Copolymers of ethylene and propylene

Many monomers have been copolymerized with ethylene by a variety of polymerization methods. When ethylene is copolymerized with other olefins, the resultant hydrocarbon polymers have reduced regularity and lower density, lower softening point, and lower brittle point. 

Copolymers of ethylene and propylene are a commercially important family of materials. They vary from elastomers that can contain 80% ethylene and 20% propylene to polypropylene that is modified with small amounts of ethylene to improve impact resistance. 

Metallocene catalysts can produce both random and alternating copolymers of ethylene and propylene [85]. At present there does not appear to be any commercial utilization of alternating copolymers. They were reported to form in polymerizations catalyzed by bridged fluorenyl catalysts [85]. 

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The copolymers of ethylene and propylene (OCVP) are obtained by coordination catalysis using a derivative of vanadium and a derivative of an aluminum alkyl. Molar compositions of ethylene and propylene are usually on the order 45 and 55%. 

Some data on copolymers of ethylene and propylene (not shown) is also consistent inasmuch as the values of f decrease as the ethylene (unsubstituted) content increases. 

The economic importance of copolymers can be cleady illustrated by a comparison of U.S. production of various homopolymer and copolymer elastomers and resins (102). Figure 5 shows the relative contribution of elastomeric copolymers (SBR, ethylene—propylene, nitrile mbber) and elastomeric homopolymers (polybutadiene, polyisoprene) to the total production of synthetic elastomers. Clearly, SBR, a random copolymer, constitutes the bulk of the entire U.S. production. Copolymers of ethylene and propylene, and nitrile mbber (a random copolymer of butadiene and acrylonitrile) are manufactured in smaller quantities. Nevertheless, the latter copolymers approach the volume of elastomeric butadiene homopolymers. 

Copolymers of ethylene and propylene (EPM) and terpolymers of ethylene, propylene, and a diene (EPDM) as manufactured today are mbbers based on the early work of G. Natta and co-workers (1). A genetic formula for EPM and EPDM may be given as follows, where ra = (- GO mol%),... 

Permeation tubes are very popular devices for generating stemdard vapor concentrations. The permeation tube contains a volatile liquid sealed in an inert permeable membrane, usually Teflon or a fluorinated copolymer of ethylene and propylene, through which it diffuses at a fixed and controlled rate. The driving force for the process is the dif ce in partial... 

The preferred systematic abbreviation for ethylene-propylene terpolymer, also designated EPT. The use of the term EPR for a copolymer of ethylene and propylene, and the use of EPT for a terpolymer of these monomers with a small amount of a diene to provide double bonds is common but is not recommended. Epichlorohydrin... 

Olefins or alkenes are defined as unsaturated aliphatic hydrocarbons. Ethylene and propylene are the main monomers for polyolefin foams, but dienes such as polyisoprene should also be included. The copolymers of ethylene and propylene (PP) will be included, but not polyvinyl chloride (PVC), which is usually treated as a separate polymer class. The majority of these foams have densities <100 kg m, and their microstructure consists of closed, polygonal cells with thin faces (Figure la). The review will not consider structural foam injection mouldings of PP, which have solid skins and cores of density in the range 400 to 700 kg m, and have distinct production methods and properties (456). The microstructure of these foams consists of isolated gas bubbles, often elongated by the flow of thermoplastic. However, elastomeric and microcellular foams of relative density in the range 0.3 to 0.5, which also have isolated spherical bubbles (Figure lb), will be included. The relative density of a foam is defined as the foam density divided by the polymer density. It is the inverse of the expansion ratio . 

Another approach is to use copolymers where the structures of the copolymer are similar to that of the other phase. This is what occurs for PE and copolymers of ethylene and propylene. 

How might you prepare a block copolymer of styrene and an alternation copolymer of ethylene and propylene ... 

Fig. 2.22. Dependence of the elastic modulus E and the mechanical loss factor 6 on temperature for various polymers. Curves 1 elastomer (statistical copolymer of ethylene and propylene) curves 2 isotactic polypropylene (semicrystalline)...

Although hdpe and it-PP are crystalline, the commercial random copolymer of ethylene and propylene (EP) is an amorphous elastomer. The most widely used EP copolymer (EPDM) is produced by the copolymerization of ethylene and propylene with a small amount of an alkyldiene this permits cross-linking or vulcanization. 

Single crystals with a Tm of 423 K have been produced from low-density polyethylene (ldpe). Isotactic PP crystals have a Tm of 444 K and syndiotactic PP has a Tm of 411 K, whereas atactic PP is amorphous and has a Ts of 255 K. Isotactic polyolefins with pendant groups, such as polyhexene, have high Tm values. Random copolymers of ethylene and propylene are amorphous, but block copolymers of these monomers are crystalline. 

Several flexible polymers, such as natural rubber (NR) synthetic rubber (SR) polyalkyl acrylates copolymers of acrylonitrile, butadiene, and styrene, (ABS) and polyvinyl alkyl ethers, have been used to improve the impact resistance of PS and PVC. PS and copolymers of ethylene and propylene have been used to increase the ductility of polyphenylene oxide (PPO) and nylon 66, respectively. The mechanical properties of several other engineering plastics have been improved by blending them with thermoplastics. 

The principal polyolefins are low-density polyethylene (ldpe), high-density polyethylene (hope), linear low-density polyethylene (lldpe), polypropylene (PP), polyisobutylene (PIB), poly-1-butene (PB), copolymers of ethylene and propylene (EP), and proprietary copolymers of ethylene and alpha olefins. Since all these polymers are aliphatic hydrocarbons, the amorphous polymers are soluble in aliphatic hydrocarbon solvents with similar solubility parameters. Like other alkanes, they are resistant to attack by most ionic and most polar chemicals their usual reactions are limited to combustion, chemical oxidation, chlorination, nitration, and free-radical reactions. 

The incorporation of polar groups in unvulcanized polymers reduces their solubility in benzene. Thus the copolymer of acrylonitrile and butadiene (NBR), polychlorobutadiene (Neoprene), and fluorinated EP (the copolymer of ethylene and propylene) are less soluble in benzene and lubricating oils than the previously cited elastomers. Likewise, silicones and phosphazene elastomers, as well as elastomeric polyfluorocarbons, are insoluble in many oils and aromatic hydrocarbons because of their extremely low solubility parameters (silicons 7-8 H polytetrafluoroethylene 6.2 benzene 9.2 toluene 8.9 pine oil P.6). 

Enhanced radiation cross-linking in polyethylene, polypropylene, and poly-isobutylene and in copolymers of ethylene and propylene was found when nitrous oxide was incorporated into the polymer matrix. Mechanisms of fhis process have been proposed by several workers. ... 

A typical example belonging to this category are undoubtedly the statistical copolymers of ethylene and propylene. Because of their crystalline nature, however, no attempt has yet been made to apply TLC to this copolymer system. Thus, in this... 

Ethylene-propylene rubber (EPR or EPDM) is, basically, a copolymer of ethylene and propylene. Because of the random arrangement of the monomers in the chain, crystallization does not occur, and the material behaves as a rubber. Just as with polyisobutylene, vulcanization with sulphur is impossible (the chain is saturated). Also here, a small amount of another monomer is incorporated, which enables the vulcanization and thus the use as a technical elastomer. EPR has a high resistance against ageing and chemical attack, and is, compared with other specialty rubbers, relatively cheap. 

If the hard blocks are longer than the soft ones, such as in SBS with a high styrene content, the hard phase will be continuous, and the rubbery phase is present as domains (see Figure 9.6). In such a case SBS behaves as a high-impact PS. Another example of this type is a PP/EP block copolymer tails of EP (random copolymer of ethylene and propylene) on the PP chains segregate into rubbery domains in the PP matrix, which improve the impact strength. 

Of particular interest are random copolymers of ethylene and propylene, which are obtainable with soluble vanadium-based Ziegler-Natta catalysts such as V(Acac)3—AlEt2Cl [453], VOCl3-AlEt2Cl [72], VOC13-A1(/-Bu)2C1... 

Leclerc and Waymouth (119) and, independently, Arndt et al. (120) synthesized alternating copolymers of ethylene and propylene with zirconocene catalysts. The ethylene/propylene (EP) copolymerizations were carried out at 30 and 60°C for each of four metallocene catalysts (Me2C(3-RCp)(Flu)) ZrCl2 (R = H, Me, lsoPr, tertBu) (Fig. 10). As the size of the substituent increased, there were distinct changes in the copolymerization behavior and in the polymer microstructure. 

Toughened polypropylene may be prepared by block copolymerization in which ethylene monomer is added during the final stages of the polymerization of propylene (4). Thus, some polypropylene chains would contain an end block of rubbery ethylene-propylene copolymer. Alternatively, a blend of an elastomeric copolymer of ethylene and propylene (EPR or EPDM) with isotactic polypropylene (PP) can produce an impact-resistant polymer (5). 

G. Baeras et al.124 have studied the complex formation in the systems PAA-PEG, PMAA-PEG and PMAA-block copolymer of ethylene and propylene oxides by spectrometry when PMAA is added to the PAA complexes in the presence of a dye (bromocresol green). It is shown that PMAA is more susceptible to complex formation than PAA in the reaction with oligomers. 

Copolymers are ubiquitous and important because they allow monomers to be combined in such a way so as to provide useful and sometimes unique properties. For example, linear polyethylene (PE) and isotactic polypropylene (i-PP) are both semi-crystalline plastics, but copolymers of ethylene and propylene (EPR) (usually with other comonomers) are rubbers at room temperature (depending on composition). The homopolymers are shown in the top two figures in Figure 6-2, and if you don t know which one s which by now you should collapse in deepest humiliation. A section of an EPR copolymer chain is shown at the bottom. 

Daikin Industries DuPont Fluoroproducts Note PTFE, polytetrafluoroethylene CTFE, chlorotriflua oethylene EFEP, per-fluorinated copolymer of ethylene and propylene ETFE, copolymer of ethylene tetrafluoroethylene PFPE, perfluorinated polyether EClFE, copolymer of ethylene and chlorotrifluoroethylene HIE, ter-polymer of hexafluoropropylene, tetrafluoroethylene, and ethylene MFA, copolymer of perfluoromethyMnylether and tetrafluoroethylene PEA, copolymer of perfluoropropylvinylether and tetrafluoroethylene FEP, fluorinated ethylene-propylene copolymer PVDF, poly(vinylidene fluoride) THV, terpolymer of tetrafluoroethylene, hexafluoroprqjylene, and vinyUdene fluoride PCTFE, poly(chlorotriflua oethylene). 

Copolymers of ethylene and propylene have come to stay as important materials with diverse practical applications. They span the full range of polymeric properties, from soft elastomers to hard thermoplastics depending on the relative composition of the two monomers and the manner of their enchainment. Ethylene-propylene copolymers are manufactured commercially using Ziegler-Natta catalysts [1]. For the purposes of this discussion, we will treat these copolymers in terms of three distinct classes of materials ... 

The principles of nomenclature for copolymers are based on their structure and are given in Table 1.2, where A and B represent the names of repeating units. For example, a statistical copolymer of ethylene and propylene would be called poly(ethylene-stat-propylene), and a triblock copolymer of styrene (A) sand isoprene (B) would be called polystyrene-Z)/oeA -polyisoprene- /ocA -polystyrene. In some cases it is necessary to introduce square brackets in the nomenclature to clarify the notation. Let us see an example An alternating copolymer of styrene and maleic anhydride would be called poly[styrene-a/ (maleic anhydride)]. 

Ethylene-propylene rubbers (EPR) are basically random copolymers of ethylene and propylene, with 60-70% (w/w) ethylene. Polyethylene and polypropylene are homopolymers that display too high a degree of crystallinity to be used as elastomers. Nevertheless, random copolymerization produces linear chains with sufficient structural irregularity to prevent crystallization. The copdlymerization process leads to amorphous, fully saturated chains. 

These materials can be considered linear copolymers of ethylene and propylene or precisely methyl-branched polyethylene. In addition, copolymerizations of the methyl-containing monomers with 1,9-decadierie yield polymers with lower propylene content [50]. These materials are of great interest to the polyolefin community, especially in the physical understanding of the effects of branching on physical properties. Polyethylenes with a variety of main chain functionality have also been synthesized and analyzed [51-54]. 

A number of block copolymers prepared with Ziegler-Natta catalysts have been reported however, in most cases the compositions may include significant amounts of homopolymer. The Ziegler-Natta method appears to be inferior to anionic polymerization for synthesizing carefully tailored block copolymers. Nevertheless, bock copolymers of ethylene and propylene (Eastman Kodak s Pofyallomers) have been commercialized. Unlike the elastomeric random copolymers of ethylene and propylene, these are high-impact plastics exhibiting crystallinity characteristics of both isotactic polypropylene and linear polyethylene. They also contain homopolymers in addition to block copolymers. 

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