Stress relaxation of natural rubber during irradiation

1969 ◽  
Vol 7 (4) ◽  
pp. 725-733 ◽  
Author(s):  
D. Evans ◽  
J. T. Morgan ◽  
R. Sheldon ◽  
G. B. Stapleton
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber

Effects of accelerator type on stress relaxation behavior and network structure of aged natural rubber/chloroprene rubber vulcanizates

2016 ◽  
Vol 49 (5) ◽  
pp. 381-396 ◽  
Author(s):  
Farzad A Nobari Azar ◽  
Murat Şen
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Network Structure ◽  
Structural Changes ◽  
Relaxation Behavior ◽  
Stress Relaxation Behavior ◽  
Rubber Blends ◽  
Chloroprene Rubber ◽  
Weather Changes ◽  
Behavior Network

Natural rubber/chloroprene rubber (NR/CR) blends are among the commonly used rubber blends in industry and continuously are exposed to severe weather changes. To investigate the effects of accelerator type on the network structure and stress relaxation of unaged and aged NR/CE vulcanizates, tetramethyl thiuram disulfide, 2-mercaptobenzothiazole, and diphenyl guanidine accelerators have been chosen to represent fast, moderate, and slow accelerator groups, respectively. Three batches have been prepared with exactly the same components and mixing conditions differing only in accelerator type. Temperatures scanning stress relaxation and pulse nuclear magnetic resonance techniques have been used to reveal the structural changes of differently accelerated rubber blends before and after weathering. Nonoxidative thermal decomposition analyses have been carried out using a thermogravimetric analyzer. Results indicate that there is a strong interdependence between accelerator type and stress relaxation behavior, network structure, cross-linking density, and aging behavior of the blends. Accelerator type also affects decomposition energy of the blends.

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.

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.

Relaxation Processes in the Deformation of Unloaded Rubbers and the Influence of the Degree of Vulcanization

1951 ◽  
Vol 24 (4) ◽  
pp. 810-819
Author(s):  
B. A. Dogadkin ◽  
M. M. Reznikovskii˘
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Elastic Deformation ◽  
Relaxation Processes ◽  
Spatial Network ◽  
Relaxation Properties ◽  
Constant Rate ◽  
Different Temperatures ◽  
Kinetics Of

Abstract 1. It is shown that the process of stress relaxation at different initial elongations as well as the process of deformation at constant rate for unloaded rubbers at different temperatures (20–70° C) can be represented quantitatively by equations suggested in earlier works. Likewise the possibility of expanding the theories proposed for the kinetics of high-elastic deformation of spatial polymers is substantiated. 2. It is shown that the relaxation properties of soft unloaded vulcanizates of natural rubber and many synthetic rubbers do not undergo essential changes during vulcanization. 3. The conjecture is expressed that the invariability of the relaxation properties during vulcanization continues until the bonds of the spatial network are distributed sufficiently widely not to influence the activity or heat movement of the chain segments between them.

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.

Crystallization and Stress Relaxation in Highly Stretched Samples of Natural Rubber and Its Synthetic Analogue. Volume 39, Number 15, July 25, 2006, pp 5100−5105.

2006 ◽  
Vol 39 (19) ◽  
pp. 6784-6784 ◽  
Author(s):  
M. Tosaka ◽  
D. Kawakami ◽  
K. Senoo ◽  
S. Kohjiya ◽  
Y. Ikeda ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Synthetic Analogue
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