Polyblends crystallization

Liquid crystal polymers Cross-linked Structures Polyblends... 

By alternating layers of hard and soft materials, such as polystyrene and polypropylene, it is possible to achieve synergistic effects in properties, similar to polyblending. For example, a better combination of stiffness, ductility, and toughness can be obtained in polystyrene-polypropylene multilayer films than in either component alone. Such materials also display unusual optical behavior, such as total reflection, at certain wavelengths (Alfrey et al., 1969), because the films tend to reflect light in a manlier similar to the reflection of x-rays by crystals. 

Flory and Ronca[126,127] predicted that asymmetric molecules with aspect ratios higher than 6.417 can act as a mesogett and mesogens with different aspect ratios also form liquid crystals. According to the theoretical predictions, an anisotropic solittion of single phase composed of polymeric mesogens with different aspect ratios is prepared, which was experimentally verified[128,129]. The theoretical predictions further suggest that miscible mesomorphic polyblends may be prepared. Takayanaki et a/.[56,130] exantined the phase transition of... 

The morphology of a polyblend consisting of two crystallizable polymers can vary depending on the processing conditions and the relative rates and temperature of crystallization of the constituent polymers. These can either ciystallize at the same time (coincident crystallization, see further) or separately in a sequential... 

As a polyester, PHB can partake in many of the hydrogen-bonding type of specific interactions with other functional additives that lead to partial miscibility and compatibility. For example, the miscibility of polyesters with chlorinated polymers, polyamides, polycarbonates, cellulose derivatives and other functional polymers is well documented,and PHB is no exception to this general observation. However, these interactions are dominated by the tendency to self-crystallize with exclusion of the additive to the amorphous phase. For example, an 80/20 melt compounded and injection-moulded sample of PVC/PHB polyblend appears initially to be exceptionally tough with the PHB acting as a polymeric plasticizer. The presence of the PVC retards but does not stop crystallization of the PHB at room temperature and the material eventually becomes brittle. Under extreme circumstances, the PHB phase can actually achieve almost 100% crystallinity within the blend, as determined by X-ray analysis and DSC. Thus, plasticized formulations and polyblends involving PHB itself are limited to relatively low levels of additive because only the minor amorphous phase of the biopolymer is involved in the interaction. Even so, some plasticizers have been proposed for PHB. ... 

Radical functionalization of iPP with acrylic acid (AA) gives iPP-AA, which acts as a compatibilizer for PP/liquid crystal polyblend fibers and increases fiber crystallinity and interfacial adhesion. " The reaction of PP with maleic anhydride in xylene at elevated temperatures (120 °C) in the presence of benzoyl peroxide gives maleated iPP. Co-melting of this material with poly(e-caprolactone) (PCL) for 6 h at 120 °C gave a PP-g-PCL graft copolymer. Similar methods have been employed for the grafting of A-phenylmaleimide and maleimido benzoic acid onto iPP oligomers in order to... 

The ideal self-nucleation temperature is probably the best possible choice, because the use of the ideal self-nucleation temperature will provide the polymer with an extremely high nucleation density (typically on the order of 10 nuclei/cm ), which can produce a full completion of the nucleation step before any isothermal crystallization is performed. This novel treatment could be used to study the relative contributions of nucleation and growth in semicrystalline homopolymers and semicrystalline components within diblock copolymers or polyblends. 

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