Highly conductive and flexible composite films based on carbon nanotubes and renewable biomass

• The simple preparation process using vacuum filtration and hot pressing molding. • Converting low-value waste paper into high-added-value flexible conductive films. • The use of green, renewable biomass as the matrix material. • The development of low-cost, large-scale conductive films shows great potential. Flexible conductive films, known for their excellent electrical conductivity and flexibility, hold great promise in emerging fields such as flexible touchscreens, wearable devices. However, the development of these films is currently hindered by issues such as poor durability and high production costs. This study presents a flexible composite conductive film based on digital printing waste paper (DPWF), a green and abundant resource, and carbon nanotubes (CNTs), an efficient conductive filler. The film is fabricated using a mechanical mixing, vacuum filtration, and hot pressing process, achieving enhanced performance and sustainability. The surface of CNTs was modified with two hydrophilic group-containing coupling agents to enhance the chemical bonding between CNTs and DPWF while preserving the highly graphitized structure and thermal stability of CNTs. Additionally, different forms of silver were doped onto the coupling agent-modified CNTs via a polyol reduction method. The results showed that the electrical conductivity and tensile strength of CNTs-5-AgNWs-9 reached 183.27 S/cm and 24.17 MPa, respectively, representing increases of approximately 97-fold and 77.1 % compared to the unmodified CNTs. Furthermore, the composite exhibited excellent electrical resistance stability in humid environments. These findings provide a pathway for the development of high-conductivity, low-cost flexible conductive films and offer valuable insights into the high-value utilization of digital printing waste paper