Stress relaxation during the thermal oxidation of vulcanized natural rubber

1959 ◽  
Vol 55 ◽  
pp. 667 ◽  
Author(s):  
J. R. Dunn ◽  
J. Scanlan ◽  
W. F. Watson
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Thermal Oxidation

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.

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

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.

Phenothiazine as an Antifatigue Agent for Natural Rubber, Synthetic Polyisoprene and SBR

1965 ◽  
Vol 38 (3) ◽  
pp. 661-665
Author(s):  
Z. N. Tarasova ◽  
I. I. Eitingon ◽  
L. G. Senatorskaya ◽  
T. V. Fedorova ◽  
B. A. Dogadkin
Keyword(s):  
Mechanical Properties ◽  
Synergistic Effect ◽  
Natural Rubber ◽  
Thermal Oxidation ◽  
Fatigue Resistance

Abstract Phenothiazine has no effect on vulcanization of rubber or standard mechanical properties of the vulcanizates. Phenothiazine considerably increases fatigue resistance of vulcanizates of the rubbers studied, under different fatigue conditions. Under the effect of thermal oxidation and repeated deformation phenothiazine or its conversion products combine with the vulcanizate. The phenothiazine does not combine when subjected only to heating. When used with certain inhibitors of oxidation phenothiazine has a synergistic effect.

Study on Dehydration Process of Wet Natural Rubber by Single Screw Dehydrator and Properties of Dry Natural Rubber

2011 ◽  
Vol 418-420 ◽  
pp. 544-547
Author(s):  
Mei Chen ◽  
Fu Quan Zhang ◽  
Yong Zhou Wang ◽  
Mao Fang Huang ◽  
Wei Yong Deng
Keyword(s):  
Natural Rubber ◽  
Thermal Oxidation ◽  
Hammer Mill ◽  
Dehydration Process ◽  
Hot Air Drying ◽  
Single Screw ◽  
Hot Air ◽  
Unit Value ◽  
Better Than ◽  
Dehydration Effect

In this work, one self-invented closed single screw dehydrator was used to dehydrate wet natural rubber, instead of current three opened crepers and one hammer mill at home and abroad. The dehydration technology and the properties of the obtained dry natural rubber were studied. The results show that single screw dehydrator can simplify dehydration process. The water consumption of single screw dehydrator is 20% of current productive technology, meaning a lower wastewater discharge and treatment cost of wastewater. The moisture content of dehydrated natural rubber is lower than 20%, a good dehydration effect. The dry natural rubber dehydrated with single screw dehydrator has an improved thermal-oxidation ageing resistance whether dried by hot-air or microwave. The thermal-oxidation ageing resistance of natural rubber dried by microwave is better than that of hot-air drying, the value of initial plasticity (P0) and plasticity retention index (PRI) are 29.3 unit value and 19.26 unit value greater than that of SCR5 in GB/T 8081, respectively.

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.

Stress relaxation of peroxide and sulfur vulcanizates of natural rubber

1955 ◽  
Vol 18 (88) ◽  
pp. 201-213 ◽  
Author(s):  
J. P. Berry ◽  
W. F. Watson
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber
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