The microstructure and morphology of polyolefins, polyolefin blends, and composites in fabricated objects are widely studied over length scales spanning 10-9 to 10-2 m. Such studies include microstructure and morphology changes during deformation and fracture. These comprehensive studies have proven vital to understand and advance product performance. In the case of granules, the replication model and reactor granule concept have also proven useful for understanding and advancing basic granule morphology, but there is still much to learn about the nascent polyolefin structure created during olefin polymerization on a supported catalyst, including the distinct roles of the support, catalyst, and process. This holds especially for the length scale range 10-9 to 10-6 as well as for unusual morphologies, such as fibrils. In this work, we examine the structures of products with fibrous and globular or pseudo-globular morphologies using a variety of tools including: optical microscopy, electron microscopy (SEM, low voltage SEM, STEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), Raman, X ray scattering (wide and small angle), and NMR. Supported catalysts that have created these structures for this endeavor include metallocene catalysts supported on non-porous fumed silica (catalysts characterized by a variety of methods prior to use) as well as spray dried silica, and Zeigler Natta catalysts (supported with both silica and MgCl2) Structural, morphological, physical, and spectroscopic information are linked to support structure and catalyst performance during olefin polymerization as well as the unique state of nascent semicrystalline polymer formed directly in the polymerization step. The results provide new insights regarding catalytic polymer growth and suggest pathways to new products; for example, a high yield in-situ route to high surface area fibrous high density polyethylene with fiber diameter 0.3-0.6 x 10-6 m.

Examination of nascent polyolefin structure formed during polymerization on supported Zeigler-Natta and metallocene catalysts

253rd National Meeting (2017)

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