The Capillary Suspension Concept Is Used to Obtain Polymer-Free Particle Contacts Enhancing Conductivity of Highly Filled Polymer Composites

Usually, particle morphology and surface treatment are adjusted to achieve high conductivity in highly filled conductive polymer composites. Here, we demonstrate that this key property can be further improved by keeping the particle contact regions free of polymer using an extension of the capillary suspension concept. If the secondary liquid is chosen such that it remains in the contact areas between conductive particles during solidification of the polymer phase, then the composite conductivity substantially increases. For both a thermoset and a thermoplastic model system including 40 vol.% silver particles in the paste, the conductivity was more than doubled compared to the respective binary system, reaching conductivity values up to (4.3 ± 0.2) × 106 Sm−1. SEM images clearly show the polymer-free contact regions in samples with enhanced conductivity. However, conductivity only increases if the secondary fluid is removed after solidification of the polymer phase. Thus, the capillary suspension concept can be used for a controlled modification of particle–particle contacts and represents a generic, viable strategy for enhancing conductivity in highly filled polymer composites. The concept helps to save precious (silver) resources and may find application in various fields of printed electronics, e.g., metallization of thermosensitive solar cells.