A Peroxide Curing Butyl Rubber

1969 ◽  
Vol 42 (4) ◽  
pp. 1147-1154 ◽  
Author(s):  
C. E. Oxley ◽  
G. J. Wilson
Keyword(s):  
Natural Rubber ◽  
Chain Scission ◽  
Butyl Rubber ◽  
Polymer Chains ◽  
The Other ◽  
Cross Linking ◽  
Ethylene Propylene ◽  
Peroxide Curing ◽  
Polymer Reactions ◽  
Crosslinking Reactions

Abstract The reactions of peroxides with polymers have been studied for some time. They form an extensive part of vulcanization technology. Two types of reactions are generally recognized, those leading to crosslinking between polymer chains and those leading to scission of the chains. Natural rubber, polybutadiene and ethylene-propylene rubber are examples of polymers in which crosslinking reactions take place to a greater extent than reactions leading to chain scission and these polymer reactions with peroxides form a useful method of vulcanization. On the other hand, polyisobutene is an example of a polymer which degrades extensively and for polyisobutene and butyl rubber, peroxides have not found use as cross-linking agents.

Vulcanization Reactions in Butyl Rubber. Action of Dinitroso, Dioxime, and Related Compounds

1946 ◽  
Vol 19 (4) ◽  
pp. 900-914 ◽  
Author(s):  
John Rehner ◽  
Paul J. Flory
Keyword(s):  
Natural Rubber ◽  
Chemical Reactions ◽  
Active Agent ◽  
Butyl Rubber ◽  
Nitroso Compounds ◽  
Cross Linking ◽  
Oxidizing Agent ◽  
Nitroso Group ◽  
Oxidizing Agents ◽  
Related Compounds

Abstract Experiments have been carried out to determine the chemical reactions that occur when Butyl rubber is vulcanized by quinone dioxime or related compounds. Observations have been made of the reactions of these substances with simple olefins, and of the effect of oxidizing agents on the dioxime-type of vulcanization of Butyl in solution. The theory is proposed that, in the vulcanization of Butyl by quinone dioxime or its esters, in presence of oxidizing agents, the active agent is p-dinitrosobenzene formed by oxidation of the dioxime. Chemical reactions are suggested for the subsequent cross-linking or vulcanizing steps, and the results of confirmatory experiments are presented. p-Dinitrosobenzene and other polynitroso compounds are active vulcanizing agents for Butyl, natural rubber, Buna-S, Buna-N, and Neoprene, and do not require the addition of an oxidizing agent. It is suggested that vulcanization of natural rubber by polynitro compounds involves their reduction to corresponding nitroso compounds as the first step, and that the nitroso group adds to rubber to produce cross-linkages.

Tire Black Sidewall Surface Discoloration and Non-Staining Technology: A Review

1998 ◽  
Vol 71 (3) ◽  
pp. 590-618 ◽  
Author(s):  
Walter H. Waddell
Keyword(s):  
Fatigue Life ◽  
Natural Rubber ◽  
Outer Surface ◽  
Chain Scission ◽  
Butadiene Rubber ◽  
Ethylene Propylene ◽  
Polymer Decomposition ◽  
Sidewall Surface

Abstract The tire black sidewall is the outer surface that protects the casing against weathering. It is formulated for resistance to weathering, ozone aging, abrasion, tearing and cracking, and for good fatigue life by using blends of natural rubber and cis-butadiene rubber. Protection against ozone aging is of particular interest since reaction with these olefinically unsaturated elastomers results in polymer decomposition via chain scission. Use of N-alkyl, N′-aryl-para-phenylenediamine antiozonants has proved most effective. However, their use also results in a surface discoloration, and thus they can be used in only limited amounts when tire appearance is also an important factor. A review is made of the literature describing this surface discoloration problem and approaches to formulate a black sidewall compound to eliminate this surface discoloration upon exposure to ozone. Methods include use of non-staining antiozonants, and uses of elastomers with saturated backbones such as ethylene-propylene-diene terpolymers, halobutyl rubbers and brominated-isobutylene- co-para-methylstyrene.

Peroxide Curing of Ethylene-Propylene Elastomers

1988 ◽  
Vol 61 (2) ◽  
pp. 238-254 ◽  
Author(s):  
Robert C. Keller
Keyword(s):  
Free Radicals ◽  
Service Life ◽  
Chain Scission ◽  
Organic Peroxides ◽  
Stress Strain ◽  
Ethylene Propylene ◽  
Compression Set ◽  
Ethylene Content ◽  
Peroxide Curing ◽  
Improved Performance

Abstract 1. Ethylene-propylene elastomers, suitably compounded for extrusion applications, can be readily vulcanized with organic peroxides to meet emerging requirements of improved performance and longer service life. 2. Aralkyl or dialkyl classes of peroxides produce the preferred cure performance, highest physical properties, and lowest compression set. Choice of peroxide governs rate of cure but not necessarily the optimum in crosslinking efficiency. 3. Coagents are essential to the development of optimum cure and stress-strain properties. The bis-maleimide is very effective in compounds that contain significant quantities of process oil, antioxidants for increased heat resistance, or other materials that consume free-radicals. 4. Ethylene-propylene compositional parameters influencing vulcanization activity are the diene, both type and concentration, and the ethylene content. Reactivity of the terpolymers is dependent on the type and amount of diene utilized in the polymer synthesis. High ethylene content improves crosslinking efficiency because there are fewer propylene sequences where chain scission can occur. 5. Increasing levels of hydrocarbon process oil needed in fast extruding compounds require higher peroxide concentrations to maintain cure and stress-strain properties.

Ethylene Propylene Dicyclopentadiene Terpolymerization

1965 ◽  
Vol 38 (3) ◽  
pp. 620-626 ◽  
Author(s):  
G. Sartori ◽  
A. Valvassori ◽  
S. Faina
Keyword(s):  
Double Bond ◽  
Liquid Phase ◽  
Butyl Rubber ◽  
The Other ◽  
Relative Reactivity ◽  
Ethylene Propylene

Abstract Monomers (both monoolefinic and diolefinic) containing the bicyclo[2.2.1] heptene system copolymerize with ethylene and propylene by opening the double bond of the endo-methylenic system without rupture of the bicycloheptene system itself. Therefore, only diolefinic monomers produced unsaturated terpolymers. The rate of ethylene-propylene-dicyclopentadiene terpolymerization and the relative reactivity of ethylene and propylene are influenced by the concentration of dicyclopentadiene present in the liquid phase. The rate of vulcanization of ethylene-propylene-dicyclopentadiene terpolymers is slower than that of the other synthetic elastomers (butyl rubber, ethylene-propylene-cyclooctadiene-1,5 terpolymer).

Different Curing Systems for Ethylene-Propylene Elastomers

1992 ◽  
Vol 65 (5) ◽  
pp. 869-878 ◽  
Author(s):  
Luis González Hernández ◽  
Andrés Rodríguez Díaz ◽  
Juan Luis de Benito González
Keyword(s):  
Physical Properties ◽  
Dynamic Mechanical Analysis ◽  
Chain Scission ◽  
Mechanical Analysis ◽  
Curing Agent ◽  
Ethylene Propylene ◽  
Dynamic Mechanical ◽  
Peroxide Curing ◽  
Chain Scission Reaction ◽  
Curing Systems

Abstract The scope of this paper is to review peroxide curing of ethylene-propylene elastomers, where apart from crosslinking, other reactions occur, such as chain scission, which account for the drop in physical properties. The results are compared with an alternative crosslinking system which is being assessed in our laboratory. With the new curing agent the chain-scission reaction is not present and the physical properties of the vulcanizates are improved. The effects of the different crosslinking systems on the reaction transitions are studied with the aid of dynamic mechanical analysis.

Mechanisms Involved in the Recycling of NR and EPDM

1999 ◽  
Vol 72 (4) ◽  
pp. 731-740 ◽  
Author(s):  
M. A. L. Verbruggen ◽  
L. van der Does ◽  
J. W. M. Noordermeer ◽  
M. van Duin ◽  
H. J. Manuel
Keyword(s):  
Natural Rubber ◽  
Crosslink Density ◽  
Main Chain ◽  
Chain Scission ◽  
Ethylene Propylene ◽  
Temperature Range ◽  
Lower Reactivity ◽  
Ethylene Propylene Diene Rubber ◽  
Diene Rubber ◽  
Crosslink Densities

Abstract The thermochemical recycling of natural rubber (NR) and ethylene-propylene-diene rubber (EPDM) vulcanizates with disulfides was studied. NR sulfur vulcanizates were completely plasticized when heated with diphenyldisulfide at 200 °C. It could be concluded that both main chain scission and crosslink scission caused the network breakdown. NR peroxide vulcanizates were less reactive towards disulfide at 200 °C, and only reacted through main chain scission. For EPDM a temperature range of 200–275 °C was studied. In the presence of diphenyldisulfide at 200 °C there was almost no devulcanization of EPDM sulfur vulcanizates, and at 225 and 250 °C there was only slightly more devulcanization. A decrease in crosslink density of 90% was found when 2×10−4 mol diphenyldisulfide/cm3 vulcanizate was added and the EPDM sulfur vulcanizates were heated to 275 °C. EPDM peroxide vulcanizates showed a decrease in crosslink density of ca. 40% under the same conditions. The lower reactivity of EPDM towards disulfide compared with NR is the result of higher crosslink densities, the presence of a higher percentage of more stable monosulfidic crosslinks and the fact that EPDM is less apt to main chain scission relative to NR.

Chain Scission Efficiency in the Oxidation of Natural Rubber Vulcanizates

1957 ◽  
Vol 30 (4) ◽  
pp. 1146-1161
Author(s):  
A. G. Veith
Keyword(s):  
Natural Rubber ◽  
Elevated Temperatures ◽  
Density Ratio ◽  
Direct Consequence ◽  
Chain Scission ◽  
Polymer Chains ◽  
Published Report ◽  
Relaxation Measurements ◽  
A Chain ◽  
Chain Scission Reaction

Abstract Natural rubber when it degrades under the action of oxygen does so primarily by a chain scission reaction. A technique has been developed by Tobolsky and coworkers for assessing the magnitude of this chain scission reaction in vulcanizates by means of continuous stress relaxation measurements. Since the result of the oxygen attack on the rubber is a chain scission reaction, the question of the efficiency of the reaction comes to mind. The influence of antioxidants is of importance in this regard as is the type of vulcanizate or network structure. This paper describes some measurements of the chain scission efficiency of a simple benzothiazolyl disulfide (MBTS) vulcanizate and the effect of several antioxidants on this chain scission reaction. Some of the complications inherent in this type of measurement are discussed. The first published report on the efficiency of the chain scission reaction in vulcanizates was given by Tobolsky, Metz, and Mesrobian in 1950. A more recent publication is that of Baxter, Potts, and Vodden in 1955. Tobolsky has interpreted the stress decay of gum vulcanizates at elevated temperatures as a direct consequence of the cutting of polymer chains of the network. The reduced stress is postulated as being equal to the chain density ratio:

Effects of Frequency and Sonication Time on Ultrasonic Degradation of Natural Rubber Latex

2013 ◽  
Vol 747 ◽  
pp. 721-724 ◽  
Author(s):  
S. Utara ◽  
U. Moonart
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Average Molecular Weight ◽  
Natural Rubber Latex ◽  
Gel Permeation Chromatography ◽  
Chain Scission ◽  
Polymer Chains ◽  
Rubber Latex ◽  
Ultrasonic Degradation ◽  
The Fourier Transform

Ultrasonic degradation of fresh latex was investigated at frequencies of 20 and 25 kHz, at a constant temperature of 25o C (±1o C) to avoid temperature-related effects. The time-dependent evolution of the molecular weight of the natural rubber latex was determined using gel permeation chromatography, and its structure by means of the fourier transform infrared (FTIR) technique. A 10 minute period of sonication resulted in reduction in the molecular weight of both the 20 and 25 kHz treated samples, the lowest average molecular weight () being obtained in the case of the 25 kHz sample. The of the 25 kHz sample also decreased with increasing latex concentration. However, after 30 minutes, fluctuations had occurred in both samples with respect to the and and also the molecular weight distributions, an effect possibly explained by the competing processes of chain scission and radically-induced cross-linking of the polymer chains. The FTIR results also suggest that the structure of polyisoprene is unaltered by ultrasonic wave treatment at these frequencies.

Dependence of Tensile Strength of Vulcanized Rubber on the Degree of Cross-Linking

1950 ◽  
Vol 23 (1) ◽  
pp. 27-43
Author(s):  
Paul J. Flory ◽  
Norman Rabjohn ◽  
Marcia C. Shaffer
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Chain Scission ◽  
General Character ◽  
Cross Linking ◽  
Vulcanized Rubber ◽  
Relationship Of ◽  
The Relationship ◽  
Considerable Detail ◽  
Proportionality Relationship

Abstract The suitability of disazodicarboxylates as quantitative cross-linking agents for the preparation of rubber vulcanizates of known degrees of cross-linking has been emphasized previously. In a recent paper we have presented the results of an investigation on the dependence of the equilibrium force of retraction on the elongation and degree of cross-linking of rubber and GR-S vulcanized with these compounds. The present paper reports an extension of these investigations of the relationship of physical properties of rubberlike materials to their network structure. Specifically, the tensile strength of azo vulcanized natural rubber has been explored as a function of the degree of cross-linking and of the extent of modification of the chain units. The tensile strengths of natural rubber specimens vulcanized to various extents using sulfur alone or sulfur in conjunction with various accelerators have been investigated in considerable detail recently by Gee, who has emphasized the critical dependence of the tensile strength on the degree of cross-linking. Values for the latter quantity, however, were deduced indirectly from the equilibrium force of retraction using the simple proportionality relationship between force of retraction and degree of cross-linking afforded by the theory of rubber elasticity. This relationship is known to be only approximately valid. Furthermore, the effects on the force of retraction of chain scission, which doubtless accompanied some of the vulcanizations to a considerable degree, were disregarded. For these reasons, Gee's values for the degrees of cross-linking occurring in his vulcanizates are only approximate estimates, and in a few cases they may be seriously in error. Nevertheless, the general character of the relationship between tensile strength and degree of cross-linking which he obtained is confirmed by our results on rubber samples quantitatively cross-linked with measured proportions of decamethylene-dismethyl azodicarboxylate.

Oxidation of GR-S and Other Elastomers

1947 ◽  
Vol 20 (3) ◽  
pp. 747-759
Author(s):  
John O. Cole ◽  
James E. Field
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Physical Properties ◽  
Experimental Methods ◽  
Chain Scission ◽  
Cross Linking ◽  
Antioxidant Action ◽  
Mechanism Of Oxidation ◽  
Natural Rubber Vulcanizates

Abstract The effect of heat aging on the physical properties of an elastomer is generally considered the result of oxidation, which produces both chain scission and cross-linking in the polymer. Early in the development of GR-S, a marked difference in the aging of GR-S and natural rubber vulcanizates was observed. From the effect of aging on hardness, tensile strength, modulus, and elongation it appeared that cross-linking occurred more rapidly than chain scission with GR-S, but the reverse was true with natural rubber. The work reported here was undertaken to provide a better understanding of the differences in aging of GR-S and natural rubber and to introduce new experimental methods for studying the mechanism of oxidation and antioxidant action in elastomers.

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