Temperature Coefficient of Vulcanization of Buna-S

1944 ◽  
Vol 17 (2) ◽  
pp. 412-420
Author(s):  
La Verne E. Cheyney ◽  
Robert W. Duncan
Keyword(s):  
Temperature Coefficient ◽  
Chemical Nature ◽  
The United States ◽  
Rate Of Change ◽  
Effect Of Temperature ◽  
Physical Test ◽  
Temperature Coefficients ◽  
Chemical Combination ◽  
General Range

Abstract Temperature coefficient of vulcanization may be defined as the increase in time of vulcanization necessary to produce a given property in the vulcanizate per unit range of temperature decrease, the latter being taken usually as either 10° F or 10° C. Coefficients of vulcanization for natural rubber stocks have been determined by several investigators. Although the data vary somewhat with the worker and with the stock investigated, the general range of temperature coefficients is close to 2.0 per 10° C. This is regarded as evidence of the chemical nature of the vulcanization reaction. The values obtained from physical test data do not always agree with those from combined sulfur analyses. This has been interpreted as an indication that the chemical reaction between the rubber and sulfur is not a simple bimolecular one, and that the rate of change of physical properties is not directly related to the rate of chemical combination of rubber and sulfur. A number of studies were published recently on the effect of variables on the vulcanization of Buna-S (now called GR-S in the United States) and on the properties of the resulting vulcanizates. In addition, compounding reports have been issued by manufacturers of rubber chemicals, as well as confidential reports submitted to the Rubber Director's office by rubber manufacturers. None of the published investigations, however, have been concerned with the determination of numerical relations among the properties of vulcanizates obtained at various temperatures. The properties of Buna-S vulcanizates differ markedly from those of rubber in certain characteristics, while possessing certain similarities in others. The only published mention of the effect of temperature on Buna-S stocks was in a release from the office of the Rubber Director, giving tables for conversion of cure to a standard temperature. These tables are based on a temperature coefficient of 1.43 per 10° F. The source of this information is not available, however.

scholarly journals Boundary lubrication.—The temperature coefficient

1922 ◽  
Vol 101 (713) ◽  
pp. 487-492 ◽  
Keyword(s):  
Experimental Method ◽  
Temperature Coefficient ◽  
Boundary Lubrication ◽  
Static Friction ◽  
Effect Of Temperature ◽  
Dry Air ◽  
Electric Grids ◽  
Continuous Sheet ◽  
A Current

The experimental method employed was that described in earlier papers. A slider having a spherical face is made to slide over a plate in an atmosphere of rigorously clean and dry air. The friction measured is static friction and the object of the experiments the determination of the effect of temperature. This has now been studied over a range of 15°C. to 110°C., and it may be said at once that the relations discovered are of a totally unexpected character. More than one attempt to study the effect of temperature was defeated by the fact that lubricating vapours were given off from the walls of the chamber in which the plate and slider were enclosed. This difficulty was completely removed by using a chamber with double walls, the inner wall being a continuous sheet of nickel. Between the walls were placed the electric grids for heating the chamber. The stream of dry air with which the chamber was flooded was also heated by being passed through a tube of silica, which was maintained at the required temperature by a coil of wire through which a current was passing. The temperature of the stream of air and the temperature of the chamber were recorded electrically.

scholarly journals The effect of temperature on the viscosity of air

1926 ◽  
Vol 110 (753) ◽  
pp. 141-167 ◽  
Keyword(s):  
Kinetic Theory ◽  
Temperature Coefficient ◽  
Effect Of Temperature ◽  
Kinetic Theory Of Gases ◽  
Molecular Models ◽  
Large Measure ◽  
Viscosity Coefficients ◽  
Molecular Forces ◽  
Coefficient Of Viscosity

The Kinetic Theory of Gases leads to a number of relations between the diffusion, conductivity and viscosity coefficients of gases, and the large measure of confirmation of these has been the greatest triumph of that theory. Most of these relations have been shown by S. Chapman and Enskog to be independent of any particular model of the molecule. In the case of the dependence of viscosity upon temperature, however, the theory gives different results for different molecular models, and the determination of the temperature coefficient of viscosity can therefore be of service in the elucidation of molecular forces.

scholarly journals XX.—The Bifilar Magnetometer, its Errors and Corrections, including the Determination of the Temperature Coefficient for the Bifilar employed in the Colonial Observatories

1861 ◽  
Vol 22 (3) ◽  
pp. 467-489
Author(s):  
John Allan Broun
Keyword(s):  
Temperature Coefficient ◽  
Royal Society ◽  
Temperature Coefficients

In 1845, a paper by me on the balance magnetometer was read to the Royal Society of Edinburgh (see Trans. vol. xvi. p. 67), which contained an examination of some of the difficulties to be considered and overcome in relation to that instrument. No similar examination has yet appeared, as far as I am aware, of the bifilar magnetometer. When it is considered that the value of the results obtained from this instrument in so many observatories is dependent on an exact knowledge and elimination or correction of its errors; and, as will appear hereafter, that the temperature coefficients employed in the discussion of the Colonial observations are in some cases so erroneous that the unconnected observations would have been nearer the truth than after correction, the following communication may not appear unnecessary.

scholarly journals DETERMINATION OF THE STANDARD RESISTOR TEMPERATURE COEFFICIENTS AND THEIR UNCERTAINTIES

2019 ◽  
Vol 21 (3) ◽  
pp. 219
Author(s):  
Muhammad Azzumar ◽  
Lukluk Khairiyati ◽  
Agah Faisal
Keyword(s):  
Temperature Coefficient ◽  
Numerical Approach ◽  
Alpha Coefficient ◽  
Measurement Result ◽  
Temperature Coefficients ◽  
Taylor Series Approximation ◽  
Measurement Results ◽  
Beta Coefficient ◽  
Definition Of

<p>SNSU TK-BSN’s capability in determining the temperature coefficients of a standard resistor has been improved. The temperature coefficient is one of the important parameter in determining the definition of the standard resistor. Currently, the measurement result has been reported together with the measurement uncertainty. The determination itself is based on a numerical approach of Taylor Series Approximation (TSA) instead of based on a fitting to a certain equation. And by this determination, the uncertainty was calculated. The determination was validated by comparing the measurement result committed by SNSU TK-BSN to that of by the manufacturer. The equation for the temperature coefficient follows the parabolic equation with an alpha coefficient of -5.30 x 10-8 Ω/Ω/°C and beta coefficient of -4.70 x 10-8 Ω/Ω/°C<sup>2</sup>, with the respective uncertainties of 2.4 x 10-8 Ω/Ω/°C and 1.6x 10-8 Ω/Ω/°C<sup>2</sup>, respectively. SNSU TK-BSN measurement results in determining the temperature coefficient in agreement with the manufacturer's measurement results show an appropriate value. This correspondence has an equivalent degree of 0.20 for the alpha temperature coefficient and 0.27 for the beta coefficient.</p>

Effect of Temperature and Pressure on Oxygen Pressure Aging

1943 ◽  
Vol 16 (2) ◽  
pp. 453-465 ◽  
Author(s):  
A. M. Neal ◽  
H. G. Bimmerman ◽  
J. R. Vincent
Keyword(s):  
Temperature Coefficient ◽  
Oxygen Pressure ◽  
The State ◽  
Effect Of Temperature ◽  
Individual Study ◽  
Aging Rate ◽  
Temperature Coefficients ◽  
Pressure Test ◽  
Temperature And Pressure

Abstract An increase in the temperature of the oxygen pressure test from 70° to 80° C greatly increases the rate of aging of rubber vulcanizates. The temperature coefficients of aging rate for the six stocks tested vary between 1.63 and 3.48. The state of cure markedly affects the temperature coefficient of some stocks. It is obvious that no change in the specification from 70° to 80° C should be made without first determining the temperature coefficient of the stock involved. A decrease in the pressure of the oxygen pressure test decreases the rate of aging, but the rate is not proportional to pressure. The relative rates of aging between 0.5 and 300 pounds oxygen pressure for the stocks tested vary between 1.09 and 4.87 for the normal cures, and between 1.50 and 6.74 for the longer cures. The state of cure markedly affects the change in rate of aging with change in pressure. The data show that changes in the pressure of the oxygen pressure test must be accompanied by a revision of all aging specifications, which will involve an individual study of each stock and every cure of each stock, since no correlation between stocks seems to exist for the changes in rate of aging that occur with changes in pressure.

State-by-State Use of AMA Guides

2019 ◽  
Vol 24 (5) ◽  
pp. 3-7, 16
Keyword(s):  
Expert Testimony ◽  
Narrow Range ◽  
The United States ◽  
Workers Compensation ◽  
Federal Employees ◽  
Permanent Disability ◽  
Sixth Edition ◽  
History Of ◽  
Canadian Provinces

Abstract This article presents a history of the origins and development of the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), from the publication of an article titled “A Guide to the Evaluation of Permanent Impairment of the Extremities and Back” (1958) until a compendium of thirteen guides was published in book form in 1971. The most recent, sixth edition, appeared in 2008. Over time, the AMA Guides has been widely used by US states for workers’ compensation and also by the Federal Employees Compensation Act, the Longshore and Harbor Workers’ Compensation Act, as well as by Canadian provinces and other jurisdictions around the world. In the United States, almost twenty states have developed some form of their own impairment rating system, but some have a narrow range and scope and advise evaluators to consult the AMA Guides for a final determination of permanent disability. An evaluator's impairment evaluation report should clearly document the rater's review of prior medical and treatment records, clinical evaluation, analysis of the findings, and a discussion of how the final impairment rating was calculated. The resulting report is the rating physician's expert testimony to help adjudicate the claim. A table shows the edition of the AMA Guides used in each state and the enabling statute/code, with comments.

Current perspectives in antithrombotic therapy

2001 ◽  
Vol 21 (03) ◽  
pp. 82-96 ◽  
Author(s):  
D. Hoppensteadt ◽  
O. Iqbal ◽  
R. L. Bick ◽  
J. Fareed
Keyword(s):  
Blood Coagulation ◽  
Antithrombotic Therapy ◽  
Thrombotic Event ◽  
The United States ◽  
Vascular Thrombosis ◽  
Common Cause ◽  
Coagulation Protein ◽  
Coronary Events ◽  
Platelet Defects

SummaryThrombotic disorders are the most common cause of death in the United States. About two million individuals die each year from an arterial or venous thrombosis or related disorders. About 80% to 90% of all cases of thrombosis can now be defined with respect to cause. Of these, over 50% occur in patients who harbor a congenital or acquired blood coagulation protein or platelet defect which caused the thrombotic event. It is obviously of major importance to define those individuals harboring such a defect as this allows: 1) appropriate antithrombotic therapy to decrease risks of recurrence; 2) determination of the length of time the patient must remain on therapy for secondary prevention; and 3) allow for testing of family members of those harboring a blood coagulation protein or platelet defect which is hereditary (about 50% of all coagulation and platelet defects mentioned above). Aside from mortality, significant additional morbidity occurs from both arterial or venous thrombotic events, including, but not limited to paralysis (non-fatal thrombotic stroke), cardiac disability (repeated coronary events), loss of vision (retinal vascular thrombosis), fetal waste syndrome (placental vascular thrombosis), stasis ulcers and other manifestations of post-phlebitic syndrome, etc.

Performance Testing of Coal Fired Power Plants

2007 ◽  
Author(s):  
Shane E. Powers ◽  
William C. Wood
Keyword(s):  
Power Plant ◽  
Power Plants ◽  
Performance Test ◽  
Model Development ◽  
Performance Testing ◽  
The United States ◽  
Plant Performance ◽  
Cycle Performance ◽  
Test Program

With the renewed interest in the construction of coal-fired power plants in the United States, there has also been an increased interest in the methodology used to calculate/determine the overall performance of a coal fired power plant. This methodology is detailed in the ASME PTC 46 (1996) Code, which provides an excellent framework for determining the power output and heat rate of coal fired power plants. Unfortunately, the power industry has been slow to adopt this methodology, in part because of the lack of some details in the Code regarding the planning needed to design a performance test program for the determination of coal fired power plant performance. This paper will expand on the ASME PTC 46 (1996) Code by discussing key concepts that need to be addressed when planning an overall plant performance test of a coal fired power plant. The most difficult aspect of calculating coal fired power plant performance is integrating the calculation of boiler performance with the calculation of turbine cycle performance and other balance of plant aspects. If proper planning of the performance test is not performed, the integration of boiler and turbine data will result in a test result that does not accurately reflect the true performance of the overall plant. This planning must start very early in the development of the test program, and be implemented in all stages of the test program design. This paper will address the necessary planning of the test program, including: • Determination of Actual Plant Performance. • Selection of a Test Goal. • Development of the Basic Correction Algorithm. • Designing a Plant Model. • Development of Correction Curves. • Operation of the Power Plant during the Test. All nomenclature in this paper utilizes the ASME PTC 46 definitions for the calculation and correction of plant performance.

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