High Temperature Vulcanization of Elastomers

1979 ◽  
Vol 52 (4) ◽  
pp. 725-734 ◽  
Author(s):  
A. K. Bhowmick ◽  
R. Mukhopadhyay ◽  
S. K. De
Keyword(s):  
Thermal Conductivity ◽  
Plastic Material ◽  
Plastic Properties ◽  
Microwave Curing ◽  
The Past ◽  
Vulcanized Rubber ◽  
Upper Limit ◽  
Rubber Compounds ◽  
Higher Temperature ◽  
Made In

Abstract Vulcanization is a process which decreases the plastic properties of rubber while maintaining or improving the elastic properties. The term vulcanization has been applied in the past mainly to the reaction of rubber with sulfur, but now is generally used for the process which results in changes in properties, by sulfur or some other agent. There are four principal changes brought about by vulcanization: (1) rubber is changed from essentially a plastic to a non-plastic material; (2) rubber is changed from a material soluble in a number of solvents to one which is insoluble; (3) rubber is changed to a material with greatly improved physical properties; (4) these properties of vulcanized rubber are maintained over a much wider range of temperature than those of unvulcanized rubber. What is meant by high vulcanizing temperature? There is no unique answer. About 160°C can be taken conveniently as the lower limit; this temperature has been suggested as the highest suitable for some normally compounded sulfur curing rubbers. The upper limit may be 220°C, above which the polymer may begin to degrade. The range in practice extends up to about 250°C in fluid beds and salt baths. Practical vulcanization processes apply heat to the outside of the article being cured and rely on the conduction of heat to the inside. Since no drastic change can be made in the thermal conductivity of practical rubber compounds by compounding modifications, higher temperature is a common method of achieving faster vulcanization. Higher curing temperatures are used in the newer curing or molding processes such as injection molding, the liquid curing medium (LCM) process, and microwave curing.

The Impact Resiliometer

1934 ◽  
Vol 7 (3) ◽  
pp. 591-598 ◽  
Author(s):  
Paul Lüpke
Keyword(s):  
Elastic Properties ◽  
Physical Science ◽  
Sustained Load ◽  
Plastic Properties ◽  
Dual Nature ◽  
Hardness Tester ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
The Impact ◽  
Average User

Abstract Original Purpose The writer's first conception of an instrument for quickly measuring the resilience of rubber samples arose in connection with the basic idea for and development of the present A.S.T.M. hardness tester, in an endeavor to provide a reproducible means of measuring and expressing those properties of rubber compounds superficially apparent to the average user. It seemed that if the resistance to pressure (indenting or flexing) and the pressure, or force, of recovery, of a sample were duplicated, the article produced would “feel” the same as the sample, and under normal conditions of use would act mechanically the same. Nature of Problem This problem of measurement, as is generally known, is complicated by the time-hysteresis characteristic of vulcanized rubber compounds, arising through a dual nature, and causing them to manifest both elastic and plastic properties. Any instrument which applies load momentarily measures the almost purely elastic properties, while one which applies a more or less sustained load measures elastic properties modified by the material's partially plastic nature. These ideas are expressed from commercial and industrial viewpoints without regard to their possible deviations from the strict definitions accepted in physical science.

Measurement of the Absorption of Oxygen by Vulcanized Rubber in Air

1939 ◽  
Vol 12 (2) ◽  
pp. 261-268
Author(s):  
A. G. Milligan ◽  
J. E. Shaw
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Tensile Tests ◽  
Direct Measure ◽  
Mean Values ◽  
Reasonable Time ◽  
Aging Period ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Made In

Abstract It is generally agreed that oxidation is the controlling factor in the decay of rubber compounds. Measurements of the decay of any physical properties—commonly tensile strength—can be made in a convenient time only if the decay is greatly accelerated, and there is always a grave doubt about the equality of the acceleration for different materials. There is also a difficulty in selecting a universally suitable aging period, since the decay of the physical properties is not linear. A direct measure of the rate of oxidation is, in our view, more fundamental and less equivocal. It can, moreover, be made in a reasonable time at a temperature not far removed from service temperatures. Again, whereas tensile tests require several samples of each point in the timecurve to give acceptable mean values, here a single sample suffices for the whole test, and this sample can be simply prepared from a specimen of any form by rasping. The merits and simplicity of the method should commend it to rubber technologists.

Rubber-Lined Equipment. Fundamental Principles of Design

1937 ◽  
Vol 10 (3) ◽  
pp. 564-573 ◽  
Author(s):  
J. R. Hoover ◽  
H. C. Klein
Keyword(s):  
Hydrochloric Acid ◽  
Physical Properties ◽  
Steel Shell ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Wide Range ◽  
Steel Tank ◽  
New Material ◽  
Principles Of Design ◽  
Made In

Abstract IN 1924 a process known as Vulca-lock, discovered by chemists of The B. F. Goodrich Company, made possible the first successful steel tank car for hydrochloric acid service. The tank was lined with acid-resisting vulcanized rubber bonded to the steel shell with adhesion exceeding 500 pounds per square inch. A new material of chemical construction was thus made available in practical form. The resulting widespread and rapidly increasing use of rubber-lined equipment in the processing industries is well known. Basically, the value of such construction lies in properly combining the unique corrosion- and abrasion-resistant properties of rubber with the rigidity, strength, and adaptability of steel or other structural materials. It is essential, therefore, that chemical engineers be familiar with certain principles of design, upon which the successful use of rubber-lined equipment depends. No attempt will be made in this paper to define the broad field of usefulness or the limitations of rubber linings. The fact must be emphasized, however, that an extremely wide range of chemical and physical properties is available in commercial rubber compounds and that these compounds, like metals and alloys, are designed for specific uses.

scholarly journals Limits for thermal conductivity of nanofluids

2010 ◽  
Vol 14 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Chandrasekar Murugesan ◽  
Suresh Sivan
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Particle Shape ◽  
Large Degree ◽  
The Past ◽  
Upper Limit ◽  
Upper Limits ◽  
Transfer Mechanisms

Nanofluids have offered challenges to thermal engineers and attracted many researchers over the past decade to determine the reasons for anomalous enhancement of thermal conductivity in them. Experiments on measurement of nanofluid thermal conductivity have ended in a large degree of randomness and scatter in their values. Hence in this paper, lower and upper limits for thermal conductivity of nanofluids are developed. The upper limit is estimated by coupling heat transfer mechanisms like particle shape, Brownian motion and nanolayer while the lower limit is based on Maxwell's equation. Experimental data from a range of independent published sources is used for validation of the developed limits.

Masonry: the brittle or plastic material?

2019 ◽  
pp. 22-28
Keyword(s):  
Plastic Material ◽  
Experimental Studies ◽  
Point Of View ◽  
Plastic Properties ◽  
Plastic Deformations ◽  
Base Materials ◽  
Stress States ◽  
Creep Deformations ◽  
Structural Point

The results of experimental studies of masonry on the action of dynamic and static (short-term and long-term) loads are presented. The possibility of plastic deformations in the masonry is analyzed for different types of force effects. The falsity of the proposed approach to the estimation of the coefficient of plasticity of masonry, taking into account the ratio of elastic and total deformations of the masonry is noted. The study of the works of Soviet scientists revealed that the masonry under the action of seismic loads refers to brittle materials in the complete absence of plastic properties in it in the process of instantaneous application of forces. For the cases of uniaxial and plane stress states of the masonry, data on the coefficient of plasticity obtained from the experiment are presented. On the basis of experimental studies the influence of the strength of the so-called base materials (brick, mortar) on the bearing capacity of the masonry, regardless of the nature of the application of forces and the type of its stress state, is noted. The analysis of works of prof. S. V. Polyakov makes it possible to draw a conclusion that at the long application of the load, characteristic for the masonry are not plastic deformations, but creep deformations. It is shown that the proposals of some authors on the need to reduce the level of adhesion of the mortar to the brick for the masonry erected in earthquake-prone regions in order to improve its plastic properties are erroneous both from the structural point of view and from the point of view of ensuring the seismic resistance of structures. It is noted that the proposal to assess the plasticity of the masonry of ceramic brick walls and large-format ceramic stone with a voidness of more than 20% is incorrect, and does not meet the work of the masonry of hollow material. On the basis of the analysis of a large number of research works it is concluded about the fragile work of masonry.

South Asian Developmental Crisis (Review Article)

1973 ◽  
Vol 12 (2) ◽  
pp. 181-188
Author(s):  
Rafiq Ahmad
Keyword(s):  
Second World War ◽  
World War ◽  
The Past ◽  
The Great Depression ◽  
Political Independence ◽  
Integrated Theory ◽  
Pass Through ◽  
Developed World ◽  
Second World ◽  
Made In

Like nations and civilizations, sciences also pass through period of crises when established theories are overthrown by the unpredictable behaviour of events. Economics is passing through such a crisis. The challenge thrown by the Great Depression of early 1930s took a decade before Keynes re-established the supremacy of economics. But this supremacy has again been upset by the crisis of poverty in the vast under-developed world which attained political independence after the Second World War. Poverty had always existed but never before had it been of such concern to economists as during the past twenty five years or so. Economic literature dealing with this problem has piled up but so have the agonies of poverty. No plausible and well-integrated theory of economic development or under-development has emerged so far, though brilliant advances have been made in isolated directions.

SCHMELZMETALL HOVADUR CCZ

Alloy Digest ◽  
2020 ◽  
Vol 69 (9) ◽  
Keyword(s):  
Thermal Conductivity ◽  
Spot Welding ◽  
Zirconium Alloy ◽  
High Strength ◽  
Heat Treating ◽  
Softening Temperature ◽  
Aged Condition ◽  
Heat Treated ◽  
High Softening Temperature ◽  
Made In

Abstract Schmelzmetall Hovadur CCZ is a heat-treatable, copper-chromium-zirconium alloy. In the solution heat-treated and artificially aged condition, this alloy exhibits high thermal and electrical conductivity along with high strength and a high softening temperature. Hovadur CCZ evolved from CuCr1 (CW105C), a precipitation-hardenable alloy first made in the 1930s for spot welding electrodes, for which strength and hardness at temperatures up to 500 °C (930 °F), as well as good electrical and thermal conductivity, are essential. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on forming, heat treating, machining, and joining. Filing Code: Cu-912. Producer or source: Schmelzmetall AG.

850.0 and 852.0 ALUMINUM ALLOY BEARING BARS

Alloy Digest ◽  
1988 ◽  
Vol 37 (9) ◽  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Heat Treating ◽  
Light Metal ◽  
General Purpose ◽  
High Ductility ◽  
Higher Temperature ◽  
Bearing Alloy

Abstract 850.0 ALUMINUM Alloy can be considered the general purpose light metal bearing alloy. Its good thermal conductivity keeps operating temperatures low. It has high ductility. In many applications it has been found to be superior to steel backed bearings. 852.0 ALUMINUM Alloy has higher mechanical properties making it suitable for heavier load and higher temperature applications. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear strength. It also includes information on corrosion resistance as well as heat treating and machining. Filing Code: Al-290. Producer or source: Federated Bronze Products Inc..

Mass Spectrometry Techniques: Principles and Practices for Quantitative Proteomics

2020 ◽  
Vol 21 ◽  
Author(s):  
Rocco J. Rotello ◽  
Timothy D. Veenstra
Keyword(s):  
Mass Spectrometry ◽  
Quantitative Proteomics ◽  
Protein Identification ◽  
Dynamic Nature ◽  
Complete Coverage ◽  
The Past ◽  
Proteome Level ◽  
A Cell ◽  
Quantitative Changes ◽  
Made In

: In the current omics-age of research, major developments have been made in technologies that attempt to survey the entire repertoire of genes, transcripts, proteins, and metabolites present within a cell. While genomics has led to a dramatic increase in our understanding of such things as disease morphology and how organisms respond to medications, it is critical to obtain information at the proteome level since proteins carry out most of the functions within the cell. The primary tool for obtaining proteome-wide information on proteins within the cell is mass spectrometry (MS). While it has historically been associated with the protein identification, developments over the past couple of decades have made MS a robust technology for protein quantitation as well. Identifying quantitative changes in proteomes is complicated by its dynamic nature and the inability of any technique to guarantee complete coverage of every protein within a proteome sample. Fortunately, the combined development of sample preparation and MS methods have made it capable to quantitatively compare many thousands of proteins obtained from cells and organisms.

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