Linear polyethylene lamellar crystalline

A) is much smaller than the lamellar length of ordinary PE crystals ( 100A), thus the PE chains are prevented from folding. In this manner, extended-chain crystalline nanofibers of linear polyethylene with an ultrahigh molecular weight (6,200,000) and a diameter of 30 to 50 nm are formed. 

Hocquet, S. et al.. Lamellar and crystalline layer thickness of single crystals of narrow molecular weight fractions of linear polyethylene, Macromolecules 35 (13), 5025-5033, 2002. 

H. G. Kilian, M. Pietralla (Polymer 7P, 664-672, 1978) derive from the anisotropy A of the thermal diffusivity a = X/cpp of oriented polyethylenes that the intrinsic anisotropy Ai of the orienting, partly crystalline lamellar clusters increases with the degree of crystallinity (Aj = 7 to 26, linear extrapolation yields Aj = 2 for the fully amorphous and Aj = 50 for a completely crystalline cluster) the average degree of orientation of the lamellae, , as determined from thermal measurements agrees very well with X-ray data the observed increase of orientation with draw ratio is more rapid than it would be in affine deformation. 

The mechanical melting model (alternatively known as the premelting model) predicts that the yield stress of a polyethylene sample should be proportional to its heat of fusion and hence its degree of crystallinity, which is found to be the case experimentally [98-100]. The observed increase in yield stress as a function of lamellar thickness can be explained by the approximately linear relationship between lamellar thickness and degree of crystallinity [98]. 

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