Stress Relaxation Measurement as a High-Speed Method for Predicting the Long-Term Behavior of Vulcanized Rubber

1983 ◽  
Vol 56 (1) ◽  
pp. 31-50 ◽  
Author(s):  
R. Clamroth ◽  
L. Ruetz
Keyword(s):  
Stress Relaxation ◽  
High Speed ◽  
Elevated Temperatures ◽  
Pure Oxygen ◽  
Relaxation Measurement ◽  
Hot Air ◽  
Vulcanized Rubber ◽  
Relaxation Measurements ◽  
The Times ◽  
Speed Method

Abstract Intermittent stress relaxation is well suited for quantifying aging processes in rubber. For NR, the effects of different antioxidants can be measured by the rates at which the modulus falls. In synthetic rubbers (SBR, NBR, and CR), it can be measured through the modulus increases caused by oxygen crosslinking. Equal-value times, e.g., t0.75 for NR and t1.25 for SBR, NBR, and CR, are the times taken by the modulus to decrease or increase to a given percentage of its original level. They are better measures of aging than the modulus change after a given time. For NR, it has been shown that stress relaxation measurements at elevated temperatures and in pure oxygen correlate with the results of conventional aging methods. Thus the testing times can be drastically reduced—from up to 28 days to 1–8 hours. Discontinuous stress relaxation measurements are considerably more accurate and selective than conventional oxygen aging. For the repeatability of a single equal-value time measurement, we obtained a coefficient of variation (s/x) of 5–10% for stress relaxation measurement and about ±20% for oxygen aging. The degree of selectivity for oxygen aging and stress relaxation was found to be 3.6 and 18, respectively. The correlation between the results of stress relaxation measurements and those of the conventional oxygen and hot air aging tests was investigated for a large number of NR compounds and for some SBR, NBR, and CR compounds. The correlation is not very good, but it must be remembered that the equal-value times determined according to the two methods show relatively pronounced variability. With the conventional aging methods, the results also depend on what quantity is measured, e.g., the change in tensile strength or hardness, and on what equal-value time is chosen, e.g., the time taken by the property concerned to decrease to 90 or 75% of its original value. The conclusion of the investigations described above is that intermittent modulus measurement is an interesting high-speed method for the assessment of aging behavior. It will acquire a firm position in the arsenal of rubber testing methods, but will probably supplement, and not completely replace, the aging methods currently used.

scholarly journals Numerical Analysis on Effect of Additional Gas Injection on Characteristics around Raceway in Melter Gasifier

2019 ◽  
Vol 38 (2019) ◽  
pp. 837-848
Author(s):  
Du Kaiping ◽  
Gao Xiangzhou ◽  
Sun Haibo
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Gas Injection ◽  
Coke Oven ◽  
Pure Oxygen ◽  
Small Scale ◽  
Gas Temperature ◽  
Fuel Gas ◽  
Hot Air ◽  
Flow Circulation

AbstractThe raceway plays an important role in the mass and heat transportation inside a melter gasifier. Considering that pure oxygen at room temperature instead of hot air is injected into the melter gasifier, a two-dimensional mathematical model at steady state is developed in the current work to describe the effect of the additional gas injection on the characteristics around the raceway in melter gasifier. The results show that a high-speed jet with a highest temperature above 3500 K could be found in front of tuyere. Furthermore, a small scale of gas flow circulation occurs in front of tuyere that results in a more serious thermal damage to tuyere. In order to decrease the gas temperature in the raceway to prevent the blowing-down caused by tuyere damage, the additional gas, including N2, natural gas (NG) and coke oven gas (COG) should be injected through the tuyere. Compared with N2, additional fuel gas injection gives full play to the high temperature reduction advantage of hydrogen. In addition, considering the insufficient hearth heat after injecting NG and the effective utilization of secondary resource, an appropriate amount of COG is recommended to be injected for optimizing blast system.

Tensile Stress—Strain and Stress Relaxation Behavior of Raw Elastomers Using a High Speed Tester

1974 ◽  
Vol 47 (2) ◽  
pp. 307-317 ◽  
Author(s):  
H. H. Bowerman ◽  
E. A. Collins ◽  
N. Nakajima
Keyword(s):  
Stress Relaxation ◽  
High Speed ◽  
Strain Rates ◽  
Time Behavior ◽  
Stress Strain ◽  
Strain Behavior ◽  
Relaxation Measurements ◽  
Ultimate Properties ◽  
Short Time ◽  
Acrylonitrile Copolymers

Abstract A high-speed, tensile-testing device was used to determine the stress—strain behavior of uncompounded butadiene—acrylonitrile copolymers over a range of temperatures and deformation rates. The strain rates were varied from 267 to 26,700 per cent/sec and the temperature was varied from 25 to 97° C. The high-speed tester was also used for stress—relaxation measurements by applying the strain nearly instantly in conformity with theoretical requirements in order to obtain the short time behavior. The WLF equation was obtained from the stress—relaxation data and then used to reduce the ultimate properties to one temperature over four decades of the strain rates. The ultimate properties could be represented by a failure envelope similar to those obtained for vulcanizates.

Stress Relaxation during the Thermal Oxidation of Vulcanized Natural Rubber

1960 ◽  
Vol 33 (2) ◽  
pp. 423-432
Author(s):  
J. R. Dunn ◽  
J. Scanlan ◽  
W. F. Watson
Keyword(s):  
Free Radical ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Thermal Aging ◽  
Elevated Temperatures ◽  
The Other ◽  
Tetramethylthiuram Disulfide ◽  
Oxidative Aging ◽  
Relaxation Measurements ◽  
Cross Links

Abstract The photoinitiated oxidative aging of peroxide vulcanized natural rubber (which contains only carbon-carbon cross-links) was found by stress relaxation measurements to be autocatalytic and to be sensitive to the presence of free radical retarders and catalysts. Similar behavior would be expected in thermal aging. However, earlier work in these laboratories indicated that the thermal aging of peroxide vulcanizates was not autocatalytic. Because of this discrepancy the stress relaxation of peroxide vulcanizates at elevated temperatures has now been reinvestigated and the study has been extended to include also the aging of the other types of networks which are produced on vulcanization by tetramethylthiuram disulfide in the absence of sulfur, by sulfenamide-sulfur, and by sulfur alone.

The Thermal and Oxidative Stability of Chlorosulfonated Polyethylene Vulcanizates as Measured by Stress Relaxation

1971 ◽  
Vol 44 (5) ◽  
pp. 1410-1420
Author(s):  
F. Haaf ◽  
P. R. Johnson
Keyword(s):  
Stress Relaxation ◽  
Elevated Temperatures ◽  
Oxidative Degradation ◽  
Activation Energies ◽  
Polymer Chains ◽  
Chlorosulfonated Polyethylene ◽  
Thermal And Oxidative Stability ◽  
Relaxation Measurements ◽  
Accelerator System ◽  
Interchange Reactions

Abstract Stress relaxation measurements of chlorosulfonated polyethylene vulcanizates show that curing with m-phenylene-bis-maleimide gives thermally more stable crosslinks than the conventional metal oxide/sulfur accelerator system. The superior thermal stability of the bis-maleimide cure is based on the covalent nature of the crosslinks. In conventionally cured vulcanizates interchange reactions of the metal sulfonate and polysulfide crosslinks occur at elevated temperatures. The interchange reactions of the crosslinks cause a rapid stress decline at the beginning of the stress relaxation process. Over longer aging periods stress relaxation due to oxidative degradation becomes apparent in vulcanizates of both types. The activation energies of oxidative stress relaxations are very similar for the bis-maleimide and the conventional cure. The similarity of the activation energies indicates that oxidative degradation follows the same path. The site of the oxidative attack is established for bis-maleimide cured vulcanizates. Oxidative degradation is found to occur in the polymer chains rather than in the crosslinks. The effects of fillers and stabilizers are investigated and their mode of action is explained on the basis of the stress relaxation results.

Chemical Stress-Relaxation and Other Studies on Styrene-Butadiene Rubber

1974 ◽  
Vol 47 (5) ◽  
pp. 1265-1274 ◽  
Author(s):  
S. H. Kalfayan ◽  
R. Rakutis ◽  
R. H. Silver
Keyword(s):  
Stress Relaxation ◽  
Elevated Temperatures ◽  
Activation Energies ◽  
Hydroxyl Group ◽  
Styrene Butadiene Rubber ◽  
Chemical Stress ◽  
Butadiene Rubber ◽  
Relaxation Rates ◽  
Relaxation Measurements ◽  
Styrene Butadiene

Abstract The aging of styrene—butadiene rubber (SBR) was studied by three methods: stress relaxation, infrared spectroscopy, and swelling measurements, with the purpose of supplying information pertinent to understanding the basic mechanism of its aging. Stress-relaxation measurements in air and nitrogen at elevated temperatures indicated that atmospheric oxygen is the principal cause of chemical stress relaxation of SBR, rather than heat. Intermittent stress-relaxation measurements showed scission and crosslinking occurring simultaneously during network breakdown, and it was concluded that random scission in the backbone is indicated to take place in preference to scission in the crosslinks. Activation energies obtained from relaxation rates at several temperatures was 28 ± 0.5 kcal, comparable to literature values of 30 ± 2 kcals. The rates of carbonyl and hydroxyl group formation in SBR in air at various temperatures were determined by ir spectroscopy, both induction and maximum rates, νm, being measured. Activation energies calculated from these rates showed lower values compared to those obtained from stress-relaxation measurements. This may be due to the possibility that the processes being measured are not the same in each case. The three peaks appearing in the carbonyl region were ascribed to carboxyl, ketone, or aldehyde, and perester. The presence of these groups was confirmed by microanalytical methods. The absorption centered at 3450 cm−1 was attributed to hydrogen-bonded OH groups, i.e., alcohols and hydroperoxides. Positive chemical tests were obtained for hydroperoxide. The number of new network chains formed, νe, obtained from swelling measurements agreed well with those obtained from stress-relaxation measurements. It was found that the rate of the number of new network chains formed increased rapidly during the latter states of oxidation.

WIELAND-K88

Alloy Digest ◽  
2005 ◽  
Vol 54 (12) ◽  
Keyword(s):  
Thermal Conductivity ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Stress Relaxation ◽  
Copper Alloy ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
Relaxation Resistance ◽  
Temperature Performance ◽  
Very High

Abstract Wieland K-88 is a copper alloy with very high electrical and thermal conductivity, good strength, and excellent stress relaxation resistance at elevated temperatures. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: CU-738. Producer or source: Wieland Metals Inc.

RED CUT COBALT

Alloy Digest ◽  
1980 ◽  
Vol 29 (8) ◽  
Keyword(s):  
Fracture Toughness ◽  
Cast Iron ◽  
High Speed ◽  
Elevated Temperatures ◽  
High Speed Steel ◽  
Heat Treating ◽  
High Speeds ◽  
Red Hardness ◽  
Nonferrous Alloys ◽  
Cutting Point

Abstract RED CUT COBALT steel is made by adding 5% cobalt to the conventional 18% tungsten -4% chromium-1% vanadium high-speed steel. Cobalt increases hot or red hardness and thus enables the tool to maintain a higher hardness at elevated temperatures. This steel is best adapted for hogging cuts or where the temperature of the cutting point of the tool in increased greatly. It is well adapted for tools to be used for reaming cast-iron engine cylinders, turning alloy steel or cast iron and cutting nonferrous alloys at high speeds. This datasheet provides information on composition, physical properties, and hardness as well as fracture toughness. It also includes information on forming, heat treating, and machining. Filing Code: TS-367. Producer or source: Teledyne Vasco.

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.

Geometrical design of a crystal growth system guided by a machine learning algorithm

CrystEngComm ◽  
2021 ◽  
Author(s):  
Wancheng Yu ◽  
Can Zhu ◽  
Yosuke Tsunooka ◽  
Wei Huang ◽  
Yifan Dang ◽  
...  
Keyword(s):  
Machine Learning ◽  
Crystal Growth ◽  
High Speed ◽  
Learning Algorithm ◽  
Computational Techniques ◽  
Machine Learning Algorithm ◽  
Geometrical Design ◽  
Large Numbers ◽  
Growth System ◽  
Speed Method

This study proposes a new high-speed method for designing crystal growth systems. It is capable of optimizing large numbers of parameters simultaneously which is difficult for traditional experimental and computational techniques.

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