Tire Tread Compounds Research Articles

SILICA GRAFTED WITH EPOXIDIZED LIQUID POLYBUTADIENES: ITS BEHAVIOR AS FILLER FOR TIRE TREAD COMPOUNDS

ABSTRACT 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.

Influences of temperature and load on the dry friction behaviour of tire tread compounds in contact with rough granite

The temperature and load dependence of the sliding friction behaviour of a racing tire tread compound on coarse and fine rough granite substrates is analysed by experimental and theoretical techniques. Based on dry friction measurements at different temperatures, friction master curves are constructed by shifting the data horizontally on the velocity axis using the same shifting factors as found from viscoelastic master curves. The obtained isothermal friction curves increase rapidly with increasing sliding velocities and show a more or less pronounced plateau over a broad velocity range, which decreases with increasing load. For analysing this behaviour, the Klüppel and Heinrich theory of rubber friction and contact mechanics is applied, which considers the multi-scale contacts and excitations of the rubber sliding on rough surfaces in the frame of a linear viscoelastic approach. The extension of this theory to more realistic surfaces with two or more scaling ranges is described in some detail. It takes adhesion and hysteresis contributions into account referring to the viscoelastic response of the rubber on different frequency scales. The theory predicts that under isothermal conditions the coefficient of friction decreases with load, which is more pronounced for the adhesion than for the hysteresis contribution. This result is found to be in fair agreement with the measure friction curves confirming the contact mechanical approach of the theory.

The preparation of microcrystalline cellulose–nanoSiO2 hybrid materials and their application in tire tread compounds

ABSTRACTMicrocrystalline cellulose (MCC) was hybridized with nano‐SiO2 to improve its interaction with a rubber matrix. The hybrids (MCC–SiO2) were prepared with the “microreactor” and “sol–gel” technologies, using MCC as the carrier and tetraethoxysilane as the precursor. The structure and morphology of the hybrids were studied by infrared spectrometry, thermogravimetric analysis, and scanning electron microscopy. The results showed that the nano‐SiO2 had been loaded successfully on the surface of the MCC with a loading ratio of approximately 30%. The nano‐SiO2 can take on the morphologies of particles, tubes, or rods by controlling the size of the “microreactor”. The hybrids were then used in silica/SSBR compounds to replace part of the silica, and their effects on the physio‐mechanical and dynamic properties were discussed. The results showed that the vulcanizates with the hybrids had improved physio‐mechanical and dynamic properties. The vulcanizates of MCC–SiO2 also had a higher wet‐skid resistance and a lower rolling resistance than did the silica vulcanizates when they were used in tire tread compounds. The SEM photos showed that the interfacial adhesion between the MCC and rubber was improved. The size of the MCC hybrids was also in situ decreased during the processing of the rubber compounds. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44796.

Effects of Blend Ratio and SBR Type on Properties of Carbon Black-Filled and Silica-Filled SBR/BR Tire Tread Compounds

This work aimed at investigating the effects of blend ratio between styrene butadiene rubber (SBR) and butadiene rubber (BR) and SBR type (E-SBR and S-SBR) on properties of SBR/BR tire tread compounds. Influences of these parameters on properties of the tread compounds reinforced by 80 parts per hundred rubber (phr) of carbon black (CB) and silica were also compared. Results reveal that hardness, strengths, and wet grip efficiency were impaired whereas rolling resistance was improved with increasing BR proportion. Surprisingly, the presence of BR imparted poorer abrasion resistance in most systems, except for the CB-filled E-SBR system in which an enhanced abrasion resistance was observed. Obviously, S-SBR gave superior properties (tire performance) compared to E-SBR, particularly obvious in the silica-filled system. Compared with CB, silica gave comparable strengths, better wet grip efficiency, and lower rolling resistance. Carbon black, however, offered greater abrasion resistance than silica.

FUNCTIONALIZED SBRs IN SILICA-REINFORCED TIRE TREAD COMPOUNDS: EVIDENCE FOR INTERACTIONS BETWEEN SILICA FILLER AND ZINC OXIDE

ABSTRACT Unlike carbon black, silica is polar and naturally not compatible with nonpolar hydrocarbon elastomers. This lack of interaction or compatibility between the filler and the elastomer typically causes lower properties compared with carbon black–filled compounds. A common approach to deal with this problem is to use silane coupling agents in the system to link the silica and the polymer chains via covalent bonds. An alternative is the introduction of polar functional groups or chemically reactive groups into the elastomer chains, which can improve the compatibility of elastomers with fillers such as silica. In this article, the effect of three functionalized SBRs, one backbone modified with carboxylate moieties, one modified with dithiol groups, and one partially Si-coupled, on the dynamic and mechanical properties of a silica-reinforced tire tread compound will be discussed and compared with a reference compound that contains unmodified s-SBR as the main polymer. The results show the significant potential of two of these modified SBRs to reduce the rolling resistance of tire treads made thereof, while no major change in wet grip occurs. Zinc oxide is known as the best activator for sulfur vulcanization. Zn ions combine with accelerators to form an active complex that catalyzes the vulcanization process. However, in silica-filled compounds, ZnO may interfere with the silanization process because of its alkaline nature, and it may compete with the silanes in reacting with the acidic –OH groups on the surface of silica particles. When functionalized SBRs with higher polarity are used in silica compounds, ZnO may interact with these moieties as well. To investigate the effect of ZnO on the properties of the silica-reinforced tread compound, a series of compounds have been prepared, in which the addition of ZnO in a later stage was compared with conventional mixing. The dynamic and mechanical properties of the final compounds are discussed.

Properties of Epoxidized Natural Rubber Tread Compound: The Hybrid Reinforcing Effect of Silica and Silane System

Modification of natural rubber via epoxidation process increases its compatibility with highly polar filler like silica. In this work, epoxidized natural rubber (ENR) reinforced with silica compound is evaluated for truck tire tread compound. The rheological, physical and dynamic properties as well as the bound rubber content of ENR-silica tread compound are discussed. The results show that ENR-silica compound has high chemically bound rubber indicating the good interaction and bonding between rubber and silica. In addition, the dynamic test shows the ENR-silica vulcanizate exhibit higher Tan delta at 0 °C and lower tan delta at 60 °C as compared to conventional natural rubber-carbon black vulcanizate, which gives indication of higher wet grip and lower rolling resistance of the ENR vulcanizate. The use of ENR reinforced with silica filler in tread compound is a unique combination that offers renewable material for greener tire application.

Styrene Butadiene Rubber/Epoxidized Natural Rubber (SBR/ENR50) Nanocomposites Containing Nanoclay and Carbon Black as Fillers for Application in Tire-Tread Compounds

ABSTRACTNanocomposite vulcunizates based on a SBR/ENR50 (50/50%wt) rubber blend containing nanoclay (5 or 10 phr) with and without carbon black (CB 20 phr) were prepared by melt blending in an internal mixer. The compound containing 35 phr carbon black (only) was prepared as a reference sample. Microstructure of nanocomposite samples was investigated by using X-ray diffraction (XRD), melt rheo-mechanical spectroscopy (RMS), and scanning electron microscopy (SEM). The XRD patterns revealed that the distance between the clay layers were increased by adding CB to the nanocomposite samples; they caused better diffusion of chains between the layers and resulted in an intercalated structure. The RMS results also indicated the formation of the filler-filler networks. SEM images of fracture surfaces showed the presence of much roughness in the samples containing both nanoclay and CB compared to the other samples. The results obtained from application of the Flory–Rhener equation showed a high crosslink density for the sample with 10 phr nanoclay and 20 phr CB. Dynamic mechanical behavior, mechanical properties, and abrasion resistance of the nanocomposites were evaluated. The results indicated that the sample containing 10 phr nanoclay and 20 phr CB had an increased dynamic elastic modulus, reduced maximum loss factor (tanδ)max,, and an improved tensile strength and abrasion resistance compared to the reference sample. Also, this sample showed the lowest maximum loss factor, at 50–60°C, so it can be a candidate for tire-tread application.

Development of cooler running PCR tire tread using SBR–ENR–nano clay composite

In this investigation, the emphasis is given to the partial replacement of carbon black by an optimized level of Cloisite 15A, an organoclay in a typical styrene-butadiene rubber (SBR) based passenger car tire tread compound. The effect of epoxidized natural rubber with 50 % epoxidation (ENR 50) on the properties of organoclay-SBR composite was also studied. Curing studies shows that both ENR 50 and nanoclay decreases the scorch time and cure time due to the activation of an adjacent double bond by the presence of epoxide group in the ENR and the amine groups present in the organic modifier in the nanoclay structure. The incorporation of ENR showed better dispersion and exfoliation of nanoclay in the rubber matrix. Synergistic reinforcement effect of high abrasion furnace carbon black (HAF/N330) on the mechanical properties, dynamic mechanical properties, heat build up and abrasion resistance in the SBR–ENR–clay nanocomposites having the optimized clay level was investigated. SBR–ENR–carbon black hybrids with 25 phr N330 and 6 phr nanoclay have shown better reinforcement, significantly lower heat generation, comparable/similar rolling resistance (indicated by tan δ at 60 °C) and wet skid resistance with that of conventional SBR–carbon black (40 phr N330) loaded composites.

Rubber–Road Contact: Comparison of Physics-Based Theory and Indoor Experiments

ABSTRACT For tire designers, rubber friction is a topic of pronounced practical importance. Thus, development of a rubber–road contact model is of great interest. In this research, to predict the effectiveness of the tread compound in a tire as it interacts with the pavement, the physics-based multiscale rubber-friction theories developed by B. Persson and M. Klüppel were studied. The strengths of each method were identified and incorporated into a consolidated model that is more comprehensive and proficient than any single, existing, physics-based approach. In the present work, the friction coefficient was estimated for a summer tire tread compound sliding on sandpaper. The inputs to the model were the fractal properties of the rough surface and the dynamic viscoelastic modulus of rubber. The sandpaper-surface profile was measured accurately using an optical profilometer. Two-dimensional parameterization was performed using one-dimensional profile measurements. The tire tread compound was characterized via dynamic mechanical analysis. To validate the friction model, a laboratory-based, rubber-friction test that could measure the friction between a rubber sample and any arbitrary rough surface was designed and built. The apparatus consisted of a turntable, which can have the surface characteristics of choice, and a rubber wheel in contact with the turntable. The wheel speed, as well as the turntable speed, could be controlled precisely to generate the arbitrary values of longitudinal slip at which the dynamic coefficient of friction was measured. The correlation between the simulation and the experimental results was investigated.

Reinforcement of natural rubber latex with silica modified by cerium oxide: preparation and properties

Variable masses of nano cerium oxide (CeO2) were added into nano silica (SiO2) to prepare the well-dispersed SiO2-CeO2 suspension (SiO2-CeO2), cetyltrimethyl ammonium bromide (CTAB) was used to adjust the compatibility of SiO2-CeO2 with rubber matrix, then SiO2-CeO2 modified by CTAB and curing formulas were mixed with fresh natural rubber (NR) latex to prepare NR/SiO2-CeO2 nanocomposites that contained 0-10 parts of CeO2 by a new emulsion compounding method. The morphologies, cure characteristics, mechanical properties and thermal-oxidative stability of NR/SiO2-CeO2 nanocomposites were investigated. The results revealed that the presence of CeO2 in NR/SiO2-CeO2 nanocomposites was favorable for enhancing the interaction between NR matrix and fillers, helped to get smaller SiO2-CeO2 particles with narrower particle size distribution, further improved the crosslink densities and mechanical properties of NR/SiO2-CeO2 nanocomposites vulcanizates. Meanwhile, the addition of CeO2 increased the active energy at least 4.66%, obviously improved the thermal-oxidative aging-inhibiting properties of NR/SiO2-CeO2 nanocomposites. Additionally, nanocomposites containing CeO2 promoted Tg shift to high temperature direction, causing the nanocomposites featured higher tanδ at 0 °C and lower tanδ at 60 °C and exhibited comparable wet grip and lower rolling resistance when NR/SiO2-CeO2 nanocomposites were used in tire tread compound.

Effects of silanization temperature and silica type on properties of silica‐filled solution styrene butadiene rubber (SSBR) for passenger car tire tread compounds

ABSTRACTInfluence of silanization temperature on properties of silica‐filled solution polymerized styrene butadiene rubber was investigated. Two types of silica, i.e., highly dispersible silica (HDSi) and conventional silica (CSi), were compared. Results show that the increased silanization temperature leads to the enhanced rubber–filler interaction, filler dispersion, and cross‐link density giving rise to the improvement in vulcanizate properties such as modulus, heat build‐up (HBU), and dynamic set, as well as tire performance, e.g., wet grip (WG), rolling resistance (RR), and abrasion resistance. Great care, however, must be taken to avoid the scorching phenomenon during the mixing process at too high temperature. Taken as a whole, the balanced properties are found at the silanization temperature of 140°C. Surprisingly, HDSi provides insignificant differences in degree of filler dispersion, WG, and RR, compared to CSi, despite its claimed greater dispersability. Probably, the relatively long mixing time used in this experiment may override the influence of silica type. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43342.

Effect of Vulcanization Additive on Cure Characteristics and Physical Properties of Silica Filled Epoxidised Natural Rubber Truck Tyre Tread Compound

The challenges of using Epoxidised Natural Rubber (ENR) in truck tyre tread are to achieve good cure reversion resistant and physical properties especially on abrasion resistance towards long vulcanization time. The objectives of the project are to study the effects of vulcanization additive on cure characteristics and physical properties of silica filled ENR compound. In this work, a variation of curing systems were employed and a standard carbon black filled Natural Rubber/Butadiene Rubber (NR/BR) compound as a comparison. Greater reversion resistance and physical properties were observed with inclusion of vulcanization additive in the silica compound as compared to compound containing any. The abrasion resistance on the hand improved in spite of long vulcanisation time which commonly practices in truck tyre manufacturing. Keywords: ENR, silica, vulcanization additive, cure reversion, abrasion resistance

Rubber friction on road surfaces: Experiment and theory for low sliding speeds.

We study rubber friction for tire tread compounds on asphalt road surfaces. The road surface topographies are measured using a stylus instrument and atomic force microscopy, and the surface roughness power spectra are calculated. The rubber viscoelastic modulus mastercurves are obtained from dynamic mechanical analysis measurements and the large-strain effective modulus is obtained from strain sweep data. The rubber friction is measured at different temperatures and sliding velocities, and is compared to the calculated data obtained using the Persson contact mechanics theory. We conclude that in addition to the viscoelastic deformations of the rubber surface by the road asperities, there is an important contribution to the rubber friction from shear processes in the area of contact. The analysis shows that the latter contribution may arise from rubber molecules (or patches of rubber) undergoing bonding-stretching-debonding cycles as discussed in a classic paper by Schallamach.

"학습관리시스템의 대시보드 설계를 위한 학습자 중심 요구분석: 분석과 설계 도구로서 활동이론의 적용"

Highly aromatic (HA) oils are common processing aids used in tire tread compounds. However, they often bleed and evaporate from the vulcanizates during tire use. Thus, the mechanical and dynamical properties of the tire decrease. To overcome this problem, we investigated nonfunctionalized liquid butadiene rubber (LBR-305, Kuraray) and center-functionalized liquid butadiene rubber (C-LqBR), polymerized by anionic polymerization. In addition to the liquid butadiene rubbers, p-tert-octylphenol (P-Resin) and C5 hydrocarbon (H-Resin) tackifier resins, which can induce entanglement of rubber compounds, were researched as a processing aid to solve the bleeding problem. Liquid butadiene rubbers have significantly reduced extraction loss by crosslinking with the main rubber chain. They have also increased the abrasion resistance and showed similar or better mechanical and dynamical properties against HA oils. However, resin compounds did not show differences in extraction loss compared to HA oil compounds; instead, they showed increased wet traction.

Investigation of fatigue crack growth characteristics of NR/BR blend based tyre tread compounds

Tyre tread directly comes in contact with various road surfaces and is prone to damage due to cuts from sharp objects during service. As tyres undergo millions of fatigue cycles, these cuts propagate continuously and lead to catastrophic failure. Therefore fatigue crack growth (FCG) characteristics should be an essential criterion for tread compound selection. The present study investigates FCG behavior of blends comprising of Natural Rubber (NR) and Polybutadiene Rubber (BR) over a wide range of tearing energy. Pure shear specimens with a notch on both edges were tested in a Tear Analyser. Rapid increase in FCG rate after a certain strain level was observed. This transition point appeared in a strain range of 20–35 %, depending on the blend composition. The higher BR containing compounds exhibited better FCG characteristics below the transition point but reversal of ranking was seen above this point. The influence of temperature, R ratio, waveforms and cure system on FCG characteristics was also investigated in NR and 60–40 NR/BR blend compounds. Higher FCG rate was achieved under pulse loading compared to the sine waveform. The relaxation time between pulse cycles played an important role. With an increase in relaxation time, FCG rate decreases significantly. The higher sensitivity towards R ratio was observed in NR compound. The 60–40 NR/BR blend showed higher FCG rate with increase in temperature compared to the NR compound. The NR compound with high Sulfur/Accelerator (S/Ac) ratio showed better FCG characteristics whereas for 60–40 NR/BR blend with low S/Ac ratio achieved superior FCG characteristics.

Silica-reinforced tire tread compounds compatibilized by using epoxidized natural rubber

Silica-reinforced natural rubber (NR) tire tread compounds with epoxidized natural rubber (ENR) as a compatibilizer are investigated. The ENRs consisting of 10, 38 and 51mole% epoxide are used in a range of 2.5–15.0 parts per hundred parts of rubber (phr). The addition of ENRs, especially ENR-38 and ENR-51, decreases the Mooney viscosity, Payne effect, flocculation rate constant and filler networking factor, which implies an improvement of silica dispersion in the compounds. Chemically bound rubber contents and interaction parameters of the compounds also increase with higher epoxide-contents of the ENRs, indicating more interactions and/or reaction between the epoxide-groups of the ENR and silanol groups on the silica surface. Tensile strength of the vulcanizates is improved with increasing mole% epoxide, and the optimum value is observed at 7.5phr of ENR-51. The overall results show that silica-reinforced NR can be substantially improved by adding ENR as a compatibilizer, when compared to a compound without ENR, but somewhat less than with using a silane coupling agent.

Poly(styrene‐r‐butadiene)‐b‐poly(poly(ethylene glycol) methyl ether methacrylate) as a silica dispersant in rubber compounds

To improve the dispersion of silica in silica‐filled styrene–butadiene rubber tire tread compounds, we synthesized poly(styrene‐r‐butadiene)‐b‐poly(poly(ethylene glycol) methyl ether methacrylate) (p(SB‐b‐PEGMA)) as a silica dispersant. p(SB‐b‐PEGMA) was synthesized by combining living anionic polymerization (LAP) and atom transfer radical polymerization (ATRP). Initially, α‐bromoisobutyryl‐terminated poly(styrene‐r‐butadiene) (pSB‐Br) was prepared by LAP of styrene and butadiene and sequential additions of ethylene oxide and α‐bromoisobutyryl bromide. pSB‐Br was then used as the macroinitiator in the ATRP of PEGMA (Mn = 300 g mol−1). The structure of p(SB‐b‐PEGMA) was characterized using gel permeation chromatography and 1H NMR spectroscopy. The application of p(SB‐b‐PEGMA) as a silica dispersant in styrene–butadiene rubber/silica decreased the optimal vulcanization time and improved the mechanical properties, which included 100% and 300% moduli, crosslinking density and silica dispersion. © 2013 Society of Chemical Industry

Optimization of Epoxidation Degree and Silane Coupling Agent Content for Silica-Filled Epoxidized Natural Rubber Tire Tread Compounds

Parallel studies on the influence of epoxide contents in epoxidized natural rubbers (ENRs) in the absence of bis-(triethoxysilylpropyl) tetrasulfide (TESPT) coupling agent, as well as a combination of ENRs with different loadings of TESPT on the properties of ENR compounds, are carried out in this work. The results suggests that the best possible combination to optimize processibility and to improve reinforcement efficiency is to utilize ENR with an epoxide content in the range of 20 30 mol%, together with 2 4 wt% relative to the silica content of TESPT. This leads to a reduction of TESPT when compared to the conventional natural rubber compounds.

Effect of Non‐Rubber Components of NR on the Carbon Nanotube (CNT) Localization in SBR/NR Blends

Carbon nanotubes (CNTs) are mixed into SBR/NR and SBR/IR blends using a wet mixing process. The phase specific localization of CNTs in rubber blends is predicted theoretically using surface energy data of blend components and determined experimentally by means of the wetting concept. Almost all CNTs are found to be localized in the SBR matrix of SBR/IR blends due to the better affinity of CNTs to SBR than to IR. In contrast, a high CNT loading localized in the NR phase of SBR/NR blends results from the presence of phospholipids in NR. Electrical and mechanical properties of the rubber blends depend strongly on CNT localization. A lower CNT loading in SBR matrix of SBR/NR blends imparts a better wet grip and lower rolling resistance to tire tread compounds.

Tire Pulverizing Rate and Countermeasures of Complete Set of Equipment

The utilization of waste tire rubber powder processing complete sets of equipment there is imbalance problems. Tire tore cutter crusher production capacity surplus and large particles. Using small tires and non-free cutting tire for cracking machine in order to reduce the tire cracking machine and large particles of investment cost. Cracking down into tire surface rubber cut and tear broken tire surface rubber two process. Tire tread compound using cutting subdivision controlled again after cutting depth of rubber cutting block method. To tear cut machine tool feed depth is an effective method in control tire broken rubber block size. Tread colloid axial uniform circular cutting technical measures is to ensure that the plastic piece of particle uniform distribution.