Copolymer ethylene-propene

In some very recent work by Karssenberg et al. [130], attempts have been made to improve the analytical ability of a technique like NMR spectroscopy to effectively predict the distribution of sequence lengths in polyethylene-alkene copolymers. They analyzed the entire [ C-NMR spectrum for homogeneous ethylene-propene copolymers. They used quantitative methods based on Markov statistics to obtain sequence length distributions as shown in Figure 22 [130]. The... 

Figure 22 Sequence length distributions for ethylene-propene copolymers (Karssenberg et al. [130]). Top normalized ethylene sequence length distribution bottom normalized propylene sequence length distribution. Reproduced from Karssenberg et al. [130]. Copyright 2006, John Wiley Sons, Inc. Reprinted with permission of Wiley-Liss, Inc., a subsidiary of John Wiley Sons, Inc.

C NMR of ethylene-propene copolymers of low ethylene content produced by initiators that yield isotactic polypropene shows that the isotactic propene units on each side of an ethylene unit have the same configuration (i.e., all-R or all-5) [Zambelli et al., 1971, 1978, 1979]. For stereocontrol by the propagating chain end, the amount of polymer in which the polypropene blocks on either side of an ethylene unit have the same configuration would equal that in which the blocks have the opposite configuration. 

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). 

Zambelli, A., Bajo, G. and Rigamonti, E. (1978). Model compounds and carbon-13 NMR investigation of isolated ethylene units in ethylene/propene copolymers. Makromolek. Chem., 179, 1249-1259. 

For the packaging of sensitive foods, PP films are coated with polyvinylidene chloride, polyvinyl acetate, EVAcopolymers, polyacrylates, styrene-butadiene copolymers, LDPE, poly-l-butene or random copolymers of propene with ethylene and 1-butene. By using these various coatings PP has recently sharply reduced the use of regenerated cellulose (cellophane), the previous market leader in this area. 

Coordination polymerizations are often accompanied by isomerization. By means of the ternary catalytic system VC14, (acac)3Fe, and Et3Al, propene can yield crystalline polyethylene and the amorphous ethylene—propene copolymer. Many more such cases have, of course, been observed. Probably of greatest importance are those where a non-polymerizing 2-alkene is is-omerized to 1-alkene prior to propagation [355]. 

No other groups of compound have clearly defined chain transfer activity. Ethyl trichloroacetate reduces the molecular weight of ethylene/propene copolymers using VOCl3/Al2Et3Cl3 [108] but as the rate of polymerization is also increased the effect may be caused by an increase in the number of active centres. a-Olefins and allenes reduce the molecular weights of cis polybutadiene obtained with soluble cobalt catalysts [139], but in this case it is not clear whether transfer or termination processes are involved. 

The uncertainties and poor j eement in determinations of ethylene/ propene reactivity ratios from monomer and polymer composition [m = (Mj/Mj) monomer p = (Mi/M2) polymer] and the copolymerization equation p = (1 + rjm)/(l + rj/m) give particular interest to approaches based on the analysis of monomer unit distributions in the copolymer. 

Both the early data and the more precise values given in Table 20A differ significantly from published estimates based on monomer and polymer composition (e.g. rj r2 = 0.60 in Table 19). As all the data relate to the, in general, more consistent soluble vanadium systems, this work reinforces doubts concerning the accuracy of much of the published information. A complication is that since C2 and C4 sequences are observed in ethylene/propene copolymers inverted head to head prop-ene units must be present and this will reduce the accuracy of analyses of EP sequences. In copolymers prepared by VC /AlEtj 4% of head to head propene sequences have been reported with the catalyst VCl4/AlEt2Cl which is syndiospecific for polypropene 8% of head to head sequences was found [295]. ... 

A) Monomer feed and copolymer composition for ethylene/propene copolymerization with the catalyst VCl4/AlEt2Cl at —78°C have been shown to fit accurately empirical relationships [322]... 

The copolymerization of ethylene and carbon monoxide to give alternating copolymers has attracted considerable interest in both academia and industry over recent decades [1, 2]. Attention was focused on aliphatic polyketones such as poly(3-oxotrimethylene) (1) because of the low cost and plentiful availability of the simple monomers. The new family of thermoplastic, perfectly alternating olefin/ carbon monoxide polymers commercialized by Shell provides a superior balance of performance properties not found in other commercial materials the an ethylene/ propene/CO terpolymer is marketed by Shell imder the tradename Carilon . About the history of polyketones see Refs. [3-11],... 

Ethylene Propene Rubber Stereospecific copolymers of ethylene with propylene. Used as impact modifiers for plastics. Also called EPR. 

Many acrylic copolymers are currently used in the textile industry as binders for nonwoven fabrics. The purpose of these fibers is to stabilize the material. In many instances, these copolymers are used in conjunction with amino resins. Casanovas and Rovira have done a study of methyl methacrylate-ethyl acrylate-N-methylol-acrylamide by PY/GC-MS. Among the products identified were methane, ethylene, propene, isobutene, methanol, propionaldehyde, ethanol, ethyl acetate, methyl acrylate, methyl isobutyrate, ethyl acrylate, methyl methacrylate, n-propyl acrylate, and ethyl methacrylate. In this sample, clearly monomer reversion is the primary degradation process occurring however, several other degradation mechanisms are at work. When the sample contains an amino resin in the mixture, acrylonitrile is observed in the pyrogram. Another effect of the amino presence was a marked increase in the amount of methanol detected. Other products detected were meth-oxyhydrazine, methyl isocyanate, and methyl isocyanide. 

FEP (fluoro-ethylene-propene copolymer) tubing Popcorn bags French fry box... 

When comonomers are introduced, this destroys chemical regularity of chain units. It thereby reduces or even eliminates crystallinity, depending on the comonomer content. An illustration which is also important in applications is provided by ethylene copolymers. If propene is introduced into polyethylene, the level of crystallinity is reduced (therefore also diminishing its modulus and density). This is because it limits the possibilities for a crystalline structure to those sequences made up of (CH2)i units. A whole family of new compounds, called Low Density Linear PolyEthylenes (LDLPE), was developed during the 1980s. Ethylene/propene (50/50) copolymers form amorphous compounds which are used as elastomers (EPDM). 

One of the main difficulties for the quantification of Crystaf is the nonimiver-sality of its calibration curves. Even for a series of ethylene/a-olefin copolymers, the calibration curves will vary as a function of comonomer type, as illustrated in Figure 15. The general rule of thumb for these copolymers (from propene to 1-octene) is, the longer the a-olefin, the lower the crystallization temperature for a given a-olefin molar fraction. This has been explained by several authors on the basis of the difference in the degree of inclusion of the a-olefin in the crystalline lattice shorter a-olefins are more likely to cocrystallize with ethylene and therefore depress the crystallization temperature to a lesser extent. 

Poly(ethylene-copolymer poly(ethylene-propylene) polypro, polypropylene-polyethylene copolymer 9010-79-1 1 -Propene, polymer with ethene R (C3H6C2H4),... 

Poly(ethylene-co-propylene-tf)- 5-methylene-2-norbomene) Ethylene-ethylidenebicycloheptene-propene copolymer ethylene— ethylidenenorbomene-propylene polymer 25038-36-2 Bicyclo(2.2. 1 )hept-2-ene, 5-ethylidene-, polymer with ethene and 1-propene R (C9H12 -t-iHa C2H4>4... 

Cyclopentadienyl ligands have become extremely important in catalysis for metal such as Ti, Zr, and Hf (Chapter 10) and in academic studies of related elements such as Ta. Ethylene polymerisation with the use of CpiTiCE (alkylated with aluminium alkyl compounds) has been known for many decades, but the intensive interest in derivatives of these compounds started in the early 1980 s following the discovery of MAO (methaluminoxane - see chapter 10) which boosted metallocene catalyst activities by several orders of magnitude. Commercial interest focussed on ethylene copolymers (LLDPE where more homogeneous comonomer incorporation resulted in greatly improved copolymer properties) and in enantiospecific polymerisations for propene, styrene, etc. 

The polymer chain end control model is supported by the observation that highly syndiotactic polypropene is obtained only at low temperatures (about —78°C). Syndiotacticity is significantly decreased by raising the temperature to —40°C [Boor, 1979]. The polymer is atactic when polymerization is carried out above 0°C. 13C NMR analysis of the stereoerrors and stereochemical sequence distributions (Table 8-3 and Sec. 8-16) also support the polymer chain end control model [Zambelli et al., 2001], Analysis of propene-ethylene copolymers of low ethylene content produced by vanadium initiators indicates that a syndiotactic block formed after an ethylene unit enters the polymer chain is just as likely to start with an S- placement as with an R-placement of the first propene unit in that block [Bovey et al., 1974 Zambelli et al., 1971, 1978, 1979]. Stereocontrol is not exerted by chiral sites as in isotactic placement, which favors only one type of placement (either S- or R-, depending on the chirality of the active site). Stereocontrol is exerted by the chain end. An ethylene terminal unit has no preference for either placement, since there are no differences in repulsive interactions. 

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