Effect of the cure system on aging resistance of natural rubber compounds

2019 ◽  
Vol 52 (5) ◽  
pp. 397-409 ◽  
Author(s):  
Luciana Ribeiro Honorato ◽  
Regina Celia Reis Nunes ◽  
Jaqueline Guimarães Lima Cosme ◽  
Leila Lea Yuan Visconte ◽  
Augusto Cesar de Carvalho Peres ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Mechanical Performance ◽  
Dynamic Properties ◽  
Lower Number ◽  
Cross Link ◽  
Rubber Compounds ◽  
Before And After ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density

This work investigates natural rubber (NR) composites vulcanized with different combinations of accelerators in efficient cure systems. The NR compounds were characterized for cross-link density, hardness, tensile strength, and dynamical–mechanical properties, before and after aging. Among the cure systems used, that containing the highest amount of free sulfur presented the best mechanical performance, before and after aging; concerning dynamic properties after the aging, the composition with a lower number of cross-links was the best.

scholarly journals Magnetic composites based on NR and strontium ferrite

2019 ◽  
Vol 12 (1) ◽  
pp. 63-69
Author(s):  
Ján Kruželák ◽  
Andrea Kvasničáková ◽  
Rastislav Dosoudil ◽  
Ivan Hudec
Keyword(s):  
Carbon Black ◽  
Strontium Ferrite ◽  
Rubber Matrix ◽  
Cross Link ◽  
Magnetic Composites ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density ◽  
The Cross ◽  
Thermo Physical Properties

Abstract Two types of composites based on natural rubber (NR) and strontium ferrite were tested in this study. Composites of the first type were prepared by incorporation of strontium ferrite in the concentration range ranging from 0 to 100 phr (parts per hundred rubber) into pure NR based rubber matrix, while with those of the second type, strontium ferrite was dosed in the same concentration level into NR based rubber batch with constant amount of carbon black — 25 phr. For rubber matrices cross-linking, a standard sulfur based curing system was used. This work is focused on the effect of magnetic filler content on physico-mechanical, magnetic and thermo-physical properties of composite materials. Subsequently, the cross-link density and the structure of the formed sulfidic cross-links were examined. The results showed that the cross-link density of both types of composites increased with the increasing content of magnetic filler, while the structure of the sulfidic cross-links was almost not influenced by the amount of strontium ferrite. Tensile strength of rubber composites with pure rubber matrix was slightly improved by the incorporation of ferrite, while in case of composites based on a carbon black batch, the incorporation of magnetic filler resulted in the decrease of this characteristic. The presence of magnetic filler in both types of composites leads to a significant increase of the remanent magnetic induction.

PERFORMANCE COMPARISON OF VARIOUS SURFACE MODIFYING AGENTS ON PROPERTIES OF SILICA-FILLED CHLOROPRENE RUBBER

2017 ◽  
Vol 90 (1) ◽  
pp. 146-158 ◽  
Author(s):  
Chomsri Siriwong ◽  
Pongdhorn Sae-Oui ◽  
Chakrit Sirisinha
Keyword(s):  
Dynamic Properties ◽  
Coupling Efficiency ◽  
Performance Comparison ◽  
Cross Link ◽  
Bound Rubber ◽  
Link Density ◽  
Cross Link Density ◽  
Chloroprene Rubber ◽  
Filler Dispersion ◽  
Rubber Filler

ABSTRACT Influence of the surface modifying agents (SMAs) polyethylene glycol (PEG), 3-aminopropyl triethoxysilane (APTES), and bis-(3-triethoxysilylpropyl)tetrasulfide (TESPT) on properties of silica-filled chloroprene rubber (CR) was investigated. Results reveal that the presence of SMAs greatly improves mechanical and dynamic properties of the silica-filled CR because of the reduced filler–filler interaction and improved rubber–filler interaction as evidenced by the Payne effect and bound rubber content results, respectively. When compared at the same SMA dosage, TESPT gives the best overall vulcanizate properties. This effect is attributed to high coupling efficiency of TESPT and its ability to donate sulfur atoms during vulcanization, leading to the improved filler dispersion, rubber–filler interaction, and cross-link density. APTES gives high coupling efficiency, but because of the lack of sulfur atoms, its performance is slightly inferior to that of TESPT. In contrast, PEG can only reduce filler–filler interaction, with no significant impact on rubber–filler interaction and cross-link density; therefore, PEG provides lower property improvement.

scholarly journals Influence of trans-polyoctylene rubber content on styrene-butadiene rubber properties

2020 ◽  
Vol 13 (1) ◽  
pp. 1-5
Author(s):  
Patrik Macúrik ◽  
Rafal Anyszka ◽  
Ivan Hudec ◽  
Terézia Malčeková ◽  
Ján Kruželák
Keyword(s):  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Curing Time ◽  
Cross Link ◽  
Rubber Content ◽  
Elongation At Break ◽  
Rubber Compounds ◽  
Link Density ◽  
Cross Link Density ◽  
Styrene Butadiene

AbstractThe study was focused on the investigation of trans-polyoctylene (TOR) influence on cross-linking as well as mechanical and rheological properties of rubber compounds based on styrene-butadiene rubber (SBR). SBR was compounded with different proportions of TOR in the concentration range from 0 to 30 phr. Integration of TOR into rubber leads to the prolongation of the optimum curing time and scorch time and thus the decrease of the curing rate. Higher content of TOR led to less viscous rubber due to the plasticizing effect. Cross-link density of vulcanizates was reduced, which correlates with higher elongation at break. Tensile strength and hardness of vulcanizates increased with the increasing TOR content, probably due to the increasing amount of the crystalline phase.

Reclaiming of waste guayule natural rubber vulcanizate—reclaim rubber for green tire applications: An approach for sustainable development

2018 ◽  
Vol 51 (3) ◽  
pp. 193-210 ◽  
Author(s):  
Soumyajit Ghorai ◽  
Dipankar Mondal ◽  
Sawar Dhanania ◽  
Santanu Chattopadhyay ◽  
Madhusudan Roy ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Polymer Chains ◽  
Cross Link ◽  
Scanning Calorimetry ◽  
Infrared Study ◽  
Differential Scanning Calorimetry Study ◽  
Link Density ◽  
Cross Link Density ◽  
Silica Dispersion ◽  
The Fourier Transform

This article illustrates the reclaiming of guayule natural rubber (GNR) vulcanizate by bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT), and as-grown reclaim rubber facilitates the silica dispersion in GNR product application without adding any coupling agent. This article deals with the performance evaluation of silica-filled revulcanizates with promising application in green tire. The extent of reclaiming was monitored through the measurement of sol content, cross-link density, Mooney viscosity, and degree of reclaiming. The differential scanning calorimetry study was carried out to evaluate the fraction of immobilized polymer chains and its dependence on cross-link density of the vulcanizates. The Fourier transform infrared study and also sulfur analysis independently indicate the attachment of the fragmented TESPT with the polymer chain and cross-link bonds. The study of mechanical properties clearly shows that in revulcanized GNR, the optimum property is achieved when reclaiming time is set for 40 min. The effect of reclaiming time on dynamic mechanical behavior such as storage modulus and loss tangent was studied. The scanning electron microscopy studies show the coherency and homogeneity of silica-filled revulcanize rubber with reclaiming time.

ROLE OF COAGENTS IN PEROXIDE VULCANIZATION OF NATURAL RUBBER

2013 ◽  
Vol 86 (3) ◽  
pp. 488-502 ◽  
Author(s):  
Rejitha Rajan ◽  
Siby Varghese ◽  
K. E. George
Keyword(s):  
Natural Rubber ◽  
Hydrogen Abstraction ◽  
Polymer Chains ◽  
Hydrocarbon Chains ◽  
Equilibrium Swelling ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density ◽  
Curing Agents

ABSTRACT The drawbacks of peroxide vulcanization can largely be overcome by introducing suitable co-curing agents (coagents) in the formulation. The role of various coagents, such as zinc diacrylate (ZDA), trimethylolpropane trimethacrylate (TMPTMA), and triallyl cyanurate (TAC) in the peroxide vulcanization of natural rubber (NR) was studied by Fourier transform infrared spectroscopy. Cross-link density was measured by the equilibrium–swelling technique. Cross-linking mechanism of peroxide in NR was interpreted by comparing the spectra of cured and uncured vulcanizates. The predominance of hydrogen abstraction over the radical addition was established (at 160 °C). Coagent ZDA produces ionic as well as covalent cross-links in the vulcanizate. Ionic cross-links have the ability to slip along the hydrocarbon chains and thus resemble polysulfidic cross-links. Hence, ZDA can be chosen for applications where good mechanical properties are required. Coagent TMPTMA produces covalent cross-links between polymer chains and is suitable for high-modulus applications. TAC, although it bridges through covalent cross-links, is not a suitable coagent for highly unsaturated rubbers like NR.

PEROXIDE CROSS-LINKING OF EPDM USING MOVING DIE RHEOMETER MEASUREMENTS. I: EFFECTS OF THE THIRD MONOMER CONCENTRATION AND PEROXIDE CONTENT

2015 ◽  
Vol 88 (1) ◽  
pp. 40-52 ◽  
Author(s):  
He Wang ◽  
Ying Ding ◽  
Shugao Zhao ◽  
Claus Wrana
Keyword(s):  
Network Structure ◽  
Monomer Concentration ◽  
Cross Linking ◽  
Cross Link ◽  
Peroxide Content ◽  
Entanglement Density ◽  
The Third ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density

ABSTRACT The influence of the third monomer 5-ethylene-2-norbornene (ENB) and peroxide content on cure behavior and network structure of peroxide-cured EPDM were investigated by moving die rheometer, NMR relaxation, and dynamic mechanical thermal spectroscopy. According to the rubber elasticity theory, the torque measurement results showed the network structure of peroxide-cured EPDM contained chemical cross-links via combination reaction (Ccom), chemical cross-links via addition reaction (Cadd), and the contribution of entanglement density and network defects to the total cross-link density (CEN). The total cross-link density (Ctot) increased linearly with the peroxide content. The increase of ENB concentration was beneficial for the improvement of cross-linking efficiency of peroxide, but it made the diene conversion of EPDM decrease. CEN was dependent on the third monomer content, which also provided the dominant contribution to the Ctot at low peroxide contents. Furthermore, Ccom and Cadd were dependent on peroxide content linearly, and the latter also was governed by the ENB level.

VULCANIZATION CHARACTERISTICS OF NATURAL RUBBER COAGULATED BY MICROORGANISMS

2018 ◽  
Vol 91 (1) ◽  
pp. 64-78
Author(s):  
Si-Dong Li ◽  
Jing Chen ◽  
Le-Fan Li ◽  
Zhi-Fen Wang ◽  
Jie-Ping Zhong ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Natural Rubber ◽  
Transverse Relaxation Time ◽  
Cross Link ◽  
Mass Percentage ◽  
Transverse Relaxation ◽  
1H Nuclear Magnetic Resonance ◽  
Link Density ◽  
Cure Time ◽  
Cross Link Density

ABSTRACT The network variations of natural rubber (NR) during the vulcanization process were investigated by 1H chemical shift by liquid-state 1H nuclear magnetic resonance (NMR) spectroscopy. NR latex coagulated by microorganisms (NR-m) was contrasted with NR latex coagulated by acid (NR-a). The influences of the coagulation process on the structures, vulcanization characteristics, and mechanical properties of NR were analyzed. The results show that the cross-link density (XLD) and mass percentage of cross-link network (A(Mc)) can be increased with the increment of the vulcanization time; while the mass percentage of dangling free ends of the hydrocarbon and small molecules (A(T2)), the longitudinal relaxation time (T1), transverse relaxation time (T2), and molecular mass of inter–cross-link chains (Mc) decreased with the prolonging of vulcanization time both NR-m and NR-a. NR-m exhibits shorter scorch times (ts1, ts2) and optimum cure time (t90) and shows higher maximum torque (MH) and minimum torque (ML) than that of NR-a. It is obvious that the higher XLD and A(Mc) and lower A(T2), T1, T2, and Mc values of NR-m result in higher stress, tensile strength, and tear strength of NR compounds.

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