The Oxidation Products of Rubber

1939 ◽  
Vol 12 (2) ◽  
pp. 225-234
Author(s):  
A. van Rossem ◽  
P. Dekker
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperature ◽  
Tensile Properties ◽  
High Speed ◽  
Accelerated Aging ◽  
Direct Determination ◽  
Oxidation Products ◽  
Vulcanized Rubber

Abstract In their summary of the aging of vulcanized rubber, Porritt and Scott state that three factors are responsible for the changes in mechanical properties of vulcanized rubber during aging, viz.: (a) oxidation of the rubber; (b) after-vulcanization; (c) some colloidal change of the rubber, sometimes termed aggregation. Of these factors, oxidation is by far the most important because it is responsible for the decrease in mechanical properties, which leads to the general deterioration of rubber from a technical standpoint. It was Marzetti who proved that the decrease of mechanical properties in accelerated aging is due to oxidation. Later, Kohman confirmed this in a more concise way and showed that even such small amounts as 0.5% of oxygen absorbed by vulcanized rubber are sufficient to decrease tensile properties to 50% of their original value. When studying aging, three ways of tackling this problem are possible, viz.: (1) Investigations of the mechanical properties, either under normal conditions, or under special conditions such as elevated temperature or high speed. (2) Determination of oxidation products, which are formed during oxidation of the rubber. (3) Direct determination of the amount of oxygen which is absorbed by the rubber. It is clear that any of these methods may be combined with accelerated aging tests.

The Direct Determination of Oxygen in Rubber. The Adaptation of the Ter Meulen Method to Rubber and Its Application to the Study of Aging

1939 ◽  
Vol 12 (2) ◽  
pp. 269-282 ◽  
Author(s):  
H. I. Cramer ◽  
I. J. Sjothun ◽  
L. E. Oneacre
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Direct Determination ◽  
Sulfur Poisoning ◽  
Oxidation Products ◽  
Oxygen Bomb ◽  
Vulcanized Rubber ◽  
Relationship Of ◽  
The Relationship

Abstract The ter Meulen method for the direct determination of oxygen has been adapted, with modifications, to the analysis of raw and vulcanized rubbers. Raney nickel has been found to be quite effective as the reducing catalyst and to be satisfactorily resistant to sulfur poisoning. The method has been applied to the study of the aging of vulcanized rubber in the Geer oven and oxygen bomb. From this study the following conclusions may be drawn: (1) The increase in combined oxygen is greater in the oxygen bomb than in the Geer oven. (2) Deterioration of rubber in the oxygen bomb involves oxidation primarily, whereas that occurring in the Geer oven involves not only oxidation but also thermal decomposition followed by volatilization of oxidation products. (3) The effectiveness of an antioxidant in retarding the absorption of oxygen in oxygen-bomb aging agrees well with its ability to maintain the physical properties of the stock in which it is present. (4) The deterioration in physical properties of a rubber stock in the oxygen bomb during the early stages of aging is a linear function of the increase in combined oxygen. For stocks containing antioxidants and diphenylguanidine as the accelerator, an increase in combined oxygen of approximately 1.2% corresponds to a decrease in tensile strength of 50%. (5) The relationship of increase in combined oxygen to decrease in tensile strength seems to be affected not only by antioxidants, but also by accelerators of vulcanization.

The use of a high-speed digital computer for the direct determination of crystal structures. I

1955 ◽  
Vol 227 (1171) ◽  
pp. 486-500 ◽  
Keyword(s):  
Crystal Structure ◽  
Fourier Series ◽  
Crystal Structures ◽  
Digital Computer ◽  
High Speed ◽  
Electronic Computer ◽  
Direct Determination ◽  
Direct Methods ◽  
Weighting Factor

A method is described whereby an electronic computer, the EDSAC, may be used to select a set, or sets, of signs for the coefficients F (h) of a Fourier series, such that the Fourier series, satisfies a certain condition. This condition is expressed as X ≡ Ʃ h Ʃ h ' P (h,h') S (h) S (h') S (h+h')≽ X 0 , where S (h) denotes the sign of F (h) and P (h, h') is a weighting factor related to the probability that S (h) S (h') = S (h+h'). In certain circumstances the determination of a crystal structure which is beyond the range of other direct methods is possible by this procedure.

Determination of Tensile Properties of Power Plant Steels by Testing of Miniature Specimens

2013 ◽  
Author(s):  
Ivan Klevtsov ◽  
Andrei Dedov
Keyword(s):  
Mechanical Properties ◽  
Power Plant ◽  
Flat Plate ◽  
Tensile Properties ◽  
Standard Size ◽  
Term Operation ◽  
University Of Technology ◽  
Miniature Specimens

Long-term operation of the power plant components in the conditions of the creep leads to the degradation of the short-term mechanical properties of the material. Therefore, in order to predict the degree of the metal degradation and integrity of the component the determination of the mechanical properties of the actual component in service material is required. Since the standard tests requiring a significant volume of sample material cannot be applied the technique of the tensile testing of miniature flat plate specimens has been developed in Tallinn University of Technology and described in this paper. The results of the tests of miniature flat plate specimens have been compared with testing results of cylindrical specimens with standard size and at the same time the comparison has shown a good agreement of the results. The data analysis has also shown the high repeatability of the tests results of miniature specimens. Thus, the developed technique of the miniature flat plate specimens testing could be considered as accurate and reliable method and could be definitely used for evaluation of the tensile properties of the metal.

The use of a high-speed digital computer for the direct determination of crystal structures. II

1957 ◽  
Vol 243 (1233) ◽  
pp. 281-288 ◽  
Keyword(s):  
High Speed ◽  
Electronic Computer ◽  
Direct Determination ◽  
Preceding Paper ◽  
Contour Maps ◽  
Unknown Structure ◽  
New Criterion ◽  
High Degree ◽  
Selection Of

This paper discusses some possible procedures for crystal structure determination using the X criterion developed in the preceding paper of the series. In that paper it was shown that, under favourable circumstances, the signs of the largest terms in the Fourier series representa­tion of ρ , the electron density in the unit cell, can be determined directly. The magnitudes of these terms can be found by experiment. In less favourable cases the correct set of signs, to a high degree of probability, lies among several hundred possible sets which can be determined by the processes described. A new criterion is proposed for selection of a lesser number, say a dozen, ‘most probable’ sets of signs. These latter sets can be tested by inspection of the corre­sponding contour maps of ρ . The new criterion has been successfully used in determining the unknown structure of nitroguanidine. Techniques for the selection of most probable sets and also for evaluation of ρ at suitable points in space using an electronic computer, the EDSAC, are described.

scholarly journals RECYCLING OF CONSTRUCTION WASTE USING HIGH-SPEED MILLING PROCESS: DETERMINATION OF WASTE CONCRETE

2019 ◽  
Vol 22 ◽  
pp. 88-93
Author(s):  
Zdeněk Prošek ◽  
Pavel Tesárek ◽  
Jan Trejbal ◽  
Tereza Horová
Keyword(s):  
High Speed ◽  
Direct Determination ◽  
Microscopic Analysis ◽  
Mechanical Tests ◽  
Milling Process ◽  
High Speed Milling ◽  
X Ray ◽  
Waste Concrete ◽  
Recycled Material

This paper deals with the use of high-speed milling process for recycling old concrete and direct determination of the potential of input waste. For this purpose, three different types of waste concrete were used: prefabricated railway sleeper, structural concrete of monolithic pillar and prefabricated drainage gutter. The paper directly examines the chemical and phase composition by XRF, X-Ray Diffraction (XRD), Energy Dispersive X-ray Spectrometry (EDS) and microscopic analysis, particle size distribution and pH of the recycled material. Results of those analysis are used to select suitable recycled material. The suitability of choice is supported by mechanical tests of 28-day old cement pastes, where the compressive strength and dynamic modulus of elasticity are observed properties. Specimens measuring 40 × 40 × 160mm are composed of 70 wt.% Portland cement and rest is micronized concrete. In all cases, the results are compared with the reference material.

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