Orientation characterization in polypropylene

a knowledge of the polymer orientation produced by the different processes mentioned above is critical for establishing the process conditions and the final properties of the oriented PP. There is a long history of investigations of orientation in polymers [2]. The simplest 

Two of the three factors are independent since the sum of the cos t)y) is equal to 1. In the case of biaxial orientation, more than one orientation factor is needed to specify the orientation states of the polymer. White and Spruiell [3] defined the following biaxial orientation factors for a polymer chain, where the indices 1 and 2 refer to the orientation directions (machine and transverse)  

Details on PP structure and crystalline forms can be foimd elsewhere in this handbook. 

The orientation is calculated from birefringence simply by the ratio  

Infrared dichroism is based on the interaction between linearly polarized infrared radiation and the oriented material. The atoms of a polymer molecule vibrate in characteristic normal modes, each of which produces a change in dipole moment (the transition moment) that has a specific direction. Each mode absorbs infrared energy at a characteristic frequency, giving rise to peaks in the infrared spectrum. The peak intensity (i.e. the absorbance) depends on the angle between the transition moment and the electric field vector of the radiation, and it is this that provides information on the molecular orientation. The orientation is defined in terms of the second moment of the orientation function Pjlcos 0), where  

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