Thiuram Disulfides in Compounding

Abstract Perhaps the chief drawback to the greater employment of thiuram disulfides has been the fear, often groundless, of scorching during processing, and for this reason the work detailed in this paper is devoted entirely to this aspect of their use. The scorching tendency, taken as the commencement of cure, and the rate of vulcanization were studied by means of a modified Goodrich type of plastometer, and the results are expressed as the percentage recovery against time in minutes at 120° C. This temperature (equivalent to 15 lbs. per sq. in. steam pressure) was chosen as being the highest likely to be reached in normal mixing, calendering and extrusion. The rubber compounds tested were prepared from one large batch of base stock comprising: smoked sheet rubber, 100 parts; zinc oxide, 5 parts; and stearic acid, 2 parts. After mixing, the stock was divided into the required number of portions and to these were added the various ingredients detailed later; in all cases the same milling time and temperatures were adhered to so that results would be comparable, especially plasticity. An interval of 24 hours at room temperature was allowed in each case before cutting plastometer test-pieces to dissipate strains imposed in the stock during mixing and sheeting. The test-pieces were then placed in an oven at 120° C, and percentage recovery determinations were made at 5-minute intervals over a range of 5 to 60 minutes.

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Natural Rubber Compounds for Truck Tires

Rubber Chemistry and Technology ◽

10.5254/1.3536090 ◽

1985 ◽

Vol 58 (4) ◽

pp. 740-750 ◽

Cited By ~ 6

Author(s):

D. Barnard ◽

C. S. L. Baker ◽

I. R. Wallace

Keyword(s):

Stearic Acid ◽

Heat Generation ◽

Rolling Resistance ◽

Synthetic Compound ◽

Wear Performance ◽

Test Pieces ◽

Truck Tire ◽

Truck Tires ◽

Rubber Compounds ◽

Lower Severity

Abstract An 80 NR/20 BR truck tread compound containing a semi-EV cure system and modified with a 6.0 phr level of stearic acid has been shown to exhibit excellent resistance to reversion when compared to a similar compound containing a normal 2.0 phr level of stearic acid. Improvements in the retention of laboratory abrasion resistance, heat generation, and most physical properties have been identified on test pieces subjected to typical truck retread overcure conditions. In highway fleet testing trials of 1100 × 22.5 truck retreads fitted to both third and fourth drive axles of tipper trucks, the modified compound displayed a 42% improvement in treadwear performance over the normal compound in the lower severity third axle positions while performance in the higher severity fourth axle positions was inferior by 20%. In comparison to a 55 SBR/45 BR truck tread, both NR compounds displayed superior wear performance on the fourth axles while some further adjustments of the modified compound are required to match the synthetic compound on the third axles. The reversal of wear performances for all compounds between third and fourth axles is due to the different abrasion mechanisms encountered. Laboratory abrasion rankings do not correlate with wear performances of compounds on the fourth drive axle of trucks, but they do correlate with wear performances on third drive axles. Despite the reversion characteristics of the normal semi-EV compound, no significant adverse effect on treadwear performance was evident at the start of tire life. The low heat generation of the modified compound in laboratory tests is confirmed in actual tire testing. Advantages in rolling resistance characteristics are also evident for the modified compound. Current studies at MRPRA suggest that further modifications of cure system design, in combination with the optimization of NR/BR ratios and mixing methods, will potentially provide NR dominant truck tread compounds which will exhibit superior wear performance in both the higher and lower abrasion severities encountered in heavy-duty truck tire service conditions.

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Vulcanization of Rubber Compounds

Rubber Chemistry and Technology ◽

10.5254/1.3546569 ◽

1940 ◽

Vol 13 (4) ◽

pp. 918-925 ◽

Cited By ~ 2

Author(s):

E. W. Booth ◽

D. J. Beaver

Keyword(s):

Zinc Oxide ◽

Hydrogen Sulfide ◽

Carbon Black ◽

Physical Properties ◽

Room Temperature ◽

Appreciable Effect ◽

Vacuum Oven ◽

Rubber Compounds ◽

Sulfide Content ◽

Hydrogen Sulfide Content

Abstract 1. Rubber dissolves approximately one per cent of hydrogen sulfide when saturated at room temperature. 2. All types of commercial accelerators are retarded in rate of vulcanization as a result of treatment with hydrogen sulfide, and the retardation is directly proportional to the hydrogen sulfide content. 3. The physical properties of mercaptobenzothiazole types of accelerators and diphenylguanidine are not permanently affected by hydrogen sulfide, but dithiocarbamates, thiuram sulfides, aldehydeamines and litharge are permanently affected. 4. Rubber compounds containing mercaptobenzothiazole types of accelerators or diphenylguanidine, which have been treated with hydrogen sulfide and then degassed in a vacuum oven, show normal rate of vulcanization. Compounds containing aldehydeamines, litharge or carbon black show permanent retarding, even after degassing. 5. Increased zinc oxide or sulfur has no appreciable effect on the retardation. 6. Little or no zinc sulfide is formed as a result of treatment with hydrogen sulfide. 7. Hydrogen sulfide treatment of rubber compounds retards the rate of combination of sulfur with rubber. 8. In no case did hydrogen sulfide treatment improve the physical properties of the vulcanizate.

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Scorching, and Other Plasticity Changes in Rubber Compounds on Heating

Rubber Chemistry and Technology ◽

10.5254/1.3547517 ◽

1931 ◽

Vol 4 (4) ◽

pp. 552-559

Author(s):

E. O. Dieterich ◽

J. M. Davies

Keyword(s):

Temperature Effects ◽

Room Temperature ◽

Degree Of Cure ◽

Test Pieces ◽

Rubber Compounds ◽

Operating Temperatures ◽

Safe Operating

Abstract A method is described which employs the Goodrich plastometer for detecting the initial stages of vulcanization of uncured rubber compounds. Reduction in plasticity, at standard room temperature, of test pieces previously heated for various intervals at selected temperatures is used to determine the degree of cure and thus to estimate safe operating temperatures and periods. Examples of the application of the method to a variety of compounds are presented. Other temperature effects, such as heat stiffening and softening, which have not previously been reported, are illustrated.

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Investigation on the Influence of Various Kinds of Soaps on the Mechanical Properties of Silica Filled Composites Based on Natural Rubber

Polymers and Polymer Composites ◽

10.1177/096739111802600407 ◽

2018 ◽

Vol 26 (4) ◽

pp. 325-334

Author(s):

Omar A. Al-Hartomy ◽

Ahmed A. Al-Ghamdi ◽

Said A. Fahra Al-Said ◽

Nikolay Dishovsky ◽

Mihail Mihaylov ◽

...

Keyword(s):

Mechanical Properties ◽

Zinc Oxide ◽

Fatty Acid ◽

Stearic Acid ◽

Natural Rubber ◽

Rubber Compounds ◽

Zinc Salts

The aim of this study was to investigate the influence that different fatty acid zinc salts had on the rheological, curing and mechanical properties of natural rubber based composites filled with silica and containing bi-functional organosilanes in the presence or absence of zinc oxide. The results demonstrated that the combination of zinc oxide and zinc soaps had a strongly pronounced anti-reversion effect. The absence of reversion in the cure curves of the rubber compounds comprising a combination of zinc oxide, stearic acid and zinc soaps, results in retention of their mechanical properties, even after overcure.

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Stearic Acid in Litharge-Cured Rubber Compounds

Rubber Chemistry and Technology ◽

10.5254/1.3535409 ◽

1929 ◽

Vol 2 (4) ◽

pp. 638-655

Author(s):

J. R. Sheppard

Keyword(s):

Zinc Oxide ◽

Stearic Acid ◽

Organic Acid ◽

Marked Effect ◽

The Other ◽

Low Grade ◽

Rubber Compounds ◽

Wide Range ◽

High Zinc ◽

Full Activation

Abstract Although an organic acid is essential to vulcanization with litharge, smoked sheet usually has enough natural acid for full activation. For example, when 5 per cent stearic acid (or similar softeners) was added to a standard smoked sheet in a high zinc oxide stock the properties were lowered. On the other hand, a “low-grade” rubber, Lapori, was greatly improved in a high zinc oxide formula by stearic and by other acids. Acidic softeners in a high zinc oxide stock increased set, even when they promoted vulcanization. In a pure gum litharge formula with smoked sheet, 1 per cent stearic had but little effect, while in a high gas black formula, 4 per cent stearic raised the tensile (probably due to improved dispersion) but had no marked effect on rate of cure. When litharge was used as the activator for mercaptobenzothiazole, stearic acid had but little effect either in pure gum or high gas black stocks. On the contrary, when zinc oxide was used proper curing was highly dependent on stearic, especially with gas black. The litharge-mercaptobenzothiazole compounds with gas black in tread stock proportions, either with or without stearic, yielded a high tensile over a wide range of cures.

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The effect of the compositional curing activator formation on the properties of elastomers

Proceedings of the Voronezh State University of Engineering Technologies ◽

10.20914/2310-1202-2019-4-178-183 ◽

2020 ◽

Vol 81 (4) ◽

pp. 178-183

Author(s):

O. V. Karmanova ◽

A. Y. Fatneva ◽

S. G. Tikhomirov ◽

L. V. Popova

Keyword(s):

Mechanical Properties ◽

Fatty Acids ◽

Zinc Oxide ◽

Stearic Acid ◽

Silicon Dioxide ◽

Physical And Mechanical Properties ◽

Rubber Compound ◽

Regulatory Requirements ◽

Rubber Compounds ◽

Positive Effect

The properties of rubber compounds and vulcanizates made using a compositional curing activator with a low content of zinc oxide were studied in this work. Technological modes of obtaining new curing activator activators in the form of an alloy of zinc oxide with a mixture of fatty acids have been developed. To give a convenient outlet shape, finely dispersed fillers of various types were introduced into the experimental products: silicon dioxide, carbon black, microcellulose, bentonite, shungite. The physicochemical properties of compositional curing activator were studied and it was established that, according to the values of acid and iodine numbers, the experimental products satisfy the regulatory requirements for stearic acid. A comparative analysis of the properties of elastomers of experimental products with widely used as curing activator activators of zinc oxide and stearic acid is carried out. It was found that the use of experimental products improves the processability of the compositions due to their better dispersion in an elastomeric medium. The ratios of the compositional curing activator components are determined, which ensure the optimal complex of vulcanization and physical and mechanical properties of elastomers made on their basis. The effectiveness of the action of composite vulcanization activator in the manufacture of elastomeric products is shown - a reduction in the mixing cycle of experimental compositions by an average of 10% is noted compared to the standard rubber compound. The analysis of the research results confirmed the improvement of technological and vulcanization properties of rubber compounds, resistance to scorching. It is shown that the use of compositional curing activators provides the required level of physical and mechanical properties of rubbers even with a decrease in the content of zinc oxide in the experimental product to 20 wt%, and also improves the dispersion of the components of the rubber compound, having a positive effect on the technological and vulcanization properties of rubber compounds.

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