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In this work a global view of flow-induced orientation in isotactic PB-1 is presented. The shear cell used in this work submits the sample to a homogeneous flow field and can be operated from the low shear rate region up into the highly oriented regime close to industrial processing conditions. For varying levels of shear rate and shear strain and for several crystallization temperatures, the transmitted intensity and birefringence are measured throughout the complete crystallization process and characteristic crystallization times are defined. Different regimes of flow-induced crystallization are observed as a function of an increased level of molecular orientation and stretch. Results concerning the Fase II to Fase I transformation in PB-1 are also presented.

The effect of particles with different diameters on flow-induced crystallization from low shear rates to processing speeds is studied using mixtures of polypropylene and zinc oxide with diameters between 35 nm and 1 μm. The nucleating efficiency of the particles was characterized by means of the Lotz efficiency scale using DSC. Flow-induced crystallization at processing speeds was studied by means of the birefringence and transmitted intensity measurements using a specially designed sliding-plate flow cell. For crystallization under quiescent conditions and after shear steps at low shear rates, there are significant differences between the kinetics of the neat polymer, the mixture with the 1 μm zinc oxide, and the mixtures with the midrange particles, which are in agreement with the nucleating efficiency of the particles. As the shear rate is increased, the crystallization kinetics of the mixtures and neat polymer become similar, independent of particle diameter. The transition to highly oriented shish-kebab structures occurs somewhat earlier as the nucleating efficiency is higher, but at the highest shear rates, the kinetics of all materials are equal. This suggests a gradual shift in dominance from the influence of particle addition on the crystallization process at low speeds to the influence of flow at high speeds.

Shear enhanced isothermal crystallization of i-PP was studied using a newly developed sandwich type shear cell and an optical setup with a modulated spinning laser. Considering a limited set of conditions, one temperature (140 °C) and one shear strain (100 units), we illustrate how this setup enables the characterization of the orientation development in homogeneous samples from the low shear rate region with spherulitic structures up into the highly oriented regime with row nucleated structure. At the same time, our choice of sample thickness allows us to measure the evolution of transmitted intensity. Further study of these features holds promise of a better characterization of the morphology development using optical techniques.