Interpreting of effective interphase depth in carbon nanofiber polymer composites by the amount of conduction transferring via an incomplete interphase: A unique method to optimize the charge transferring

Polymer nanocomposites often contain an incomplete interphase, which weakens their properties; however, this issue has not been addressed in previous studies. This manuscript introduces the effective interphase depth ( t_eff ) in carbon nanofiber (CNF)-filled composites (PCNFs), defined by Y as the extent of conduction transfer through an incomplete interphase. Actually, Y expresses the capability of polymer – CNF interphase for the transferring of conduction. t_eff is used to determine the actual CNF concentration, while Y approximates the real opposite aspect ratio. Additionally, a model is proposed to describe the conductivity of PCNFs with an incomplete interphase using the effective parameters. The effects of key factors on t_eff , network ratio, and PCNF conductivity are analyzed and visualized. A CNF radius ( R ) of 30 nm and Y = 10 result in t_eff = 35 nm, while Y < 3.7 leads to t_eff = 0. Similarly, a CNF length ( l ) of 120 μm with straight nanofibers yields t_eff = 40 nm, whereas l = 30 μm reduces t_eff to 5 nm. Thinner, larger, and less-waved CNFs, along with higher Y , optimize t_eff , enhancing PCNF conductivity. Furthermore, strong fitting among the tested and theoretic conductivity data corroborates the proposed model. The tunneling data confirm that electron tunneling plays a significant role in determining PCNF conductivity.