Some Results Obtained in a Study of the Development of Stickiness by Vulcanized Rubber

1953 ◽  
Vol 26 (1) ◽  
pp. 136-142
Author(s):  
Lucien Toullec
Keyword(s):  
Natural Aging ◽  
Advanced Stage ◽  
Agent System ◽  
Experimental Conditions ◽  
Oxygen Bomb ◽  
Vulcanized Rubber ◽  
Aging Conditions ◽  
Small Capacity ◽  
Extreme State

Abstract The experiments described in the present paper show the possibility of reproducing artificially the stickiness which appears during natural aging, and the results show the experimental conditions which are most favorable to a study of the phenomenon. The indications are that it is best to use an oxygen bomb of small capacity, at a temperature of 60–70° C, and with a pressure of 1–4 kg. per sq. cm. of oxygen. The factor which under no conditions must be disregarded if almost certain failure is to be avoided is unquestionably the problem of ventilation. The Geer oven does not seem to be of any service in such experimentation. The appearance of stickiness during aging is not indicative of an advanced stage of deterioration, but is a manifestation of one form or type of aging rather than the consequence of an extreme state of deterioration. Finally, the influence of certain factors has been established. As far as factors inherent to the rubber mixtures themselves are concerned, the accelerator-vulcanizing agent system plays a determinant part. The character of the phenomenon depends on the aging conditions, particularly on the rate of oxidation. The tendency of a vulcanizate to become sticky on aging is particularly great when the temperature is relatively low and the pressure of oxygen is likewise low.

Accelerated Aging of Vulcanized Rubber. Factors Determining the Relation between Oven and Bomb Aging

1947 ◽  
Vol 20 (3) ◽  
pp. 760-768 ◽  
Author(s):  
R. G. Newton ◽  
J. R. Scott
Keyword(s):  
Accelerated Aging ◽  
Natural Aging ◽  
Relative Importance ◽  
Temperature Coefficients ◽  
Vulcanized Rubber ◽  
Relative Response ◽  
Aging Conditions ◽  
Moderate Range ◽  
Natural Rubber Vulcanizates ◽  
Theoretical Considerations

Abstract A study has been made of the influence of the following factors on the relative rates of tensile deterioration of natural rubber vulcanizates in the Geer oven and oxygen bomb, both at 70° C : period of vulcanization, sulfur ratio, nature of accelerator. Expressing this relation as the oven/bomb ratio, i.e., the ratio between oven and bomb aging periods that give the same deterioration, the following conclusions are drawn. (1) Varying the period of vulcanization of a given mix over a moderate range (2:3) around the optimum does not noticeably alter the oven/bomb ratio, except in unaccelerated mixes, where overvulcanization gave an abnormally low ratio, owing to the rubber perishing very rapidly in the oven. (2) The effect of varying the sulfur ratio within the usual limits for soft rubbers is small, and appears to result from the quicker vulcanization of the mixes richer in sulfur. (3) The nature of the accelerator profoundly affects the ratio, values ranging from 3 to 27 being found among the present mixes ; this effect is believed to be exerted through the influence of the accelerator both on rate of vulcanization and on the oxidizability of the vulcanizate. Theoretical considerations indicate that a rubber which vulcanizes quickly and (or) oxidizes slowly should give a low oven/bomb ratio, whereas one that vulcanizes slowly and(or) oxidizes quickly should give a higher ratio. The experimental data are generally in accord with this, and there is evidence that both rate of vulcanization and oxidizability can have an important effect, but the data do not enable the separate effect of each to be assessed exactly. The bearing of the results on the use of the oven and bomb tests is briefly discussed. It is shown that they demonstrate the fallacy of using a single factor for converting oven to bomb aging periods or vice versa, and that the relative natural aging resistances of widely different vulcanizates cannot be reliably assessed by either test, a limitation arising from the fact that the relative importance of oxidative decay and aftervulcanization varies from one type of mix to another, and that the temperature coefficients of these processes are not necessarily the same. These facts are very important in relation to the choice and application of accelerated aging tests for specification purposes, since these usually have to be applied to rubbers of unknown compositions, which are likely to vary widely in their relative response to different aging conditions.

Aging of Rubber in the Oxygen Bomb at Room Temperature

1943 ◽  
Vol 16 (4) ◽  
pp. 924-925
Author(s):  
J. R. Scott
Keyword(s):  
Tensile Strength ◽  
Oxygen Concentration ◽  
Room Temperature ◽  
Accelerated Aging ◽  
Natural Aging ◽  
Tensile Tests ◽  
Oxygen Bomb ◽  
Vulcanized Rubber ◽  
Accelerated Aging Test ◽  
Aging Test

Abstract The work described below was carried out as a first step in determining whether an oxygen-bomb test at room temperature could be used as an accelerated aging test for unvulcanized rubber compositions, e.g., as used on surgical and adhesive plasters and for combining shoe fabrics, because a high-temperature test is unsatisfactory in such cases, owing to the melting of the compositions. The only infallible way of assessing the value of an accelerated test for such compositions is by comparison with natural aging, but as this is a very lengthy process and as the deterioration is difficult to measure quantitatively, it was decided to make preliminary tests on the effect of high oxygen concentration at room temperature by using vulcanized rubber. Although the results proved to be negative so far as the original purpose of the work was concerned, it is considered of interest to place them on record in view of the prominence given in some papers on aging to the relationship between oxygen concentration and rate of oxidation and deterioration of rubber. A mix composed of rubber 100, sulfur 3, zinc oxide 5, stearic acid 1, and diphenylguanidine 0.75, was vulcanized for 30 minutes at 153° C. Tensile tests, using standard ring-specimens and the Schopper machine, were made on unaged specimens and on specimens that had been aged (1) in an oxygen bomb at 300 lb. per sq. in. oxygen pressure and at room temperature (about 10° C), (2) in a Geer oven at 70° C. Four rings were used for each test, the tensile strength and breaking elongation figures quoted being the average for the two rings giving the highest tensile strength, and the figures for the elongations at constant loads the average of all four rings.

Influence of Exposing Vulcanized Rubber to Light on Its Subsequent Aging in the Dark

1944 ◽  
Vol 17 (1) ◽  
pp. 216-220
Author(s):  
J. R. Scott
Keyword(s):  
Tensile Strength ◽  
Accelerated Aging ◽  
Subsequent Aging ◽  
Oxygen Bomb ◽  
Vulcanized Rubber ◽  
Effect Of Light

Abstract The present experiments confirm the observations of Morgan and Naunton by showing that exposure of vulcanized rubber to light may affect the results of oxygen-bomb aging tests made some days, or perhaps even weeks, afterwards. They show also that a few days' exposure to even diffused daylight may noticeably lower the tensile strength of unaged rubber. With normal, i.e., not transparent, rubbers the effect of light on subsequent aging is small, and indeed does not seem to be noticeable at all in relatively slow aging tests, such as that in the Geer oven. Nevertheless, it is clearly advisable, as a precaution, to avoid unnecessary exposure to light of rubbers that are to be subjected to 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.

scholarly journals Quantitative Trait Locus Mapping of Seed Vigor in Soybean under −20 °C Storage and Accelerated Aging Conditions via RAD Sequencing

2021 ◽  
Vol 43 (3) ◽  
pp. 1977-1996
Author(s):  
Rongfan Wang ◽  
Fengqi Wu ◽  
Xianrong Xie ◽  
Cunyi Yang
Keyword(s):  
Quantitative Trait ◽  
Accelerated Aging ◽  
Natural Aging ◽  
Storage Conditions ◽  
Seed Vigor ◽  
C Storage ◽  
Poor Seed ◽  
Aging Conditions ◽  
Trait Locus ◽  
Locus Mapping

Due to its fast deterioration, soybean (Glycine max L.) has an inherently poor seed vigor. Vigor loss occurring during storage is one of the main obstacles to soybean production in the tropics. To analyze the genetic background of seed vigor, soybean seeds of a recombinant inbred line (RIL) population derived from the cross between Zhonghuang24 (ZH24, low vigor cultivar) and Huaxia3hao (HX3, vigorous cultivar) were utilized to identify the quantitative trait loci (QTLs) underlying the seed vigor under −20 °C conservation and accelerated aging conditions. According to the linkage analysis, multiple seed vigor-related QTLs were identified under both −20 °C and accelerated aging storage. Two major QTLs and eight QTL hotspots localized on chromosomes 3, 6, 9, 11, 15, 16, 17, and 19 were detected that were associated with seed vigor across two storage conditions. The indicators of seed vigor did not correlate well between the two aging treatments, and no common QTLs were detected in RIL populations stored in two conditions. These results indicated that deterioration under accelerated aging conditions was not reflective of natural aging at −20 °C. Additionally, we suggest 15 promising candidate genes that could possibly determine the seed vigor in soybeans, which would help explore the mechanisms responsible for maintaining high seed vigor.

A Study of the Mechanism of the Deactivation Effect

1954 ◽  
Vol 27 (1) ◽  
pp. 157-164 ◽  
Author(s):  
Jacques Le Foll
Keyword(s):  
Chemical Structure ◽  
A Priori ◽  
Natural Aging ◽  
Chain Scission ◽  
Nitro Compounds ◽  
Active Part ◽  
Relaxation Phenomena ◽  
Chain Molecules ◽  
Vulcanized Rubber ◽  
The Subject

Abstract The only method by which significant differences between the effects of antioxygenic agents and deactivating agents can be detected has been found to be a study of relaxation phenomena. An investigation by this method has also furnished further support to the theories of Tobolsky and his coworkers. The changes which take place during aging in the physical properties of vulcanized rubber are the result of two independent phenomena which occur simultaneously: (1) chain scission, and (2) formation of intermolecular bonds. As far as the aging of vulcanizates of natural rubber under normal conditions, e.g., socalled natural aging, is concerned, the chief phenomenon involved is scission of the chain molecules. In principle, therefore, there are two methods for combatting the deterioration of rubber on aging: (1) to impede chain scission by obstructing the fixation of oxygen, and (2) to promote the progressive formation of intermolecular bonds which compensate for the effects of the scission process. The first of these processes is that in which antioxygenic agents play the active part; in the second process, deactivating agents play the active part. From this viewpoint, deactivating agents play a part analogous to that of accelerators, and they may be regarded as representing a special type of acceleration. This theory makes possible a better understanding of a number of facts which, a priori, seem surprising: (1) the relationships of both chemical structure and mode of action of accelerators and deactivating agents, and (2) the protective effect of litharge, peroxides, and nitro compounds, all of which are vulcanizing agents. With respect to the intimate mechanism of the deactivating effect, one question remains unanswered, viz., how are intermolecular bonds formed under the influence of deactivating agents? This question recalls the question of the function of vulcanization accelerators, which has been the subject of many investigations, but which still remains a mystery.

Natural vs. Artificial Aging

1930 ◽  
Vol 3 (1) ◽  
pp. 148-155
Author(s):  
Stanley Krall
Keyword(s):  
Oxygen Pressure ◽  
Artificial Aging ◽  
Natural Aging ◽  
First Grade ◽  
Pneumatic Tire ◽  
Oxygen Bomb ◽  
Short Period ◽  
Aging Properties ◽  
American Society

Abstract A CONSIDERABLE number of types of artificial aging are being used today in an endeavor to determine the aging properties of rubber stocks in a short period of time without waiting for natural aging results. The data reported here were taken from some that are being obtained by Sub-Committee XV, Committee D-11 of the American Society for Testing Materials. Experimental Three types of pneumatic tire stocks were aged by two natural and two artificial methods: (1) Slabs were hung separately in the dark. (2) Slabs were hung separately exposed to the weather. (3) One-inch (2.5-cm.) wide strips were hung separately in the Geer (2) oven at 158° F. (70° C.). (4) One-inch (2.5-cm.) wide strips were hung separately in the Bierer (1) oxygen bomb at 158° F. (70° C.) and 300 pounds (21 kg. per sq. cm.) oxygen pressure. The stocks tested were a pure gum stock, a first grade, and a reclaim tread stock as follows:

scholarly journals PREDICTING POLYMER DEGRADATION AND MECHANICAL PROPERTY CHANGES FOR COMBINED RADIATION-THERMAL AGING ENVIRONMENTS

2018 ◽  
Vol 91 (1) ◽  
pp. 27-63 ◽  
Author(s):  
Kenneth T. Gillen ◽  
Mathew Celina
Keyword(s):  
Dose Rate ◽  
Accelerated Aging ◽  
Absolute Temperature ◽  
Factor X ◽  
Experimental Conditions ◽  
Radiation Dose Rate ◽  
Initiation Rate ◽  
Dose Rate Effects ◽  
Aging Conditions ◽  
Property Changes

ABSTRACT A new approach is presented for conducting and extrapolating combined environment (radiation plus thermal) accelerated aging experiments. The method involves a novel way of applying the time-temperature-dose rate (t-T-R) approach derived many years ago, which assumes that by simultaneously accelerating the thermal-initiation rate (from Arrhenius T-only analysis) and the radiation dose rate R by the same factor x, the overall degradation rate will increase by the factor x. The dose rate assumption implies that equal dose yields equal damage, which is equivalent to assuming the absence of dose-rate effects (DRE). A plot of inverse absolute temperature versus the log of the dose rate is used to indicate experimental conditions consistent with the model assumptions, which can be derived along lines encompassing so-called matched accelerated conditions (MAC lines). Aging trends taken along MAC lines for several elastomers confirms the underlying model assumption and therefore indicates, contrary to many past published results, that DRE are typically not present. In addition, the MAC approach easily accommodates the observation that substantial degradation chemistry changes occur as aging conditions transition R-T space from radiation domination (high R, low T) to temperature domination (low R, high T). The MAC-line approach also suggests an avenue for gaining more confidence in extrapolations of accelerated MAC-line data to ambient aging conditions by using ultrasensitive oxygen consumption (UOC) measurements taken along the MAC line both under the accelerated conditions and at ambient. From UOC data generated under combined R-T conditions, this approach is tested and quantitatively confirmed for one of the materials. In analogy to the wear-out approach developed previously for thermo-oxidative aging, the MAC-line concept can also be used to predict the remaining lifetimes of samples extracted periodically from ambient environments.

Effect of Aging Precipitates on the Bendability of an Al-Mg-Si Alloy

2014 ◽  
Vol 794-796 ◽  
pp. 572-577 ◽  
Author(s):  
Hidetaka Nakanishi ◽  
Mineo Asano ◽  
Hideo Yoshida
Keyword(s):  
Shear Bands ◽  
Natural Aging ◽  
Bending Test ◽  
Heat Radiation ◽  
Plate Material ◽  
Bake Hardening ◽  
Β Phase ◽  
Phase Precipitate ◽  
Aging Conditions ◽  
Better Than

Al-Mg-Si alloys are usually applied a T4 temper as the plate material for automobile bodies due to the necessity of a high bake hardening property. Many reports about the improvement in the bendability of Al-Mg-Si alloys applied a T4 temper have been published, because they easily crack during the hemming process. On the other hand, Al-Mg-Si alloys applied T6 and T7 tempers are used as the material of wiring plates and heat radiation devices. A high electrical conductivity and good bendability are necessary for these devices. In this study, the effect of the aging conditions on the bendability was investigated. As a result, the bendability at the T6 temper significantly decreased. The bendability under the aging temper, and over the aging temper was better than that at the T6 temper. Samples treated by natural-aging at high temperature before the T6 temper easily cracked during the bending test. It was postulated that the formation of shear bands was significant and the bendability decreased during the bending test under the high density and fine β phase precipitate conditions.

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