Characterizing the Impact of Shear and Cooling Rate on Crystallinity of a Polymer Melt Through Optical Techniques
The crystalline growth of an isotactic polypropylene material was measured using a Peltier plate in combination with Peltier hood from Anton Paar. The measurements were coupled with a polarized microscope for visual imaging in-situ with rheological testing under varying temperature rates and applied shear conditions.
Understanding the morphology is critical in polymer rheology as the degree of crystallization can impact various material properties. Solidification of a semicrystalline polymer is more impacted by increase in crystallinity, than by decrease in temperature, which impacts the flowability of the polymer.
Understanding how to characterize and control this behavior is important from a processing standpoint. Despite its importance, this field of study struggles with the ability to accurately measure the rheology and evolution of the crystalline structure in-situ. Various attempts have been implemented with specialty setups. However, in most cases, the two properties are measured on separate devices. In this work, an optical module was adapted to a rotational rheometer. This combination allows characterizing the viscoelastic properties of a material, while changes in the morphology can be studied through microscopic imaging, in the form of ictures or videos.
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