High density polyethylene single crystal

In the Richmond laboratory, the single crystal disc electrode is mounted on the end of a hollow Kel-F shaft which extends outside of the electrochemical cell. The shaft is connected to a stepping motor and is interfaced to a computer. All parts of the electrochemical cell are constructed from either Kel-F, teflon, or high density polyethylene. The edges and back of the electrode are sealed from contact with the... 

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

In direct fluorination of powdered high-density polyethylene with the gas, diluted with helium or nitrogen, the accompanying exotherm causes partial fusion. In addition, there is some destruction of the crystalline regions [137]. On the other hand, fluorination of single crystals of polyethylene can result in fluorine atoms being placed on the carbon skeleton without disruption of the crystal structure. The extent of cross-linking, however, is hard to assess [138]. The reaction has all the characteristics of free-radical mechanism [139] ... 

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). 

Chang et al. [16] prepared single crystals of high density polyethylene (HDPE) by casting a xylene suspension on carbon coated glass slides and evaporating the solvent. Carbon platinum shadowed specimens (see Section 4.7.2.2) were studied to determine the nature of the... 

Figure 33 Dendritic single crystals of high density polyethylene grown from dilute solution in xylene. (From Ref. 105.)...

Figure 1.6 Melting of high-density polyethylene showing calculation of the heat of fusion from the area under the curve, and melting point measured from the peak maximum, unlike single crystal melt. The accuracy of the heat of fusion needs to be assessed in conjunction with the sample weight and the balance used and is unlikely to extend beyond a decimal point.

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. 

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