Effect of thermoelectric nonuniformity of electrodes on readings of a differential thermocouple

Abstract The heat of vulcanization of rubber compounds containing various quantities of sulfur and several organic vulcanization accelerators were traced by means of a differential thermocouple during the vulcanization. The profiles of the heating curves were similar to those obtained in the case of unaccelerated compounds, but the temperature maxima appeared sooner with accelerated than with unaccelerated compounds. The vulcanizates corresponding to the temperature-maxima were analyzed chemically by ordinary methods and the ratios of the free to total sulfur were calculated. They vary a little from 50 per cent, and show that the extent of sulfur combination is not much different from that with unaccelerated compounds. The accelerators tested were hexamethylenetetramine, aldehyde-ammonia diphenylguanidine, di-o-tolylguanidine, p-nitrosodimethylaniline, thiocarbanilide, “Vulkacit P”, “Vulkacit PX”, “Vulkacit M”, and tetramethylthiuramdisulfide The results of the experiments show that these accelerators promote the disaggregation of the micellar structure of rubber (as shown in reports II and III 0. this work) before chemical combination of rubber and sulfur occurs. By thus making the single micelle of rubber smaller, they increase the number of chemical units of rubber coming into reaction with sulfur; i. e., the probability of combination of rubber and sulfur becomes greater. The times for the temperature maxima to appear in the experiments above, which are shortened by accelerators, show that this theory holds good, when it is considered that the temperature maxima correspond to the disaggregation maxima of the rubber hydrocarbon under consideration.

Download Full-text

Differential Thermocouple up to 2450°C and Thermographic Investigation of Refractory Silicides

Advances in Instrumentation ◽

10.1007/978-3-0348-7413-7_49 ◽

1972 ◽

pp. 549-559 ◽

Cited By ~ 1

Author(s):

Ju. A. Kocherzhinsky

Keyword(s):

Differential Thermocouple ◽

Thermographic Investigation

Download Full-text

High-Resolution Differential Thermocouple Measurements Using an Improved Noise Cancellation and Magnetic Amplification Technique

10.1063/1.1627259 ◽

2003 ◽

Author(s):

K. C. Sloneker

Keyword(s):

High Resolution ◽

Noise Cancellation ◽

Differential Thermocouple ◽

Amplification Technique

Download Full-text

Studies of Conditions Affecting the Vulcanization of Rubber. IV. Heat Reaction during Vulcanization

Rubber Chemistry and Technology ◽

10.5254/1.3535499 ◽

1930 ◽

Vol 3 (3) ◽

pp. 384-385

Author(s):

Yutaka Toyabe

Keyword(s):

Electric Furnace ◽

Present Author ◽

Contact Point ◽

Glass Tube ◽

The Other ◽

Thermal Resistivity ◽

Horizontal Line ◽

Differential Thermocouple ◽

The Absolute ◽

Heating Medium

Abstract The heat reaction during vulcanization was traced by means of a differential thermocouple, of which one contact point was placed in a sealed glass tube enclosed in the sample and the other in the heating medium of a small electric furnace, e. g., asbestos yarn windings. Specially prepared rubber precipitated from latex by acetone was milled with varying quantities of sulfur and was vulcanized at 155° C. The heat change was observed during the vulcanization. The curves are shown in Fig. 1. Although the absolute or relative amount of heat evolved seems to be shown by the ordinate of the curves, it is not the case because of the uneven thermal resistivity of the samples. From these curves, therefore, it may only be seen that the profiles of them are similar to each other, showing maximum points at 60 to 70 minutes and decreasing asymptotically to a horizontal line, i. e., the temperature of the heating medium of the furnace. It is observed that the maximum points lie at about the same period, though the sulfur contents of the samples were varied. Similar results are shown by Perks (J. Soc. Chem. Ind., 1926, 142T). The present author analyzed the vulcanizates corresponding to the maximum points of the curves, the results of which are shown in the following table.

Download Full-text