Oxidative Stress Relaxation of Natural Rubber Vulcanized with Di-Tertiary-Butyl Peroxide

1956 ◽  
Vol 29 (3) ◽  
pp. 1043-1046 ◽  
Author(s):  
Svein Ore
Keyword(s):  
Oxidative Stress ◽  
Stress Relaxation ◽  
Carbon Black ◽  
Natural Rubber ◽  
First Grade ◽  
Main Reaction ◽  
Reaction Products ◽  
Hydrogen Atoms ◽  
Tertiary Butyl ◽  
Butyl Peroxide

Abstract It has been shown by Farmer and Moore that natural rubber can be vulcanized with di-tert.-butyl peroxide (DTBP), Presumably the free radicals formed by the unimolecular decomposition of the peroxide abstract some of the more labile (e.g., α-methylenic) hydrogen atoms, leading to direct C—C crosslinks between the rubber molecules, with tert.-butanol and acetone as the main reaction products. This preliminary communication presents some of the results of an investigation of the oxidative stress relaxation of the following types of DTBP vulcanizates. (A) First grade pale crepe, DTBP, and carbon black (MPC) mixed on the mill and vulcanized in a press. The carbon black was added to minimize the deleterious effect of impurities. (B) Purified rubber vulcanized: (1) in aqueous heating media; (2) in the press; (3) in DTBP vapor.

scholarly journals Oxidative Stress Relaxation of Natural Rubber Vulcanized with Di-Tertiary-Butyl Peroxide.

1955 ◽  
Vol 9 ◽  
pp. 1024-1026
Author(s):  
Svein Ore ◽  
Georg Andersson ◽  
Gustav Sundkvist ◽  
Gustav Sundkvist
Keyword(s):  
Oxidative Stress ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Tertiary Butyl ◽  
Butyl Peroxide

Longitudinal Cracking in a Carbon Black Filled Natural Rubber Vulcanizate during Chemical Stress Relaxation

1998 ◽  
Vol 71 (2) ◽  
pp. 157-167 ◽  
Author(s):  
G. R. Hamed ◽  
J. Zhao
Keyword(s):  
Stress Relaxation ◽  
Carbon Black ◽  
Natural Rubber ◽  
Longitudinal Crack ◽  
Chemical Stress ◽  
Loading Direction ◽  
Rubber Vulcanizate ◽  
Edge Cracks ◽  
Forced Air ◽  
Oxidative Attack

Abstract Thin specimens of a black-filled, natural rubber vulcanizate have been held in uniaxial tension at 72°C and 200% elongation in a forced air oven. After substantial oxidative attack (inferred from stress relaxation), small edge cracks formed. Initially, these cracks grew perpendicular to the loading direction, but, upon reaching about 0.1 mm in depth, longitudinal crack growth commenced and fracture progressed by a kind of 0°-peel process with “splitting-off” of successive strands of rubber. This phenomenon is attributed to anisotropy in strength caused both by straining and by oxidative attack.

Pyrolysis of trifluoroacetaldehyde, initiated by di-tertiary-butyl peroxide decomposition

1979 ◽  
Vol 57 (17) ◽  
pp. 2201-2210 ◽  
Author(s):  
Leon F. Loucks ◽  
Michael T. H. Liu ◽  
David G. Hooper
Keyword(s):  
Thermal Decomposition ◽  
Decomposition Product ◽  
Reaction Order ◽  
Methyl Radicals ◽  
Reaction Products ◽  
Decomposition Products ◽  
Tertiary Butyl ◽  
Decomposition Reactions ◽  
Peroxide Decomposition ◽  
Butyl Peroxide

The thermal decomposition of 95:5 mixtures of trifluoroacetaldehyde (TFA) and di-tert-butyl peroxide (DTBP) has been studied at 100 Torr over the temperature range of 390 to 440 K. The major decomposition products included CO, CF3H, CH3COCH3, and CH4 while C2F6, CF3CHOHCH3, CF3CH3, CF3COCH3, C2H6, (CF3)2CHOH, and H2 were also found. In addition to the usual reactions for TFA thermal decomposition, reactions of methyl radicals with TFA to form isopropoxyl radicals were found. The alcohol products result from H atom abstraction reactions of the isopropoxyl radicals while CF3COCH3 is a decomposition product. Arrhenius parameters for several reactions were determined: for DTBP decomposition, log k = 15.82 − 37.73/2.303RT; for H abstraction from TFA by CH3, log k = 8.30 − 7.37/2.303RT; for H abstraction from TFA by CF3, log k = 8.98 − 8.61/2.303RT. Consideration has also been given to several rate constant ratios for the formation and decomposition of isopropoxyl radicals.A study of the reaction order for the formation of CF3H, C2F6, and CH4 showed that the orders were 3/2, 1, and 1 respectively for these three products. A reaction mechanism involving 14 individual steps is proposed to explain the reaction products and the observed orders of reaction.

OXIDATIVE STRESS RELAXATION OF NATURAL RUBBER GUM VULCANIZATES CONTAINING VARIOUS ANTIOXIDANTS. I: EFFECT OF SAMPLE THICKNESS

2017 ◽  
Vol 90 (4) ◽  
pp. 633-641
Author(s):  
Junling Zhao ◽  
G. R. Hamed
Keyword(s):  
Oxidative Stress ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Aging Time ◽  
Oxygen Concentration ◽  
Chain Scission ◽  
Sample Thickness ◽  
Oxygen Absorption ◽  
Square Root ◽  
Diffusion Controlled

ABSTRACT Conventional sulfur-vulcanized natural rubber gums containing various antioxidants have been subjected to oxidative stress relaxation at 72 °C and 25% strain. Oxidation is diffusion controlled, even for samples as thin as 0.15 mm. Assuming that the rate of chain scission is proportional to the rate of oxygen absorption, which previously has been shown to depend on the square root of the oxygen concentration, an equation is derived predicting that stress decay is proportional to aging time to the three-quarters power. Moreover, slopes of these plots are predicted to depend inversely on thickness. Experimental results are in reasonable accord with these predictions.

Effect of Extraction and Rubber Purity on Stress Relaxation of Cumyl Peroxide Vulcanizates

1965 ◽  
Vol 38 (2) ◽  
pp. 370-373 ◽  
Author(s):  
J. R. Dunn
Keyword(s):  
Oxidative Stress ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Natural Antioxidant ◽  
Acetone Extraction

Abstract Oxidative stress relaxation of peroxide vulcanizates of various grades of natural rubber has been investigated at 100° C. The rubbers were examined both with and without hot acetone extraction before or after cure. Highly purified rubber vulcanizates exhibited autocatalytic relaxation, but those based on crepe or smoked sheet did not, because they retained natural antioxidant even after extraction. Autocatalysis was no longer found in extracted purified rubber vulcanizates if these were prepared from a mix containing phenyl-β-naphthylamine. The antioxidant reduced network scission but had less effect upon the amount of crosslinking taking place during aging.

Relaxation Processes in Vulcanized Rubber. III. Relaxation at Large Strains and the Effect of Fillers

1963 ◽  
Vol 36 (3) ◽  
pp. 697-708 ◽  
Author(s):  
A. N. Gent
Keyword(s):  
Stress Relaxation ◽  
Carbon Black ◽  
Natural Rubber ◽  
Progressive Failure ◽  
Large Strains ◽  
Relaxation Processes ◽  
Vulcanized Rubber ◽  
Rubber Vulcanizate ◽  
Finite Extensibility ◽  
Creep And Stress Relaxation

Abstract Some experimental measurements are described of stress relaxation and creep at room temperatures in vulcanizates of natural rubber, butyl, and SBR. In an unfilled natural rubber vulcanizate the rate of stress relaxation is found to rise sharply for extensions of more than about 200%. Reasons are given for attributing this to the growth of a crystalline phase. Similar rates are observed at all extensions for a carbon black filled natural rubber vulcanizate. This is shown to be in satisfactory accord with the Mullins-Tobin model structure for filled vulcanizates, when the whole of the observed relaxation occurs in “softened” regions at rates appropriate to the high local deformations. The failure of rubber-carbon black associations with time does not appear to constitute a major relaxation process. In noncrystallizing unfilled vulcanizates the rate of relaxation is found to decrease somewhat with extension, possibly due to finite-extensibility effects. Preliminary measurements on a filled SBR vulcanizate suggest that a significant contribution to the observed relaxation arises from progressive failure of rubber-filler associations in this case. The relation derived previously between the rates of creep and stress relaxation at equivalent deformations is confirmed in all cases, within experimental error. Its validity in highly-irreversible systems is thus established experimentally.

scholarly journals Lumped Kinetics for Homogeneous Reactions of n-Hexadecane and n-Decene as Model Compounds for PE Pyrolysis Primary Tars

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5466
Author(s):  
Osvalda Senneca ◽  
Teresa Tucciullo
Keyword(s):  
Kinetic Model ◽  
Soot Formation ◽  
Reaction Network ◽  
Kinetic Scheme ◽  
Good Alternative ◽  
Main Reaction ◽  
Residence Times ◽  
Reaction Products ◽  
Hydrogen Atoms ◽  
Gaseous Oxygen

The focus of this paper is to establish a lumped kinetic scheme for secondary reactions of tar produced from pyrolysis of plastics or polymer-based wastes. Notably, the focus is not on the detailed yield of all reaction intermediates and products but on the propensity to form soot. Based on the assumption that that primary tar from pyrolysis of plastic wastes is mostly formed by aliphatics which can undergo progressive aromatization to polycyclic aromatic hydrocarbons (PAHs) and soot, a reaction network with 198 species and 6307 reactions proposed by Ranzi and coworkers was lumped into a very simple five reaction mechanism. The lumped kinetic model has been used to predict PAHs and soot formation in different conditions and proved to be a good alternative to comprehensive kinetic models up for relatively low temperature and short residence times (of up to 1 min at 1200 K, up to 1 s at 1400 K). At higher temperature/longer residence times, the simplified model still provides reasonable qualitative trends but the amount of PAHs and soot is underestimated. The timescale of aromatization under inert conditions appears similar for all the alkanes and alkenes examined and also the yields in main reaction products seem to scale well with the number of carbon and hydrogen atoms of the parent alkane/alkene. Evolution of the young aliphatic tar into large aromatics is prevented as long as gaseous oxygen being available for oxidation. The lumped kinetic model has been used to highlight the effect of different modes of oxygen feeding and of incomplete mixing of fuel and oxygen on the formation of PAH and soot.

Oxidative Stress Relaxation of Natural Rubber Vulcanizates at High Strains

1966 ◽  
Vol 39 (5) ◽  
pp. 1577-1583
Author(s):  
C. L. M. Bell
Keyword(s):  
Oxidative Stress ◽  
Tensile Strength ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
High Strain ◽  
Oxidative Degradation ◽  
Relaxation Measurement ◽  
Premature Failure ◽  
Surface Flaws ◽  
Natural Rubber Vulcanizates

Abstract The effect of high strain on the oxidative stress relaxation of several natural rubber vulcanizates has been investigated. In peroxide and CBS accelerated vulcanizates, the rate of stress relaxation increases with increasing strain, and this increase appears to be due to an increase in the rate of oxidation of the network. TMTD and MBT vulcanizates showed marked premature failure at high strains and no oxidative stress relaxation measurement could be made. The tensile strength of a TMTD vulcanizate was at least 20 per cent higher in vacuum than in oxygen, due, it is believed, to stress-induced oxidative degradation at the tip of surface flaws in the rubber.

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