Crystallization of PEs

Figure 2 DTA curves of melting and crystallization of PE at 200 MPa. Numbers in the figure correspond to the experimental conditions described in the text. (From Ref. 52.)...

Vill. EFFECT OF MOLECULAR WEIGHT ON THE MELTING-CRYSTALLIZATION OF PE UNDER HIGH PRESSURE... 

Important differences in crystallization behavior were observed between the two crystallizable blocks within PE-fr-PEP-fr-PEO triblock copolymers. The crystallization of PE occurs without confinement from a homogeneous mixture of PE and PEP segments, but for PEO blocks, the crystallization takes place exclusively at high supercoolings in small isolated MDs. 

FIGURE 8-52 Single crystals of PE (Courtesy Ian Harrison, Penn State University). 

FIGURE 8-53 Single crystals of PE [reproduced with permission from D, Renicker and P. H. Geil, J. Appl. Phys., 31,1916 (I960)]. 

Figure 4.11. (a) Schematic representation of a screw dislocation in a lamellar single crystal of PE. The chain direction is [001], (b) Dependence of yield stress cr on crystal thickness ic for crystals of branched PE ( ) and linear PE ( ). The continuous line is calculated from eq. (4.10). (After Young, 1988.)... 

The kinetics of crystallization of PE-containing diblocks have been studied using simultaneous SAXS and WAXS [9,11]. The development of PE crystallites (with an enhanced scattering contrast compared with the initial melt state) was followed via the SAXS invariant using Eq. (2). For PE-PEE diblocks (and PE... 

The presence of one phase In the xnelt for PB/EMA or PE/EMA-salt blends is not inconsistent with the thermal analysis results presented previously (17). It has been determined that there is separate crystallization of PE and EMA or EMA-salt in PE/EMA of PE/EMA-salt blends. In fact, even for two polymers which form one phase in the melt, co-crystallization is quite difficult to Induce. Kyu et al. (42) have shown that blends of linear and branched polyethylenes do not have the ability to cocrystallize and Prud homme (43) has shown that it suffices to have a small difference in molecular weight between two poly(ethylene oxides) to have separate crystallization. Therefore, homogeneity in the melt does not hinder the separate crystallization of the two conqponents of the mixture. 

Like other crystalline polymers, liquid crystalline polymers can also exhibit multiple melting peaks when studied with DSC. Multi-melting is common to crystalline polymers including single crystals of polyethylene. For example, Bair et al. (1967) found the single crystals of PE grown... 

Table 17.1 Temperatures and Enthalpies of Fusion/Crystallization of PE Phase of MIX, COP, COP 120, and Their Fractions .

The polyethylenes with higher functionality were soluble in epoxy resin and required lower temperamre and time for forming homogeneous blend systems. The miscibility of the polymers was dependent on the type of epoxy resin also. Cycloaliphatic epoxy resin showed more miscibility with the polymers compared to DGEBA resin and phase separation occurred in these blend systems as a result of crystallization of PE. Upper critical solution temperature (UCST) behavior was... 

Identical forms of preferentially oriented crystallization of PE on flat (104) surfaces of calcite crystals were also observed with the same range of oriented crystallization in HDPE (Bartczak et al. 1999c). In these experiments, AFM observations furnished dramatic visual evidence of end-on stacking of crystalline lamellae on calcite surfaces as shown in Fig. 13.36 in the form of star shaped-origins of clusters of lamellae similar to the TEM observations of Fig. 13.31 and the discoid-shaped clusters in Nylon-6. 

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