Macromolecules high-density polyethylene

Bartczak, Z., Argon, A. S., and Cohen, R. E. (1992) Deformation mechanisms and plastic resistance in single-crystal textured high density polyethylene, Macromolecules, 25,... 

Z. Bartczak, A. S. Argon, and R. E. Cohen, Deformation Mechanisms and Plastic Resistance in Single Crystal Textured High Density Polyethylene , Macromolecules 25, 5036-5053 (1992). 

Galeski A, Bai tczak, Argon A S and Cohen R E (1992) Morphological alterations during texture producing plane strain compression of high density polyethylene. Macromolecules 25 5705-5718. 

Ito M, Kanamoto T, Tanaka K, Porter RS. Pulsed NMR studies of crystalline-state extrusion of high-density polyethylene. Macromolecules 1981 14 1779. 

Krishnaswamy RK, Yang Q, Femandez-BaUester L, Komfield JA Effect of the distribution of short-chain branches on crystallization kinetics and mechanical properties of high-density polyethylene. Macromolecules 41(5) 1693—1704, 2008. 

Barbalata, A. Bohossian, T. Prochazka, K. Delmas, G., "Characterization of the Molecular Weight Distribution of High- Density Polyethylene by a New Method Using Turbidity at a Lower Critical Solution Temperature," Macromolecules, 21, 3186 (1988). 

Deur-Siftar [255] demonstrated that in some instances Py-GC permits the degree of crystallinity of low- and high-density polyethylenes, which is associated with the branched structure of the macromolecules of this polymer, to be determined. 

Bellare A., H. Schnablegger, and R.E. Cohen. 1995. A small-angle x-ray scattering study of high-density polyethylene and ultra-high molecular weight polyethylene. Macromolecules 17 2325-2333. 

Matthew JK, Virginia AD (2009) Viscoelasticity and shear stability of single-walled caibon nanotube/unsaturated polyester resin dispersions. Macromolecules 42(17) 6624—6632 Mehta H, Wangshul H, Kanagaraj S (2011) Studies on mechanical properties of carbon nanotubes/ high-density polyethylene nanocomposites by small punch technique. Int J Nanosci 10(1-2) 247-251... 

Fig. 2.19 TEM micrographs of (a) a sphemlite centre in a thin film of high density polyethylene stained with RUO4, (b) section of polyethylene-atactic polypropylene block copolymer stained with RUO4. Reproduced with permission (a) from Figure 15 in Trent, Scheinbeim and Couchman, Macromolecules, 1983, 16 589-598 (Copyright 1983) American Chemical Society, (b) fi om Figure 3 in Hong, Copyright (2001) with permission from Elsevier...

The development of a hierarchical architecture, that is, the existence of more than only one distinct morphological feature, is a universal aspect of the semicrystalline polymers. The scale of relevant structural details ranges from some nanometers to millimeters and is controlled by the architecture of the macromolecules and the processing history. The easiest example of a macromolecule is a linear arrangement of CH2 groups in high-density polyethylene (HDPE). Constitutions of some typical semicrystalline polymers are collected in Table 2.1. 

BAR Baibalata, A., Bohossian, T., Prochazka, K., and Delmas, G., Characterization of the molecular weight distribution of high-density polyethylene by a new method using the turbidity at a lower critical solution temperature, Macromolecules, 21. 3286, 1988. 

MJ Citra, DB Chase, RM Ikeda, KH Gardner. Molecular orientation of high-density polyethylene fibers characterized by polarized Raman spectroscopy. Macromolecules 28 4007-4012, 1995. 

Trujillo M, Arnal ML, Muller AJ, Laredo E, Bredeau St, Bonduel D, et al. Thermal and morphological characterization of nanocomposites prepared by in situ polymerization of high density polyethylene on carbon nanotubes. Macromolecules 2007 40(17) 6268-76. 

The polyethylene obtained (the already cited HDPE) is more highly crystalline and more rigid and dense and has a much more regular structure than the one previously known and obtainable at very high temperature and pressure and which had been industrially produced in the previous 15 years (now called low-density polyethylene, LDPE). The latter shows macromolecules with both long and short branches and is consequently less crystalline than the almost completely linear HDPE. It is obvious that polyethylene does not present tertiary carbon atoms in its constitutional unit, hence it does not show problems of stereoisomerism. 

Free radical vinyl polymerization, the oldest process, leads to branched low density polyethylene (LDPE). Macromolecules have numerous short branches, which reduce the melting point, tensile strength and crystallinity. Polymers are relatively flexible because of the high volume of the branched molecule and the low crystallinity. 

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