The Effect of Processing on Crystallization in Mixed Polyolefins

The production of useful products from mixed waste-stream polyolefins requires processing strategies that account for the complex crystallization kinetics of such immiscible blends. While the topics of polymer crystallization and blending are both well-established in the literature, there is considerably less knowledge of how the fundamental parameters that govern polymer blending affect crystallization. Here we utilize the rheo-Raman-microscope and phase contrast microscopy under shear to explore the model immiscible system of isotactic polypropylene and high density polyethylene. We find a strong dependence of domain size, shear rate and cooling rate on crystallization kinetics and its associated rheology. These results underscore the complex multi-variate space that must be understood in order to control the behavior of mixed waste-stream materials in processing operations.