Smart self-switchable and reusable composite fuse enabled by phase change materials

Stimulus-responsive materials have garnered significant attention for their ability to respond to external stimuli, enabling diverse applications in intelligent devices. Semi-crystalline polymers offer temperature-dependent functionality through reversible transitions between crystalline and amorphous states. For the first time, a series of smart, self-switchable, and reusable composite fuses were developed using a ternary composite system of high-density polyethylene (HDPE)-a recyclable polymer and paraffin wax (PW)-adsorbed expanded graphite (EG). These composites demonstrate automatous control of electrical conductivity through PW's phase transition within a temperature range of 60–80 °C. For instance, the through-plane and in-plane electrical conductivity of HDPE/PW/25 vol% EG decreased from 0.62 and 72.28 S·m⁻¹ to 0.04 and 28.18 S·m⁻¹, achieving switching ratios of 15.5 and 2.6, respectively. During high-current impulse testing (i.e., heat impact), it achieved a switching ratio of 5.5, maintaining performance after 100 current impacts. The exceptional electrical conductivity (72 S·m⁻¹) of the composite surpasses most reported polymeric fuses (<1 S·m⁻¹). This work introduces advanced, durable, and reusable functional composites that promote sustainability by enhancing resource efficiency, paving the way for innovative applications in green functional materials and devices.