Ethylene-propene-diene

Copolymers and terpolymers of ethylene and propene, commonly known as EPM and EPDM polymers, respectively, are useful elastomers [Ver Strate, 1986], EPM and EPDM are acronyms for ethylene-propene monomers and ethylene-propene-diene monomers, respectively. The terpolymers contain up to about 4 mol% of a diene such as 5-ethylidene-2-norbomene, dicyclopentadiene, or 1,4-hexadiene. A wide range of products are available, containing 40-90 mol% ethylene. The diene, reacting through one of its double bonds, imparts a pendant double bond to the terpolymer for purposes of subsequent crosslinking (Sec. 9-2b). 

Homogeneous vanadium-based catalysts formed by the reaction of vanadium compounds and reducing agents such as organoaluminum compounds [10-12] are used industrially for the production of elastomers by ethylene/propene copolymerization (EP rubber) and ethylene/propene/diene terpolymerization (EPDM rubber). The dienes are usually derivatives of cyclopentadiene such as ethylidene norbomene or dicyclopentadiene. Examples of catalysts are Structures 1-4. Third components such as anisole or halocarbons are used to prevent a decrease in catalyst activity with time which is observed in the simple systems. 

A/EPDM/S acrylonitrile/ethylene-propene-diene/styrene... 

Scheme 16.36. Polymerization and structure of ethylene/ propene/diene terpolymer (EPDM), with 5-ethylidene-2-norbornene (ENB) given as an example for the diene.

Two classes of diene have been copolymerized successfully with ethylene/propene, in both of which one double bond is deactivated such that the monomer behaves as a mono-olefin. These are unconjugated diolefins, such as cis and trans 1,4-hexadiene or 3,7-dimethyl 1,6-octa-diene, and compounds containing the 2-norbornene structure... 

A comonomer for the synthesis of ethylene/propene elastomers - 2-ethylidene-norbomene (7) - is synthesised via a Diels-Alder cycloaddition of cyclopenta-diene and butadiene followed by an isomerization with titanium-based catalysts of the intermediate 2-vinyl derivative 6 in excellent yield (98 %) (eq. (12)) [22]. 

Ethylene/propylene/diene terpolymer n-hexane and propene 2001VLI... 

CuCl(COT)] , [Cu2Cl2(cyclooctene)3], [Ag(alkene)2]X, [Ag(alkene)3]Bp4, [Ag(diene)]X (alkene = ethylene, propene, cyclohexene, etc. diene = cyclopentadiene. 

Free-radical Reactions.—Publications have appeared dealing with the bidirectional addition of trifluoroiodomethane and hydrogen bromide across the C=C bond in the olefin CF3 CH CHMe, peroxide-initiated addition of 1,2-dibromotetrafluoroethane to ethylene, propene, and isobutene, the addition of pentafluoroiodoethane to 3,3,4,4-tetrafluorohexa-l,5-diene (see p. 29), peroxide-initiated cyclodimerization of 3,3,4,4-tetrafluoro-4-iodobut-l-ene (see p. 29), and telomers from tribromofluoromethane or tetrabromomethane and bromotrifluoroethylene as high-density fluids for gyroscope flotation. The telomerization of chloromethanes with tetra-fluoroethylene provides a measure of the relative reactivity for both chlorine and hydrogen abstraction by the CF2 CF2 radical. The chain-transfer... 

The Diels-Alder cycloadclition reaction occurs most rapidly if the alkene component, or dienophile ("diene lover"), has an electron-withdrawing substituent group. Thus, ethylene itself reacts sluggishly, but propenal, ethyl propenoate, maleic anhydride, benzoquinone, propenenitrile, and similar compounds are highly reactive. Note also that alkynes, such as methyl propynoate, can act as Diels-Alder dienophiles. 

Nowadays silenes are well-known intermediates. A number of studies have been carried out to obtain more complex molecules having Si=C double bonds. Thus, an attempt has been made to generate and stabilize in a matrix 1,1-dimethyl-l-silabuta-l,3-diene [125], which can be formed as a primary product of pyrolysis of diallyldimethylsilane [126] (Korolev et al., 1985). However, when thermolysis was carried out at 750-800°C the absorptions of only two stable molecules, propene and 1,1-dimethylsilacyclobut-2-ene [127], were observed in the matrix IR spectra of the reaction products. At temperatures above 800°C both silane [126] and silacyclobutene [127] gave low-molecular hydrocarbons, methane, acetylene, ethylene and methylacetylene. A comparison of relative intensities of the IR... 

Absolute rates for the addition of the methyl radical and the trifluoromethyl radical to dienes and a number of smaller alkenes have been collected by Tedder (Table l)3. Comparison of the rate data for the apolai4 methyl radical and the electrophilic trifluoromethyl radical clearly show the electron-rich nature of butadiene in comparison to ethylene or propene. This is also borne out by several studies, in which relative rates have been determined for the reaction of small alkyl radicals with alkenes. An extensive list of relative rates for the reaction of the trifluoromethyl radical has been measured by Pearson and Szwarc5,6. Relative rates have been obtained in these studies by competition with hydrogen... 

The primary decompositions occurring by parallel first-order processes yield cyclohexene, butadiene plus ethylene, and four cyclopropyl-propenes. The cyclopropylpropenes formed initially decompose to yield various Ce dienes at rates comparable with those of the primary reactions, and this leads to a complex reaction mixture that contains at least seventeen products. 

Traditional Ziegler-Natta and metallocene initiators polymerize a variety of monomers, including ethylene and a-olefins such as propene, 1-butene, 4-methyl-1-pentene, vinylcyclo-hexane, and styrene. 1,1-Disubstituted alkenes such as isobutylene are polymerized by some metallocene initiators, but the reaction proceeds by a cationic polymerization [Baird, 2000]. Polymerizations of styrene, 1,2-disubstituted alkenes, and alkynes are discussed in this section polymerization of 1,3-dienes is discussed in Sec. 8-10. The polymerization of polar monomers is discussed in Sec. 8-12. 

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