Structure and Properties of Loaded Rubber Mixtures. X. Alteration of Carbon Black Structures by Heat Treatment

1953 ◽  
Vol 26 (4) ◽  
pp. 821-831 ◽  
Author(s):  
B. A. Dogadkin ◽  
K. Pechkovskaya ◽  
Ts Mil'man
Keyword(s):  
Heat Treatment ◽  
Carbon Black ◽  
Electric Resistivity ◽  
Structure And Properties ◽  
Prolonged Heating ◽  
Carbon Blacks ◽  
Exponential Law ◽  
Carbon Structures ◽  
Carbon Carbon Bonds ◽  
Carbon Bonds

Abstract 1. Raising the temperature of vulcanizates containing carbon black causes changes in the carbon structures, which can be estimated by the value of specific electric resistivity ρ and the index n in the equation: I=cVn, relating the strength of the current I with the voltage V. 2. These changes are nearly independent of the type of rubber and are governed chiefly by the type of carbon black. 3. The change of electric resistivity of vulcanizates with temperature follows an exponential law, and can be expressed by the equation : ρt=ρ0 eαt. 4. The sign of the coefficient α is negative for vulcanizates containing channel carbon black, and positive for those containing nozzle black or lamp black. 5. Heating of vulcanizates (up to 100°) for 30 minutes causes destruction of the nozzle black and lamp black particles, but causes little apparent destruction of channel black structures. 6. Prolonged heating (10 hours or more) at temperatures above 60° C causes destruction of the particles of all the carbon blacks studied. This detruction is more extensive in the case of nozzle and lamp blacks than in the case of channel black. 7. During heat treatment of mixtures containing channel black, it is chiefly the carbon-rubber bonds that are destroyed (the index n decreases); whereas in mixtures containing nozzle, furnace and lamp blacks, it is chiefly the carbon-carbon bonds that are destroyed (the index n increases). 8. The higher the temperature during deformation and relaxation, the greater is the degree of restoration of the carbon structures which are destroyed during deformation. 9. The degree of restoration of the carbon structures under identical conditions of deformation and relaxation of vulcanizates containing nozzle black is greater than that of corresponding vulcanizates containing channel black.

Structure and Properties of Loaded Rubber Mixtures. IX. Modification of Carbon Structures by Repeated Deformations

1953 ◽  
Vol 26 (4) ◽  
pp. 810-820 ◽  
Author(s):  
K. Pechkovskaya ◽  
Ts Mil'man ◽  
B. Dogadkin
Keyword(s):  
Carbon Black ◽  
Small Proportion ◽  
Electric Resistivity ◽  
Structural Development ◽  
Carbon Structure ◽  
Rubber Mixture ◽  
Carbon Blacks ◽  
Opposite Case ◽  
Carbon Carbon Bonds ◽  
Carbon Bonds

Abstract 1. The structure of the carbon black phase of a rubber-carbon black vulcanizate is characterized first of all by a specific number of rubber-carbon black and carbon black-carbon black bonds (or contacts) and, in turn, by a specific proportion of these two types of bond. 2. The total number of bonds in the carbon structure, or the degree of their development, is indicated by the specific electric resistivity ρ of the vulcanizate, which decreases with the development of this structure. 3. Measurement of the proportion of carbon-carbon bonds in the structure establishes the factor n of the equation I=CVn, relating the energy of the current which flows through the test-specimen to the constant by the difference of the potentials. If n=1, all the bonds in the carbon structure which take part in the transmission of the current are of the carbon-carbon type, and the rubber mixture possesses a purely ohmic conductivity; in all other cases n>1. 4. During the deformation of loaded vulcanizates, changes of the specific resistivity ρ, and also of the factor n, take place. In the first cycle of stretching, ρ at first increases and then decreases slightly. During recovery after stressing, the electric resistivity sharply increases, reaching after the stress is removed a value several times greater than the maximum on the p curve of the first cycle of deformation. In succeeding deformation cycles, the change of resistivity proceeds with relatively slight hysteresis effects. 5. In the deformation of loaded rubbers, the weaker bonds are largely destroyed, and consequently the proportion of bonds of the stronger type increases. In cases where the carbon-carbon bonds are stronger than the rubber-carbon bonds, the value of n after deformation is smaller than that of n0 before deformation, or n0/n>1; in the opposite case, n0/n<1. 6. Both parameters (n and ρ) depend on the type of rubber; their greatest values, corresponding to a less developed structure with a small proportion of carbon-carbon bonds, are observed in the case of butadiene-styrene rubber; in sodium-butadiene rubbers, the degree of structural development and proportion of carbon-carbon bonds are much higher; the most highly developed carbon structure and the greatest proportion of carbon-carbon bonds are found in Butyl and natural rubbers. Hence, the value of n0/n is hardly related to the type of rubber. 7. Both parameters also depend on the type of carbon black. The most highly developed structures, with a large proportion of carbon-carbon bonds, are observed with channel carbon black, where these bonds are stronger than the rubber-carbon bonds, i.e., n0/n>1. The least developed structure, with a small proportion of carbon-carbon bonds, is observed with nozzle black and lampblack, in which cases these bonds are weaker than the rubber-carbon bonds, i.e., n0/n<1. Furnace blacks occupy an intermediate position. Thus, the carbon blacks studied are classified according to the value of n and the relation n0/n in the same sequence as when classified according to their reinforcing effects. The possible causes of this distribution are discussed. 8. The great strength of the bond between the particles of more active (channel) carbon blacks is one of the reasons for the greater heat formation in rubbers containing these carbons. Heat formation in rubbers containing less active carbon blacks (nozzle black, lamp black) which possess a weaker bond between their particles when all other conditions are equal, is much less.

ADSORPTION STUDIES ON A SERIES OF HEAT TREATED SHAWINIGAN ACETYLENE CARBON BLACKS

1957 ◽  
Vol 35 (12) ◽  
pp. 1542-1554 ◽  
Author(s):  
J. M. Holmes ◽  
R. A. Beebe
Keyword(s):  
Heat Treatment ◽  
Carbon Black ◽  
Low Oxygen ◽  
Carbon Blacks ◽  
Heat Treated ◽  
Treated Carbon ◽  
Derivatives Of ◽  
Graphitic Material ◽  
Acetylene Carbon ◽  
Acetylene Carbon Black

An experimental study has been made of the adsorption of a nitrogen, sulphur dioxide, carbon dioxide, and ammonia on Shawinigan acetylene carbon black and several derivatives of this material produced by heat treatment up to temperatures of 3000°. The effect of the heat treatment of the Shawinigan carbon black on its adsorption of the polar and non-polar gases studied is compared with the behavior of other heat treated carbon blacks. In particular, the effect of the low oxygen content of the Shawinigan black is considered. The isosteric heats of adsorption for ammonia on the most highly graphitized material (Shawinigan 3000) have been calculated. The results are in general agreement with previous calorimetric work of this laboratory. A special type of hysteresis for the system ammonia – Shawinigan black has been observed. This may be due to a reversible swelling of the graphitic material.

Structure and Properties of Carbon Black - Changes Induced by Heat Treatment

1953 ◽  
Vol 45 (8) ◽  
pp. 1721-1725 ◽  
Author(s):  
W. D. Schaeffer ◽  
W. R. Smith ◽  
M. H. Polley
Keyword(s):  
Heat Treatment ◽  
Carbon Black ◽  
Structure And Properties

Effects of the Types of Rubber and Carbon Black on the Formation of Carbon-Rubber Gel

1959 ◽  
Vol 32 (4) ◽  
pp. 1185-1191
Author(s):  
Z. V. Chernykh ◽  
V. G. Epshtein
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Gel Formation ◽  
Active Carbons ◽  
Carbon Blacks ◽  
Bond Stability ◽  
Carbon Structures ◽  
Bound Rubber

Abstract 1. Carbon-rubber gels are formed in mixtures containing all the types of carbon black tested (channel, acetylene, nozzle, furnace, thermal) and not only active carbons. 2. The amount of carbon-rubber gel formed depends on the amount of carbon black added. With carbon blacks which readily form continuous carbon structures (channel, acetylene) the amounts of gel are greater than with nonstructural blacks, for the same amount of black added. 3. The amount of gel is greater in synthetic than in natural rubber mixtures. 4. More intense extraction conditions do not cause disappearance of the gel, but increase the amount of bound rubber and decrease the amount of carbon in the gel. 5. The carbon-rubber gels formed from structural carbons contain larger amounts of bound rubber. 6. It is suggested that bond stability between carbon black particles (characterized by the formation of a carbon black structure) is one of the basic causes of carbon-rubber gel formation.

Microstructural Variations in Commercial Carbon Blacks

1968 ◽  
Vol 41 (2) ◽  
pp. 356-372 ◽  
Author(s):  
W. M. Hess ◽  
L. L. Ban ◽  
F. J. Eckert ◽  
V. Chirico
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Carbon Black ◽  
Crystallite Size ◽  
Surface Activity ◽  
Chain Structure ◽  
Rate Of Change ◽  
Degree Of Crystallinity ◽  
Crystallite Orientation ◽  
Carbon Blacks

Abstract Conventional and diffracted beam electron microscopy can be used to resolve the ultimate crystallite units in standard and heat treated carbon blacks. They are very sensitive in the detection of small differences in crystallite size and orientation. Combined with x-ray diffraction methods and conventional vulcanizate testing, high resolution electron microscopy appears to be a useful and practical means to study carbon black surface activity. All commercial blacks appear to conform in part to the Heckman and Harling concentric crystallite model. Surface activity appears to be related to the extent of this alignment; the less the tangential orientation of the graphite layer planes to the surface, the greater the surface activity. Heating carbon blacks in an inert atmosphere for varying times and temperatures (850 to 1400° C) causes a gradual depression of surface activity with increasing treatment severity, defined by increases in the size and concentric orientation of surface crystallites. At no time was the effect of carbon black on vulcanizate properties changed significantly by heat treatment without disrupting the initial orientation of surface crystallites. Carbon blacks differ in the rate of change of crystallite orientation in response to heat treatment. The initial degree of crystallinity, porosity, and surface volatile content all appear to affect the rate of crystallite orientation and growth. Increases in average crystallite height, Lc, are a good measure of effects of heat treatment in excellent agreement with changes in surface crystallite size and orientation observed with the electron microscope. Commercial ISAF carbon blacks of varied structure have relatively minor differences in surface crystallite orientation, indicating small differences in surface activity. The higher modulus and treadwear associated with the use of high structure blacks appear to be predominantly a result of the chain structure itself. Further evidence was obtained showing that black structure and surface activity are independent properties each of which can have a significant influence on vulcanizate properties such as modulus, treadwear, and hysteresis.

scholarly journals Broad scope gold(i)-catalysed polyenyne cyclisations for the formation of up to four carbon–carbon bonds

2017 ◽  
Vol 15 (10) ◽  
pp. 2163-2167 ◽  
Author(s):  
Zhouting Rong ◽  
Antonio M. Echavarren
Keyword(s):  
Single Step ◽  
Simultaneous Formation ◽  
Broad Scope ◽  
Carbon Carbon Bonds ◽  
Carbon Bonds ◽  
First Time ◽  
High Stereoselectivity

The polycyclisation of polyeneynes catalyzed by gold(i) has been extended for the first time to the simultaneous formation of up to four carbon–carbon bonds, leading to steroid-like molecules with high stereoselectivity in a single step with low catalyst loadings.

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