Polyethylene Phases

The algorithm we used for solvent/polydisperse polymer equilibria calls for only one solvent/polymer interaction parameter. The interaction parameter (pto) i ed in the algorithm can be determined from essentially any type of ethylene/polyethylene phase equilibrium data. Cloud-point data have been used (18). while Cheng (16) and Harmony ( ) have done so from gas sorption data. 

The compatibilizing effect of poly(ethylene-g-vinyl chloride), the characteristic constituent of these VC/PE graft copolymers, may be shown by electron photomicrographs of films consisting of a PVC-PE/50-50 mixture on the one hand, and of a VC/PE (50-50) graft copolymer containing about 50 of poly(ethylene-g-vinyl chloride), 25 of polyethylene and 25 of polyvinyl chloride on the other hand (see Figure 8). The films were obtained from a solution in o-dichlorobenzene. In the first case, the polyvinyl chloride and polyethylene phases are clearly separated in the second case, they interpenetrate closely. 

Mechanical tests indicate that these blends do not behave like conventional blends and suggest that the polystyrene phase is continuous in the substrate. The moduli of the blends as a function of blend composition is plotted in Figure 10.6. The Voigt and Reuss models are provided for comparison (Nielsen, 1978) These are the theoretical upper and lower bounds, respectively, on composite modulus behavior our data follows the Voigt model, suggesting that both the polystyrene and polyethylene phases are continuous. In most conventional composites of polystyrene and HDPE, the moduli fall below the Voigt prediction indicating that the phases are discontinuous and dispersed (Barentsen and Heikens, 1973 Wycisk et al., 1990). 

Fig. 1 Polyethylene phase-diagram solid state NMR data solid lines) according to [13]...

HDPE -I- polystyrene and LDPE + polystyrene were compatibilized by adding ethylene/styrene random copolymers, which were semimiscible in the polyethylene phase. They decreased domain size and increased interfacial adhesion, ultimate elongation, and tensile toughness. Increasing their molecular weight also increased toughness [59]. 

Wittmann JC, Lotz B. Epitaxial crystaUization of monoclinic and orthorhombic polyethylene phases. Polymer 1989 30 27-34. 

In the case of the photooxidation of polyethylene/polyamide-6 blends, the mechanism reported for these blends shows the involvement of polyethylene, the component with the lower stability under the action of UV light. The degradation starts in polyamide fraction and the diffusion of radical into polyethylene phase... 

Figure 3.14 Raman spectra of polyethylene. Phase fractions (a) 30% amorphous, 68% C7stalline (b) 70% amorphous, 15% crystalline. Remainder interfacial phase. Adapted with permission from Ref [194] 1995, American Chemical Society.

Let us consider the crystallization of a model polyethylene phase (PE) that is present in strongly segregated and in miscible diblock copolymers in order to compare two very different cases where conhnement or extreme dilution can both induce fractionated crystallization. 

On the basis of these measurements and related physicochemical studies, it is possible to process a structure for ethylene-based ionomers. The un-ionized acid copolymer is thought to consist of two phases a crystalline polyethylene phase and an amorphous phase consisting of polyethylene crosslinked by hydrogen-bonded carboxylic dimers. The ionized copolymers exhibit three distinct phases a crystalline polyethylene phase, an amorphous polyethylene phase, and a dispersed ionic phase consisting of ionic domains. 

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