Structure and Properties of Polyethylenes

The relationship between structure and properties of polyethylene is largely in accord with the principles enunciated in Chapters 4, 5 and 6. The polymer is essentially a long chain aliphatic hydrocarbon of the type 

Polyethylene, in essence a high molecular weight alkane (paraffin), would be expected to have a good resistance to chemical attack and this is found to be the case. 

The polymer has a low cohesive energy density (the solubility parameter 5 is about 16.1 MPa ) and would be expected to be resistant to solvents of solubility parameter greater than 18.5 MPa. Because it is a crystalline material and does 

Structure and Properties of Polyethylene 213 Table 10.1 Crystallinity data for polyethylene 

The polymer, in the absence of impurities, would also be expected to be an excellent high-frequency insulator because of its non-polar nature. Once again, fact is in accord with prediction. 

Jenkins, A. D. (Ed.), Polymer Science, North-Holland, Amsterdam (1972). 

At the present time there are available many hundreds of grades of polyethylene, most of which differ in their properties in one way or another. Such differences arise from the following variables  

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It is difficult to resist a comparison between the structure and properties of acetal polymers and those of polyethylene. 

Poly(ethylene naphthalate) (PEN), 20, 21, 25. See also PEN entries structure and properties of, 44-46 Poly(ethylene oxide) (PEO), 359 Polyethylenes... 

The OEt-substituted Zr(IV)-boratabenzene complex has been employed in an interesting dual-catalyst approach to the synthesis of branched polyethylene.47 Capitalizing on the ability of this boratabenzene complex to generate 1-alkenes (Scheme 25) and the ability of the titanium complex illustrated in Scheme 27 to copolymerize ethylene and 1-alkenes, with a two-catalyst system one can produce branched polyethlene using ethylene as the only monomer (Scheme 27). The structure and properties of the branched polyethylene can be altered by adjusting the reaction conditions. 

Epacher, E., Krohnke, C. and Pukhanszky, B., Effect of Catalyst Residues on the Chain Structure and Properties of a Phillips Type Polyethylene, Polym. Eng. Set, 40, 1458 (2000)... 

Yamamoto, T., Miyagi, H. and Asai, K. Structure and properties of high pressure phase of polyethylene. Japan. J. Appl. Phys. 16, 1891 (1977)... 

To get a better insight into the chlorination reaction, we wanted to avoid a heterogeneous process. Instead of polyethylene or polypropylene, we used polyisobutene, which is soluble in carbon tetrachloride, as are its chlorination products. In addition, we were interested in the structure and properties of the chlorinated products, especially in comparison with polyvinyl chloride (PVC) and vinyl chloride/isobutene (VC/IB) copolymers. 

In all the low pressure PE processes the polymer is formed through coordination polymerisation. Three basic catalyst types are used chromium oxide, Ziegler-Natta and single-site catalysts. The catalyst type together with the process defines the basic structure and properties of the polyethylene produced. Apart from the MWD and comonomer distribution that a certain catalyst produces in polymerisation in one reactor, two or more cascaded reactors with different polymerisation conditions increase the freedom to tailor... 

In what follows, we first describe general processing techniques used to make synthetic polymeric fibers, followed by a description of the processing, structure, and properties of some important low modulus organic fibers. Finally, we describe, in some detail, two commercially important, high-stifihess fibers aramid and polyethylene. 

Compare and contrast the structures and properties of low-density polyethylene, high-density polyethylene, and linear low-density polyethylene. 

Murthy, N. S., et al., "Structure and Properties of Talc-Filled Polyethylene and Nylon 6 Films," Journal of Applied Poly. Science, 31, 2569-2582 (1986). 

Dirix, Y., Bastiaansen, C., Caseri, W., and Smith, R, Preparation, structure and properties of uniaxiaUy oriented polyethylene-silver nanocomposites, J. Mater ScL, 34, 3859-3866 (1999b). 

Valenza, A., Spadaro, G., Calderaro, E., Aciemo, D., Structure and properties of nylon-6 modified by gamma-irradiated linear low-density polyethylene. Polymer Engineering and Science 1993,33(13), 845-850. 

Pesetskii, S. S., Krivoguz, Y. M., and Jurkowski, B. 2004. Structure and properties of polyamide 6 blends with low-density polyethylene grafted by itaconic acid and with neutralized carboxyl groups. Journal of Applied Polymer Science 92 1702-1708. 

A. Sharif, J. Aalaie, H. Shariatpanahi, H. Hosseinkhanli, A. Khoshniyat, Study on the structure and properties of nanocomposites based on high-density polyethylene/starch blends. Journal of Polymer Research 18 (6) (2011) 1955-1969. 

W. Trochimezuk, Changes in Structure of Polyethylene/Styrene divinyl benzene System, presented at the Structure and Properties of Polymer Networks, Jablonna, Poland, April 1979. Polyethylene/poly(styrene-co-divinyl benzene) semi-II IPNs. Scanning electron microscopy of etched samples. Morphology goes from PS discontinuous to PS continuous as DVB level is increased passed 2%. Polyethylene crystal size is decreased with increasing DVB content. 

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