ACTIVATION ENERGIES OF THERMO-OXIDIZED NITRILE RUBBER COMPOUNDS OF VARYING ACRYLONITRILE CONTENT

2019 ◽  
Vol 92 (1) ◽  
pp. 129-151 ◽  
Author(s):  
Richard J. Pazur ◽  
T. Mengistu
Keyword(s):  
Chain Scission ◽  
Activation Energies ◽  
Nitrile Rubber ◽  
Network Chain ◽  
Elongation At Break ◽  
Diffusion Limited ◽  
Rubber Compounds ◽  
Nitrile Rubbers ◽  
Oxidative Behavior ◽  
Recombination Reactions

ABSTRACT The thermo-oxidative behavior of carbon black–reinforced sulfur-cured nitrile rubber compounds with varying acrylonitrile (ACN) content (18–49 wt%) was investigated. Accelerated heat aging was carried out from 40 °C to 115 °C for various aging times. Ambient aging was also included. Samples were tested for hardness, 10% tensile stress, tensile strength, elongation at break, network chain density by equilibrium solvent swell, and toluene-soluble fraction. Diffusion-limited oxidation affected data at high temperatures and was eliminated for time-temperature superposition. Linear Arrhenius kinetic behavior was confirmed throughout the whole temperature range, and calculated activation energies varied from 75 to 93 kJ/mol. Activation energies calculated through the hardness data were found to increase steadily with ACN concentration, whereas the other test responses showed less direct correlation, likely because of the influence of the underlying NBR microstructure, which changes as a function of ACN content. The high-temperature thermo-oxidative process consists of both oxidative crosslinking and chain scission reactions. Sulfur reversion and alkyl radical recombination reactions are likely prevalent at low temperatures during the buildup of hydroperoxides up to 60 °C. The shelf life of nitrile rubbers strongly depends on their ACN level, with lower ACN nitriles being more susceptible to degradation, leading to shorter shelf lives, than higher ACN-containing nitriles.

HEAT AGING OF A BROMOBUTYL TIRE INNER LINER UNDER AEROBIC AND ANAEROBIC CONDITIONS

2021 ◽  
Author(s):  
M. Yerxa ◽  
C. Porter ◽  
R. J. Pazur
Keyword(s):  
Crosslink Density ◽  
Chain Scission ◽  
Double Quantum ◽  
Elongation At Break ◽  
Small Areas ◽  
Diffusion Limited ◽  
Low Field ◽  
Aging Conditions ◽  
Crosslinking Reactions ◽  
Aerobic And Anaerobic

ABSTRACT A bromobutyl tire inner liner compound was prepared and subjected to aerobic and anaerobic heat aging at a temperature of 100 °C for seven aging times up to 8 weeks. Hardness and mechanical properties were monitored, and the evolution of the crosslink density was followed using equilibrium solvent swell and low field double quantum (DQ) nuclear magnetic resonance (NMR). The hardness and the 300% tensile stress increased with heat aging, while both tensile strength and elongation at break dropped. Both chain scission and crosslinking reactions were taking place. Equilibrium swelling and DQ NMR results confirmed that a larger crosslink density increase was seen under aerobic versus anaerobic aging conditions. The network distribution consisting of a dominant low crosslinking zone and small areas of higher crosslinking slowly broadened and shifted toward higher crosslink densities upon heat aging. The compounds aged heterogeneously. Attenuated total reflectance–Fourier transform infrared spectroscopy confirmed the presence of an oxidized surface layer, and therefore diffusion-limited oxidation effects, but only under aerobic aging conditions. Reaction mechanisms are proposed to explain the net crosslink rise with heat aging.

Determination of Combined and Second Order Factor Effects for Simultaneous Optimization of Physical and Mechanical Properties of NR/BR Blend System

2014 ◽  
Vol 42 (4) ◽  
pp. 290-304
Author(s):  
Rajarajan Aiyengar ◽  
Jyoti Divecha
Keyword(s):  
Physical And Mechanical Properties ◽  
Second Order ◽  
Simultaneous Optimization ◽  
Order Effects ◽  
Elongation At Break ◽  
Five Factors ◽  
Rubber Compounds ◽  
Polybutadiene Rubber ◽  
Contour Plots

ABSTRACT The blends of natural rubber (NR), polybutadiene rubber (BR), and other forms of rubbers are widely used for enhancing the mechanical and physical properties of rubber compounds. Lots of work has been done in conditioning and mixing of NR/BR blends to improve the properties of its rubber compounds and end products such as tire tread. This article employs response surface methodology designed experiments in five factors; high abrasion furnace carbon black (N 330), aromatic oil, NR/BR ratio, sulfur, and N-oxydiethylene-2-benzothiazole sulfenamide for determination of combined and second order effects of the significant factors leading to simultaneous optimization of the NR/BR blend system. One of the overall optimum of eight properties existed at carbon 44 phr, oil 6.1 phr, NR/BR 78/22 phr with the following values of properties: tensile strength (22 MPa), elongation at break (528%), tear resistance (30 kg/mm), rebound resilience (67%), moderate hardness (68 International rubber hardness degrees) with low heat buildup (17 °C), permanent set (12%), and abrasion loss (57 mm3). More optimum combinations can easily be determined from the NR/BR blend system models contour plots.

Effect of Ground Vulcanizate Modification Methods on Properties of Oil-Petroleum-Resistant Rubber

2021 ◽  
Vol 903 ◽  
pp. 127-133
Author(s):  
Vadim Myadelets ◽  
Vjaceslavs Lapkovskis ◽  
Andrey V. Kasperovich
Keyword(s):  
Chemical Nature ◽  
Nitrile Rubber ◽  
Rubber Crumb ◽  
Elongation At Break ◽  
Compression Set ◽  
Peg 400 ◽  
Peg 4000 ◽  
Modification Method ◽  
Resistant Rubber ◽  
Set Up

In this paper, the influence of the modification method applied to ground vulcanizate (GV) on the properties of elastomeric compositions based on nitrile rubber is discussed. Modified GV has been mixed with the elastomeric composition, which is used for the manufacturing of oil-petroleum-resistant rubber products.The work takes into consideration two types of GV with different chemical nature. The first GV type is rubber crumb produced from end-of-life tires. The second GV type was obtained from rubber wastes based on nitrile rubber. Three methods of the modification are compared in the research: mechanical activation in a planetary ball mill, swelling in a Polyethylene glycol (PEG-400) medium, and the mechano-chemical transformation of GV with PEG-4000. It is shown that depending on the dosage addition of GV modified with PEG-4000 reduce the compression set up for (16.1±0.7%), the strength decreases only by 2.1–8.3%, and the elongation at break increases by 0.8–10.3% compared to rubber without additives.

INFLUENCE OF THE CROSSLINK STRUCTURE ON THE ACTIVATION ENERGY CALCULATED UNDER THERMO-OXIDATIVE CONDITIONS

2018 ◽  
Vol 91 (1) ◽  
pp. 205-224 ◽  
Author(s):  
Richard J. Pazur ◽  
T. Mengistu
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
High Temperature ◽  
Oxidation Process ◽  
Activation Energies ◽  
Structure Stability ◽  
Temperature Oxidation ◽  
Network Chain ◽  
Temperature Activation ◽  
Sulfur Donor

ABSTRACT A series of six carbon black reinforced brominated poly(isobutylene-co-isoprene) (BIIR) compounds has been developed varying only in cure system type: sulfur, sulfur donor, zinc oxide, peroxide, phenolic resin, and ionic. Compounds were aged from room temperature up to 115 °C, and hardness, mechanical properties, and network chain density were measured. Non-Arrhenius behavior was observed due to data curvature from 70 to 85 °C. The oxidation process was adequately described by assigning low (23–85 °C) and high (85–115 °C) temperature regimes. Heterogeneous aging due to diffusion limited oxygen (DLO) occurred for heat aging above 85 °C, and all measured responses except tensile strength were strongly affected, causing lower activation energies. The activation energy for the high temperature oxidation process is in the range of 107 to 133 kJ/mol in the following ascending order: zinc oxide, ionic, sulfur donor, sulfur, peroxide, and resin. The midpoint of the high temperature activation energies is of the same order as the BIIR and poly(isobutylene) elastomers. The low temperature activation energy is in the range of 55–60 kJ/mol and is likely due to a combination of oxidative chain scission (crosslink density loss) and crosslinking recombination (network building) reactions. Apart from the crosslink structure stability, the presence of unsaturation along the polymer chain after vulcanization affects the high temperature activation energy.

Effect of nitrile rubber on properties of silica-filled natural rubber compounds

2005 ◽  
Vol 24 (1) ◽  
pp. 32-38 ◽  
Author(s):  
Hexiang Yan ◽  
Kang Sun ◽  
Yong Zhang ◽  
Yinxi Zhang
Keyword(s):  
Natural Rubber ◽  
Nitrile Rubber ◽  
Rubber Compounds

scholarly journals Devulcanization of ground tire rubber: microwave and thermomechanical approaches

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Dániel Ábel Simon ◽  
Dávid Zoltán Pirityi ◽  
Tamás Bárány
Keyword(s):  
Microwave Treatment ◽  
Chain Scission ◽  
Polymer Chains ◽  
Tire Rubber ◽  
Ground Tire Rubber ◽  
Elongation At Break ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density ◽  
Internal Mixer

Abstract We devulcanized ground tire rubber (GTR) in a laboratory microwave oven and an internal mixer, measured the soluble content and the cross-link density of the samples, and then used Horikx’s analysis. The results showed that microwave treatment caused severe degradation of the polymer chains, while in the case of thermomechanical devulcanization, the selective scission of covalent cross-links is more common. Four devulcanized ground tire rubber (dGTR) samples were chosen for further study and three groups of samples were produced: dGTR samples containing vulcanizing agents and different amounts of paraffin oil (dGTR-based mixtures), natural rubber-based rubber mixtures with different dGTR contents and reference rubber mixtures with dGTR-based mixtures (increased vulcanizing agent contents). Cure characteristics showed a plasticizer-like effect of dGTR. Tensile and tear strength decreased drastically with increasing dGTR content; however, elongation at break values did not follow such a trend. Mechanical properties improved with increased vulcanizing agent contents. The examined properties of the samples improved even further with the use of thermomechanically devulcanized samples. Horikx’s analysis showed that this is attributable to moderate polymer chain scission.

EFFECT OF THERMO-OXIDATION ON PERMEATION RESISTANCE OF BROMOBUTYL COMPOUNDS

2017 ◽  
Vol 90 (1) ◽  
pp. 195-206 ◽  
Author(s):  
Richard J. Pazur ◽  
T. Mengistu
Keyword(s):  
Transport Process ◽  
Methyl Salicylate ◽  
Aging Process ◽  
Permeation Rate ◽  
Chemical Agent ◽  
Network Chain ◽  
Diffusion Limited ◽  
Ultimate Properties ◽  
The Impact

ABSTRACT The impact of thermo-oxidation on the permeation process in a series of BIIR or bromobutyl compounds has been investigated. Methyl salicylate (MS) was used as the simulating chemical agent, and the permeation rate was measured gravimetrically using vapometers. Heat aged samples at 120 °C increased in stiffness with an accompanying decline in ultimate properties and network chain density. A reduction in permeability was found, driven primarily by the reduced solubility of MS in the thermo-oxidized BIIR matrix. The formation of a secondary oxidized chain network has been proposed to explain the decline in MS solubility. The loss of plasticizer during the heat aging process is responsible for the reduction of the MS diffusibility. Diffusion-limited oxidation during thermo-oxidation is also a likely factor in affecting the MS transport process.

The Effect of Second Filler on Cure Characteristic and Mechanical Properties of Si-69 Treated Precipitate Silica/NR Composite

2009 ◽  
Vol 79-82 ◽  
pp. 2183-2186 ◽  
Author(s):  
Chanchai Thongpin ◽  
C. Sripetdee ◽  
N. Papaka ◽  
N. Pongsathornviwa ◽  
Narongrit Sombatsompop
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Fly Ash ◽  
Rubber Compound ◽  
Maximum Torque ◽  
Elongation At Break ◽  
Rubber Vulcanizate ◽  
Rubber Compounds ◽  
Cure Time ◽  
Cure Characteristic

Silica has been widely used as non-black reinforcing filler, however, the filler-filler interaction has been an important issue. Cure characteristic and mechanical properties of the rubber compound and rubber vulcanizate were affected both by filler-rubber interaction and filler-filler interaction. There have been, presently, a number of natural fillers which are also used as fillers for the rubber, i.e. fly ash, sawdust and zeolite. This work therefore will study the effect of second filler added into the 13% Si-69 treated precipitate silica (PSi) filled natural rubber compounds. It was revealed that the scorch and cure time of the rubber compound increased with the content of treated PSi. This was the effect of excess of the silane treated onto PSi which would agglomerate and form the cluster of polysiloxane and would then be able to absorb vulcanizing accelerator resulting in extending the scorch and cure time of the rubber compounds. However, this effect was over ruled with the reinforcing effect as could be seen by the increasing, with the contents of PSi, of maximum torque and mechanical properties of the vulcanizates. The NR compounded with treated PSi content of 20 phr selected to study the effect of excess silane on the cure characteristic of hybrid fillers NR composite. The addition of sawdust led to longer scorch time and cure time but not much change of the maximum torque. As expected, the modulus of the rubber vulcanizate increased with the sawdust content whereas the tensile strength and elongation at break decreased with the sawdust content. The incorporation of zeolite could accelerate the cure reaction therefore both scorch time and cure time decreased. The maximum torque also increased with the content of zeolite. Both modulus and tensile strength increased with the content of the zeolite whereas elongation at break tended to be unchanged. In the case of using fly ash as the second filler, the cure time tended to be unchanged. However, the maximum torque tended to be increased with the content of fly ash. It was found that the modulus, tensile strength increased but elongation at break decreased. Interestingly, the excess of Si-69 used effect pronouncedly for the addition of zeolite and fly ash cases as the excess silane could promote the interaction between fillers surface and rubber molecule accept for sawdust

Effect of Methyl Methacrylate Content in Carbon Black Filled Natural Rubber Compounds

2012 ◽  
Vol 501 ◽  
pp. 3-7
Author(s):  
Abu Bakar Rohani ◽  
Mustafa Kamal Mazlina ◽  
Fauzi Mohd Som
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Methyl Methacrylate ◽  
Proton Nuclear Magnetic Resonance ◽  
Performance Parameters ◽  
Rubber Content ◽  
Elongation At Break ◽  
Compression Set ◽  
Rubber Compounds ◽  
Emulsion Polymerisation

Natural rubber-grafted-poly(methyl methacrylate) containing 30 and 50 percent of methyl methacrylate (MMA) monomer per 100 parts by weight of the dry rubber content denoted as NR-g-PMMA 30 and NR-g-PMMA 50, respectively were prepared via emulsion polymerisation technique. The occurrences of graft copolymerisation of PMMA onto NR were confirmed by proton Nuclear Magnetic Resonance (1H NMR) and Fourier Transform Infrared (FTIR) following purifications. The reinforcement of rubber by fillers is of great practical and technical importance. Thus, these fillers are added to rubber formulations to optimize the properties to meet a given application or set of performance parameters. In this study, the effect of carbon black in NR-g-PMMA 30 and NR-g-PMMA 50 rubber compounds were evaluated. Our results demonstrated that tensile strength, elongation at break and compression set reduced, while the hardness and solvent resistance increased in the presence of carbon black filler in comparison to the unfilled compound.

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