scholarly journals Aging of Natural Rubber in Air and Seawater

2001 ◽  
Vol 74 (1) ◽  
pp. 79-88 ◽  
Author(s):  
P. H. Mott ◽  
C. M. Roland
Keyword(s):  
Natural Rubber ◽  
Oxygen Concentration ◽  
Failure Strain ◽  
Accelerated Aging ◽  
Activation Energies ◽  
Effect Of Temperature ◽  
Arrhenius Law ◽  
Fatigue Lifetime ◽  
Rubber Vulcanizate ◽  
The Difference

Abstract Accelerated aging experiments were carried out on a natural rubber vulcanizate exposed to air and to seawater. Failure strain, shown to correlate well with the fatigue lifetime, was used to monitor the extent of degradation. The effect of temperature on the rate of aging followed an Arrhenius law, with activation energies equal to 90 ± 4 and 63 ± 3 kJ/mol for air and seawater aging, respectively. The difference can be accounted for by the difference in oxygen concentration for the two environments.

Crystallization and the Relaxation of Stress in Stretched Unvulcanized Natural Rubber

1956 ◽  
Vol 29 (4) ◽  
pp. 1195-1198
Author(s):  
A. V. Tobolsky ◽  
G. M. Brown
Keyword(s):  
Natural Rubber ◽  
Temperature Region ◽  
Effect Of Temperature ◽  
Careful Study ◽  
Rubber Vulcanizate ◽  
Crystallization Region ◽  
Different Temperatures ◽  
Made In

Abstract The first observation made in this laboratory in 1946 on the effect of crystallization on stress decay at constant extension was made on a vulcanized Neoprene GN gum stock. It was found that this rubber showed only slight stress decay after 100 hours at 35° C and 50 per cent extension. However, a complete decay of stress to zero stress was observed after only 50 hours at 0° C and 50 per cent extension. Furthermore, the sample after reaching zero stress began to increase in length (spontaneous elongation). This phenomenon was attributed to crystallization. Observations of spontaneous elongation, but no stress decay measurements, were previously reported for vulcanized and unvulcanized natural rubber and for vulcanized and unvulcanized ether polysulfide rubber. It was decided to make a careful study of the effect of temperature and elongation on the stress-decay curves of unvulcanized rubber (cast latex sheet) in the temperature region of crystallization. Some time after these studies were completed, two papers have appeared in which stress decay to zero stress in rubber vulcanizates due to crystallization were reported. In one of these a rather thorough study was made of the decay of stress and change in volume of a natural rubber vulcanizate at −26° C and maintained at four different extension ratios. Our own work on unvulcanized natural rubber was carried out at seven different temperatures in the crystallization region, and were made at five different extension ratios. Quite surprisingly, four of these are the same as were used by Gent. There are interesting differences as well as similarities between our work and the results reported for vulcanized natural rubber.

scholarly journals The Respiration of some Planktonic copepods II. The Effect Of Temperature

1953 ◽  
Vol 31 (3) ◽  
pp. 447-460 ◽  
Author(s):  
D. T. Gauld ◽  
J. E. G. Raymont
Keyword(s):  
Respiratory Rate ◽  
The Body ◽  
The Other ◽  
Effect Of Temperature ◽  
Acartia Clausi ◽  
Temora Longicornis ◽  
Different Temperatures ◽  
Planktonic Copepods ◽  
The Difference ◽  
The Relationship

The respiratory rates of three species of planktonic copepods, Acartia clausi, Centropages hamatus and Temora longicornis, were measured at four different temperatures.The relationship between respiratory rate and temperature was found to be similar to that previously found for Calanus, although the slope of the curves differed in the different species.The observations on Centropages at 13 and 170 C. can be divided into two groups and it is suggested that the differences are due to the use of copepods from two different generations.The relationship between the respiratory rates and lengths of Acartia and Centropages agreed very well with that previously found for other species. That for Temora was rather different: the difference is probably due to the distinct difference in the shape of the body of Temora from those of the other species.The application of these measurements to estimates of the food requirements of the copepods is discussed.

Mechanochemical devulcanization of natural rubber vulcanizate by dual function disulfide chemicals

2016 ◽  
Vol 129 ◽  
pp. 34-46 ◽  
Author(s):  
Soumyajit Ghorai ◽  
Satyaban Bhunia ◽  
Madhusudan Roy ◽  
Debapriya De
Keyword(s):  
Natural Rubber ◽  
Dual Function ◽  
Rubber Vulcanizate

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.

scholarly journals Four Types of LME Cracks in RSW of Zn-Coated AHSS

2020 ◽  
Vol 99 (3) ◽  
pp. 75s-92s ◽  
Author(s):  
SIVA PRASAD MURUGAN ◽  
◽  
YEONG-DO PARK ◽  
VIJEESH VIJAYAN ◽  
CHANGWOOK JI
Keyword(s):  
Tensile Stress ◽  
Synergetic Effect ◽  
High Strength Steels ◽  
High Strength ◽  
Liquid Zinc ◽  
Effect Of Temperature ◽  
Advanced High Strength Steels ◽  
Type D ◽  
The Difference

Zinc-coated advanced high-strength steels are known to be susceptible to liquid metal embrittlement (LME) cracking during resistance spot welding (RSW). Despite numerous reports with regard to LME during RSW, a systematic approach has not been proposed for the classification of cracks based on the cracking mechanism. The objective of this study was to characterize the LME cracks at various RSW locations, and thereby propose a classification method to identify the mechanism of the LME cracks at each location. The experimental results revealed the LME cracks were concentrated at certain weld locations and exhibited different features in terms of length, number, and orientation, owing to the synergetic effect of temperature, stress, microstructure, time of exposure to liquid zinc, and time of exposure to tensile stress at the corresponding lo-cations. Thus, the LME cracks were classified into four categories, namely type A, type B, type C, and type D, based on the formation location. The effect of time of exposure to liquid zinc and tensile stress on LME cracking revealed the time dependency of LME in RSW. The nature of contact be-tween the electrode and the sheet, and the heat input during welding, were found to be the main reasons for the difference in the thermal, mechanical, and metallurgical characteristics of various crack locations, which caused the formation of various LME crack types.

Accelerated Aging and Lifetime Prediction of Graphene-Reinforced Natural Rubber Composites

2018 ◽  
Vol 26 (11) ◽  
pp. 998-1003 ◽  
Author(s):  
Eunjoo Kong ◽  
Bumyong Yoon ◽  
Jae-Do Nam ◽  
Jonghwan Suhr
Keyword(s):  
Natural Rubber ◽  
Accelerated Aging ◽  
Lifetime Prediction ◽  
Rubber Composites ◽  
Natural Rubber Composites
Sign in / Sign up

Export Citation Format

Share Document