Polyethylene Crystallization
“Crystallization of polymers is a process associated with partial alignment of their molecular chains. These chains fold together and form ordered regions called lamellae, which compose larger spheroidal structures named spherulites. Polymers can crystallize upon cooling from the melt, mechanical stretching or solvent evaporation. Crystallization affects optical, mechanical, thermal and chemical properties of the polymer. The degree of crystallinity is estimated by different analytical methods and it typically ranges between 10 and 80%, thus crystallized polymers are often called "semicrystalline". The properties of semicrystalline polymers are determined not only by the degree of crystallinity, but also by the size and orientation of the molecular chains.” (Wikipedia, Polymer Crystallization, 6/23/2011)
Polyethylene
Polymer Crystallization
Polymers /Resins
Polyolefins
Recent Journal Articles
Annealing of Single Lamella Nanoparticles of Polyethylene
(4845–4851) Macromolecules 44 #12 (2011)
Rochette et al, Germany, used small-angle X-ray scattering and cryogenic transmission electron microscopy, to show that a doubling of the crystalline lamella sandwiched between two amorphous polymer layers is obtained by annealing the nanoparticles at 125 °C. This thickening of the crystalline lamella can be understood in terms of an unlooping of polymer chains within a single nanoparticle. In addition, a variation of the annealing temperature from 90 to 115 °C demonstrates that the inverse of the crystalline lamellar thickness increases linearly with the annealing temperatures leading to a recrystallization line in a Gibbs–Thomson graph. Since the nanoparticles consist of about only eight polymer chains, they can be considered as a ideal candidates for the experimental realization of equilibrium polymer crystals. (RDC 6/22/2011)