Fabrication of PLA/CB composites with excellent electrical conductivity and stiffness-ductility balance based on coupling extensional stress with thermal field

[Display omitted] •Extensional stress and thermal field are coupled to fabricate PLA/CB composites.•PLA/CB exhibits excellent electrical conductivity and stiffness-ductility balance.•The electrical conductivity is enhanced by ∼ 109 compared to neat PLA.•Outstanding enhancement in ductility (352.0 %) and strength (41.1 %) is obtained.•This facile fabrication method can be transfer to other bio-based conductive PMCs. A newfound scalable strategy of “annealing stretching-thermal treatment” is proposed to tune electrical conductivity and stiffness-ductility balance of polylactide/carbon black (PLA/CB) conductive composites. The extensional stress-induced orientation and crystallization lead to a significant increase in tensile strength (from 69.3 MPa to 102.0 MPa) and elongation at break (from 9.8 % to 48.7 %). Further thermal treatment effectively reconstructs the conductive network destroyed by the strong extensional stress, causing a sharp increase in electrical conductivity to 5.75 S/m, which is surprisingly ∼ 109 higher than that of neat PLA (5.61 × 10-9 S/m). Besides, the ductility (44.3 %) and strength (97.8 MPa) are well preserved after thermal treatment, attributed to the preservation of oriented amorphous phase and the perfection of oriented crystals, respectively. Moreover, the heat resistance is also improved after thermal treatment. This work could provide significant guidance for facile and efficient fabrication of high-performance bio-based conductive polymer composites.