Electrical impedance spectroscopy (EIS) analysis of carbon black distribution in Co-continuous PP/EVA blend

This study investigates how carbon black (CB) distribution in co-continuous polypropylene (PP)/poly(ethylene-co-vinyl acetate) (EVA) blends affects electrical impedance spectroscopy (EIS) properties. PP:CB and EVA:CB masterbatches with 1, 2, or 3 vol% CB were prepared by the melt-mixing method. PP:CB and EVA:CB masterbatches with different CB volume fractions were mixed together to form PP/EVA blends (40/60 vol%) with CB distributions of 1/3, 2/2, or 3/1 vol%. A 60/40 vol% PP/EVA blend with 2/2 vol% CB was also prepared to study morphology effects. Samples were characterized using EIS, scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, and dynamic rheometry. SEM and AFM confirmed co-continuous morphology in all samples. EIS revealed that uneven CB distribution, particularly in the PP:CB 3 vol%/EVA:CB 1 vol% blend, reduced the real part of impedance and increased the frequency cut-off (fc), indicating higher capacitance in Nyquist plots. The 60/40 vol% PP/EVA blend with 2/2 vol% CB exhibited a 38-fold capacitance increase compared to the 40/60 vol% blend, attributed to lower impedance in the PP:CB phase. These findings demonstrate that tailoring CB distribution optimizes electrical energy storage performance and establishes EIS as a robust tool for characterizing conductive particle distribution in immiscible polymer blends.