The Use of Coagents

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The Use of Coagents in the Radical Cure of Elastomers

Steven K. HenningSartomer Company, Inc.

Exton, PA, USA610-363-8454 [email protected]

AbstractThe present article will review the use of coagents in the radicalcure of elastomers, and introduce the concept of improvingvulcanizate performance by proper coagent selection through anunderstanding of structure-property relationships. A wide variety

of commercially available coagent types will be discussed, alongwith relevant application data supporting their use in peroxidecured systems. Illustrative examples include elastomers used inthe wire and cable industry. A brief extension into electron beam

curing of elastomers offers a comparison between peroxide-derived radical cure and cure initiated by incident radiation.

Keywords: coagent; peroxide; electron beam; cure; elastomer;EPDM; CM; NBR; wire; cable

1. IntroductionBy crosslinking elastomeric polymers, useful materials can be

formed which possess physical properties such as high tensilestrengths, low compression set, recoverable elongations, high tearenergies, and improved dynamic performance. The quantity andquality of the linkages formed by the crosslinking reactions

determine the properties of the resulting network.

There are many types of vulcanization systems. Deciding whichsystem is optimal for a given application depends on the required

curing conditions, the elastomer or elastomer blend employed, andthe desired physical properties of the final vulcanizate. Often,free radicals are used to facilitate cure. Radicals can be formed

either through the thermal decomposition of peroxides or

spontaneously by incident radiation. Peroxides are capable ofvulcanizing most polymer types, including standard unsaturated

and saturated elastomer grades, fluoroelastomers, and silicones.Electron-beam irradiation is also a facile method. The synergisticuse of coagents in radical-cure systems helps expand the utility ofthe vulcanization process.

Networks formed from radical vulcanization typically possessgood heat-ageing stability and low compression set. Thesequalities are a direct manifestation of the chemical composition ofthe crosslinks formed. Synergistic use of multifunctional

coagents can improve upon these properties by increasing thecrosslink density of the network and by altering the crosslinkcomposition. There are many functional compounds that have

been used as coagents for radical cure. The final properties of the

formed network will depend on the reactivity and structure of thecoagent. In the wire and cable market, application of radical-cured thermoset components include insulation and jacketing.The use of coagents can improve the physical properties of these

compounds, including modulus, tensile strength, tear, and evenadhesion and dynamic properties.

The present article will review the use of peroxides to cureelastomer systems, and introduce the concept of improvingvulcanizate performance by proper coagent selection. Many

commercially available coagent types will be discussed, and theirutility demonstrated as a function of elastomer type. The use of

coagents in electron-beam curing will also be reviewed.Particular attention will be focused on the understanding ofstructure-property relationships to facilitate coagent selection.

2. Peroxide Cure Using CoagentsThe basic chemistry of peroxide decomposition and subsequentcrosslink-forming reactions is well established for various

unsaturated and saturated elastomer systems.[1 , 2 , 3 , 4 ] Anexcellent review article outlines the scope of peroxide cure anddiscusses the complexity of reaction pathways in terms of

competing reactions, only some of which result in effectivecrosslink formation.[5]

2.1 Coagent UtilityOf course the desired reaction pathway for a radical species iscrosslink formation. The competitive reactions include polymerscission or other deleterious reactions. Unfortunately, many of

the destructive reactions are kinetically favored, and typicallyonly a very high concentration of reactive sites on the polymer

backbone allows for effective crosslink formation to occur at all.

However, productive crosslink formation can be favored throughthe use of very reactive, multifunctional coagent products.Coagents favor network formation by increasing the localconcentration of highly reactive groups. In borrowing the themeof competing reactions, the utility of coagents is derived from

promoting more efficient crosslink formation by establishing a

higher concentration of reactive sites and reducing the chance ofdeleterious radical side reactions. Of course, the incorporation ofcoagents into the network can also favorably impact the physical

properties of the vulcanizate.

2.2 Coagent Structure-Property RelationshipsCoagents are classified based on their contributions to cure andthus divided into two basic types. Type I coagents increase boththe rate and state of cure. Type I coagents are typically polar, low

molecular weight multifunctional compounds which propagatevery reactive radicals through addition reactions. Thesemonomers can be homopolymerized or grafted to polymerchains. Type I coagents include multifunctional acrylate and

methacrylate esters and phenylene dimaleimide (PDM). The zincsalts of acrylic (ZDA) and methacrylic acid (ZDMA) also belong

to this class.

Type II coagents form less reactive radicals and contribute only tothe state of cure. They form radicals primarily through hydrogenabstraction. Type II coagents can include allyl-containingcyanurates, isocyanurates and phthalates, homopolymers of

dienes, and co-polymers of dienes and vinyl aromatics. Table 1identifies commonly used coagent products. Figure 1demonstrates the departures from a standard peroxide curerheometer profile when coagents from each Type are applied.

International Wire & Cable Symposium 587 Proceedings of the 56th IWCS


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Figure 1. The influence on cure profiles of Type Icoagents (A), Type II coagents (B), compared withperoxide alone (C). The shift in scorch time (ts2), curerate (t90), and state of cure (MH) is noted.

2.3 Coagent Role in Network FormationBecause of their reactivity, coagents generally make moreefficient use of the radicals derived from peroxides, whetheracting to suppress non-network forming side reactions duringcure[6,7] or to generate additional crosslinks.[8] The mechanism

of crosslink formation using coagents appears to be at leastpartially dependent on their class. Most Type I coagents canhomopolymerize and graft-to forming viable crosslinks throughradical addition reactions. Certain Type II coagents, containing

extractable allylic hydrogen, have been shown to participate inintramolecular cyclization reactions as well as intermolecular

propagation reactions.[9] Trifunctional allylic coagents (TAC andTAIC) may form crosslinks through the cyclopolymerization

products as well as grafting through pendant allyl groups. Thepolymeric coagents, typically high vinyl poly(butadienes)(HVPBD), simply increase the concentration of reactive pendantunsaturation, further promoting crosslinking reactions.

Table 1. Examples of some commonly used coagentproducts.

Chemical Name Code Type Commercial Product

trifunctional acrylate, scorch retarded TA Type I Saret SR519HP

t ri func tional methacrylate , scorch re tarded TMA Type I Saret SR517HP

zinc diacrylate, scorch retarded ZDA Type I Saret SR633

zinc dimethacrylate, scorch retarded ZDMA Type I Saret SR634

N, N-m-phenylene dimaleimide PDM Type I SR525

polybutadiene diacrylate PBDDA Hybrid SR307

triallyl cyanurate TAC TypeII SR507

triallyl isocyanurate TAIC Type II SR533

high vinyl polybutadiene HVPBD Type II Ricon 154

Network enhancement through the grafting of coagents betweenpolymer chains,[8, 10 ] the formation of an interpenetratingnetwork of homopolymerized coagents,[11] and the formation of

higher modulus filler-like domains of thermoset coagent [9,12]

has been suggested. Rather than the above cases being distinctoutcomes of vulcanization, the resulting network is likely defined

by a distribution of the above crosslink structures. The actual

population of the distribution is determined by a host a factorsincluding coagent loading, solubility of the coagent in theelastomer, and the relative reactivity of the coagent compared tothe elastomer. Figure 2 provides an ideal representation of the

spectral nature of crosslink structures derived from peroxide cureusing coagents.

Figure 2. Idealized network derived from a peroxide-coagent cure system. Crosslinks can be derived from(A) polymer radicals, (B) coagent forming effectivecrosslinks, and (C) thermoset domains of coagentgrafted to polymer chains.

3. Coagent SelectionWhile most coagents will increase the crosslink density in radical

cured thermoset systems, the relative amount of improvement inthe physical properties of the vulcanizate is determined by anumber of factors.[ 13 , 14 ] Again, coagent solubility andreactivity in a particular system is important in determining thequantity of crosslinks formed and typically drives the selection

process. However, the structure of the crosslink is alsodetermined by the coagent product and can be tuned to impartcertain adventitious properties to the compound. Thus, the qualityof the crosslinks can also be manipulated by proper coagent

selection.

3.1 Crosslink QuantityThe number of crosslinks formed is determined by several factors,

including the reactivity of the coagent, the number of reactivegroups (functionality), and the loading and solubility of the

coagent in the elastomer. The relationship between crosslinkdensity and tensile, compression, and tear has been previouslyestablished.[15] Torque rheometry is a standard method used tomeasure the amount of crosslink density by comparing the amount

of torque generated during cure (delta torque, MH-ML).

3.1.1 Differentiation by Elastomer. To demonstrate relativeimprovements in crosslink density for a Type I and Type IIcoagent, Figure 3 compares the addition of a trifunctional acrylateester monomer or HVPBD resin to a dicumyl peroxide curesystem in a variety of standard elastomer grades. The series offers

insight as to the importance of coagent selection as a function ofelastomer structure. The elastomers used in the study are definedin Table 2.

Table 2. ASTM designations of commonly usedelastomers.

ASTM Polymer

Designation Structure

NR natural rubber

NBR nitrile rubber

EPDM ethylene propylene diene rubber

HNBR hydrogenated nitrile rubber

CSM chlorosul fonated polyethylene

CM chloronated polyethylene



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Moving left to right in Figure 3 the elastomer grades becomemore saturated, and were less effectively cured by peroxide alone.

The overall state of cure decreased as a function of elastomersaturation. The addition of a Type I coagent provided ameasurable improvement in the state of cure for all elastomers,

but the percent improvement was greatest for the fully saturated

grades (CM, CSM). The use of a Type II coagent only providedappreciable improvement in the less reactive grades (HNBR,EPDM, CSM, CM). Coagents with less reactive groups (allylic,

Type II) could not compete effectively with the highconcentration of unsaturation in the diene-based elastomers (NR,

NBR) and their contribution to cure state was minimized.

Figure 3. Influence on crosslink density (delta torque,MH-ML) for a Type I (TA) or Type II (HVPBD) coagentcompared to peroxide cure as a function of elastomergrade. (ASTM D 5289)

3.1.2 Differentiation by Coagent. Two of the mostcommon elastomers used in wire and cable applications areEPDM and CM. Model compounds using these elastomer gradeswere prepared to highlight the effects of various coagent

structures on cure kinetics and physical properties. Highlighted inthe figure below are both a comparison between grades ofelastomers (EPDM, 5% unsaturation and CM, fully saturated),

and the influence of coagent addition on properties in these gradesas a function of coagent structure.

Figure 4 provides a comparison of crosslink density (delta torque)as a function of coagent type in these elastomers. Again, EPDMdisplyed higher baseline crosslink density compared to CM.Density increased with coagent addition for both grades. InEPDM, increases were greater for Type I coagents versus Type II.

However in the case of CM, the highest increase in crosslinkdensity was found for TAC, a Type II coagent.

Scorch times provide a measurement of process safety, indicating

the latent period at a given temperature before appreciablevulcanization occurs. The data in Figure 5 demonstrates thatType I coagents typically reduce scorch times while Type II

coagents minimize the loss of scorch safety. Also, scorch timesare reduced more dramatically when coagents were applied to lessinherently reactive elastomer grade (CM).

Figure 4. Delta torque (MH-ML) for EPDM and CM basedcompounds as a function of coagent type. Coagentloading at 1 phr. (ASTM D 5289)

Figure 5. Scorch times (ts2) for EPDM and CM basedcompounds as a function of coagent type. Coagentloading at 1 phr. (ASTM D 5289)

Modulus values typically follow delta torque, as both can be

directly correlated to crosslink density. Figure 6 provides 100%modulus data for the previous EPDM and CM series. All the

coagents surveyed increase the modulus of the compoundcompared to the peroxide control. The differences in the absolute

values of modulus are related to the composition of the modelformulations themselves and are not attributable to elastomer-coagent interactions.

Figure 6. 100% modulus for EPDM and CM basedcompounds as a function of coagent type. Coagentloading at 5 phr. (ASTM D 412)



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While increasing the quantity of crosslinks is perhaps the singlemost important attribute of applied coagent technology,

differentiation in certain physical properties of the vulcanizate canfurther be attained by changing the quality of crosslinks as well.

3.2 Crosslink QualityBy judicious selection of coagent structure, the quality ofcrosslinks can be influenced along with the quantity. When acoagent is incorporated as a crosslink in the network, it becomes a

load bearing member. By changing the chemical structure of thecoagent, the response of the entire network to induced strains can

be favorably altered. Measurable physical properties such as tearstrength, dynamic flexural fatigue, and compression set areaffected. In addition, surface properties such as adhesion can also

be promoted.

The zinc salts of acrylic and methacrylic acid (ZDA, ZDMA) areunique in the field of coagents as they contain an ionic bond.

When included in a peroxide cure system, the zinc-based coagentsform crosslinks and manifest physical properties attributable tothe ionic nature of their structure. The dissociation energy of the

Zn-O bond has been calculated to lie between carbon-carbonbonds and polysulfidic bonds (Table 3.) Peroxide cure generates

mainly carbon-based linkages, and heat resistance and lowcompression set are well-known attributes static applications. Theuse of polysulfidic crosslinks dominates dynamic applications, asthe labile linkages are known to break and reform under strain toalleviate stress.[ 16 ] As a result, networks comprised of

polysulfidic linkages display excellent tear and flexural fatigueproperties.

Table 3. Bond dissociation energies for selectedcrosslink structures.

Dissociation Energy

Cure System Bond Type Structure (kJ/mol)

Peroxide -C-C- carbon 335

Sulfur -S-C monosulfidic 314

Sulfur -Sx- polysulfidic 147Peroxide, Coagent -Zn-O- ionic 293

3.2.1 Tear Strength. Tear properties can be improved byincorporating ionic crosslink density into the network.[17] Anillustrative example is provided in Figure 7. For a series of Type I

and Type II coagents in an EPDM formulation, only ZDMAimproves tear strength as a function of increasing modulus.

Figure 7. Tear strength as a function of modulus forZDMA, TA, TAC, and HVPBD in an EPDM compound.Coagent loadings at 1, 5, and 10 phr. (ASTM D 624-C)

3.2.2 Flexural Fatigue. It has also been demonstrated that theflexural fatigue properties of peroxide-cured materials can beimproved thought the incorporation of ionic crosslinks fromZDMA.[ 18 , 19 ] A peroxide control, peroxide with ZDMA

coagent, and a semi-efficient sulfur vulcanization system wereeach used to cure an EPDM compound to constant modulus.Crack growth was measured on a Demattia flex tester. The resultsare summarized in Figure 8.[4] When incorporating ionic

crosslinks into the network, flexural fatigue was significantly

improved over the peroxide control and compared favorably to thesulfur vulcanized sample.

Figure 8. Number of cycles to 12.7 mm crack width asmeasured on a Demattia flex tester at 300 cpm in anEPDM compound. ZDMA loading at 5 phr. (ASTM D430-B) [4]

3.2.3 Adhesion. Adhesion of rubber to most metals must beengineered as it is not an inherent property. With the notable

exception of sulfur cured rubber and brass, most rubber systemsmust utilize applied adhesives or functional additives to facilitatean adhesive bond to metal. It has been found that zinc-basedcoagents can establish a strong bond to most metal substrates, and

also improve the adhesion of peroxide-cured rubber to treatedpolar fabrics.[20 ] In Figure 9, several Type I and Type II

coagents have been added to a peroxide cured EPDM compoundat 5 phr. Lap shear adhesion to steel was measured. Coagents

ZDMA and ZDA provided a high level of adhesion with samplesexhibiting cohesive failure. The use of other coagents resulted inadhesive failure.

Figure 9. Lap shear adhesion of a peroxide-curedEPDM compound with cold rolled steel. Coagentloading at 10 phr. (ASTM D 816-B)



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Producing adhesion through the use of zinc-based coagents is atechnology which is dependent on the cure process. Adhesion is

only adequately generated if the rubber sample is cured-in-placeadjacent to the substrate to which is to be adhered.

3.2.4 Compression Set. While compression set is largelydetermined by the number of crosslinks formed (quantity), the

bond strength of the crosslinks also influences the amount of

permanent set. ZDMA contains an ionic bond with significantly

lower calculated dissociation energy than the other monomericand polymeric coagents. Whereas this structural feature isadvantageous for other physical properties, it can negatively affectcompression set. Figure 10 demonstrates the influence of coagent

addition on compression set in EPDM and NBR formulations.Standard coagents, regardless of type, reduced permanent set ascrosslink density increases. However, despite increased crosslinkdensity, the addition of ZDMA did not follow the same trend and

resulted in increased permanent set.

Figure 10. Compression set for EPDM and NBR basedcompounds as a function of delta torque (MH-ML).Coagent loading at 5 phr. (ASTM D 5289, 395)

Spatial homogeneity of the crosslink density is also an importantfactor in minimizing compression set. The solubility parameter of

the coagent should be well matched to the elastomer to which it isapplied to maximize dispersion of the coagent and promoteeffective crosslinking.

Most Type I coagents show poor solubility in hydrocarbon-based

elastomers (dienes, EPM, EPDM) as they are quitepolar.[ 21 , 22 , 23 ] The largest impact on cure kinetics andvulcanizate properties are often derived from structures having theleast solubilitymultifunctional acrylates or zinc salts with a highreactive group densitytranslating to a high molar concentration

of reactivity per phr of coagent. The addition of hydrocarboncharacter to improve solubilitylonger alkyl bridging groups,

pendant methyl to tertiary butyl structures, etc.may alsodecrease the apparent reactivity by either steric hindrance or

molar dilution effects. The polymeric Type II coagents tend notto increase modulus upon curing to the extent of the Type I diene-

based coagents. These materials are typically much more solublein the elastomeric matrix, as the difference in solubility

parameters is much less pronounced. Domain formation istypically not exhibited. They can provide moderate

improvements in tensile properties and compression set while notadversely effecting elongation or tear strength.

3.3 Physical Property OptimizationAs noted above, the proper selection of coagents for a given

application sometimes involves reaching a balance betweenmutually exclusive properties. Improved properties such asmodulus and tensile strength are known to correlate withincreased crosslink density. However, modulus improvements

may often lead to decreased tear strength when using standardcoagents (Figure 7). The notable exception in the latter case is theuse of zinc-based coagents. The addition of ZDA and ZDMA can

also increase compression set, a property normally improvedwhen applying other coagent products (Figure 10). Other

properties such as elongation and flexibility are inverselyproportional to crosslink density. Figure 11 demonstrates such atrend in both the EPDM and CM formulations used previously.

Figure 11. Elongation as a function of modulus for aseries of coagents in an EPDM compound. Coagentloadings at 1, 5, and 10 phr. (ASTM D 412)

A reduction in scorch protection has been demonstrated whenapplying Type I coagents. However, the loss in scorch safety

exhibited by the Type I coagents can be mediated by the use ofcure retarders. The application of retarding species in peroxidecure has been reviewed.[1,9] Type I coagents are often available

as proprietary mixtures including radical-scavenging retarders,providing prolonged scorch safety while maintaining cure rate andgreater crosslink density.[24] Figure 12 summarizes the benefitsin using scorch retarded coagents. As shown, the addition of a

scorch retarder to the coagent can mitigate a reduction in processsafety. With a slight increase in coagent or peroxide level, totalcrosslink density and final vulcanizate properties can bemaintained.

Figure 12. Scorch times (ts2) for several Type Icoagents both with retarder package (Saret

) and

without (coagent only) in EPDM compound. Coagentloading at 5 phr. (ASTM D 5289)



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The common trade-offs in physical properties highlighted abovemust be managed relative to the desired performance targets of the

compound in a given application. Coagent selection is critical tothe optimization process. By understanding the advantages anddisadvantages of specific coagent structures, an acceptable

balance in physical properties can be achieved.

4. Electron Beam Cure Using Coagents

Radiation curing has historically been used as an alternative toperoxides in applications where the curatives themselves or side-products of vulcanization are viewed as impurities in the finalproduct. As previously noted, peroxide cure progresses through aseries of radical intermediates, each of which can undergo side

reactions which may not necessarily contribute to crosslinkdensity. Radiation cure, on the other hand, has been promoted as

a cleaner and more homogeneous cure process.

Electron beam irradiation has been used in the wire and cableindustry for longer than 30 years and applied to a wide range of

commodity and specialty elastomers. A survey of the types ofelastomers susceptible to radiation curing is available, as arereview articles describing the electron-beam curing ofcommercially significant grades.[ 25 , 26 ] Variables such as

radiation dosage and the effect of polymer microstructure andchemical additives on the efficiency of electron beam cure have

been studied.

4.1 Comparing Peroxide and Electron Beam CuringWhile both peroxide and electron beam cure involve radical-basedintermediates, differences between the mechanisms do exist.While peroxide cure is a thermally initiated event with cure

temperatures routinely in the 160C to 180C range, electron beamcure is performed at room temperature. Peroxide cure is initiated

by oxygen-centered radicals that can be differentiated from thecarbon-centered radicals produced by polymer excitation in

radiation cure. The length of cure time in each system is also verydifferent. In peroxide cure, cure time is governed by the half lifeof the peroxide at a given temperature, and can be longer than 30

minutes to reach > 99% decomposition. In contrast, electronbeam cure is practically instantaneous. The cure temperature andcure time differences can result in significantly less energyapplied to the electron beam cure process, a fact which may

contribute to variations in coagent performance between thedisparate systems.

4.2 Coagent UtilityThe addition of coagents to the electron beam cure of variouselastomer grades has also been studied.[27 ,28,29 ] Crosslinkdensity is found to be not only a function of radiation dose(parallel to peroxide loading) but also coagent loading. Like

peroxide cure, the response of the base elastomer to electron beamcure correlates primarily with the level of unsaturation in the

polymer backbone. The more highly reactive Type I coagentshave demonstrated the most utility when unsaturated polymers

have been used (HNBR, EPDM).

In order to quantify the effects of coagent addition on the electron

beam cure of EPDM, several Type I and Type II coagents wereevaluated. As a measure of crosslinking efficiency, the modulusof samples irradiated at 50, 100, and 150 kGy dosing were

compared. Figure 13 provides the results of the initial study.Increased radiation dose resulted in higher modulus regardless of

coagent Type. Differentiation based on coagent structure is alsoreadily apparent.

Figure 13. Modulus as a function of coagent type andradiation dose in an electron-beam cured EPDMformulation. Coagent loading at 5 phr. (ASTM D 412)

Figure 14 demonstrates the effect of increased coagent loading ata given radiation dose. Most coagent types increased modulus as

a function of loading, but Type I coagents provided the mostimprovement. The trifunctional methacrylate ester provided thehighest modulus increase in the compound, both as a function ofradiation dose and coagent loading.

Figure 14. Modulus as a function of coagent type andloading in an electron-beam cured EPDM formulation.150 kGy dose of radiation. (ASTM D 412)

The same coagents were studied in a peroxide cured EPDM

formulation. Again, tensile modulus was tested to provide acomparative measure of crosslink density. The results are

provided in Figure 15. Unlike the results in radiation curedsamples, the relative efficiency of the coagents did not strictly

follow trends based on Type, but were likely more influenced bythe variety of complex factors related to solubility and reactivity

outlined previously.

Although the formulations were identical save for the curechemistry and process, the data in Figures 14 and 15 demonstratethat there are clear differences in the efficiency with which certain

coagent structures contribute to crosslink density. In both curesystems the correct application of coagent technology cancontribute to higher crosslink density and improved physical

properties. As a corollary, the addition of coagents can alsoreduce the dosage of radiation required to produce adequate cure.



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Figure 15. Modulus as a function of coagent type andloading in a peroxide cured EPDM formulation. Dicumylperoxide at 3 phr actives. (ASTM D 412)

5. ConclusionCoagents are used to increase the crosslink density of peroxide-cured systems by increasing the efficiency of productive radicalreactions. The technology has progressed forward such that today

the improvements in crosslink density are generally taken forgranted, and coagent selection is now driven by the desire to

improve more than just the modulus or tensile strength of thecompound.

It is now clear that many of the beneficial properties associated

with coagent use are directly related to the chemical structure ofthe products. Reactivity and cure kinetics, the inherent strengthand flexibility of the formed network, and the affinity of theresulting compound for polar substrates can in large part be

accounted for by an inventory of the structural components of thecoagent molecule.

The use of coagents provides benefits in both peroxide and

radiation cure mechanisms. However, there are clear differencesin the efficiency with which certain coagent structures contributeto crosslink density based on cure chemistry and process. Torealize the greatest improvements in a given application or cure

type, it is crucial to understand the structure-property relationships

directing coagent performance.

6. AcknowledgmentsThe author would like to thank the Sartomer Company, Inc. forthe permission to make the information contained in this paperavailable. Gratitude must also be extended to William Boye for

his detailed work in comparing coagent types in various curesystems and elastomers. An ongoing joint project with E-Beam

Services, Inc. made possible the radiation curing data provided.

7. References

1. W. C. Endstra and C. T. J. Wreesman in Elastomer Technology

Handbook, N. P. Cheremisinoff, ed., CRC Press, Ann Arbor, 1993.2. B. Class, Paper # 1, Spring Technical Meeting, Rubber Division, ACS,

Indianapolis, IN, May 5-8, 1998.

3. A. H. Johansson, Paper # 10, Fall Technical Meeting, Rubber

Division, ACS, Cleveland, OH, Oct. 14-17, 2003.4. L. H. Palys and P. A. Callais,Rubber World229 (3), 35 (2003).

5. P. R. Dluzneski,Rubber Chem. Technol. 74, 451 (2001).

6. J. C. Garcia-Quesada and M. Gilbert,J. Appl. Polym. Sci. 77, 2657

(2000).

7. A. Busci and F. Szocs,Macromol. Chem. Phys.201, 435 (2000).

8. R. C. Keller,Rubber Chem. Technol.61, 238 (1988).

9. H. G. Dikland, Coagents in Peroxide Vulcanizations of EP(D)M

Rubber, Gegevens Koninklije Bibliotheek, Netherlands, 1965.10. Z. H. Murgic, J. Jelencic and L. Murgic,Polym. Eng. Sci.38, 689

(1998).

11. J. Class,Rubber World220 (11), 35 (1999).

12. L. Liu, Y. Luo, D. Jia and B. Guo,Intern. Polymer Processing

XIX(4), 374 (2004).13. S. K. Henning and R. Costin,Rubber World233 (5), 28 (2006).

14. S. K. Henning and J. Klang,Rubber World235 (6), 30 (2007).

15. A. Y. Coran in Science and Technology of Rubber, F. R. Eirich, ed.,

Academic Press, 1978, p. 291.

16. W. L. Cox and C. R. Parks,Rubber Chem. Technol.39, 785 (1966).17. R. Costin, W. Nagel, and R. Ekwall,Rubber Chem. Technol. 64, 152

(1991).

18. C. B. McElwee and J. S. Burke,Rubber World228 (5), 36 (2003).

19. S. X. Guo and W. von Hellens,Rubber World 225 (5), 51 (2002).

20. R. Costin in Handbook of Rubber Bonding, B. Crowther, ed.,RAPRA Technology Ltd., Shawbury, United Kingdom, 2003.

21. Y. Lu, L. Zhang, Y. Wu and L. Liu, Paper # T5, IRC, Beijing, China,

Sept. 22-24, 2004.

22. E. S. Castner and M. P. Mallamaci, Paper # 85, Fall TechnicalMeeting, Rubber Division, ACS, Orlando, FL, Sept. 21-24, 1999.

23. J. R. Beatty,Rubber Chem. Technol.37, 1341 (1964).

24. US 4857571, Reiter, et al. Sartomer Company, Inc., 1989.25. G. C. A. Bhm and J. O. Tveekrem,Rubber Chem. Technol.55, 575

(1982).

26. A. K. Bhowmick and V. Vijayabaskar,Rubber Chem. Technol.79,402 (2006).

27. R. J. Eldred,Rubber Chem. Technol.47, 924 (1974).

28. G. L. M. Vroomen and G. W. Visser,Rubber World205 (2), 23

(1991).

29. M. La Rosa, C. Wrana, D. Achten, Electron Beam Curing of EVMand HNBR for Cable Compounds, presented at the 55th

International Wire and Cable Symposium Conference, Providence, RI,

Nov. 12-15, 2006.

Steven K. [email protected]

Steven K. Henning received a Bachelors Degree in MaterialScience and Engineering from the Pennsylvania State Universityin 1994 and was conferred a Masters Degree in Polymer Science

from the University of Akron in 2003.

Between 1995 and 2004 he was employed at The Goodyear Tireand Rubber Company (Akron, OH) developing new tireelastomers for the Chemical Division as Team Leader for Anionic

and Emulsion Polymer Development.

Since 2004, he is the Senior Chemist in charge of SartomerssRubber Lab (Exton, PA) coordinating projects which focus on the

development of functional additives for improved elastomers cure.


The Use of Coagents

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