Advanced Characterization of Phase Separation in HDPE/COC Blends: From Raw Materials to Industrial Products Using Co-localized AFM-Raman

Polymer blends are an industrially important class of materials with numerous applications in coatings, electronics, packaging, automotive, and medical materials. Many desirable material properties can be obtained from the proper control of blend morphology and processing, necessitating in-depth studies relating processing, structure, and properties of these materials. Here, we study the mixing and processing of a polymer system consisting of high-density polyethylene (HDPE) and cyclic olefin copolymer (COC) using atomic force microscopy (AFM) in combination with Raman spectroscopy and optical microscopy. Phase separation is observed, even at COC concentrations as low as 5%. The morphology of the phase separation can be described as a droplet-matrix of COC in HDPE, combined with a co-continuous blend morphology at higher concentrations (12%) of COC. In this system, the topography combined with mechanical property data from AFM provides unambiguous images of the phase separation while co-localized Raman spectroscopy provides complementary chemical identification. This work provides a methodology to obtain an informative physical and chemical picture of the phase separation in this polymer system both before and after processing which can contribute to the improved design, processing, and quality control of industrial polymer blends.