Macroscopic drawing ratio

According to his deduction the common finding of ellipsoidal deformation of the reflections is indicative for affine deformation. Moreover, he arrives at an equation that permits to determine with high accuracy the microscopical draw ratio, Xd, of the structural entities from the ellipticity of the deformed Debye sphere. This value can be compared to the macroscopical draw ratio. Even the intensity distribution along the ellipsoidal ridge is predicted for a bcc-lattice of spheres, and deviations of experimental data are discussed. 

Figure 9.1 Dependence of birefringence lAnI on the macroscopic draw ratio XatT = 135 °C for PMMA. 1 experimental data [6] 2 calculation by Equation (9.3) ...

As can be seen, the crystalline fraction (orthorhombic plus monoclinic) decreases from 0.70 to 0.54 at a draw ratio of 50 times and increases to 0.82 at the largest draw ratio. The amorphous phase that appears at a lower draw ratio decreases with increasing draw ratio, accompanying the decrease of the interphase. Such phase structure as elucidated here will reflect on the various macroscopic properties of samples. 

The formation of microvoids (or micropores) in drawn /3-PP is a well-known feature, used successfully to produce breathable films and membranes. Macroscopically their occurrence is correlated with an opacification (i.e. whitening) of the specimen. Their amount can, for example, be measured at given strain rate/draw ratio by liquid porosimetry (e.g. mercury intrusion), gas absorption or by the determination of the density of the deformed sample [129,177,178]. 

In uniaxial macroscopic deformation, the term draw ratio (DR) is customarily used to denote nominal draw (not molecular draw), or the change from the sample s initial dimension to its deformed state at each drawing step. Even though this is by no means a rigorous definition, it applies to deformations induced during simple sample extension or during stretching by differential roll speed. DR assumes full extension efficiency. 

Now we shall consider examples of using the dimension D for the solution of applied problems. When polymer samples are obtained by solid-phase extrusion, the macroscopic (extrusion) draw ratio is determined by the ratio [122, 142,143] ... 

Recent research has also addressed two issues. First, to what extent does the macroscopic measured draw ratio reflect the network draw ratio, and whether slippage occurs at a molecular level. Although curve matching attempts to resolve this problem it has also been instructive to invite more sophisticated molecular studies, for example by scanning near-field optical microscopy [97]. 

---