire treads, several alternative approaches have been adopted in order to improve silica dispersion and filler-rubber interaction. Some of those approaches are reviewed in this section. Among them the use of polar polymers, such as polychloroprene rubber, acrylonitrile-butadiene rubber, epoxidized rubbers, as compatibilizers for silica-reinforced rubber compounds. Particular attention is given to chemically modified natural rubber which can potentially be used for silica-reinforced natural rubber compounds, as investigated in this thesis. The chapter ends by providing the motivation for this thesis.
Rubber Chemistry and Technology, 2017
ABSTRACTA performance comparison among three types of styrene butadiene rubber (SBR), that is, emulsion polymerized SBR (ESBR), solution polymerized SBR (SSBR), and functionalized solution polymerized SBR (F-SSBR), was of interest. Effect of silica type, that is, highly dispersible silica and conventional precipitated silica, was also investigated. It is found that SSBR demonstrates significantly better heat build-up, dynamic set, abrasion resistance, including wet grip (WG) with comparable fuel efficiency, as compared to ESBR. As expected, the best tire performance, that is, abrasion resistance, WG, and fuel efficiency, is found in F-SSBR vulcanizates, attributed mainly to the greatest improvement in magnitude of rubber–filler interaction and degree of filler dispersion. Results reveal that the reactive functional group, that is, propylaminedimethoxysilane, which is chemically anchored at chain ends of F-SSBR, plays a crucial role in tire performance. Unexpectedly, silica type does...
2021
Krispon ADVANCING SCIENCE between the fiber and the matrix renders the matrix stiffer and lowers the abrasion loss. The nanosilica also improved the thermal stability of the hybrid composite better than the commercial silica. All the composites underwent two-step thermal degradation. Kinetic studies showed that the degradation of composites followed a first-order reaction. Conclusions: Nanosilica was found to be effective reinforcing filler in natural rubber compound. Filler-matrix interaction was better for nanosilica than the commercial silica. Minimum torque, maximum torque and cure time increased with silica loading. Cure rate increased with fiber loading and decreased with silica content. The hybrid composites showed improved mechanical properties in the presence of nanosilica. Hybrid composites showed anisotropy in mechanical properties. The nanosilica also improved the thermal stability of the hybrid composite better than the commercial silica. All the composites underwent two-step thermal degradation. Kinetic studies showed that the degradation of composites followed a first-order reaction.