Influence of processing conditions in small‐scale melt mixing and compression molding on the resistivity and morphology of polycarbonate–MWNT composites

Polycarbonate (PC) composites containing 1 wt % multiwalled carbon nanotubes (MWNT) were produced in a small‐scale DACA microcompounder under variation of mixing temperature and mixing speed at fixed mixing time according to a two‐factor and three‐level factorial design. The extruded strands were compression molded under comparable conditions, and their volume resistivity values indicated differences of about 14 orders of magnitude as well as big differences in the state of MWNT agglomerate dispersion (evaluated as macrodispersion index) are observed. The results indicate that mixing at high melt temperature and high speed can lead to the composites having low resistivity and high dispersion index at low mixing energy input. The influence of compression molding parameters was investigated on precompounded PC composites containing 1 and 2 wt % MWNT. Compression molding parameters such as temperature, time, and speed were varied according to a three‐level and three‐factor factorial design. By adjusting compression molding parameters, the volume resistivity of PC with 1 wt % MWNT composites can be varied over eight orders of magnitude, whereas for 2 wt % MWNT, the variation was within one decade. The electrical volume resistivity results indicate the highest influence of the compression molding temperature followed by time.