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.

The Heat Aging of Natural Rubber Vulcanized with Tetramethylthiuram Disulfide

1958 ◽  
Vol 31 (2) ◽  
pp. 327-328 ◽  
Author(s):  
W. P. Fletcher ◽  
S. G. Fogg
Keyword(s):  
Natural Rubber ◽  
Heat Resistance ◽  
Major Part ◽  
Aging Behavior ◽  
Tetramethylthiuram Disulfide ◽  
Acetone Extraction ◽  
Aging Resistance

Abstract Acetone extraction of the TMTD stock, which is known to remove the ZnDMDC formed during vulcanization, also leads to a reduction in heat aging resistance. Addition to the extracted vulcanizate of the appropriate quantity of ZnDMDC from a solution improves the aging behavior although not to the level of the untreated vulcanizate. This failure to restore in full the aging resistance of the initial stock by swelling in the appropriate quantity of ZnDMDC is hardly surprising since it is likely that the ZnDMDC will be present in the original and in the dosed vulcanizate in somewhat different physical forms and distributions. The results demonstrate that the dithiocarbamate formed in situ during TMTD vulcanization plays a major part in conferring heat resistance to such vulcanizates.

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.

EFFECT OF ZINC DITHIOCARBAMATES AND THIAZOLE-BASED ACCELERATORS ON THE VULCANIZATION OF NATURAL RUBBER

2012 ◽  
Vol 85 (1) ◽  
pp. 120-131 ◽  
Author(s):  
Md. Najib Alam ◽  
Swapan Kumar Mandal ◽  
Subhas Chandra Debnath
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Reaction Mechanism ◽  
Natural Rubber ◽  
High Performance ◽  
Binary Systems ◽  
Synergistic Activity ◽  
Tetramethylthiuram Disulfide

Abstract Several zinc dithiocarbamates (ZDCs) as accelerator derived from safe amine has been exclusively studied in the presence of thiazole-based accelerators to introduce safe dithiocarbamate in the vulcanization of natural rubber. Comparison has been made between conventional unsafe zinc dimethyldithiocarbamate (ZDMC) with safe novel ZDC combined with thizole-based accelerators in the light of mechanical properties. The study reveals that thiuram disulfide and 2-mercaptobenzothiazole (MBT) are always formed from the reaction either between ZDC and dibenzothiazyledisulfide (MBTS) or between ZDC and N-cyclohexyl-2-benzothiazole sulfenamide (CBS). It has been conclusively proved that MBT generated from MBTS or CBS reacts with ZDC and produces tetramethylthiuram disulfide. The observed synergistic activity has been discussed based on the cure and physical data and explained through the results based on high-performance liquid chromatography and a reaction mechanism. Synergistic activity is observed in all binary systems studied. The highest tensile strength is observed in the zinc (N-benzyl piperazino) dithiocarbamate-accelerated system at 3:6 mM ratios. In respect of tensile strength and modulus value, unsafe ZDMC can be successfully replaced by safe ZDCs in combination with thiazole group containing accelerator.

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.

Low Sulfur-Sulfenamide Accelerator Combinations for Injection Molding of Cis-1,4-Poly(Isoprene)

1972 ◽  
Vol 45 (5) ◽  
pp. 1403-1411 ◽  
Author(s):  
J. F. O'Mahoney
Keyword(s):  
Carbon Black ◽  
Injection Molding ◽  
Sulfur Concentration ◽  
Cure Rate ◽  
Tetramethylthiuram Disulfide ◽  
Excellent Method ◽  
Injection Molded ◽  
Low Levels ◽  
Low Sulfur ◽  
Made In

Abstract Earlier work with cis-l,4-poly(isoprene) suggested that low levels of sulfur and high levels of sulfenamide accelerator with high levels of secondary accelerator was an excellent method for curing injection molded stocks. However, subsequent experience showed that despite the benefits of reduced sulfur concentrations on reversion, increased sulfur, increased sulfenamide, and reduced secondary accelerator concentrations were necessary for adequate cure and safety. From that experience we explored further and found that, if the sulfenamide concentration is held constant at a higher level and the secondary accelerator concentration is increased as sulfur concentration is decreased, nearly equivalent hardness and modulus can be maintained throughout most cure conditions with no loss in safety and cure rate and much improvement in reversion resistance. Studies were made in a carbon black filled stock with N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-oxodiethylene-2-benzothiazole sulfenamide (DBS), and N-morpholinyl-2-benzothiazolyl disulfide (MBD) as primary accelerators and tetramethylthiuram monosulfide (TMTM) and tetramethylthiuram disulfide (TMTD) as secondary accelerators.

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.

Effects of Bio-Fuels on Common Static Sealing Elastomers

2009 ◽  
Vol 82 (3) ◽  
pp. 369-378 ◽  
Author(s):  
F. J. Walker
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
High Temperature ◽  
Volume Change ◽  
Low Sulfur

Abstract The purpose of this investigation was to explore the effects of bio-fuels on several common static sealing elastomers. This study explored ethanol-enriched gasoline and soy-based diesel. Exposed to these fuels were fifteen common static sealing elastomer compounds. These were comprised of eight FKM compounds, and two NBR compounds. In addition, other compositions were also included in the study. These comprised VMQ, FVMQ, AEM di-polymer, HNBR and a high temperature ACM. The percentage of ethanol enrichment was varied from zero to 100 percent. The bio-diesel section of this study examined comparative effects of conventional low-sulfur diesel, twenty percent soy diesel, and 100 percent soy diesel. Effects on conventional mechanical properties of hardness, tensile strength, elongation and volume change were measured.

Investigations in the Field of Rubber Vulcanization. VII. Influence of Organic Accelerators on the Kinetics of Vulcanization and the Properties of Natural-Rubber Vulcanizates

1950 ◽  
Vol 23 (3) ◽  
pp. 563-575
Author(s):  
B. Dogadkin ◽  
B. Karmin ◽  
A. Dobromyslova ◽  
L. Sapozhkova
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Oxidative Destruction ◽  
Tetramethylthiuram Disulfide ◽  
Vulcanization Kinetics ◽  
Strength Curve ◽  
Increasing Temperature ◽  
Low Sulfur ◽  
Natural Rubber Vulcanizates ◽  
Kinetics Of

Abstract 1. Vulcanization accelerators change all parameters of the kinetic strength curve during the vulcanization of natural-rubber mixtures with low sulfur contents. 2. Calculation of the kinetic constants of the fundamental vulcanization equation proposed by Dogadkin, Karmin, and Gol'berg shows that vulcanization accelerators affect both the kinetics of the interaction of rubber with sulfur and the kinetics of the interaction of rubber with oxygen. 3. Direct experiments on the oxidation of rubber have shown that tetramethylthiuram disulfide and diphenylguanidine retard the process of addition of oxygen to rubber, while mercaptobenzothiazole accelerates this process. 4. Data on the rate of plasticization and change in viscosity of rubber solutions during oxidation indicate that tetramethylthiuram disulfide and diphenylguanidine promote the disintegration of molecular chains of rubber during the oxidative destruction of the latter. 5. The activation energy of the process of oxidation of rubber in the presence of mercaptobenzothiazole corresponds to the activation energy calculated from the fundamental vulcanization reaction for the process of oxidative destruction. This provides additional proof of the participation of oxygen in the vulcanization process. 6. It has been established with the aid of the methyl iodide reaction that accelerators increase the bridge-sulfur content of the vulcanizate, which is present in the form of monosulfides, with one sulfur atom connected to an allyl type radical. 7. With increasing temperature, the tensile strength at the vulcanization optimum increases in mixtures containing tetramethylthiuram disulfide, decreases in mixtures containing mercaptobenzothiazole, and remains unchanged in mixtures containing diphenylguanidine. The limiting strength decreases in all cases with increasing temperature. This phenomenon is explained on the basis of the proposed concepts of the character of vulcanization kinetics and of the nature of the vulcanization optimum.

Studies of Hard Rubber Reactions. III. Changes in Acetone-Extractable Substances during Vulcanization

1937 ◽  
Vol 10 (4) ◽  
pp. 787-791
Author(s):  
Seiiti Numajiri
Keyword(s):  
Tensile Strength ◽  
Turning Point ◽  
Acetone Extract ◽  
Acetone Extraction ◽  
Maximum Value ◽  
Rubber Compounds ◽  
Preceding Communication ◽  
Definite Period ◽  
Consequent Increase

Abstract 1. To explain chemically the fundamental hard rubber reactions which take place during the vulcanization, changes in the acetone-extractable substances, as well as in tensile strength, elongation, and hardness, during vulcanization were studied. 2. Preliminary experiments on acetone extraction with the author's apparatus indicated that a 20-hour extraction was ideal for the purposes of the investigation, and extractions extending to extremely long periods were unsuitable in the present experiments. 3. The corrected acetone extract or organic acetone-soluble substances do not either increase or diminish steadily throughout vulcanization, but show a maximum value at a definite period of vulcanization. The appearance of this maximum value, which also corresponds to characteristic changes in tensile strength, elongation, and hardness (cf. the preceding Communication) is a turning point where the hard rubber reaction diminishes rapidly. 4. To explain chemically the appearance of a maximum value and consequent increase and decrease in the percentage of acetone-soluble substances (corrected) it may be considered that the rubber or rubber compounds with different degrees of vulcanization are polymerized at a certain period of vulcanization, depending on the action of heat, accelerators and agencies, and that the amount of acetone-soluble substances is governed by these factors.

The Aging of Vulcanized Rubber under Varying Elongation

1930 ◽  
Vol 3 (1) ◽  
pp. 131-143
Author(s):  
A. A. Somerville ◽  
J. M. Ball ◽  
W. H. Cope
Keyword(s):  
Carbon Black ◽  
Tetramethylthiuram Disulfide ◽  
Vulcanized Rubber ◽  
Synthetic Rubber ◽  
Aging Curve ◽  
Low Sulfur

Abstract 1—Deterioration in the oven is approximately 30 per cent greaterat 100 per cent elongation than at 0 per cent elongation. 2—Deterioration in the bomb is almost independent of elongation. 3—Deterioration in ozone is greatest at 5 and 10 per cent elongations. 4—Deterioration in sunlight with respect to stretch is analogous to deterioration in ozone. 5—Cracking of the test rings occurs in both ozone and sunlight when the rings are stretched, but not in the oven or bomb. This cracking is greatest at 5 and 10 per cent elongations. 6—A 40 per cent carbon-black stock shows marked deterioration and cracking in both ozone and sunlight at about 10 per cent elongation. 7—High sulfur causes greater deterioration in ozone and sunlight than low sulfur. 8—Undercures show greater deterioration than the optimum cure in ozone and sunlight. 9—Loading with a filler such as whiting does not change the shape of the ozone- and sunlight-aging curves, and does not materially affect the percentage deterioration. 10—Rubber bands show progres sively poorer aging in the bomb as the stretch increases from 0 to 700 per cent, while in ozone they give an aging curve having the characteristic dip at about 10 per cent elongation, showing the least deterioration at about 400 per cent elongation. 11—Tetramethylthiuram disulfide (3 per cent) as a vulcanizing agent causes rather low percentages of deterioration in ozone and sunlight, and gives fairly flat aging curves. 12—Mineral rubber (24 per cent) causes a smaller percentage deterioration than 4 per cent except at the critical elongation of about 10 per cent. 13—Paraffin (1 per cent) causes pretty bad deterioration in ozone but provides some protection in sunlight. 14—Added antioxidant does not change the shape of the ozone- or sunlight-aging curves but may lessen the amount of deterioration. 15—Two antioxidants may give comparable results in both oven and bomb, but quite different results in ozone and sunlight. 16—Synthetic rubber gives a characteristic ozone-aging curve.

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