Amplifying Effect in the Size Statistics of the Residual Particles and Its Applications in Analyzing Nanoparticle Dispersion in Polymer Nanocomposites

Nanoparticle size dispersion within polymer nanocomposites is crucial for ensuring material properties and performance. Monitoring the evolution of particle size distribution during processing proves to be critical for elucidating fundamental mechanisms and optimizing manufacturing parameters. The size dispersion evaluation relies on microscopy imaging of the nanoparticles inside the polymer matrix. However, current imaging techniques face significant challenges due to resolution limitations. In this study, we introduce a method that, despite having a microscopy resolution larger than the minimal particle size, effectively assesses the evolution of nanoparticle size dispersion during the fabrication process of polymer nanocomposites. We show that this method has an amplifying effect on the observation of nanoparticles with larger size, namely, the probabilities of the "residues" of the size statistics are larger than the corresponding original probabilities. We demonstrate the utility of this method to assess the agglomeration of nanoparticles during the fabrication processes of polymer nanocomposites. We prepare zinc oxide (ZnO) nanoparticles, incorporate them into polyethylene terephthalate (PET) chips, subsequently process them into ZnO/PET composite fibers, and apply the method to inspect the whole process of the fabrication. Our findings indicate that the developed method provides a reliable evaluation of nanoparticle size dispersion across different material forms. We observed that the fabrication process from ZnO/PET chips to ZnO/PET fibers increases the degree of aggregation, whereas the step from ZnO nanoparticles to ZnO/PET chips maintains a relatively fine size dispersion. Our developed method shows a novel "residue imaging" strategy and can be listed as a useful way to inspect the filler particle dispersion in polymer nanocomposites.