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.

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.

Translucent Thermoplastic Elastomers

2009 ◽  
Vol 82 (1) ◽  
pp. 94-103
Author(s):  
Maria D. Ellul ◽  
D. R. Hazelton
Keyword(s):  
Thermal Stability ◽  
Thermoplastic Elastomer ◽  
Thermoplastic Elastomers ◽  
New Materials ◽  
Dynamic Vulcanization ◽  
Ethylene Propylene ◽  
Fluid Delivery ◽  
Compression Set ◽  
Ethylene Content

Abstract Thermoplastic elastomer vulcanizates, TPVs, having the property of optical translucence have been prepared by dynamic vulcanization. The new materials are based on a polypropylene homopolymer principally containing propylene units of exactly alternating configuration and having a syndiotactic pentad fraction of at least 0.86. The dispersed elastomer phase consists of a crosslinked ethylene propylene copolymer rubber having an ethylene content of at least 74 weight %. These thermoplastic elastomer compositions have significantly lowered Gardner haze values, while maintaining the desirable properties of low compression set and thermal stability. The compositions have utility in molded mechanical rubber goods as well as extruded articles for fluid delivery applications.

Rubber Process Oils for Peroxide Curing of Ethylene—Propylene Elastomers

1992 ◽  
Vol 65 (2) ◽  
pp. 385-395 ◽  
Author(s):  
Kent L. Chasey
Keyword(s):  
Free Radical ◽  
Analytical Methods ◽  
Molecular Structures ◽  
Combined Effects ◽  
Stress Strain ◽  
Ethylene Propylene ◽  
Peroxide Curing

Abstract Ten rubber process oils were evaluated in a peroxide-cured EPDM compound. The effects of the process oil on cure-development characteristics and stress—strain properties are discussed. Certain types of molecular structures in the oil can significantly interfere with free-radical vulcanization, and analytical methods for the detection of these structures are provided. The combined effects of the process oil and the peroxide—coagent concentration are also described.

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.

Compressive Deformation and Energy Absorption Characteristics of Conductive Carbon Black Reinforced Microcellular EPDM Vulcanizates

2005 ◽  
Vol 24 (4) ◽  
pp. 209-222 ◽  
Author(s):  
S.P. Mahapatra ◽  
D.K. Tripathy
Keyword(s):  
Carbon Black ◽  
Compressive Stress ◽  
Energy Absorption ◽  
Filler Loading ◽  
Maximum Efficiency ◽  
Stress Strain ◽  
Blowing Agent ◽  
Compression Set ◽  
Rate Dependent ◽  
Conductive Carbon Black

Compressive stress-strain properties of unfilled and conductive carbon black (VulcanXC 72) filled oil extended EPDM (keltan 7341A) microcellular vulcanizates were studied as a function of blowing agent (density) and filler loading. With decrease in density, the compressive stress-strain curves for microcellular vulcanizates behaved differently from those of solid vulcanizates. The compressive stress-strain properties were found to be strain rate dependent. The log-log plots of relative density of the microcellular vulcanizates showed a fairly linear correlation with the relative modulus. The compression set at a constant stress increased with decrease in density. The efficiency of energy absorption E, was also studied as a function of filler and blowing agent loading. From the compressive stress-strain plots the efficiency E and the ideality parameter I, were evaluated. These parameters were plotted against stress to obtain maximum efficiency and the maximum ideality region, which will make these materials suitable for cushioning and packaging applications in electronic devices.

scholarly journals Scission, Cross-Linking, and Physical Relaxation during Thermal Degradation of Elastomers

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1280 ◽  
Author(s):  
Zaghdoudi ◽  
Kömmling ◽  
Jaunich ◽  
Wolff
Keyword(s):  
Operating Time ◽  
Thermal Exposure ◽  
Chain Scission ◽  
Cross Linking ◽  
Butadiene Rubber ◽  
Compression Set ◽  
Model Compression ◽  
Relaxation Measurements ◽  
Thermally Driven

Elastomers are susceptible to chemical ageing, i.e., scission and cross-linking, at high temperatures. This thermally driven ageing process affects their mechanical properties and leads to limited operating time. Continuous and intermittent stress relaxation measurements were conducted on ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) samples for different ageing times and an ageing temperature of 125 °C. The contributions of chain scission and cross-linking were analysed for both materials at different ageing states, elucidating the respective ageing mechanisms. Furthermore, compression set experiments were performed under various test conditions. Adopting the two-network model, compression set values were calculated and compared to the measured data. The additional effect of physical processes to scission and cross-linking during a long-term thermal exposure is quantified through the compression set analysis. The characteristic times relative to the degradation processes are also determined.

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.

Stress Relaxation of Sugi (Cryptomeria japonica D.Don) Wood in Radial Compression under High Temperature Steam

Holzforschung ◽  
1999 ◽  
Vol 53 (5) ◽  
pp. 541-546 ◽  
Author(s):  
W. Dwianto ◽  
T. Morooka ◽  
M. Norimoto ◽  
T. Kitajima
Keyword(s):  
High Temperature ◽  
Stress Relaxation ◽  
Cryptomeria Japonica ◽  
Chain Scission ◽  
Strain Recovery ◽  
Crystalline Lattice ◽  
Compressive Deformation ◽  
Radial Compression ◽  
Stress Strain ◽  
Permanent Fixation

Summary To clarify the mechanism of the permanent fixation of compressive deformation of wood by high temperature steaming, stress relaxation and stress-strain relationships in the radial compression for Sugi (Cryptomeria japonica D.Don) wood were measured under steam at temperatures up to 200°C. The stress relaxation curves above 100°C were quite different in shape from those below 100°C, showing a rapid decrease in stress with increasing temperature. In the stress-strain relationships measured above 140°C, the stress reduced as pre-steaming time increased when compared at the same strain. The recovery of compressive deformation (strain recovery) was decreased with steaming time and reached almost 0 in 10 min at 200°C. The relationship between the residual stress and the strain recovery at the end of relaxation measurements could be expressed by a single curve regardless of time and temperature. The permanent fixation of deformation by steaming below 200°C was considered to be due to chain scission of hemicelluloses accompanying a slight cleavage of lignin. In some cases, the increase in regularity of the crystalline lattice space of microfibrils or the formation of crosslinks between the cell wall polymers seemed to play an important role in the permanent fixation of compressive deformation.

Polyisocyanates as Curing Adjuvants for Ethylene—Propylene Terpolymers

1964 ◽  
Vol 37 (4) ◽  
pp. 927-933
Author(s):  
J. R. Wolfee ◽  
J. R. Albin
Keyword(s):  
Tensile Strength ◽  
Low Cost ◽  
New Method ◽  
Mineral Filler ◽  
High Modulus ◽  
Stress Strain ◽  
Ethylene Propylene ◽  
Reinforcing Fillers ◽  
Light Color ◽  
Mineral Fillers

Abstract Ethylene—propylene—nonconjugated diene terpolymers yield vulcanizates of high modulus and tensile strength in the presence of strongly reinforcing fillers. In many applications where low cost, light color, or nonconductivity are required, it is necessary to use poorly reinforcing mineral fillers. The combination of poorly reinforcing mineral filler and amorphous EP terpolymer yields vulcanizates which do not have the excellent stress-strain properties characteristic of many black loaded stocks. The purpose of this paper is to present a new method of obtaining superior properties in mineral filled EP terpolymer vulcanizates.

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