PROPENE COPOLYMER

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.

Syndiospecific catalytic systems based on metallocenes are highly regioreg-ular. As a consequence, their stereoselectivity in possible regioirregular insertions has been experimentally investigated for propene copolymers only.78,79 However, an analysis of the stereoselectivity of possible secondary propene insertions on syndiospecific catalytic models based on -symmetric metallocenes is reported here, also due to its relevance to the rationalization of the dependence of regiospecificity on the type of stereospecificity (see Section 3.1.4.1).80... 

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. 

Although both linear polyethene and isotactic polypropene are crystalline polymers, ethene-propene copolymers prepared with the aid of Ziegler catalysts are excellent elastomers. Apparently, a more or less random introduction of methyl groups along a polyethene chain reduces the crystallinity sufficiently drastically to lead to an amorphous polymer. The ethene-propene copolymer is an inexpensive elastomer, but having no double bonds, is not capable of vulcanization. Polymerization of ethene and propene in the presence of a small amount of dicyclopentadiene or 1,4-hexadiene gives an unsaturated heteropolymer, which can be vulcanized with sulfur in the usual way. 

Reimann, C., U. Siewers, H. Skarphagen, and D. Banks. 1999. Does bottle type and acid-washing influence trace element analyses by ICP-MS on water samples A test covering 62 elements and four bottle types High density polyethene (HDPE), polypropene (PP), fluorinated ethene propene copolymer (FEP) and perfluoroalkoxy polymer (PFA). Sci. Total Environ. 239 111-130. 

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. 

Table 18. Mechanical properties of syndiotactie polypropene compared to a random ethene/ propene copolymer [156]...

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. 

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]. ... 

The degradations of vulcanized polybutadienes (Bozkurt 1989 Ziimreoglu 1992 Hummel 1993a) and of cross-linked blends with ethene/propene copolymer (Hummel 1987b) have also been studied. 

Syndiospecific catalytic systems based on Cj-sym-metric metallocenes are more regioselective than the C2-symmetric metallocenes of class II. As a consequence, the enantioselectivity in regioirregular insertions have been experimentally investigated for propene-based copolymers only. In particular, NMR characterization of ethene-l- C/propene copolymers suggests that the very low amount (0.03—... 

Using micro-Raman imaging three blends consisting of polypropene/polyethene/ethene-propene copolymer, PBTP/polycarbonate/LDPE, and styrene-acrylonitrile copolymer/styrene-maleic anhydride copolymer/ polydimethylphenylene oxide were studied with regard to compositional and morphological heterogeneities. The general structure of PE fibres in an epoxy resin matrix was also studied. 59 refs. 

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

W Heinen, M van Duin, CH RosenmoUer, CB WenzeL HIM de Groot, J Lugtenburg. C NMR study of the grafting of maleic anhydride on polyethylene polypropylene and ethene-propene copolymers. Macromolecules 29 1151—1157, 1996. 

Datta, S. Lohse, D. J. Graft copolymer compatibUizers for blends of isotactic polypropylenes and ethene-propene copolymers. Macromolecules 1993, 26, 2064—2076. 

Molten Polymers.—A few other studies of molten polymers have been made in addition to those mentioned above. " Inequalities between the values of nT, for the backbone C nuclei in CH groups (n = 1 or 2) in molten trans-buta-l,4-diene/propene copolymer " and cis- and trans-polyisoprene " have been... 

Heinen, W., Rosenmoller, C. H., Wenzel, C. B., Groot, H. J. M. de, Lugtenburg J., and Duin, M. van (1996). 13C NMR Study of the Grafting of Maleie Anhydride onto Polyethene, Polypro-pene, and Ethene-Propene Copolymers. Macromolecules 29(4), 1151-1157... 

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