Fibrillar State of Order

Small angle X-ray scattering experiments provide insight into the crystalline-amorphous structure of the fibrils and the changes following from annealing processes. Of importance is also the question of the drawability of semicrystalline polymers. It is controlled by the properties of the entanglement net- 

An appropriate measure for the degree of orientation in an uniaxially drawn sample is the orientational order parameter of the monomeric units, S, de- 

Here 9 denotes the angle between the long axis of a monomer and the unique axis, i.e., the direction of drawing. For an isotropic sample we have 

The maximum value reached for a perfectly oriented sample where all monomers, they can be incorporated in crystallites or part of sequences in the amorphous regions, are aligned with their long axes in drawing direction is 

Favorable conditions are met for a cold-drawn fiber or film when its birefringence An = n - nx can be determined (ny and nx denote the refractive indices along and perpendicular to the drawing direction). Here, S can be directly deduced from An, using the relation 

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