Some Properties of Vulcanized Rubber under Strain - Degree of Crystallization as Calculated from Temperature Coefficient of Elastic Tension

1951 ◽  
Vol 43 (2) ◽  
pp. 362-365 ◽  
Author(s):  
B. B. S. T. Boonstra
Keyword(s):  
Temperature Coefficient ◽  
Vulcanized Rubber ◽  
Degree Of Crystallization

Some Properties of Vulcanized Rubber under Strain. Degree of Crystallization as Calculated from Temperature Coefficient of Elastic Tension

1951 ◽  
Vol 24 (4) ◽  
pp. 845-852
Author(s):  
B. B. S. T. Boonstra
Keyword(s):  
Natural Rubber ◽  
Temperature Coefficient ◽  
Thermodynamic Calculation ◽  
Energy Change ◽  
Thermodynamic Evaluation ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Calorimetric Measurements ◽  
Degree Of Crystallization

Abstract To elucidate the crystallization phenomenon in natural rubber and to investigate the applicability of thermodynamic calculation to measurements of the elastic tension as a function of temperature, it seemed necessary to check whether crystallization determined by x-ray analysis (and combined with density) lined up reasonably with the percentage of crystallization computed from the energy change found by applying thermodynamics to stretched vulcanized rubber) on stretching. Calorimetric measurements were desirable, as no accurate figures are available for the heat of crystallization of rubber crystallites. The heat of melting of rubber crystallites was determined to about 66 joules per gram, which is of the same order as that of isoprene. The spreading in the results was large; the determination is based on the degree of crystallization found by x-ray analysis of raw rubber. The heat of crystallization on stretching, found by thermodynamic evaluation of the elastic tension and its temperature coefficient, is combined with the value of 66 joules for the heat of melting of the pure rubber crystallites. The degree of crystallization calculated in this way agrees reasonably well with the direct x-ray measurements of Goppel and Arlman. Crystallization as determined by x-ray analysis and that responsible for the energy change on stretching are much the same. This also means that thermodynamic evaluation of the change of stress with temperature is justified if pufficient relaxation of stress has taken place.

The Degree of Crystallinity in Natural Rubber. IV. The Degree of Crystallization in Frozen Raw Rubber and Stretched Vulcanized Rubber

1950 ◽  
Vol 23 (2) ◽  
pp. 310-319 ◽  
Author(s):  
J. M. Goppel ◽  
J. J. Arlman
Keyword(s):  
Natural Rubber ◽  
Experimental Evidence ◽  
Theoretical Investigation ◽  
Degree Of Crystallinity ◽  
X Ray ◽  
Crystallization Point ◽  
Vulcanized Rubber ◽  
Degree Of Crystallization ◽  
The Degree Of Crystallinity

Abstract An improved x-ray technique has been worked out to determine the degree of crystallinity in natural rubber. Inaccuracies which sometimes occur in quantitative x-ray measurements were eliminated, and it has been shown that the amount of crystalline rubber, both in frozen samples of raw rubber and in stretched vulcanized rubber, could be determined fairly accurately. More experiments were carried out and the results are described. These results, which confirm the current views on the problem of crystallization, point to relatively low degress of crystallization, even in highly stretched rubber, and they agree with some other experimental evidence and with a recent theoretical investigation.

An X-Ray Study of the Proportion of Crystalline and Amorphous Components in Stretched Rubber

1941 ◽  
Vol 14 (3) ◽  
pp. 555-571 ◽  
Author(s):  
J. E. Field
Keyword(s):  
Physical Properties ◽  
Structural Characteristics ◽  
Quantitative Measure ◽  
Crystalline Material ◽  
Amorphous Halo ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Maximum Value ◽  
Degree Of Crystallization ◽  
And Performance

Abstract A method is described for obtaining a quantitative measure of crystalline hydrocarbon present in stretched rubber samples by comparing the intensities of the diffraction spots and the amorphous halo appearing in the x-ray diagrams. This method has been applied to a study of the crystallinity of stretched vulcanized rubber as it is affected by different vulcanization accelerators, variations in extension, temperature, and cure. To illustrate a connection between the physical performance of a rubber vulcanizate and its degree of crystallization, measurements were made of the relation of crystallinity to creep when the rubber was stretched to different initial elongations under constant loads. The creep as a function of the elongation has a maximum value at the same intermediate elongation for which crystallization becomes appreciable. At higher elongations, increased crystallinity results in a diminution of the creep. The ultimate strength and extensibility generally associated with stretched vulcanized rubber is the result of the combined effect of primary valence cross-linkages formed by vulcanization and the formation of crystallites caused by stretching. Crystallization is an important factor in maintaining the relatively high strengths of vulcanizates having a greater range of extensibilities. In general, the physical properties and performance of vulcanized rubber is related to the amount of crystalline material formed on stretching, which depends on the structural characteristics of the vulcanizate.

The Dependence of the Stress on the Temperature of Rubber Elongated to a Constant Degree

1939 ◽  
Vol 12 (3) ◽  
pp. 520-528 ◽  
Author(s):  
V. Hauk ◽  
W. Neumann
Keyword(s):  
Temperature Coefficient ◽  
Absolute Temperature ◽  
Experimental Results ◽  
Constant Degree ◽  
Vulcanized Rubber ◽  
The Absolute

Abstract An instrument for measuring stresses was constructed, whereby changes in tension brought about by changes in temperature in rubber maintained at constant elongation were measured. These measurements were carried out with three types of vulcanizates. After measures were taken in the case of weakly vulcanized samples to eliminate the disturbing factors arising from crystallization, the fact was established that stress is directly proportional to the absolute temperature for all types of vulcanized rubber, as required by theory. It is shown that under some conditions the stress-temperature coefficient depends on the degree of vulcanization, the coefficient decreasing with increase in the degree of vulcanization. The experimental results are discussed, and an explanation is offered to account for the dependence of the stress-temperature coefficient on the degree of vulcanization.

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.

EVANOHM

Alloy Digest ◽  
1960 ◽  
Vol 9 (4) ◽  
Keyword(s):  
Electrical Resistivity ◽  
Low Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Temperature Coefficient ◽  
Base Alloy ◽  
Nickel Base Alloy ◽  
Temperature Coefficient Of Resistance ◽  
High Electrical Resistivity ◽  
Nickel Base

Abstract EVANOHM is a nickel-base alloy having low temperature coefficient of resistance and high electrical resistivity. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on joining. Filing Code: Ni-57. Producer or source: Wilbur B. Driver Company.

EVANOHM ALLOY S

Alloy Digest ◽  
1989 ◽  
Vol 38 (7) ◽  
Keyword(s):  
Electrical Resistivity ◽  
Corrosion Resistance ◽  
Physical Properties ◽  
Tensile Properties ◽  
Temperature Coefficient ◽  
Electromotive Force ◽  
Temperature Coefficient Of Resistance ◽  
Resistance Wire ◽  
High Electrical Resistivity ◽  
Optimum Stability

Abstract EVANOHM alloy S offers optimum stability and flexibility with regard to both size and required temperature coefficient of resistance. Its extremely low electromotive force vs copper together with its high electrical resistivity are highly desirable properties in a precision resistance wire. This datasheet provides information on composition, physical properties, and tensile properties. It also includes information on corrosion resistance as well as joining. Filing Code: Ni-373. Producer or source: Wilbur B. Driver Company.

ISO-ELASTIC

Alloy Digest ◽  
1957 ◽  
Vol 6 (8) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Low Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Temperature Coefficient ◽  
Nickel Alloy ◽  
Modulus Of Elasticity ◽  
Heat Treating ◽  
Precision Instrument ◽  
Iron Nickel

Abstract ISO-ELASTIC is an iron-nickel alloy having low temperature coefficient of the modulus of elasticity. It is suitable for precision instrument springs. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and machining. Filing Code: Fe-14. Producer or source: John Chatillon & Sons.

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