Supplementary information files for "Dual enhancement of Joule heating and positive temperature coefficient behaviour in biodegradable nanocomposites via hybrid carbon nanofiller networks"

Supplementary information files for article "Dual enhancement of Joule heating and positive temperature coefficient behaviour in biodegradable nanocomposites via hybrid carbon nanofiller networks"Conductive polymer composites with positive temperature coefficient (PTC) behaviour hold promises in various applications, such as temperature sensing, over-current protection, and self-regulating heating components. However, achieving efficient Joule heating while maintaining a robust PTC effect remains a significant challenge, which strongly limits the use of these materials in applications such as domestic heating or preheating electronics. Herein, a biodegradable polycaprolactone (PCL) matrix reinforced with hybrid fillers containing graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) is developed. The hybrid filler nanocomposites achieve a dual enhancement in both Joule heating efficiency (~266 %) and PTC intensity (~3 orders of magnitude increase in resistive change) compared to single filler nanocomposites. And both properties are tuneable through filler weight ratio variations. The hybrid filler system also increases electrical conductivity significantly (~4 orders of magnitude increase), making this PTC composite suitable for heating applications requiring a modest voltage supply. The further boosted PTC intensity confirms the self-regulating capability of this bio-nanocomposite, ensuring extra safety for wearable or electronic pre-heating devices. An underlying mechanism of the synergistic effect of the hybrid filler system is proposed and verified based on the analysis of the composites’ morphology, pyro-resistive performance and thermal properties. In addition, the hybrid filler system endows the biodegradable PCL-based nanocomposites with an excellent electrical stability under external degradation conditions and an improved cyclability of self-regulating heating over cycles.