Regulating the temperature‐sensing behavior of poly(lactic acid) by incorporating multiwalled carbon nanotubes and graphene nanoplatelets

Abstract In this work, the synergistic effect of using multiwalled carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) to regulate the temperature response of electrical conductivity ( σ ) for poly(lactic acid) (PLA) composites were reported. The addition of CNTs into PLA/GNPs composites markedly enhanced their crystallization capacity and σ , resulting in a reduction of percolation threshold from 2.87 (for PLA/GNPs) to 0.39 wt% (for PLA/GNPs/CNTs), which is attributed to the formation of a three‐dimensional conductive network within PLA consisting of CNTs and GNPs. Furthermore, elevating the heat treatment temperature from 80 to 140°C resulted in a reduced response time of PLA/CNTs/GNPs composites from 57 to 43 s at the T end of 140°C. Notably, the combined use of CNTs and GNPs considerably amplified the value and stability of max . For example, the maximum increased from 120% for PLACNT 0.6 to 240% for PLA/(CNT 1 /GNP 1 ) 0.6 . The suppression of volume expansion of PLA led to a negative temperature coefficient (NTC) effect at relatively low temperatures, resulting in a reduction of NTC transition temperature from about 160 to 110°C. Additionally, the PLA/(CNT 1 /GNP 1 ) 0.6 exhibited a swift and sensitive response to temperature fluctuations in various heating scenarios, which demonstrated a potential for use as a thermosensitive material with fast response and temperature‐sensing ability. Highlights PLA‐based composites with NTC effect was prepared by adding CNTs and GNPs. The transition temperature from PTC to NTC effect decreased by adding hybrid fillers. The addition of hybrid CNTs and GNPs favored the formation of conductive network. The mechanism for NTC transition was explained.