A Manometric Test for Oxygen Absorption by Vulcanized Rubber

1942 ◽  
Vol 15 (1) ◽  
pp. 83-90
Author(s):  
Robert H. Johnson
Keyword(s):  
Tensile Strength ◽  
Oxygen Absorption ◽  
Aging Behavior ◽  
Strength Deterioration ◽  
Oxygen Bomb ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Manometric Method ◽  
Set Up ◽  
Bomb Method

Abstract An apparatus can be set up in laboratory glassware that will confirm the results obtained by Dufraisse in his manometric test for oxygen absorption. It has been shown that different rubber compounds possess different tendencies to absorb oxygen. It has also been shown that the differences in the rate at which rubber compounds absorb oxygen are comparable with those differences found in the rate of tensile-strength deterioration of the same compounds aged in the oxygen bomb. This modified Dufraisse manometric method is convenient, efficient, accurate and, above all, a speedy method for measuring the relative aging behavior of vulcanized rubber compounds. Within two hours it is possible to have the results by this method, whereas it is necessary to wait from four days to two weeks for such information by the oxygen bomb method.

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.

Preliminary Study on Curing of Thick Rubber Article

2015 ◽  
Vol 1134 ◽  
pp. 23-27
Author(s):  
Siti Zulaikha Ibrahim ◽  
Che Mohd Som Said ◽  
Mohamad Asri Ahmad ◽  
Azemi Samsuri
Keyword(s):  
Tensile Strength ◽  
Temperature Region ◽  
The State ◽  
Curing Temperature ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Cure Time ◽  
Zinc Diethyldithiocarbamate ◽  
Preliminary Study ◽  
Rubber Article

In this study, several batches of natural rubber (SMR L) were compounded with three different types of accelerators, which were N-cyclohexylbenzothiazole-2-sulphenamide (CBS), diphenylguanidine (DPG) and zinc diethyldithiocarbamate (ZDEC). ZDEC is known as an ultrafast accelerator. The rubber compounds were cured at 140°C, 130°C, 120°C, 110°C and 100°C in accordance with the temperature gradients observed within the thick rubber block. The main aim of this study is to cure the rubber at each temperature region to the same cure time as that of the outermost region (20 minutes at 140°C). The amount of sulfur and accelerator were adjusted accordingly at each curing temperature to match the state of cure at 140°C. The state of cure of of the vulcanized rubbers were measured using hardness and tensile strength. The same state of cure is achieved if the hardness and tensile strength value are within ±2 IRHD and ±3 MPa, respectively with that of the control vulcanized rubber (hardness and tensile strength cured at 140°C). The results shows that the hardness and tensile strength of the vulcanized rubber at each temperature region are within the expected margins. The results clearly indicated that the type and amount of accelerators, and the amount of sulfur were correctly chosen at each temperature.

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.

Measurement of the Absorption of Oxygen by Vulcanized Rubber in Air

1939 ◽  
Vol 12 (2) ◽  
pp. 261-268
Author(s):  
A. G. Milligan ◽  
J. E. Shaw
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Tensile Tests ◽  
Direct Measure ◽  
Mean Values ◽  
Reasonable Time ◽  
Aging Period ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Made In

Abstract It is generally agreed that oxidation is the controlling factor in the decay of rubber compounds. Measurements of the decay of any physical properties—commonly tensile strength—can be made in a convenient time only if the decay is greatly accelerated, and there is always a grave doubt about the equality of the acceleration for different materials. There is also a difficulty in selecting a universally suitable aging period, since the decay of the physical properties is not linear. A direct measure of the rate of oxidation is, in our view, more fundamental and less equivocal. It can, moreover, be made in a reasonable time at a temperature not far removed from service temperatures. Again, whereas tensile tests require several samples of each point in the timecurve to give acceptable mean values, here a single sample suffices for the whole test, and this sample can be simply prepared from a specimen of any form by rasping. The merits and simplicity of the method should commend it to rubber technologists.

Aging of GR-S Vulcanizates. IV. Influence of the Vulcanizing Ingredients, Antioxidant, and Softener

1950 ◽  
Vol 23 (2) ◽  
pp. 397-403 ◽  
Author(s):  
J. R. Scott
Keyword(s):  
Tensile Strength ◽  
Aging Behavior ◽  
Tetramethylthiuram Disulfide ◽  
Oxygen Bomb ◽  
Acetone Extraction ◽  
Low Sulfur ◽  
Tension Strength

Abstract The results of air aging at temperatures from 25° to 100° C and of oxygen-bomb aging are discussed in relation to the composition of the mix; notes are given also on the relation of composition to the properties before aging. The main conclusions are: (1) a low proportion of sulfur or (still better) vulcanization by tetramethylthiuram disulfide (TMT) improves the maintenance of tensile strength and elongation under all conditions examined; a low-sulfur mix containing selenium gives results intermediate between the normal low-sulfur and TMT-vulcanized mixes; (2) when judged by the stiffening and hardening during aging, the relative merits of these alternative vulcanizing agents are different, age-stiffening being generally least with low sulfur plus selenium and greatest with TMT vulcanization; (3) on the whole, mercapto-benzothiazole (MBT) gave better results than TMT as an accelerator in mixes with the same proportion of sulfur; (4) acetone extraction of raw GR-S did not lead to the bad aging expected from the removal of antioxidant, but this point needs further study in view of contrary conclusions by other workers; (5) a large proportion of softener somewhat improves maintenance of strength but increases age-stiffening; (6) in general the formulation giving the best maintenance of tension strength and elongation does not give the least age-stiffening, and vice-versa; for the former, TMT vulcanization (possibly plus softener) appears best; for the latter an MBT-accelerated low-sulfur mix, possibly plus selenium, and (7) the 100° C air and the oxygen-bomb aging tests may give misleading indications of aging behavior in air at lower temperatures.

Oxygen Absorption of Vulcanizates. A Means of Evaluating Aging Resistance

1950 ◽  
Vol 23 (2) ◽  
pp. 425-439
Author(s):  
Louis R. Pollack ◽  
Robert E. McElwain ◽  
Paul T. Wagner
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Absorption Measurement ◽  
Oxygen Absorption ◽  
Oxygen Bomb ◽  
Ultimate Elongation ◽  
Synthetic Rubber ◽  
Standard Procedures ◽  
Aging Resistance

Abstract The rates of oxygen absorption of two natural and six synthetic-rubber stocks have been measured. In addition, the course of aging in the oxygen bomb and air oven was followed by means of changes in tensile strength and in ultimate elongation of the same eight stocks. Correlation between rates of oxygen absorption and deterioration of physical properties is close enough to justify substitution of a rapid oxygen absorption measurement for longer standard procedures in evaluating the aging characteristics of rubber stocks.

Volumetric Oxygen-Absorption Test for Rubber Aging

1951 ◽  
Vol 24 (4) ◽  
pp. 981-998
Author(s):  
J. Reid Shelton ◽  
William L. Cox
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Chain Scission ◽  
Rate Of Change ◽  
Oxygen Absorption ◽  
Absorption Test ◽  
Absorption Data ◽  
Direct Function ◽  
Oxygen Bomb ◽  
Early Stages

Abstract A volumetric oxygen-absorption test for aging of rubber has been investigated from the point of view of the effect of cure and the effect of mercapto-benzimidazole on the aging behavior. The test has also been evaluated by comparison with conventional air oven and oxygen bomb aging. A compounded but uncured Hevea black stock is more resistant to oxidation than the vulcanized material, but after a reasonable cure is obtained, further heating produces only a small change in the rate of oxygen absorption. The change in physical properties corresponding to a given amount of oxygen absorbed varies somewhat with time of cure in the initial stages, but after the absorption of 4 or 5 cc. of oxygen per gram of rubber, the changes in most physical properties are a direct function of the amount of oxygen absorbed. Neither time of cure nor the presence or absence of inhibitor has any significant effect on the subsequent rate of change in such properties as tensile strength and ultimate elongation for a given amount of oxygen absorbed. Oven aging data on identical time cures confirm the reported superiority of a combination of mercaptobenzimidazole with a conventional type of anti-oxidant. Oxygen absorption data reveal, however, that mercaptobenzimidazole causes a significant decrease in the rate of oxidation of a Hevea black stock, and thus it clearly functions at least in part as an antioxidant in the usually accepted sense. The deterioration of properties is, in general, proportional to the oxygen absorbed, except in the early stages of oxidation where the mercaptobenzimidazole stocks change somewhat less than the controls for a given amount of oxygen absorbed. When the cures are selected to give comparable initial properties, however, the change in tensile strength of the mercaptobenzimidazole stocks with amount of oxygen absorbed is essentially the same as for the controls, even in the initial stages. These data suggest that the observed protection imparted by mercaptobenzimidazole results from a combination of two factors: (1) the normal antioxidant activity of mercaptobenzimidazole, which reduces the amount of oxygen absorbed; and (2) an effect on the nature of the cure attained when mercaptobenzimidazole is present, such that the absorption of a given amount of oxygen in the early stages is not accompanied by as great a change in properties. Thus, it appears that the deactivating effect may be the result of the effect of this material on the vulcanization process rather than a direct effect on the oxidation process. A comparison of the effect of oxygen absorption, air oven, and oxygen bomb aging methods on changes in physical properties of Hevea black stocks shows that the results obtained by oxygen absorption and air oven methods (both at 100° C) are similar, but that the higher oxygen concentration of the oxygen bomb test (70° C and 300 pounds per square inch) apparently results in a higher proportion of chain scission when compared to cross-linking of the polymer chains.

Vulcanizates from Natural Rubber and Bisazo Compounds. Aging Properties

1959 ◽  
Vol 32 (2) ◽  
pp. 544-556
Author(s):  
Heinz Esser
Keyword(s):  
Natural Rubber ◽  
Oxygen Absorption ◽  
Oxygen Bomb ◽  
Hot Air ◽  
Rubber Compounds ◽  
Aging Properties ◽  
Rapid Tests ◽  
Sulfur Level ◽  
Bisazo Compounds

Abstract Nonblack as well as black loaded natural rubber compounds were vulcanized by addition of hexamethylene-1,6-bis(phenyl-azomonocarbonamide) (BAA). The accelerating and vulcanizing action of BAA is discussed on the basis of modulus curves. The experiments show that BAA alone is not active as a vulcanizing agent. To achieve good vulcanization, sulfur is also needed; the optimum sulfur level is much lower than in normal compounds. Furthermore, it is shown that BAA compounds need addition of an accelerator. Aging stability of BAA vulcanizates was tested by modern rapid tests (relaxation, creep, and oxygen absorption) as well as by classical methods (hot air and oxygen bomb aging). Vulcanization in which BAA was substituted for part of the sulfur showed excellent aging, comparable only with thiuram vulcanizates in the rapid tests and in hot air aging; aging in the oxygen bomb gave only fair results.

Oxidation of Vulcanized Rubber. Effect of Temperature, State of Cure, and Thickness

1940 ◽  
Vol 13 (2) ◽  
pp. 375-388
Author(s):  
A. R. Kemp ◽  
J. H. Ingmanson ◽  
G. S. Mueller
Keyword(s):  
Tensile Strength ◽  
Effect Of Temperature ◽  
Oxygen Requirement ◽  
Tetramethylthiuram Disulfide ◽  
Strength Deterioration ◽  
Vulcanized Rubber ◽  
Hydrocarbon Content ◽  
Straight Line ◽  
Temperature State ◽  
Thickness Variations

Abstract 1. A previous investigation of the rate of oxidation of rubber over the temperature range of 60° to 80° C. has been extended to 90°, 100° and 110° C. 2. The rate of oxidation over the range which accounts for substantial deterioration of tensile strength appears to be a straight-line function of the time of aging from 60° up to an including 90° C. The rate of oxidation at 100° C. appears to diverge somewhat from a straight-line function of time decreasing as oxidation proceeds. 3. The rate of oxidation increases with increased temperature. Over the range of 60° to 110° C, the rate is doubled for each 7.5° increase in temperature, corresponding to a temperature coefficient of oxidation of 2.5. 4. Tensile strength decreases as a straight-line function of the time of aging and of the quantity of oxygen absorbed. 5. The quantity of absorbed oxygen, determined by weight gain corresponding to a 50 per cent decrease in tensile strength, varies with the temperature of oxidation. At 60° C. the oxygen requirement for 50 per cent deterioration is about 1.30 per cent, and at 110° C. about 0.65 per cent on the rubber hydrocarbon content. 6. Tensile strength increases, probably due to a mild curing effect, when specimens of the compound are heated in an atmosphere where the oxygen is replaced with carbon dioxide for the same periods of time at 80° and 110° C, were required to cause a 50 per cent deterioration in tensile strength in an oxygen atmosphere. 7. With increased time of vulcanization, the rate of oxidation increases. Oxidation appears to be autocatalytic in the case of overvulcanized rubber. 8. As time of vulcanization increases, there is a decrease in the quantity of oxygen required to cause a given decrease in tensile strength. 9. Thickness variations of 0.43 to 1.90 mm. in test-specimens of a compound containing an antioxidant do not affect quantity of oxygen absorbed or degree of tensile strength deterioration when aging is conducted at 80° C. and 3.5 kg. per sq. cm. oxygen pressure. 10. When tetramethylthiuram disulfide is used for vulcanization in place of sulfur, there appears to be no change in the mechanism of oxidation, but the rate of oxidation is reduced.

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.

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