Temperature Coefficient of Vulcanization

1940 ◽  
Vol 13 (2) ◽  
pp. 255-261
Author(s):  
R. H. Gerke
Keyword(s):  
Temperature Coefficient ◽  
Long Range ◽  
Plastic Flow ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Low Temperatures ◽  
Elevated Temperatures ◽  
Manufacturing Processes ◽  
Rubber Industry ◽  
Vulcanized Rubber

Abstract One hundred years ago rubber was the only available substance having the property of long-range elasticity which makes rubber so useful to man. The invention of vulcanization tremendously increased the usefulness of rubber, since it decreased the plastic flow at elevated temperatures and increased the resistance to hardening at low temperatures. It is now the general consensus that vulcanization is caused by a chemical reaction or at least is attended by a chemical reaction. The fact that vulcanization is the result of a chemical reaction is an all-important factor in controlling the nature of the manufacturing processes in the rubber industry. The existence of a temperature coefficient of vulcanization like other chemical reactions exerts a powerful influence on the nature of the manufacturing processes. Thus, vulcanized rubber is made by a thermosetting rather than thermoplastic process.

Mechanism of Rubber Vulcanization with Sulfur

1938 ◽  
Vol 11 (1) ◽  
pp. 107-130
Author(s):  
W. K. Lewis ◽  
Lombard Squires ◽  
Robert D. Nutting
Keyword(s):  
Natural Rubber ◽  
Temperature Coefficient ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Complex Behavior ◽  
Double Bonds ◽  
Irreversible Reaction ◽  
Sulfur Addition

Abstract THAT vulcanization of rubber with sulfur always involves a chemical reaction consisting in the addition of sulfur to the double bonds of the rubber molecule has been conclusively established (18, 28). The facts indicate that this addition of sulfur to rubber is an irreversible reaction (31). The temperature coefficient of the reaction is high, increasing about 2.65 fold per 10° C. at ordinary curing temperatures (31). Furthermore, the reaction is apparently exothermic (4, 24). It is noteworthy that catalysts are apparently necessary, since synthetic rubbers prepared from pure materials add sulfur slowly, if at all. The proteins and perhaps the resins in natural rubber undoubtedly serve as accelerators. The curves for combined sulfur vs. time of cure for typical mixes are shown in Figures 1 and 2. Figure 1 is taken from the data of Kratz and Flower (16); the composition and temperature of cure for this mix are shown in Cranor's Table I (9). Figure 2, curve 1, is from Table I of Eaton and Day (10), and curve 2 from data obtained in this laboratory (27, Table I). Superficial inspection of these curves shows extraordinary divergence of type. Figure 1 is a typical fadeaway curve, characteristic of most chemical reactions, where the reaction rate decreases with decreasing concentration of the reacting materials. Curve 1, Figure 2, is an entirely different type, where the rate of sulfur addition is constant until nearly 70 per cent of the initial sulfur has reacted. Curve 2, Figure 2, shows even more complex behavior. Again the rate is constant in the initial portions of the cure. However, following this period, the rate increases markedly but later falls off, approaching zero, to give an S-shaped eurve.

scholarly journals A Note on the Variation of the Rate of Disinfection with Change in the Concentration of the Disinfectant

1908 ◽  
Vol 8 (4) ◽  
pp. 536-542 ◽  
Author(s):  
Herbert Edmeston Watson
Keyword(s):  
Temperature Coefficient ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Empirical Law ◽  
Different Temperatures ◽  
Original Number ◽  
Time Required ◽  
Image Position ◽  
Number Of Bacteria

In a recent paper by Miss Chick on “The Laws of Disinfection”, it was pointed out that disinfection of bacteria is strictly analogous to a chemical reaction in which individual bacteria play the part of molecules. Thus, if n be the number of bacteria present at any time t during dis-infection, , where K is a constant. Also, if K1, K2 are these constants for two different temperatures is also constant, i.e. Arrhenius' formula for the temperature coefficient of chemical reactions holds good in the case of bacteria as well. In addition to this, it was found that the relation between the concentration of the disinfectant and the time of disinfection (that is, the time required to reduce the original number of bacteria by a given percentage) might abe approximately expressed by the empirical lawwhere C is the concentration at time t.

TECHALLOY NICKEL 200

Alloy Digest ◽  
1977 ◽  
Vol 26 (6) ◽  
Keyword(s):  
Physical Properties ◽  
Surface Treatment ◽  
Low Temperatures ◽  
Nickel Alloys ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
General Purpose ◽  
Commercially Pure ◽  
Electrical Components ◽  
Nickel 200

Abstract TECHALLOY Nickel 200 is commercially pure wrought nickel. It maintains good strength at elevated temperatures and is tough and ductile at low temperatures. It is a general-purpose material when the properties of nickel alloys are not needed. Its many uses include spun and cold-formed parts, electrical components, transducers and nickel-cadmium batteries. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on forming, heat treating, machining, joining, and surface treatment. Filing Code: Ni-246. Producer or source: Techalloy Company Inc..

Normal approximations for distributions arising in the stochastic approach to chemical reaction kinetics

1981 ◽  
Vol 18 (01) ◽  
pp. 263-267 ◽  
Author(s):  
F. D. J. Dunstan ◽  
J. F. Reynolds
Keyword(s):  
Reaction Kinetics ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Stochastic Approach ◽  
Algebraic Functions ◽  
Chemical Reaction Kinetics ◽  
Normal Approximations ◽  
Formal Solutions

Earlier stochastic analyses of chemical reactions have provided formal solutions which are unsuitable for most purposes in that they are expressed in terms of complex algebraic functions. Normal approximations are derived here for solutions to a variety of reactions. Using these, it is possible to investigate the level at which the classical deterministic solutions become inadequate. This is important in fields such as radioimmunoassay.

Dynamic Indentation of Copper and an Aluminium Alloy with a Conical Projectile at Elevated Temperatures

1965 ◽  
Vol 180 (1) ◽  
pp. 285-294 ◽  
Author(s):  
F. U. Mahtab ◽  
W. Johnson ◽  
R. A. C. Slater
Keyword(s):  
Strain Rate ◽  
Aluminium Alloy ◽  
Temperature Coefficient ◽  
Elevated Temperatures ◽  
Dynamic Pressure ◽  
Pure Metal ◽  
Dynamic Indentation ◽  
Strain Rate Effects ◽  
Dynamic Temperature ◽  
Temperature Range

The dynamic indentation of copper (B.S. 1433) and an aluminium alloy (B.S. 1476 HE 10) has been investigated, using cylindro-conical projectiles fired from an air-actuated gun. The experiments were performed with impact velocities varying between 1000 and 2500 in/s and at elevated temperatures up to 600°C for the copper and 550°C for the aluminium alloy. The magnitude of the corresponding range of mean strain rate was then 103-104/s, depending upon the material; impact velocity and temperature (see Appendix I). For the range of impact velocities investigated no consequential transition temperature † was encountered. The dynamic temperature coefficient† thus remained constant throughout the test temperature range for each material. This dynamic temperature coefficient was found to be equal to the static temperature coefficient corresponding to the sub-transitional temperature range for the respective materials. The mean effective dynamic indentation pressure is shown to decrease with temperature but the ratio of this dynamic pressure to the static indentation pressure increases with temperature. Strain rate effects for both materials were negligible for sub-transitional temperatures but become important at super-transitional temperatures. It was observed that the parameters on which the strain rate effect depends are in some way related to the absolute melting point of a pure metal.

Chemical Structure of Vulcanized Rubber

1939 ◽  
Vol 12 (1) ◽  
pp. 43-55
Author(s):  
J. R. Brown ◽  
E. A. Hauser
Keyword(s):  
Chemical Structure ◽  
Empirical Knowledge ◽  
Extensive Investigation ◽  
Practical Application ◽  
True Nature ◽  
Rubber Industry ◽  
Vulcanized Rubber ◽  
Metallic Salts ◽  
Other Substances

Abstract A CENTURY ago, Charles Goodyear in America and Th. Hancock in England found that the properties of crude rubber could be greatly improved by heating it with sulfur. The product resulting was more elastic, more resistant to tear and abrasion, less affected by solvents, and decidedly less thermoplastic. The treatment of rubber to give these desired properties is known generally as vulcanization and must be considered as the basis for the enormous growth of the rubber industry and the extensive use of rubber products in our everyday life. Broadly speaking, vulcanization involves the reaction, in some fashion, of sulfur with rubber. Extensive investigation has revealed other substances, such as benzoyl peroxide or polynitrobenzenes, which can transform rubber into a “vulcanized” condition. Experience has also shown that metallic salts of zinc or lead and especially certain organic compounds called “accelerators” greatly affect the rate of vulcanization, and these are favorably employed in practice. A vast amount of empirical knowledge has been gained which has greatly improved the practical application of vulcanization and the quality of rubber products, but which has failed as yet to reveal a complete picture of the true nature of the process.

THE INTERACTION OF ENZYMES AND HORMONES

PEDIATRICS ◽  
1960 ◽  
Vol 26 (3) ◽  
pp. 476-481
Author(s):  
Abraham White
Keyword(s):  
Direct Effect ◽  
Chemical Reactions ◽  
Elevated Temperatures ◽  
Enzyme System ◽  
Enzymic Activity ◽  
Hormone Interaction ◽  
Indirect Influence ◽  
Rare Exception ◽  
Hormonal Action

The majority of living forms depend for their functioning upon two classes of biocatalysts, the enzymes and the hormones. These biocatalysts permit the diverse chemical reactions of the organism to proceed at 38°C with a specificity and at rates frequently unattainable in vitro at elevated temperatures with similar reactants. The physiologic importance of enzymes and hormones is evident not only under normal circumstances, but is reflected clinically in the diverse descriptions of errors of metabolism, due to lack or deficiency of one or more enzymes, and the numerous hypo- and hyperfunctioning states resulting from imbalance of hormonal supply. Inasmuch as both enzymes and hormones function, with rare exception, to accelerate the rates of processes in cells, investigators have sought possible interrelationships and interactions of enzymes and hormones, particularly as a basis for the mechanism of hormonal action. It has seemed logical to hypothesize that hormones, while not essential for reactions to proceed but nevertheless affecting the rates of reactions, may function by altering either the concentration or activity of the prime cellular catalysts, the enzymes. This proposed influence of hormones on enzymic activity might be a primary, direct effect achieved by the hormone participating as an integral part of an enzyme system, or an indirect influence based upon the hormone altering the concentration of available enzyme and/or substrate utilized by a particular enzyme. It is the purpose of this presentation to describe a relatively few, but better defined, examples of the more direct relationships of enzymes and hormones. Five examples of enzyme-hormone interaction will be presented, based on the criterion that an effect of the hormone has been demonstrated on addition of the hormone in vitro to a purifled, or partially purified, enzyme system.

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