Oxidative stress relaxation of natural rubber vulcanizates at high strains

1965 ◽  
Vol 9 (9) ◽  
pp. 3101-3109 ◽  
Author(s):  
C. L. M. Bell
Keyword(s):  
Oxidative Stress ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Natural Rubber Vulcanizates

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.

Aging of Natural Rubber Vulcanizates in the Presence of Dithiocarbamates

1959 ◽  
Vol 32 (3) ◽  
pp. 739-747 ◽  
Author(s):  
J. R. Dunn ◽  
J. Scanlan
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Protective Action ◽  
Dicumyl Peroxide ◽  
Vulcanized Rubber ◽  
Aging Properties ◽  
Photochemical Aging ◽  
Natural Rubber Vulcanizates

Abstract The thermal and photochemical aging of extracted dicumyl peroxide-, TMTD (sulfurless)- and santocure-vulcanized rubber, in presence of a number of metal and alkylammonium dithiocarbamates, has been investigated by measurements of stress relaxation. The dithiocarbamates have a considerable protective action upon the degradation of peroxide- and TMTD-vulcanizates, but they accelerate stress decay in santocure-accelerated vulcanizates. The reasons for this behavior are discussed. It is suggested that the excellent aging properties of unextracted TMTD vulcanizates are due to the presence of zinc dimethyldithiocarbamate formed during vulcanization.

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.

Stress Relaxation during the Photoxidation of Peroxide Crosslinked Rubber

1960 ◽  
Vol 33 (2) ◽  
pp. 433-444
Author(s):  
J. R. Dunn ◽  
J. Scanlan ◽  
W. F. Watson
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Physical Properties ◽  
Chemical Reactions ◽  
Small Extent ◽  
Organic Peroxides ◽  
Physical Measurement ◽  
Crosslinked Networks ◽  
Photochemical Aging ◽  
Natural Rubber Vulcanizates

Abstract The chemical reactions involved in the thermal and photochemical aging of natural rubber vulcanizates are largely unknown. Experimental difficulties have precluded direct chemical investigation owing to the insolubility of the crosslinked networks and the small extent of reaction required for a great deterioration in physical properties. Accordingly recourse has been made to physical measurement. Tobolsky et al. (e.g. Ref. (1)) have shown that the relaxation in stress on holding a rubber strip at constant extension during aging is a convenient experimental measure capable of interpretation in terms of network breakdown. In photochemical studies the opacity of conventional sulfur vulcanizates provides a further complication. In the present work, the stress relaxation technique has been used in a study of the degradation by 365 mµ radiation of the comparatively transparent and chemically simple rubber networks obtained after crosslinking by organic peroxides.

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.

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
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