Achieving superior pyroresistive reproducibility at HDPE/PVDF composites with tailored conductive phase size

Abstract Commercial conductive polymer composites (CPCs) with positive temperature coefficient (PTC) behavior usually suffer from inherent poor reproducibility of pyroresistive property. Herein, a conductive carbon black (CB)/high density polyethylene (HDPE)/polyvinylidene fluoride (PVDF) composite with outstanding PTC reproducibility were prepared through introducing cellulose nanocrystals (CNCs) grafted with methyl methacrylate (CNC‐g‐PMMA). Following the minimum interfacial energy mechanism, the CNC‐g‐PMMA tends to locate in PVDF of binary polymer composites. A much finer morphology of conductive CB/HDPE phase is hence obtained owing to the increasement of PVDF/HDPE viscosity ratio by introducing CNC‐g‐PMMA. Undergoing multiple repeated temperature cycles, the room temperature resistance and PTC intensity of as‐prepared material keep almost unchanged, which demonstrates superior PTC reproducibility. The improving mechanism of PTC reproducibility has also been illustrated in detail. This research provides a facile and valid strategy to enhance the PTC reproducibility and will vastly expand the application of PTC composites in the field of intelligent temperature management. Highlights Assembling binary polymer‐based PTC materials with cocontinuous structure Nanocrystals enables conductive HDPE phase with finer morphology. The precise ranges of viscosity ratio ensure the co‐continuous morphology. Small conductive phase size enhances P reproducibility. Narrow spatial domain restricts the self‐aggregation of conductive fillers.