Ethylene-propylene-diene polymerization

Ethylene-propylene-diene rubber is polymerized from 60 parts ethylene, 40 parts propylene, and a small amount of nonconjugated diene. The nonconjugated diene permits sulfur vulcanization of the polymer instead of using peroxide. 

We have considerable latitude when it comes to choosing the chemical composition of rubber toughened polystyrene. Suitable unsaturated rubbers include styrene-butadiene copolymers, cis 1,4 polybutadiene, and ethylene-propylene-diene copolymers. Acrylonitrile-butadiene-styrene is a more complex type of block copolymer. It is made by swelling polybutadiene with styrene and acrylonitrile, then initiating copolymerization. This typically takes place in an emulsion polymerization process. 

Ethylene-propylene-diene terpolymers (EPDM), with their inherent complexity in structural parameters, owe their tensile properties to specific structures dictated by polymerization conditions, among which the controlling factor is the catalyst used in preparing the polymers. However, no detailed studies on correlation between tensile properties and EPDM structures have been published (l,2). An unusual vulcanization behavior of EPDMs prepared with vanadium carboxylates (typified by Vr g, carboxylate of mixed acids of Ccj-Cq) has been recently reported Q). This EPDM attains target tensile properties in 18 and 12 minutes at vulcanization temperatures of 150 and l60°C respectively, while for EPDMs prepared with V0Cl -Et3Al2Cl or V(acac) -Et2AlCl, about 50 and 0 minutes are usually required at the respective vulcanization temperatures, all with dieyclopentadiene (DCPD) as the third monomer and with the same vulcanization recipe. This observation prompted us to inquire into the inherent structural factors... 

Sulfur-containing spiro orthocarbonates, cationic polymerization of, 23 729 Sulfur-cured EPDM, 21 8041. See also Ethylene- propylene-diene monomer (EPDM) rubber Sulfur deposits... 

As was mentioned, cycloaddition of unactivated hydrocarbons, namely, that of cyclopentadiene, has practical significance. 5-Vinyl-2-norbomene is produced by the cycloaddition of cyclopentadiene and 1,3-butadiene546,547 [Eq. (6.96)] under conditions where side reactions (polymerization, formation of tetrahydroindene) are minimal. The product is then isomerized to 5-ethylidene-2-norbomene, which is a widely used comonomer in the manufacture of an EPDM (ethylene-propylene-diene monomer) copolymer (see Section 13.2.6). The reaction of cyclopentadiene (or dicyclopentadiene, its precursor) with ethylene leads to norbomene548,549 [Eq. (6.97)] 550... 

Similar approaches apply to carbon black - polybutadiene mixtures [45,46]. A thorough study of ethylene-propylene diene terpolymer (EPDM) - carbon black has been developed using NMR a clear evidence for adsorbed EPDM is given in addition to the presence of polymeric strands connecting aggregates to one another [47]. 

Butadiene could also be trimerized to give cyclododecatriene. The trimer is again used by Hulls to manufacture nylon 12 and Vestamid . The codimerization of butadiene and ethylene is used by DuPont to manufacture 1,4-hexadiene, one of the monomers of EPDM (ethylene, propylene, diene, monomers) rubber. The role of the diene monomer in EPDM rubber is to provide with two double bonds of different reactivities. The more reactive, terminal double bond takes part in the polymerization with ethylene and propylene. The less reactive internal one is used later on for cross-linking. These important catalytic reactions are shown in Fig. 7.6. 

The elastomeric/polymeric or other material constituting the principal structure of the component (e.g., high-density polyethylene, ethylene-propylene-diene rubber, and stainless steel). 

Low-temperature solution processes are state-of-the-art for the production of ethylene/propylene or ethylene/propylene/diene elastomers (EPDR or EPDM). A continuous stirred-tank reactor (CSTR) or a series of two or even more such reactors is used [2]. n-Hexane, n-heptane, or Ce, C7 fractions are the solvents. Catalyst, co-catalyst and other compounds are introduced with the solvent into the reactor. The monomers (ethylene, propylene) are injected as gases other olefins are introduced in liquid form. The polymerization process runs around 50 °C and at pressures up to 2 MPa. Downstream the catalyst/co-catalyst system is deactivated and their residues are dissolved in dilute acid or aqueous NaOH. The copolymer is stabilized with an antioxidant. Steam treatment removes the rest of the solvent and monomers, and agglomerates the product to crumbs. These crumbs are then dried and finished to bales or pellets. 

In addition to titanium-based Ziegler-Natta catalysts, vanadium-based systems have also been developed for PE and ethylene-based co-polymers, particularly ethylene-propylene-diene rubbers (EPDM). Homogeneous (soluble) vanadium catalysts produce relatively narrow molecular mass distribution PE, whereas supported V catalysts give broad molecular mass distribution.422 Polymerization activity is strongly enhanced by the use of a halogenated hydrocarbon as promoter in combination with a vanadium catalyst and aluminum alkyl co-catalyst.422,423... 

Ethylene has been co-polymerized with virtually any conceivable a-olefin, from propylene to vinyl-terminated PE and PP macromonomers. Ethylene/propylene (E/P) copolymerization to produce saturated rubbers and ethylene/propylene/diene (EPD) terpolymerization to produce unsaturated, vulcanizable rubbers will be discussed in Section 4.09.4.1.3. 1-Butene, 1-hexene, and 1-octene are the most commonly used co-monomers for the production of LLDPE. Ethylene/octene co-polymers, developed by Dow and marketed under the Engage tradename, have been shown to have improved thermal properties compared to ethylene/butene and ethylene/hexene co-polymers.503 In ethylene/a-olefin (E/O) co-polymeriza-tions, the critical parameters are co-monomer reactivity and co-monomer distribution . The former is most conveniently described by the relative reactivity parameter, R, defined as the ratio between polymer composition and reactor medium composition. 

Composition (type of polymeric components). The base polymer (which is to be modified) may be an amorphous polymer [e.g., polystyrene (PS), styrene-acrylonitrile copolymer, polycarbonate, or poly(vinyl chloride)], a semicrystalline polymer [e.g., polyamide (PA) or polypropylene (PP)], or a thermoset resin (e.g., epoxy resin). The modifier may be a rubber-like elastomer (e.g., polybutadiene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, or ethylene-propylene-diene copolymer), a core-shell modifier, or another polymer. Even smaller amounts of a compatibilizer, such as a copolymer, are sometimes added as a third component to control the morphology. 

In a typical experiment, 2g of ethylene-propylene-diene terpolymer was dissolved in freshly distilled toluene in a 3-necked flask under an argon atmosphere. Two ml of Shirakawa catalyst (Ti(OBu) /ALEt ) (9) were added to the flask by means of a syringe. Subsequently, all solvents were slowly evaporated under vacuum by rotating the flask to ensure a uniform film of the polymer on the wall of the flask. Next, acetylene gas was introduced into the flask at room temperature. The polymerization of acetylene was evident from the color change of the film (brown black). The flask was left closed and filled with acetylene overnight at room temperature. Subsequently, the... 

More homogeneous copolymer cpmpositions are obtained with soluble Zieg-ler-Natta catalysts, especially where monomer compositions are maintained relatively constant during polymerization. Commercially important ethylene-propylene binary copolymers (EPM rubbers) and ethylene-propylene-diene ternary copolymers (EPDM rubbers) are made by this process. 

As mentioned extensively, PPE is not mainly used as such, but in polymeric blends and copolymers to faciUtate the fabrication. Some of these copolymers act also as impact modifiers for example, block copolymers built from styrene, ethylene, butylene, and propylene. Naturally, the impact can be improved by using high impact poly(styrene) (HIPS) instead of ordinary PS in blends. Other impact modifiers include rubbery materials, such as poly(octenylene), and ethylene propylene diene monomer rubber. 

Morita et al. have found a relation between the increase in the LOI and the polymerization rate of phosphorus- and bromine-containing monomers in ethylene propylene diene monomer (EPDM). The polymerization of these comonomers is initiated simultaneously with the crosslinking of the polymer matrix, but the authors did not check if the comonomers are linked to the EPDM macromolecules. They assumed that the phosphorus-containing... 

Competition between NR and bio-based SR (SR made from biosourced feedstock) should not be underestimated. For example in 2012, LANXESS is planning to produce the world s first SR, i.e. ethylene propylene diene monomer (EPDM) rubber (under the brand name of Keltan Eco) from ethylene derived from sugar cane at its Triunfo plant in Brazil. The ethanol is dehydrated into ethylene and polymerized to produce EPDM rubber." Besides, bio-based SR is suggested to be the bio-based feedstock of poly(butadiene) rubber for tyre industries. 

Since EPR rubber molecules do not contain unsaturation, they can be vulcanized only by organic peroxide curing systems. If a third monomer is added during the polymerization, i.e., a diene monomer (wherein only one of the two double bonds takes part in the polymerization), unsaturation can be introduced into the molecule, and it can then be vulcanized by accelerated sulfur curing systems. A chemical structure for ethylene-propylene-diene-monomer (EPDM) rubbers can be expressed as follows ... 

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