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

2018 ◽  
Vol 91 (2) ◽  
pp. 433-452 ◽  
Author(s):  
C. Hayichelaeh ◽  
L. A. E. M. Reuvekamp ◽  
W. K. Dierkes ◽  
A. Blume ◽  
J. W. M. Noordermeer ◽  
...  
Keyword(s):  
Crosslink Density ◽  
Silica Surface ◽  
Shielding Effect ◽  
Polymer Layer ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Bound Rubber ◽  
Interfacial Compatibility ◽  
Physical Interactions ◽  
Tan Δ

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.

SILICA-REINFORCED NATURAL RUBBER TIRE TREAD COMPOUNDS CONTAINING BIO-BASED PROCESS OILS. I: ASPECTS OF MIXING SEQUENCE AND EPOXIDE CONTENT

2019 ◽  
Vol 93 (2) ◽  
pp. 360-377
Author(s):  
C. Hayichelaeh ◽  
L. A. E. M. Reuvekamp ◽  
W. K. Dierkes ◽  
A. Blume ◽  
J. W. M. Noordermeer ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Rate Constant ◽  
Silica Surface ◽  
Early Stage ◽  
Shielding Effect ◽  
Cure Reaction ◽  
Silanol Groups ◽  
Rubber Compounds ◽  
Tan Δ ◽  
Flocculation Rate

ABSTRACT A bio-based process oil for rubber compounds is one of the compounding ingredients to be used toward an eco-friendly and more sustainable rubber technology. This work investigates epoxidized palm oil (EPO) as an alternative for petroleum-based process oil in silica-reinforced natural rubber (NR) tire tread compounds. The effect of different incorporating steps of EPO on the properties of the rubber compounds is first studied, taking into account that the polar functional groups in the oil molecules may interact with the silanol groups on the silica surface. The properties of silica-reinforced NR compounds with EPO oil are compared with that of reference mixes with treated distillate aromatic extract (TDAE) and without oil. The compounds with EPO show a lower viscosity, filler–filler interaction, and flocculation rate constant but higher cure reaction rate constants compared with the compound with TDAE. The results indicate that the epoxide groups in EPO interact with the silanol groups on the silica surface, promoting a greater shielding effect on the polar surface and thus better silica dispersion and less interference with the vulcanization reaction. The different incorporating steps of EPO show no significant effect on the viscosity, filler–filler interaction, or flocculation rate constant but clearly affect the extent of crosslinking, as indicated by the cure torque difference. The presence of EPO in an early stage of the mixing together with the first half addition of silica and silane results in the lowest cure torque difference, modulus, and tensile strength (i.e., the highest tan δ at 60 °C), which indicates a possible obstruction for the interaction between the silanol groups and silane coupling agent by the EPO molecules. Comparing EPO with different epoxide contents in the range of 1–3 mol%, the increase in epoxide content gives similar Payne effects but enhances the cure reaction, resulting in improved tensile properties and tan δ at 60 °C. The results clearly prove that EPO can be used as a TDAE alternative.

REINFORCEMENT OF NATURAL RUBBER BY SILICA/SILANE IN DEPENDENCE OF DIFFERENT AMINE TYPES

2017 ◽  
Vol 90 (4) ◽  
pp. 651-666 ◽  
Author(s):  
C. Hayichelaeh ◽  
L. A. E. M. Reuvekamp ◽  
W. K. Dierkes ◽  
A. Blume ◽  
J. W. M. Noordermeer ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Natural Rubber ◽  
Health And Safety ◽  
Aliphatic Amines ◽  
Shielding Effect ◽  
Processing Temperature ◽  
Rubber Content ◽  
Payne Effect ◽  
Rubber Compounds ◽  
Bound Rubber

ABSTRACT Diphenyl guanidine (DPG) is the most commonly used secondary accelerator in silica-reinforced rubber compounds because of its additional positive effect on the silanization reaction and deactivation of free silanol groups that are left over after the silanization. However, because of health and safety concerns about the use of DPG, which decomposes to give highly toxic aniline during high processing temperature, safe alternatives are required. This work investigates the effect of various types of aliphatic amines having alkyl or cyclic structures and similar pKa (i.e., hexylamine [HEX], decylamine [DEC], octadecylamine [OCT], cyclohexylamine [CYC], dicyclohexylamine [DIC], and quinuclidine [QUI]) on the properties of silica-reinforced natural rubber (NR) compounds by taking the ones with DPG and without amine as references. When compared with the compound without amine, the use of all amine types reduces filler–filler interaction (i.e., the Payne effect) and enhances filler–rubber interaction, as indicated by bound rubber content and decreased heat capacity increment. The amines with alkyl chains can reduce the Payne effect and enhance cure rate to a greater extent compared with the amines with cyclic rings as a result of better accessibility toward the silica surface and a shielding effect because of less steric hindrance. The longer carbon tails on linear aliphatic amines ranging from HEX, DEC, to OCT lead to a lower Payne effect, lower heat capacity increment, higher bound rubber content, and higher modulus as well as tensile strength. Overall, the use of OCT provides silica-reinforced NR compounds with properties closest to the reference one with DPG and can act as a potential alternative for DPG.

Flocculation in Silica Reinforced Rubber Compounds

2009 ◽  
Vol 82 (5) ◽  
pp. 524-540 ◽  
Author(s):  
S. Mihara ◽  
R. N. Datta ◽  
J. W. M. Noordermeer
Keyword(s):  
Activation Energy ◽  
Coupling Agent ◽  
Physical Phenomenon ◽  
Interfacial Interaction ◽  
Shielding Effect ◽  
Interaction Layer ◽  
Filled Rubber ◽  
Rubber Compounds ◽  
Bound Rubber ◽  
Flocculation Rate

Abstract Flocculation plays an important role in reinforcement of silica filled rubber compounds, even if coupling agents are applied. It is well known that silica tends to flocculate during the early stages of vulcanization, when no dense rubber network has been formed yet. In the present study, flocculation was monitored by following the change in storage modulus at low strain, the so-called Payne effect, using a RPA2000 dynamic mechanical tester. The kinetic parameters: the rate constant and the activation energy of the silica flocculation were calculated according to the well-known Arrhenius equation. On basis of the value of the activation energy obtained for flocculation, it can be concluded that the silica flocculation is a purely physical phenomenon. Bound rubber measurements were also done in order to estimate the interfacial interaction layer between silica and polymer resulting from the coupling agent. The silica flocculation rate decreases with increasing interfacial interaction layer on the silica surface. This indicates that the decrease of the flocculation rate is due to the shielding effect of the coupling agent. It is argued that the attractive flux from forces related to polarity differences between the silica and the rubber is the determining factor for silica flocculation.

OPTIMIZATION OF RUBBER FORMULATION FOR SILICA-REINFORCED NATURAL RUBBER COMPOUNDS

2013 ◽  
Vol 86 (2) ◽  
pp. 313-329 ◽  
Author(s):  
W. Kaewsakul ◽  
K. Sahakaro ◽  
W. K. Dierkes ◽  
J. W. M. Noordermeer
Keyword(s):  
Silane Coupling Agent ◽  
Coupling Agents ◽  
Silane Coupling Agents ◽  
Rubber Content ◽  
Rubber Compounds ◽  
Bound Rubber ◽  
Silane Coupling ◽  
Mooney Viscosity ◽  
Tan Δ ◽  
Tear Properties

ABSTRACT The rubber formulation plays a significant role in the properties of NR compounds filled with silica. In this work, the influences of various silicas, silane coupling agents, and diphenylguanidine (DPG) on the properties of compounds and vulcanizates—that is, cure characteristics, Mooney viscosity, flocculation kinetics, bound rubber content, Payne effect, tan δ at 60°C, tensile properties, and tear properties—are investigated. The results demonstrate that compound viscosity and curing behavior, as well as vulcanizate properties of the silica-filled NR, are much improved by incorporating silane coupling agents. Bis-triethoxysilylpropyltetrasulfide clearly gives better overall properties than the disulfide-based silane bis-triethoxysilylpropyldisulfide, except for scorch safety. DPG acts as a synergist to sulfenamide primary accelerators, as well as activator for the silanization reaction. Highly dispersible (HD) silicas can significantly enhance the degree of dispersion and so lead to higher filler–rubber interaction. As a consequence, the HD silicas provide better dynamic and mechanical properties for filled NR vulcanizates compared with conventional counterparts. The optimal quantities of both silane coupling agent and DPG required in the formulation are correlated to the cetyl trimethylammonium bromide specific surface area of the silicas. Furthermore, the results reveal that the silica structure as characterized by the dibutylphthalate adsorption also strongly influences the reinforcing efficiency.

EFFECTS OF SILANE AGENTS AND CURING TEMPERATURES ON VULCANIZATE STRUCTURES

2019 ◽  
Vol 93 (2) ◽  
pp. 414-428 ◽  
Author(s):  
Byungkyu Ahn ◽  
Jong-Yeop Lee ◽  
Donghyuk Kim ◽  
Il Jin Kim ◽  
Sangwook Han ◽  
...  
Keyword(s):  
Coupling Agent ◽  
Crosslink Density ◽  
Silica Surface ◽  
Coupling Reaction ◽  
Rolling Resistance ◽  
Coupling Agents ◽  
Silane Coupling Agents ◽  
Filled Rubber ◽  
Rubber Compounds ◽  
Silane Coupling

ABSTRACT Silane coupling agents are commonly used in silica-filled rubber compounds to hydrophobize the silica surface and improve filler–rubber interaction. The coupling agent bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT) is the most widely used coupling agent. The tetrasulfide is more reactive than the disulfide in bis[3-(triethoxysilyl)propyl]disulfide (TESPD) due to its low decomposition energy, resulting in more coupling reaction with rubber molecules. Meanwhile, vulcanization temperature affects chemical networks. Polysulfide is vulnerable to heat, so it can be easily broken to form shorter crosslinks. Compounds with TESPD or TESPT were vulcanized at 160 and 180 °C. In addition to the decomposition, the reactivity of the silanes was confirmed from the cure characteristics of the compounds without the curatives. TESPD could also cause a coupling reaction without the curatives such as TESPT known to release free sulfur. By analyzing vulcanizate structures, total crosslink density was separated into chemical crosslink density and filler–rubber networks. Applying TESPT or vulcanizing at 180 °C increased the filler–rubber networks, and the higher vulcanization temperature decreased the chemical crosslink density. By correlating physical properties, effects of the vulcanizate structures on performance of tread compounds were investigated. The filler–rubber interaction was dominant for wet traction and mechanical properties in tensile test. The chemical crosslink density affected rolling resistance.

VULCANIZATE STRUCTURES AND MECHANICAL PROPERTIES OF RUBBER COMPOUNDS WITH SILICA AND CARBON BLACK BINARY FILLER SYSTEMS

2020 ◽  
pp. 000-000 ◽  
Author(s):  
Il Jin Kim ◽  
Byungkyu Ahn ◽  
Donghyuk Kim ◽  
Hyung Jae Lee ◽  
Hak Joo Kim ◽  
...  
Keyword(s):  
Carbon Black ◽  
Physical Properties ◽  
Crosslink Density ◽  
Crosslinking Density ◽  
Silica Content ◽  
Rubber Matrix ◽  
Rubber Compounds ◽  
High Elongation ◽  
Chemical Crosslinks ◽  
Tan Δ

ABSTRACT The physical properties of rubber compounds are mainly determined by the filler dispersion within the rubber matrix, filler–rubber interaction, and chemical crosslink structure caused by sulfur. Carbon black or silica is typically used as a reinforcing filler in tire tread compounds; however, binary filler systems comprising the two types of filler are also currently being used to complement each other. This study used binary filler systems to manufacture vulcanizates and classified the vulcanizate structures as chemical crosslinks caused by sulfur, physical crosslinks caused by carbon black (carbon black–bound rubber), and silica–silane–rubber networks caused by silica and silane. The effect of each vulcanizate structure on the physical properties was also calculated. In the proposed binary filler system, silica chemically bonds with rubber molecules, unlike carbon black. Therefore, the crosslink density per unit of silica content was 19% higher than that of carbon black, in which rubber molecules were physically adsorbed on the surface. Tensile properties affected by 1 unit of crosslinking density for each filler were calculated, and silica was found to contribute more in the low-elongation range, whereas carbon black contributed more in the high-elongation range. Regarding tan δ at 60 °C and abrasion resistance per unit crosslink density of filler, carbon black made a greater contribution than silica, whereas silica had a greater contribution to wet traction and snow traction.

Effect on Vulcanized Rubber Compounds of Immersion in Boiling Water

1931 ◽  
Vol 4 (3) ◽  
pp. 426-436
Author(s):  
K. J. Soule
Keyword(s):  
Water Absorption ◽  
Room Temperature ◽  
Anomalous Behavior ◽  
Boiling Water ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Different Temperatures ◽  
Actual Change

Abstract Further work is very desirable on the effect of different accelerators, antioxidants, and fluxes. It is possible that their study will throw more light on the mechanism of the swelling phenomena, and also help to explain the anomalous behavior of some of the fillers tested. It would also seem to be worth while to study the action of a few selected stocks in water, at several temperatures between room temperature and 100° C., to determine if the water absorption and swelling merely increase with rising temperatures, or whether there might be an actual change in behavior at different temperatures.

Studies in the Vulcanization of Rubber. IV—A Theory of Vulcanization of Rubber

1930 ◽  
Vol 3 (4) ◽  
pp. 659-667
Author(s):  
G. R. Boggs ◽  
J. T. Blake
Keyword(s):  
Electrical Properties ◽  
Joule Effect ◽  
Vulcanized Rubber ◽  
Chemical Theory ◽  
Rubber Compounds ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization

Abstract A new theory has been advanced which, it is believed, explains completely the various phenomena connected with the vulcanization of rubber. It is entirely a chemical theory based on the existence of two separate and distinct rubber compounds, soft vulcanized rubber and ebonite. The theory explains satisfactorily the aging of rubber, the variation in combined sulfur at optimum cure caused by acceleration, the kinetics of vulcanization, the characteristics of various vulcanizing agents, the thermochemistry of vulcanization, the electrical properties of rubber, the reclaiming of rubber, and the Joule effect. A brief review and discussion of the phenomena and past theories of vulcanization have also been given.

Crystallization of Vulcanized Rubber

1941 ◽  
Vol 14 (2) ◽  
pp. 347-355 ◽  
Author(s):  
Norman Bekkedahl ◽  
Lawrence A. Wood
Keyword(s):  
Practical Importance ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Single Exception ◽  
Quantitative Results ◽  
The Subject ◽  
Low Sulfur Content ◽  
Low Sulfur

Abstract The formation of crystals at room temperature by stretching rubber, vulcanized or unvulcanized, has been the subject of considerable study. The crystallization of unstretched rubber at low temperatures is also well known, but with a single exception to be discussed later, the effect has commonly been considered to be limited to the unvulcanized material. In the present investigation, however, the crystallization of unstretched specimens of vulcanized rubber of low sulfur content has been accomplished. In commercial vulcanized rubber products, crystallization has not hitherto been recognized as a factor of practical importance. It is probably significant in cold climates, where some rubber products slowly undergo a great increase in rigidity and permanent set. Automobile traffic counters, for example, have been rendered inoperative by the hardening of the rubber tubing used with them. Laboratory tubing and other products made of a number of different commercial rubber compounds have become rigid after storage for some weeks in a refrigerator at about 0° C. Previous work on unvulcanized rubber showed that it can be crystallized at temperatures between + 10° and −40° C, the crystals melting in a range from about 6° to 16° C. Crystallization and fusion are accompanied by changes in volume, heat capacity, light absorption, birefringence, x-ray diffraction, and mechanical properties such as hardness. x-Ray diffraction and birefringence, of course, give the most direct evidence of crystalline structure, but in the present work change of volume, measured in a mercury-filled dilatometer, was chosen as the criterion of crystallization or fusion. Quantitative results are more easily obtained in this manner, and the experimental observations are simple. Furthermore, the method is well adapted to continuous observations over long periods of time, such as were found necessary in the present work.

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