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.

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.

Heats of Vulcanization of Synthetic Rubbers

1944 ◽  
Vol 17 (2) ◽  
pp. 404-411 ◽  
Author(s):  
P. L. Bruce ◽  
R. Lyle ◽  
J. T. Blake
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Chemical Reactions ◽  
Side Reaction ◽  
Heat Evolution ◽  
Butyl Rubber ◽  
Vulcanized Rubber ◽  
Principal Reaction ◽  
Low Sulfur ◽  
Quantity Of Heat

Abstract 1. The heats of vulcanization for natural rubber and Buna-S are nearly equal. The data for both materials indicate two different chemical reactions during vulcanization. At low sulfur percentages, the principal reaction forms soft vulcanized rubber and is accompanied by little or no heat evolution. Above the 2 per cent sulfur region, a second reaction predominates, forming hard rubber and producing a relatively large quantity of heat. 2. The presence of an accelerator (Santocure) in Buna-S has little, if any, effect on heat of vulcanization. 3. The addition of carbon black to Buna-S lowers the heat of vulcanization in the region above 4 per cent sulfur. The calories evolved in a 10 per cent sulfur compound decrease linearly with percentage of carbon black. 4. The heats of vulcanization of Buna-N (Hycar OR-15) indicate the presence of two chemical reactions. Unlike natural rubber and Buna-S, the ebonite reaction does not predominate until the sulfur concentration is raised above 10 per cent. 5. The heat of vulcanization of Butyl rubber with sulfur is equal to the heat evolved with natural rubber containing 0.6 per cent sulfur. If one sulfur atom reacts per double bond, the maximum amount combining would be 0.72 per cent sulfur. During the vulcanization of Butyl rubber with p-quinone dioxime and lead peroxide, a large amount of heat is evolved by a side reaction between the vulcanizing agents. The reaction involving the Butyl rubber produces about 6 calories per gram, a considerably higher value than the 1 calorie produced by sulfur vulcanization. 6. The heat of vulcanization of Neoprene-GN without added agents corresponds to a value for smoked sheet rubber containing 4.5 per cent sulfur. The addition of zinc oxide and magnesia decreases the heat of vulcanization.

Carbon Black. I—A Study of Its Volatile Constituents

1928 ◽  
Vol 1 (3) ◽  
pp. 485-497 ◽  
Author(s):  
C. R. Johnson
Keyword(s):  
Carbon Black ◽  
Volatile Matter ◽  
Original Sample ◽  
Missing Information ◽  
Volatile Constituents ◽  
Vulcanized Rubber ◽  
Rates Of Evolution ◽  
Temperature And Pressure ◽  
The Relationship

Abstract The rates of evolution of gas from carbon black with variation of time, temperature, and pressure have been determined. Complete analyses have been made of five types of carbon black, which involve an organic combustion of the original sample, an organic combustion of the sample after the gases have been removed, a determination of the loss in weight represented by the gases removed, analyses of the gases removed, and finally a complete accounting, or balance, of the carbon in the steps considered. In an attempt to supply some missing information not revealed by the foregoing, some special gas analyses under varying conditions were made. The relationship between the amount and composition of volatile matter evolved from carbon blacks and the properties imparted to vulcanized rubber when compounded with these blacks has been studied.

Crystallization of Vulcanized Rubber

1941 ◽  
Vol 14 (2) ◽  
pp. 347-355 ◽  
Author(s):  
Norman Bekkedahl ◽  
Lawrence A. Wood
Keyword(s):  
Practical Importance ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Single Exception ◽  
Quantitative Results ◽  
The Subject ◽  
Low Sulfur Content ◽  
Low Sulfur

Abstract The formation of crystals at room temperature by stretching rubber, vulcanized or unvulcanized, has been the subject of considerable study. The crystallization of unstretched rubber at low temperatures is also well known, but with a single exception to be discussed later, the effect has commonly been considered to be limited to the unvulcanized material. In the present investigation, however, the crystallization of unstretched specimens of vulcanized rubber of low sulfur content has been accomplished. In commercial vulcanized rubber products, crystallization has not hitherto been recognized as a factor of practical importance. It is probably significant in cold climates, where some rubber products slowly undergo a great increase in rigidity and permanent set. Automobile traffic counters, for example, have been rendered inoperative by the hardening of the rubber tubing used with them. Laboratory tubing and other products made of a number of different commercial rubber compounds have become rigid after storage for some weeks in a refrigerator at about 0° C. Previous work on unvulcanized rubber showed that it can be crystallized at temperatures between + 10° and −40° C, the crystals melting in a range from about 6° to 16° C. Crystallization and fusion are accompanied by changes in volume, heat capacity, light absorption, birefringence, x-ray diffraction, and mechanical properties such as hardness. x-Ray diffraction and birefringence, of course, give the most direct evidence of crystalline structure, but in the present work change of volume, measured in a mercury-filled dilatometer, was chosen as the criterion of crystallization or fusion. Quantitative results are more easily obtained in this manner, and the experimental observations are simple. Furthermore, the method is well adapted to continuous observations over long periods of time, such as were found necessary in the present work.

Studies on the Joule Effect in Rubber. I. The Thermal Effect on Stretched Vulcanized Rubber

1935 ◽  
Vol 8 (2) ◽  
pp. 174-176
Author(s):  
Yoshio Tanaka ◽  
Shū Kambara ◽  
Hironosuke Fujita
Keyword(s):  
Carbon Black ◽  
Thermal Effect ◽  
Ultra Violet ◽  
Sulfur Compounds ◽  
The Other ◽  
Joule Effect ◽  
Ultra Violet Radiation ◽  
Vulcanized Rubber ◽  
High Heating ◽  
Violet Radiation

Abstract The experiments may be summarized as follows: 1. With an increase in the time of cure, the elongation and heating elongation diminish and the Joule effect increases. 2. An increase in the vulcanization coefficient is followed by a decrease in the elongation and heating elongation and an increase in the Joule effect. The increase in the Joule effect, however, has a limit. 3. An organic accelerator reduces the elongation and heating elongation and increases the Joule effect. 4. The greater the degree of mastication the greater the elongation and the heating elongation and the less the Joule effect. 5. By exposure to ultra-violet radiation, the elongation and heating elongation are increased and the Joule effect decreased. 6. A filler increases the heating elongation and decreases the elongation and the Joule effect. Thus samples with relatively high elongations at a definite tension have relatively high heating elongations and low Joule effects. Such specimens seem to have been affected by the disaggregation and depolymerization of the rubber molecules. The effects of the time of cure, mastication, and exposure to ultra-violet radiation prove this fact. Vulcanization increases the Joule effect, but on the other hand, it is accompanied by a disaggregation and depolymerization of the rubber molecules, so the increase in the Joule effect with the progress of vulcanization has a limit. On vulcanization with an accelerator, the combination of sulfur occurs so rapidly that the increase in the Joule effect is predominant. A filler, such as carbon black, behaves only as a diluent of Joule effect. These results lead to the conclusion that the more highly polymerized rubber molecules and their sulfur compounds seem to be the chief factor in the Joule effect of vulcanized rubber.

scholarly journals Determination of carbon black in vulcanized rubber by pyrolysis technique

1972 ◽  
Vol 21 (8) ◽  
pp. 989-992
Author(s):  
Tadaoki OKUMOTO ◽  
Tsugio TAKEUCHI ◽  
Emiko NAKAJIMA
Keyword(s):  
Carbon Black ◽  
Vulcanized Rubber

Reinforcement of Butyl with Carbon Black. II. Thermally vs. Chemically Oxidized Blacks

1964 ◽  
Vol 37 (4) ◽  
pp. 1034-1048 ◽  
Author(s):  
A. M. Gessler
Keyword(s):  
Carbon Black ◽  
Chemical Reactivity ◽  
Preceding Paper ◽  
Strain Curve ◽  
Convincing Evidence ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Carbon Particles ◽  
Vulcanized Rubber ◽  
Oxygen Functionality

Abstract The effect of oxidized blacks on the stress-strain properties and bound-rubber content of butyl and SBR was discussed in the preceding paper. Oxidized blacks, when compared with similar untreated blacks, were shown to have a greatly increased reinforcing capacity in butyl. Oxygen functionality on carbon black, it was therefore concluded, is essential in butyl to produce the chemical reactivity which is required between polymer and black if high-order reinforcement is to be obtained. Oxygen functionality on carbon black, it was also demonstrated, is not only not required for enhanced reinforcement in SBR, but it is in fact a deterrent, because it exerts severe restraining effects on the cure of the resulting vulcanizates as well. These interesting results were proposed to provide qualitative but convincing evidence that carbon-polymer bonding, which we believe is requisite to reinforcement, is achieved by different mechanisms in butyl and SBR. In butyl, the unique sensitivity of the stress-strain curve to reinforcing effects was used to speculate on the disposition of carbon blacks in “filled” and reinforced vulcanizates, respectively. With oxidized blacks, reinforcement effects were pictured as stiffening effects which, starting with the gum vulcanizates, caused the stress-strain curve to be shifted without intrinsic changes in its shape. The resulting “reinforced gum,” it was suggested, derived its physical characteristics from the fact that carbon black was included in the vulcanized rubber network. With untreated blacks, in “filled” systems, carbon black was pictured as being enmeshed or entangled in an independently formed vulcanized rubber network. The stiffening effects in this case were attributed to viscous contributions arising from steric restrictions which the occluded carbon particles were thought to impose on both initial movements and the subsequent orientation of network chains when the sample was extended.

Migration of Antioxidants and Accelerators in Natural and Synthetic Rubber II. Sulfenamide System Studies and Comparison of Age Resister Migration under Inert and Practical Conditions

1969 ◽  
Vol 42 (3) ◽  
pp. 892-902 ◽  
Author(s):  
James E. Lewis ◽  
Marvin L. Deviney ◽  
Lawrence E. Whittington
Keyword(s):  
Diffusion Coefficient ◽  
Carbon Black ◽  
Natural Rubber ◽  
Count Data ◽  
Diffusion Coefficients ◽  
Oil Migration ◽  
Carbon 14 ◽  
Synthetic Rubber ◽  
End Use ◽  
In Cis

Abstract Radiochemical techniques developed for studying extender oil migration in various elastomers have been adapted for use in investigating the migration of age resisters and curatives. This paper contains basic diffusion coefficient data for nine compounds including both staining and nonstaining antioxidants and members of the sulfenamide, thiazole and thiuram accelerator series. Techniques for synthesizing these age resisters and curatives in the carbon-14 and sulfur-35 labelled form are described. Migration was studied in natural rubber, SBR, cis-polybutadiene and EPT vulcanizates. Computer techniques were used to calculate diffusion coefficients from radiochemical count data. Results from preliminary migration studies under practical curing and end-use conditions are also presented. In the case of phenyl-2-naphthylamine migration in cis-polybutadiene, a pronounced decrease in diffusivity with increasing surface area of the carbon black filler was observed.

Infrared Study of Some Structural Changes in Natural Rubber during Vulcanization

1958 ◽  
Vol 31 (4) ◽  
pp. 719-736 ◽  
Author(s):  
Frederic J. Linnig ◽  
James E. Stewart
Keyword(s):  
Double Bond ◽  
Gamma Rays ◽  
Structural Changes ◽  
Elemental Sulfur ◽  
Carboxyl Groups ◽  
Double Bonds ◽  
Infrared Study ◽  
Tetramethylthiuram Disulfide ◽  
Vulcanized Rubber ◽  
Double Bond Shift

Abstract A knowledge of the structure of vulcanized rubber is essential to the interpretation of vulcanization and oxidation studies and the physical properties of the material. In the present work an infrared study has been made of structures resulting from a number of different methods of vulcanization. Sulfur vulcanizates show the presence of a shifted double bond, originally observed by Sheppard and Sutherland. The presence of conjugated double bonds is also indicated. Accelerators such as tetramethylthiuram disulfide and zinc dibutyl dithiocarbamate increase the rate of the double-bond shift and reduce the amount of conjugated double bonds. Neither the double-bond shift nor conjugation is observed as a result of vulcanization with tetramethylthiuram disulfide alone, hydrogen sulfide and sulfur dioxide (Peachey process), a peroxide, or gamma rays. These result in a possible decrease in carbonyl structures, and in the case of the last three, possible increased absorption due to OH and ionized carboxyl groups. Apparently, the double-bond shift and conjugation are primarily phenomena related to the use of elemental sulfur. The other vulcanization systems studied evidently involve different mechanisms. An implication of the present work is that there may be a relationship between the reported ease of oxidation of sulfur vulcanizates, accelerated vulcanizates, and sulfurless vulcanizates (tetramethylthiuram disulfide alone), which decreases in the order named, and the probable amount of conjugation in the compound, which decreases in the same order.

New Development in Rubber Reclaiming

1941 ◽  
Vol 14 (3) ◽  
pp. 717-723
Author(s):  
W. G. Essex
Keyword(s):  
Carbon Black ◽  
Milling Time ◽  
Steam Pressure ◽  
Raw Material ◽  
Manufacturing Cost ◽  
Pneumatic Motor ◽  
Vulcanized Rubber ◽  
New Development ◽  
History Of ◽  
Free Sulfur

Abstract The history of rubber reclaiming has been given by Alexander, and it is therefore intended only to make a brief reference to the well-known acid and alkali processes, the latter having proved to be by far the most successful method of reclaiming vulcanized rubber. The alkali process, introduced by Marks in 1899 had the outstanding advantage of simultaneously removing, from the waste, free sulfur, of which from 3 to 5 per cent was present, of destroying the fabric and of plasticizing the waste, this being accomplished by heating in a closed vessel under steam pressure with caustic soda. The acid process destroyed only the fabric, and plasticization by heat was performed in another operation in a separate vessel: by this method little or no free sulfur was removed from the waste. This latter disadvantage has since disappeared, for, with modern rubber compounding, there is little free sulfur left in vulcanized rubber. In recent years there have been widespread changes in the manufacture of rubber goods, particularly in the case of pneumatic motor tires, which are now the main source of raw material for reclaimed rubber. Organic accelerators, anti-oxidants and carbon black have made vulcanized rubber a very tough, resilient article, extremely resistant to aging and to heat, one of the chief agents used in rubber reclaiming. For example, modern motor tire treads, which are heavily reinforced with carbon black, are not so amenable to alkali and heat treatment, and tire treads reclaimed by this process have finally to be plasticized and made homogeneous by a much longer mechanical milling and refining treatment than was formerly necessary; in spite of this the treads still produce a proportion of rough, unrefinable material which has to be separated and rejected from the final reclaim. This increase in milling time, combined with lower finished production due to rejected unrefinable material, has had the effect of greatly increasing the manufacturing cost of the reclaim. Research was therefore started with the object of evolving a process which would successfully offset these difficulties caused by the changes in the properties and characteristics of the initial waste. The result of this work has been the creation of reclaimed rubber from which the disadvantages mentioned have been largely eliminated.

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