Wet Skid Research Articles

Preparation and performance of oleylamine modified silica‐reinforced natural rubber composites

AbstractOleylamine (OA) modified silica (SiO2‐g‐OA) was prepared using γ‐(2,3‐epoxypropoxy) propytrimethoxysilane (KH560) and OA, silica/natural rubber (NR) and SiO2‐g‐OA/NR composites were prepared by mechanical blending in an internal mixer, and SiO2‐g‐OA was characterized by Fourier transform infrared spectroscopy, thermal gravimetric analyzer, and contact angle analyzer. The mechanical properties, abrasion resistance, curing characteristics, Payne effect, and morphology of silica/NR and SiO2‐g‐OA /NR composites were investigated using universal testing machine, Akron abrasion tester, rubber processing analyzer, and scanning electron microscope, respectively. The results showed that SiO2‐g‐OA became more hydrophobic and had better compatibility with NR. Moreover, SiO2‐g‐OA/NR had weaker Payne effect, better vulcanization performance, and more excellent mechanical properties. As the content of filler was more than 30 phr, SiO2‐g‐OA/NR had lower rolling resistance and higher wet skid resistance. Compared with silica modified by other coupling agents, SiO2‐g‐OA had the best reinforcement effect on NR.

Preparation, carbon black dispersibility and performances of novel biobased integral solution-polymerized styrene–butadiene rubber with β-myrcene bottlebrush segments

A series of green myrcene-based styrene–butadiene integral rubber were designed and prepared by anionic solution polymerization for solving the fossil depletion and achieving the excellent comprehensive performances, including SBR (75) + MR (25), r-SBMR, b-SBMR and s-b-SBMR. The RPA, SAXS, SEM and TEM results revealed that flexible side chain in myrcene bottlebrush segments, which was beneficial to spread and infiltrate on the surface of the filler, could significantly improve carbon black (CB) dispersibility and inhibit the strong filler–filler interactions. The degree of improvement in CB dispersibility can be ranked as follows: SBR (unmodified rubber) < SBR (75) + MR (25) (mechanical blending rubber) < r-SBMR (26) (random copolymerized rubber) < b-SBMR (26) (block copolymerized rubber) < s-b-SBMR (26) (star block copolymerized rubber). Furthermore, for the star-shaped integral rubber, rolling resistance decreased by 40.2%, wet skid resistance increased by 74.8%, and elongation at break increased by 8.30% without sacrificing the physical and mechanical properties compared with the unmodified SSBR/CB composites. The results show that the chain segment of the bottlebrush structure has reasonably obvious advantages over than that of the random distribution structure in improving the dynamic mechanical properties of rubber. On the basis of aforementioned assessment, we believe that CB-reinforced β-myrcene-based styrene–butadiene integrated rubber is a versatile and promising candidate for future tire tread elastomers.

The Effect of Roughness on the Wet Skid Resistance of Tire Tread Compounds

The wet skid resistance is the main performance of automobile tires, and the excellent wet skid resistance can ensure the safety of the car. In this paper, 60 mesh sandpaper, 400 mesh sandpaper, 1000 mesh sandpaper and 2000 mesh sandpaper were used to pre-grind the sample, which changed the surface roughness of the sample; measured the dry and wet friction coefficient of the sample, and the measured friction pair was smooth Glass surface, rough glass surface and 180 grit sandpaper surface. The experimental results show that the rougher the surface of the sample and the surface of the friction pair, the greater the wet friction coefficient and the better the wet skid resistance.

Application of carboxylated ethylene/vinyl acetate copolymer-modified nanosilica in tire tread rubber

It is essential to keep the balance among rolling resistance, wet skid resistance and wear resistance (the so-called devil's triangle) of tire treads so as to ensure the reliability and safety of the vehicles. For this purpose, hexamethyl-disiloxane (HMDS) and carboxylated polyethylene vinyl acetate copolymer (EVA, emulsion polymer latex) were used to modify nanosilica by in situ surface-modification method, thereby obtaining surface-capped nanosilica possessing good compatibility and strong interfacial interactions with rubber matrix. The surface-capped nanosilica of the above both modifications were introduced into the blend of solution polymerized styrene butadiene rubber (SSBR) and butadiene rubber (BR), and its effect on the mechanical properties and wear resistance of the SSBR/BR-matrix nanocomposites was investigated. The results indicated that both HMDS and EVA contribute to enhancing the compatibility and interfacial interactions of nanosilica with the rubber matrix, which is favorable for improving the mechanical properties and wear resistance of SSBR/BR-matrix nanocomposites. Particularly, HMDS can endow the rubber-matrix nanocomposites with increased wet skid resistance, and EVA can ensure the low rolling resistance of the nanocomposites. Therefore, the SSBR/BR blend filled with HMDS–SiO2–EVA possesses the desired mechanical properties and wear resistance and shows promising prospective as a candidate material for fabricating high-performance tire tread.

Maleic Anhydride Modified Dicyclopentadiene Resin for Improving Wet Skid Resistance of Silica Filled SSBR/BR Composites

As commercial rubber in tires, silica-filled solution-polymerized styrene-butadiene rubber/butadiene rubber (SSBR/BR) compounds exhibited preferable wet skid resistance (WSR) properties, which could be further enhanced by the incorporation of some oligomeric resins. However, the untreated dicyclopentadiene (DCPD) resin shows a slight improvement in wet friction even if the good compatibility between DCPD and SBR owing to their common cyclic structures. For this problem to be addressed, we aimed to enhance its resin-silica interaction by reaction with maleic anhydride (MAH). In detail, the effect of MAH content on WSR, curing characteristics, physical-mechanical properties of the silica-filled SSBR/BR composites was investigated. When the MAH content is 4 wt% in the modified DCPD resin, the maximum enhancement of about 15% in tan δ values at 0 °C, as well as that of 17% in British pendulum skidding tester (BPST) index is obtained, indicating a desirable improvement in WSR. In addition of these two commonly used methods, water contact angles of the vulcanizates increase gradually with increasing MAH content, further confirming the remarkable performance of modified DCPD resin in WSR.

Stable ion bond for high damping, high wet resistance, and low rolling resistance high vinyl polybutadiene rubber‐based dicarboxylate ionomer

AbstractSince the implementation of European Union (EU) tire label, the focus of recent attention has been focused on high performance green tire with low rolling resistance, high wet resistance, low noise, and excellent auto‐braking properties. However, it is a significant challenge to simultaneously achieve these performances for rubber materials. In this research, we developed a novel concept on the construction of stable ion bonds for high performance high vinyl polybutadiene rubber (HVBR)‐based dicarboxylate ionomers. HVBR‐based dicarboxylate sodium ionomer (hereafter referred as Na ionomer) was fabricated through complexation reaction of some or all of carboxylic functional groups on the preprepared maleinized HVBR molecular chains with sodium hydroxide. In the case of Na ionomers, the formation of sodium carboxylate group was certified from Fourier transform infrared spectra. Physical and dynamic mechanical measurements indicated that the tensile strength, wear resistance, wet skid resistance, dry sliding resistance, low rolling resistance, and low heat buildup of the Na ionomer were significantly improved compared to that of HVBR, and Na ionomer simultaneously showed better damping properties and the effective damping temperature range was broadened from −8.8 to 30.1°C, which was closer to the room temperature. Consequently, the approach and results collectively represent a significant advance toward the development of high performance green tire rubber materials.

Cure characteristics and physico-mechanical properties of natural rubber/silica composites: effect of natural rubber-graft-poly(2-hydroxyethyl acrylate) content

The grafting of poly(2-hydroxyethyl acrylate) onto natural rubber (NRgPHEA) was used in order to compatibilize silica filler in NR composites. NR/silica compounds were prepared with various NRgPHEA contents from 0 to 12 phr, while the 14.5% grafting level in NRgPHEA and 20 phr silica content was held fixed. The cure characteristics of the compound were examined with a moving die rheometer. The physico-mechanical properties of NR/silica composites were analyzed by tensile testing, thermal gravimetric analysis, determination of bound rubber content and dynamic mechanical analysis. The results showed that scorch time and cure time decreased, while cure rate index increased with NRgPHEA content. The highest 100% modulus, 300% modulus, reinforcing index and tensile strength were obtained with 3 phr NRgPHEA. The addition of NRgPHEA can enhance wet skid resistance and thermal stability.

ENHANCING PERFORMANCE OF SILICA-REINFORCED NATURAL RUBBER TIRE TREAD COMPOUNDS BY APPLYING ORGANOCLAY AS SECONDARY FILLER

ABSTRACT Silica-reinforced natural rubber (NR) tire tread compounds are investigated using organoclay (OC) as secondary filler. By varying mixer temperature settings at a silica/OC ratio of 45/10 phr, dump temperatures are reached of approximately 120, 140, 150, and 160 °C. The increased dump temperature leads to a better silanization reaction resulting in lower mixing torque, Mooney viscosity, and Payne effect. The optimum mixing dump temperature was found to be around 150 °C. By varying the loadings of OC in the silica-filled NR compounds from 0 to 36 wt% relative to total filler amount, the increased OC loadings decreased the Payne effect and compound viscosities, significantly shortened scorch and cure times, and raised the tan delta at −20 and 0 °C as indications for ice traction and wet skid resistance of tire treads made therefrom. The optimum loading of OC of 9 wt% relative to total filler content shows better Payne effect, cure rate index, tan delta at −20 and 60 °C indicative for rolling resistance, and DIN (German Institute of Standardization) abrasion resistance index. The results indicate that the use of this hybrid filler may provide tires with better wet traction and lower rolling resistance and wear resistance compared with the pure silica-filled system.

Improved mechanical properties of natural rubber composites reinforced by novel SiO2@HCNFs nanofillers at a low filler loading

AbstractIn order to improve high reinforcement properties of natural rubber (NR), SiO2@HCNFs as novel double‐phase nanofillers at low content have been loaded in NR by using mechanical mixing method. The morphologies and structures of SiO2@HCNFs and NR composites were characterized, and the performances of NR composites were measured. The results show that compared with pure N330/NR, the modulus at 300% strain, tensile strength, elongation at break of NR composites increase by 10.7, 17.9, and 9.0%, respectively, at only 2.5 phr SiO2@HCNFs content. Meanwhile, the volume abrasion of NR composites is also dramatically reduced at 2.5 phr SiO2@HCNFs content, about 53.4% less than that of N330/NR, though the shore hardness increases by only 3.7%. It is also found that NR composites reinforced by SiO2@HCNFs at 2.5 phr content have much higher hardness and abrasion performance than HCNFs/NR. The DMA results show that high wet skid resistance and low rolling resistance of NR composites were also achieved by loading 6.5 phr SiO2@HCNFs. The unique structure of SiO2@HCNFs double‐phase nanofillers plays a crucial role in properties of NR composites, in virtue of the significant synergetic reinforcing effect of both HCNFs and silica.

Deep insight into interaction mechanisms between ESBR and silica modified by different silane coupling agents

AbstractIn this study, the interaction mechanisms of different silane coupling agents on the mechanical properties, dynamic viscoelastic properties, and rheological properties of emulsion styrene‐butadiene rubber (ESBR)/silica composites were investigated. It is found that the comprehensive performances are improved by the addition of silane coupling agents and the optimal performance is exhibited in ESBR filled with 50 phr modified silica. Moreover, with the addition of the bis‐(3‐triethoxysilylpropyl)‐tetrasulfide modified silica, the wet skid resistance of composites is significantly enhanced by 14.0%, whereas by the addition of 3‐octanoylthio‐1‐propyltriethoxysilane modified silica, the rolling resistance is remarkably reduced by 19.6% and the processing safety is improved. It can be attributed to the increased bound rubber contents induced by the enhanced interactions between the modified silica and rubber matrix characterized by rheological properties. Furthermore, it is pointed out that the second layer bound rubber plays a dominant role in the improved properties of the composites.

ELASTOMERIC NANOPARTICLES: EFFECTIVE ADDITIVE FOR HIGH PERFORMANCE RUBBER NANOCOMPOSITES

ABSTRACT The “magic triangle” is the most important challenge to rubber composites for the automobile industry. According to the magic triangle, it is difficult to improve the rolling resistance (energy saving), wet skid resistance (safety), and wear (life) of a tire simultaneously. However, ∼5% decrease of rolling resistance, &amp;gt;20% increase of wet skid resistance, and 15% decrease of wear were achieved after adding a small amount of elastomeric nanoparticle (ENP). The effect of ENP on the performances of rubber composites was expounded by characterization of the dispersion of filler and the relationship between filler and rubber. The main difference between ENPs and other nanoparticles was that ENPs acted as not only a part of filler but also as a part of rubber in rubber composites.

Vulcanization, interfacial interaction, and dynamic mechanical properties of in-situ organic amino modified kaolinite/SBR nanocomposites based on latex compounding method

With the help of soluble amino modifiers, the vulcanization delay of kaolinite/SBR composites is investigated to shorten the optimum curing time of the filled rubber system based on the latex compounding method (LCM). Compared to the traditional dry blending method, the LCM had better kaolinite dispersion in the rubber matrix. The two different amino modifiers, i.e., quaternary ammonium salt ((CH3)3-N-CH2-) and amino silane (H2N–(CH2)2–NH–(CH2)2–NH–(CH2)3–) were selected in the in-situ modification through two different routes: physical adsorption and chemical bonding. The Moving Die Rheometer revealed that the curing process with the amino group could accelerate the crosslinking reaction, and the kaolinite grafted KH892 nanocomposite showed the best vulcanization performance. An improvement in the curing rate and mechanical properties of kaolinite/SBR composite is ascribed to the outstanding distribution and chemical bonding of nanokaolinite lamellae in the vulcanizate. Furthermore, SEM, HR-TEM, and DMA results demonstrated that both the dispersion of kaolinite in the vulcanizate and the wet skid resistance of the kaolinite/SBR hybrid materials are superior to the composite made by the dry blending method.

Preparation and Performance of Silica/ESBR Nanocomposites Modified by Bio-Based Dibutyl Itaconate

Ester-functionalized styrene-butadiene rubber (dibutyl itaconate-styrene-butadiene rubber) (D-ESBR) was synthesized by low-temperature emulsion polymerization using dibutyl itaconate (DBI) as a modified monomer containing ester groups. Nonpetroleum-based silica with hydroxy groups was used as a filler to enhance the D-ESBR, which can provide excellent mechanical properties, low rolling resistance, and high wet skid resistance. During the preparation of the silica/D-ESBR nanocomposites, a hydrogen-bonding interface was formed between the hydroxy groups on the surface of silica and the ester groups in the D-ESBR macromolecules. As the content of ester groups in the D-ESBR increases, the dispersion of silica in the nanocomposites is gradually improved, which was verified by rubber process analyzer (RPA) and scanning electron microscopy (SEM). Overall mechanical properties of the silica/D-ESBR modified with 5 wt % DBI were improved and became superior to that of the non-modified nanocomposite. Compared with the non-modified silica/D-ESBR, the DBI modified silica/D-ESBR exhibited a lower tan δ value at 60 °C and comparable tan δ value at 0 °C, indicating that the DBI modified silica/D-ESBR had lower rolling resistance without sacrificing wet skid resistance.

Possibility of artocarpus heterophyllus latex as an alternative source for natural rubber

Abstract Natural rubber (NR) has much application in rubber product manufacturing industries, which cannot be replaced by synthetic rubber. At present, Hevea rubber tree is the only economical and commercially viable source of NR. Therefore, the objective of the present research was to find alternative source of NR. NR mainly comprise of cis-1,4 polyisoprene. Artocarpus heterophyllus latex (jackfruit latex) was collected and analyzed to investigate if it can be considered as alternative source of NR. It was found from FTIR, 1H NMR and GC-MS study that jackfruit latex contains both cis-1,4 polyisoprene and trans- 1,4 polyisoprene along with few other chemical constituents. However, molecular weight of jackfruit latex is significantly lower than the NR. Because of low molecular weight polymer and presence of several other chemical constituents as impurity, jackfruit latex does not impart significant mechanical properties in vulcanized rubber compound, but it provides additional wet skid resistance (WSR) and aid in better dispersion of carbon black in rubber compound. Therefore, jackfruit latex cannot be used to replace NR, but can be used as low molecular weight natural resin, especially to improve dispersion of carbon black in rubber compound and to enhance WSR for tire.

Effect of stone-on-stone contact on porous asphalt mixes: micromechanical analysis

ABSTRACT Within the pavement engineering community, porous asphalt (PA) mixes are regarded as mixes capable of reducing noise and improving wet skid resistance. However, these mixes are likely to have the distress of ravelling. In order to analyse the propensity of a given PA mix for ravelling, the homogenisation technique can be considered as an attractive method. Along the line of the homogenisation technique, micromechanical models have been used to predict the stiffness of asphalt mixes. However, it was found that the predicted results were not in good agreement with the experimental values due to the fact that the stiffness of interacted aggregates was not accurately accounted in the models. To deal with this issue, it is important for researchers to study the stiffness of the interacted aggregates network and its role in the behaviour of a given mix. Based on this realisation, this paper provided a methodology to estimate the stiffness of the stone-on-stone skeleton and its role in the overall response of PA mixes. The results showed that the predicted stiffness of the stone-on-stone skeleton is dependent on the loading frequency/temperature and the compaction effort. The frequency response of the stone-on-stone skeleton is similar to that of the mix.

A finite element study of rain intensity on skid resistance for permeable asphalt concrete mixes

Safe highway operations are one of the major concerns of pavement engineers and authorities. The reduction of skid resistance during rainy weather poses high risk for safe driving. Wet skid resistance varies under different rainfall intensities and is influenced by many factors such as permeability of asphalt material, pavement geometric design, and tire operating conditions. Empirical studies could offer useful understanding of mechanisms of wet skid resistance and its influencing factors, however, the applicability of the empirical relationships are restricted as soon as there is a change in one of the relevant factors. In recent years, the advancement of the finite element tools has enabled researchers to simulate the tire-fluid-pavement interaction in a more realistic way. However, to the best of the authors’ knowledge, the current available numerical models either do not include the real microstructures of the pavement or ignore the water infiltration through the pavement voids in the simulations. Therefore, this paper aims to providing a numerical tool to evaluate the wet skid resistance at various rainfall intensity conditions considering the effects of pavement geometric design, tire tread design and tire operating conditions. The surface characteristics and porous microstructures of the pavement are included in the model in a way that both the vertical water flow into the asphalt concrete and surface flow on the pavement can be captured in the simulation. The effects of several pronouncing influential factors as mentioned above are quantified. Such a model upon validation is expected to provide an easy and reliable tool for pavement engineers to evaluate wet skid resistance under rainy weather more accurately which can be incorporated into pavement management systems for safety highway operation.

Bio‐based β‐myrcene‐modified solution‐polymerized styrene–butadiene rubber for improving carbon black dispersion and wet skid resistance

ABSTRACTβ‐Myrcene, a bio‐based monoterpene derived from plants, was introduced to replace butadiene in the solution‐polymerized styrene–butadiene rubber by using the conventional anionic copolymerization technique. The anionic copolymerization of β‐myrcene was found to be stoichiometric and controllable. A series of solution‐polymerized styrene–myrcene–butadiene rubber (S‐SMBR) with 100% conversion, high‐molecular weight (150 000–200 000 Da), low polydispersity, and uniform compositions was obtained. The glass transition temperature of S‐SMBR exhibited imperceptible variation with different myrcene/butadiene ratios. Interestingly, the introduction of such a long nonpolar pendant group containing isopropylidene could greatly improve carbon black dispersibility in the rubber. Furthermore, the wet skid resistance of the rubber could be improved without impairing its low rolling resistance. The tensile strength of S‐SMBR was found to be higher than that prepared by radical emulsion copolymerization. The S‐SMBR prepared by anionic solution copolymerization is thus a promising material for tires to attain sustainable development. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48159.HIGHLIGHTS A bio‐based monomer was successfully introduced to replace diene part in SBR through anionic polymerization. Carbon black dispersibility in the rubber was greatly improved. The wet skid resistance of the rubber could be improved without impairing its low rolling resistance. Robust tensile behaviors were obtained compared with the rubber prepared by radical emulsion polymerization.

Wear resistance and wet skid resistance of composite bionic tire tread compounds with pit structure

This work was aimed to introduce the bionic non-smooth structure of pits into compound preparation by referring to the bionics concept. Four types of highly wear-resistant tire tread compounds (A1, A2, A3, A4) and 4 types of highly wet-skid-resistant tire tread compounds (B1, B2, B3, B4) were made by adjusting the rubber contents and changing the parts per hundreds of carbon black and silica. According to the characteristics of the designed bionic structures and tire treads, A2 and B3 were combined to manufacture composite bionic structured tire tread compounds (C1, C2, C3, C4) through pressured and heated vulcanization. It was found BR showed higher wear-resistance and lower wet-skid resistance than SBR. With the increasing dosages of carbon black and silica, the wear-resistance was first enhanced and then weakened, but the wet-skid resistance was gradually reduced. The wet-skid resistance of tire tread compounds was associated with the hardness and roughness of the friction surfaces, and was improved when the roughness and hardness decreased. Due to the difference in wear-resistance between A2 and B3, pits were formed after wearing, which strengthened the wear-resistance and wet-skid resistance of the tire tread compounds. Compared with A2, the wear-resistance of C2 was increased to the largest extent of 0.98%, but the increasing magnitudes of wet-skid resistance were not significantly between C3 and C4, and the highest increment magnitudes on the diamond piece surface were 20.9% and 21.1%, respectively. The coupling functions of the bionic composites prove the feasibility and practicability of bionic abrication, providing a new way to improve the compound properties.

A Comparative Study of the Dynamic-Mechanical Properties of Styrene Butadiene Rubber/Epoxidized Natural Rubber Dual Filler Nanocomposites Cured by Sulfur or Electron Beam Irradiation

The properties of (50/50 wt%) styrene butadiene rubber/epoxidized (50%) natural rubber (SBR/ENR50) blends containing nanoclay (NC, 5 or 10phr) without and with carbon black (CB 20phr) cured by sulfur or by electron beam (EB) irradiation (50 and 100kGy), were compared. A sulfur cured compound containing 35phr CB was prepared as a reference sample. Dynamic mechanical thermal analysis (DMTA) indicated that the sulfur cured sample containing 10phr NC and 20phr CB and the 100kGy irradiated sample with 5phr NC and 20phr CB had higher crosslink density, storage modulus, and tensile strength, and less loss factor and loss modulus, compared to the reference sample. Scanning electron microscopy (SEM) images of cryo- fractured surfaces confirmed the DMA and crosslink density results. We suggest a light weight 100kGy irradiated sample containing the lowest amount of NC and 20phr CB with a uniform distribution of the –C–C– bonds crosslinks, for high thermal stability applications and also for passenger cars tire treads, for its ice grip and wet skid properties especially for icy and wet roads, with improvements of 23% and 20%, respectively as compared to the reference sample.

Experimental Study on Wet Skid Resistance of Asphalt Pavements in Icy Conditions.

In this research, the durability of skid resistance during the ice melting process with temperature increasing from −5 °C to 10 °C was characterized by means of a British Pendulum Skid Tester. Four types of pavement surfaces were prepared and tested. The difference between two antiskid layers prepared with bitumen emulsion was the aggregate. The detailed angularity and form 2D index of fine aggregates used for antiskid surfaces, characterized by means of the Aggregate Image Measure System (AIMS) with micro image analysis methods, were then correlated with British Pendulum Number (BPN) values. Results indicate that skid resistance has the lowest value during the ice-melting process. The investigated antiskid layers can increase the surface friction during icy seasons. In icy conditions, the skid resistance behavior first worsens until reaches the lowest value, and then increases gradually with increasing temperature. Results from ice-melting conditions on four investigated pavement surfaces give the same temperature range where there will be lowest skid resistance. That temperature range is from 3 °C to 5 °C. A thicker ice layer will result in a lower skid resistance property and smaller “lowest BPN”.