Tire Compounds Research Articles

Silanization Efficiency of Silica/Silane in Dependence of Amines in Natural Rubber-based Tire Compounds

Silica-silane technology for low rolling resistance tire compounds requires efficient bridging between the silica surface and rubber molecules through silanization and coupling reactions. The presence of diphenylguanidine (DPG) as secondary vulcanization accelerator is also needed to catalyze the silanization reaction between the alkoxy groups of silane coupling agents and the silanol groups on the silica surface. However, DPG can liberate toxic aniline under high mixing temperatures and therefore safer alternatives are required. This study investigates the influence of amines with different structures, i.e. hexylamine (HEX), octadecylamine (OCT), cyclohexylamine (CYC) and dicyclohexylamine (DIC) on the primary silanization reaction rate constant in a model system, and on interfacial compatibility of practical silica-reinforced NR compounds. Compared to the system without, the amines clearly increase the reaction rate constant for which linear aliphatic amines work better than cyclic ones. This is due to better accessibility of the amines towards the silica surface, in agreement with the values of Payne effect as observed in the rubber compounds, except for the OCT case. The lowest Payne effect of the OCT-containing rubber compound is attributed to the additional shielding effect obtained from the long alkyl-chain that leads to more hydrophobicity, resulting in good physical interaction between silica and rubber. The presence of all amines improves the cure properties in which the linear aliphatic amines give shorter cure times than the cyclic aliphatic ones. As a result of good interfacial compatibility, the OCT-containing compound which shows lowest filler-filler interaction gives good mechanical properties that are closest to the reference compound with DPG.

Modeling of two-body abrasive wear of filled elastomers as a contact-induced fracture process

Abstract In this work, we present a non-traditional approach to modeling two-body abrasive wear due to the contact between elastomeric tire compounds and road surfaces. In this direction, the process of two-body abrasion between rubber and surface is modeled as a multiscale contact-fracture process. At the microscale, cracks are initiated and grow due to contact stresses. These initiated cracks at the microscale lead to macrocracks that grow as fatigue cracks over long periods resulting in substantial wear volume. This work is limited to modeling the phenomena at the microscale. The computational results are compared with abrasion experiments conducted on the rubber samples based on ASTM DIN 53516 standards.

Atomistic Descriptions of thecis-1,4-Polybutadiene/Silica Interfaces

Since the early 1940s, silica has been increasingly used in tire compounds as a complement to carbon blacks. The use of silica offers substantial benefits in tires, such as a low rolling resistance and a better grip on wet and icy roads. Nevertheless, coupling agents must be used to enable the mixing with rubber. The understanding of the action of silica in the reinforcement process and the role of the coupling agents at the molecular level requires the investigation of the interfacial region of the silica surface interacting with polymer chains. We report here detailed atomistic simulations of the interfacial region between different silica surfaces and cis-1,4-polybutadiene polymer chains. We describe the interfacial regions in terms of density and the radius of gyration component profiles along the normal to the substrate. We investigate how the nature of the silica surface, the surface density of silanols, and the surface coverage of grafted polymer chains and grafted OCTEO impact the molecular arrang...

Implications of the Use of Silica as Active Filler in Passenger Car Tire Compounds on Their Recycling Options.

Tires are an important vehicle component, as car handling, safety and fuel economy depend for a major part on the tire composition and construction. As a consequence, tires are improved continuously. The most prominent improvement in the recent past was the use of a silica-silane filler system in passenger car tread compounds, instead of traditionally used carbon black. For recycling and re-use of end-of-life car tire rubber one of the most promising recycling methods is devulcanization: re-plasticizing the vulcanized rubber by selectively breaking the sulfur bridges between the polymer molecules. In the present paper, the influence of silica, which is present in the passenger car tires granulate, on both devulcanization and subsequent revulcanization, is investigated. In a step-wise approach it is shown that the presence of silica influences both devulcanization and revulcanization. The best tensile strength of the revulcanizate, using a carbon-black-based revulcanization formulation, was 5 MPa. This could be improved to 6.5 MPa by using 2.8 phr of 1,3-DiPhenylGuanidine (DPG) in the revulcanization formulation. After addition of a silanization step during revulcanization by adding 3.2 phr bis[3-(TriEthoxySilyl)Propyl] Tetrasulfide (TESPT), a silane, to the formulation, the tensile strength of the revulcanizate was further improved to 8 MPa. With these results it is shown that the silica in the granulate can be used to improve the revulcanization properties. To check the benefits of using pure tire tread material for the devulcanization and subsequent revulcanization, of both a carbon black and a silica-based virgin tread compound, it is shown that a tensile strength of the revulcanizate of 13 MPa can be reached. This shows the potential of devulcanized rubber when the various tire components are separated before whole car tire material is granulated as the beginning of the recycling.

TRT EVO: Advances in real-time thermodynamic tire modeling for vehicle dynamics simulations

Vehicle performances, especially in motorsport, are deeply affected by tire behavior and in particular by tire compound proper working conditions. In this research activity, a series of innovations have been introduced on the Thermo Racing Tire (a physical-analytical tire thermal model, based on Fourier’s law of heat transfer applied to a three-dimensional domain) in order to take into account all the main aspects actively involved in the thermal behavior of the tire, as the presence of exhausted gases eventually impacting at the rear axle and the inhomogeneous distribution of local variables (pressure, stress and sliding velocity) within the contact patch, caused in example by the tire camber angle. The new model developed considers the presence of the sidewalls, actively involved in the convective heat exchanges, respectively, with the external airflow and the inner gas fluid, located inside the inflation chamber. The aim of the new version of the tire thermal model is a better physical comprehension of all the phenomena concerning the contact with the asphalt and the prediction of the link between the thermal state and the frictional performance, crucial for the definition of an optimal wheel and vehicle setup.

Durability prediction of an ultra-large mining truck tire using an enhanced finite element method

Ultra-class mining trucks used for material haulage in rugged surface mining terrains experience premature tire fatigue failure in operation. Typical failures include belt edge separation, ply turn-up separation, and tread base and sidewall cracking. The use of reinforcing fillers and processing aids in tire compounds result in the formation of microstructural in-homogeneities in the compounds. This article presents an application of the critical plane analysis technique for predicting the fatigue life of the belt package of an ultra-large mining truck (CAT 795F) tire of size 56/80R63 in a surface coal mine. Experimental data obtained from extracted specimens (sidewall, tread, and belt edge region) of the tire are used to characterize the stress–strain and fatigue behavior of the modeled tire. The tire’s duty cycle stresses and strains were obtained from finite element analysis of the rolling tire in Abaqus. Fatigue life calculations were performed in the rubber fatigue solver Endurica CL. Effects of inflation pressure, tire speed, and axle load on the fatigue life of the belt package under strain-crystallizing and non-crystallizing conditions of the belt compound are discussed. Specifically, the results show the belt edges to be critical regarding crack nucleation.

DYNAMIC PROPERTIES AND TIRE PERFORMANCES OF COMPOSITES FILLED WITH CARBON NANOTUBES

ABSTRACT Carbon nanotubes (CNTs) have been widely studied in rubber goods and tire compounds to improve, for example, antistatic and thermal conductivity performances. CNTs were applied in passenger tire tread compounds to improve comprehensive tire performances, especially wet traction. High frequency dynamic properties of CNT-filled compounds were revealed for the first time. There was good correlation between compound dynamic properties and vehicle tire test results. The influence of CNTs on tire performances and their mechanisms was investigated and explained by the dynamic properties and master curve analysis in the frequency domain. Substituting 50 phr carbon black N234 by 20 phr CNTs could maintain hardness but increased static and dynamic moduli, which was beneficial for the tire handling, with 0.25 point improvement in the subjective testing. For the CNT-filled compounds, 1.5% traction improvement on a dry road and 6.5% traction improvement on a wet road can be explained successfully by the increased hysteresis loss (tan δ) and decreased storage modulus (G′) at high frequency domain (104–108 Hz). It is implied by Williams–Landel–Ferry law calculation that a strong interaction between CNTs and rubber resulted in higher temperature dependence; however, the trade-off was a 7% higher tire rolling resistance coefficient and 33% worse wear resistance for the CNT tires. CNT-filled compounds were demonstrated to have superior handling and traction performances suitable for racing and sports car tires.

Improving the Abrasion Resistance of “Green” Tyre Compounds

Since the introduction of “Green Tyres” in the early 90’s, the use of silica as a reinforcing filler, along with a silane coupling agent, has spread and grown worldwide. The greatest advantage of using silica over carbon black as a reinforcing filler in a tyre tread compound is that a lower rolling resistance is achieved, while maintaining good wet traction. However, a previous study has shown that the wear resistance of a silica filled epoxidised natural rubber (ENR) compound was not as high as those of conventional Oil Extended Styrene Butadiene rubber (OESBR) and NR/BR compounds used in passenger car and truck tyre treads. In this work, with the aim of improving abrasion resistance, the effect of blending Butadiene rubber (BR) into a silica filled ENR compound was studied. Blends with 0 to 30 phr BR were prepared in a Polylab Haake internal mixer. The rheological properties of the compounds were measured using a Mooney viscometer and Oscilating Disc Rheometer. The hardness, tensile strength and DIN abrasion resistance were also measured. The results showed that the ENR/silica compound properties such as tensile strength and hardness were as good as those of the conventional compounds. However, the most important finding was that abrasion resistance increased significantly with BR content, exceeding that of the conventional compound at BR:ENR ratios of greater than 20:80.

PROMOTING INTERFACIAL COMPATIBILITY OF SILICA-REINFORCED NATURAL RUBBER TIRE COMPOUNDS BY ALIPHATIC AMINE

ABSTRACT Octadecylamine (OCT) as an alternative for diphenyl guanidine (DPG) in silica-reinforced NR tire compounds with bis-(triethoxysilyl-propyl)tetrasulfide (TESPT) as silane coupling agent was investigated with focus on the improvement of compatibility between the silica surface and rubber molecules, by taking the amine-free rubber compound as a reference. The quantity of OCT and DPG was varied in a range of 2.4–9.5 mmol per 100 parts of rubber by weight (i.e., 0.5–2.5 phr). Bound rubber contents, changes in heat capacity (ΔCp), and immobilized polymer layer (χim) data prove an enhanced interfacial compatibility as the amines are absorbed on the polar silica surface and catalyze the silanization reaction. Comparing the two different amine types, the rubber compounds with OCT show higher interfacial compatibility than the ones with DPG, because of an additional shielding effect promoted by the long alkyl chain that leads to more hydrophobicity. Thus, the rubber compounds with OCT show higher physically bound rubber contents and consequently higher total bound rubber, a higher immobilized polymer layer, as well as a lower Payne effect. However, the compounds with OCT show a higher flocculation rate constant because the physical interactions between amine and silanol groups decrease under thermal treatment. The compounds with OCT show a lower cure torque difference that indicates a lower crosslink density, but because of the good interfacial interaction combining both chemical and physical interactions, the vulcanized rubber with OCT at optimum loading shows better mechanical properties and tan δ at 60 °C when compared with the DPG counterpart. At high (excessive) loading of amines, the compounds with DPG clearly have higher crosslink density and thus higher modulus as well as tensile strength compared with the use of OCT.

DEVELOPMENT OF HIGH PERFORMANCE RUBBER COMPOSITES FROM ALKOXIDE-BASED SILICA AND SOLUTION STYRENE–BUTADIENE RUBBER

ABSTRACT The solution SBR and silica-based composites are prepared by hydrolysis of tetraethylorthosilicate in the presence of an organic solution of SBR and n-butylamine as catalyst. Further addition of bis[3-(triethoxysilyl)propyl]tetrasulfide, a silane coupling agent, improves the performance and properties of the composites. All the results are compared with commercial precipitated silica at similar loading conditions. The generated silica particles from this alkoxide route resulted in lower Mooney viscosity of the compound and showed less filler flocculation compared with standard commercial precipitated silica in reference compounds. A detailed dynamic mechanical study also indicated that alkoxide silica in model tire compounds could offer a lower rolling resistance and a higher wet skid resistance compared to the reference. Other properties such as heat build-up, rebound resilience, and hysteresis loss were found to be very promising for alkoxide silica composites, too. The silica particles (aggregated) developed by the alkoxide method were relatively large (∼150–200 nm) compared with the primary particles of precipitated commercial silica. The synthesis of sol–gel silica particles in presence of the polymer allowed for the trapping of some polymer molecules inside the filler aggregates and therefore offers exceptional mechanical reinforcement of the rubber.

Silane grafted natural rubber and its compatibilization effect on silica-reinforced rubber tire compounds

Natural Rubber (NR) grafted with 3-octanoylthio-1-propyltriethoxysilane (NXT) was prepared by melt mixing using 1,1′-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane as initiator at 140 °C with NXT contents of 10 and 20 parts per hundred rubber [phr] and initiator 0.1 phr. The silane grafted on NR molecules was confirmed by Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H-NMR) and scanning electron icroscopy/energy dispersive X-ray spectroscopy (SEM-EDX). Based on1H-NMR, the use of 10 and 20 phr (parts per hundred resin) of silane resulted in grafted NXT onto NR of 0.66 and 1.32 mol%, respectively, or a grafting efficiency of approx.38%. The use of NXT-grafted NR as compatibilizer in silica-filled NR compounds, to give a total amount of NXT in both grafted and non-grafted forms in the range of 0.8-6.1 wt% relative to the silica, decreases the Mooney viscosity and Payne effect of the compounds, improves filler-rubber interaction, and significantly increases the tensile properties of the silica-filled NR-compounds compared to the non-compatibilized one. At the same silane-content, the use of silane-grafted NR gives slightly better properties than the straight use of the same silane. With sulfur compensation, the use of NXT-grafted-NR with about 6 wt% NXT relative to the silica gives technical properties that reach the levels obtained for straight use of bis-(3-triethoxysilyl-propyl) tetrasulfide (TESPT) at 8.6 wt% relative to the silica.

Towards a Substantially Lower Fuel Consumption Freight Transport by the Development of an Innovative Low Rolling Resistance Truck Tyre Concept

The aim of the LORRY project is to reduce carbon footprint of truck transportation by developing an innovative low Rolling Resistance (RR) tyre concept combined with a comprehensive toolbox for fl¬eet fuel saving management. The ambition is that steering and trailer tyres developed in the framework of the project must demonstrate a minimum 20% reduction in truck tyre rolling resistance, which corresponds approximatively to a reduction of 5% in fuel consumption and CO2 emission. Truck tyre wear (10% improvement) and wet safety performance levels will also be additionally improved. This proposed concept is going beyond current state of art and stakeholder or market expectations regarding tyre rolling resistance, mileage, driving safety, driving performance and material and manufacturing sustainability. To reach this objective, a multidisciplinary approach has been initiated covering the fields of tyre technology, rubber and filler technology, nanotechnologies, composite physics, sensory, transport and road infrastructure. A complete set of complementary scientific evaluation methods enable the understanding of interactions between new tread pattern design and new material composites as well as the tyre performance dependency on tyre-vehicle operation and road conditions. Main novelties from this project are: Design of new tread pattern, Development of advancement nano-structured truck tyre compounds, Enhanced characterization through predictive tools: new testing methods and models, phenomena understanding at multi-scale and development of related predictive experimental and virtual analysis tools, Assessment of tyre performance – field evaluation, Analysis and modelisation of tyre performance.

Polymer–filler interactions in a tire compound reinforced with silica

Elastomers, usually, are reinforced with reinforcing filler in order to improve their mechanical properties like tensile strength and abrasion resistance. The efficiency of this reinforcement is correlated with different factors like filler structure, surface area, and polymer–filler interactions. This study presents a methodology to quantify the bound rubber attached to the reinforcing filler silica using the thermogravimetric analyzer. Three typical rubber compounds used in tread tire were studied. In the samples tested, the silica content was kept constant, varying only the percentage of the coupling agents. Considering the results of the thermal analysis, physical, mechanical, and rheological tests, the thermogravimetric analysis has proved to be a very useful technique in evaluating the interaction of filler and polymer.

The influence of non-carcinogenic petroleum-based process oils on tire compounds’ performance

High aromatic oils which have been widely used as process oils in tire the industry contain high concentrations of polycyclic aromatic hydrocarbons (PAHs). These aromatic compounds (PAHs) have proved to be carcinogenic as well as posing a threat to the environment. Since the beginning of 2010, the use of high aromatic process oils has been banned under the EU regulation 1907/2007 commonly called REACH (registration, evaluation, authorization and restriction of chemicals). The so-called regulation has given rise to challenges to the oil and tire industries in replacing high aromatic process oils with safer alternatives. In the present work, four types of low aromatic petroleum-based process oils, namely mild and high-viscosity naphthenic oils (LNAP and HNAP), treated distillate aromatic extract (TDAE) and mildly extracted solvate (MES), were investigated and their effect on plasticization and durability properties of two different low and high oil-extended tire formulations were evaluated. The compatibility of oils with rubber was investigated as well. The results showed that a number of properties such as abrasion resistance and tire rolling resistance were improved by using non-carcinogenic oils, while tire grip properties were declined. Considering oil–rubber compatibility, TDAE and MES were found to be more compatible with rubbers.

Design of Tire Compounds Coextrusion Die Based on Numerical Simulation

The structure of extrusion die plays a crucial role in the quality control of tire compounds profile production. But in practice, the design of coextrusion die is mainly dependent on the experience of the designer, thus many times of modifications and experiments are needed to gain an acceptable product. The three-dimensional coextrusion mold process for tire compounds(TWD40/FS10) is analyzed by using the computational fluid dynamics(CFD) package polyflow. The outlet velocity and extrusion pressure as well as the flow process are analyzed in details, and the reliability of the simulation is verified by experiment. With the simulation results of the initial die design, a non-uniform velocity distribution is observed. To solve the problem of the non-uniform velocity distribution, two steps of the die design for the tire compounds coextrusion are proposed, including heighten and widen the narrow section of the die lip, which are beneficial to balance the outlet velocity and extrusion pressure as well as to get reasonable product. The results show that the die design method based on numerical simulation is valid and it is useful to provid guidelines for the die design of the similar kind profiles of tire compounds.

Mechanical Properties of Recycled Butyl Rubber/Virgin Butyl Rubber Composite

Large amounts of butyl rubber (IIR) are used as inner tires for aeroplanes, trucks, cars, two-wheelers etc. However, after long runs when these tires are not serviceable they are discarded. Almost the entire amount of rubber from the worn out tires is discarded, which again need very long time for natural degradation due to crosslinked structure of rubbers and presence of additives. To solve this problem, recycled rubber is used as a partial substitute for new IIR in inner tire compounds. The blends with a certain amount of recycled rubber content show good mechanical properties.

ROLE OF MATERIAL COMPOSITION IN THE CONSTRUCTION OF VISCOELASTIC MASTER CURVES: SILICA-FILLER NETWORK EFFECTS

ABSTRACT One of the important aspects in the development of new tire compounds is the correlation between the dynamic mechanical properties of the rubber, measured on a laboratory scale, and the actual tire performance. The measuring protocol for dynamic mechanical properties with high precision and good correlation with tire properties is therefore of main concern. To predict wet traction, the viscoelastic behavior of the rubber materials at high frequencies (in the MHz range) need to be known. Viscoelastic master curves derived from time-temperature superposition can be used to describe the properties of the materials over a wide frequency range. The construction of master curves for tread compounds filled with different amounts of silica is discussed. From the vertical shifts as a function of temperature, activation energies are derived that apparently are in the linear response region by fulfilling the Kramers-Kronig relations, and their values correspond to physical phenomena as the underlying principle. Strain sweep viscoelastic measurements, per definition outside the linear region, lead to much higher activation energies. Because the deformation strains employed for these strain sweep measurements are more realistic for wet traction or skidding phenomena, it is concluded that the value of the above measurements in the linear region to predict traction is only limited or a first but still important indication.

Simulation and optimization of giant radial tire vulcanization process

The process of curing a pneumatic tire as one of the most important working procedures, directly identify the quality of tire, because the physical and mechanical properties of rubber in the state of overcure or undercure are significantly decreased. The finite element analysis (FEA) method was introduced to evaluate the tire's state of cure (SOC) in this paper, and the optimization of cure conditions of giant radial tire was also referred to ensure that tire constituents achieved the proper SOC and improved the quality of tire. Results indicated that when the cure time was cut down 35 minutes by optimization process, most part of tire compound is appropriate cured. So that the energy cost was remarkable cut down and the productivity was rising in evidence.

Tailoring the polymeric nanoparticles for rubber reinforcement

Polymeric nanoparticles with brush-like polydiene as the shell and crosslinked polystyrene as the core are synthesized using anionic polymerization via a self-assembly process of macromolecules in solutions. The microstructures of nanoparticles were designed to match those of the matrix polymer used for tire compounds. Desirable compound properties were obtained by tailoring the shell sizes of the nanoparticles. Depending on the core/shell structures of the nanopartilces, the addition of the nanosized particles may impart the compound ultimate physical properties. Well reinforced compounds with enhanced dynamical storage modulus (G′) without increasing their dependences on temperature and deformation strain can be obtained by the addition of the nanoparticle with lengthened shell chains. Improved tensile mechanical properties without increasing high-temperature hysteresis were also attained by such reinforcement. Passenger and truck tire applications can be advantageously benefited from these properties with improved tire handling and cornering consistence without increasing the rolling resistance and the sacrifices of other performances. A miscibility study was conducted on various binary blends of nanoparticle and rubber matrix. The compatibility between the nanoparticle and the matrix rubber along with the core concentration were demonstrated to be responsible for the observed improved compound properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Reduction of volatile organic compound emission. II. Use of alkoxy‐modified silsesquioxane for compounding silica‐filled rubbers

AbstractA class of alkoxy‐modified silsesquioxane (AMS) containing less than 5 wt % of latent alcohol that can be used for compounding silica‐filled rubbers is described. The AMS derived from octyl‐triethoxysilane (OTES) behaves as a good shielding agent in silica‐filled rubber to significantly reduce the compound Mooney viscosity and filler flocculation. The co‐AMS prepared from OTES and 3‐mercaptopropyl‐trimethoxysilane yielded an effective shielding and coupling agent for reinforcing the silica‐filled vulcanizates. The alcohols released as volatile organic compounds (VOC) are quantified during compounding and processing along with the compound properties of silica‐filled vulcanizates containing various silicon compounds such as bis‐(triethoxysilyl propyl) disulfide (TESPD), a polyhedral oligomeric silsesquioxanes (POSS), OTES, AMS, or co‐AMS. Dynamic mechanical properties such as dependences of hysteresis on temperature (HTD) and storage modulus on strain (MSD) are discussed. Stronger HTD and weaker MSD were found in stocks containing co‐AMS or a combination of AMS and a coupling agent when compared with that with TESPD. Stronger HTD and weaker MSD may benefit a tire compound with lower rolling resistance, more stable handling performance, as well as better wet traction. More importantly, the VOC released during the manufacture of rubber articles are significantly reduced in stocks containing AMS (or co‐AMS) when compared with those with a silane. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010