From the surface to the bulk: A comparison of methods for the microanalysis of an immiscible polymer blend

In this study, the morphology of an immiscible polymer blend system at various regions of interests was analyzed using different microanalytical methods with varying surface sensitivities. As a model immiscible polymer blend, a HDPE/PP (80/20 wt%) polymer film was used. The blend film was subjected to polarized light microscopy (PLM), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and time of flight secondary ion mass spectrometry (ToF-SIMS). The obtained results were compared regarding the sensitivities, informational values and overall applicability of the analytical methods. It was evaluated which methods can be applied for a fast analysis of the morphology (surface and bulk) of the immiscible polymer blend with low preparation efforts, which is especially important for the analysis of new materials, for example materials manufactured via recycling. It was demonstrated that PLM, as well as SEM on wet-etched material, provide sufficient information to evaluate the bulk morphology. Additionally, the presented study shows the advantage of applying ToF-SIMS imaging for the characterization of the surface of immiscible polymer blend. As expected, the domain distribution of HDPE and PP varied between the bulk and the surface of the films. The proposed procedures can be taken as a guideline for other investigations concerning the morphology of heterogeneous polyolefin systems.