Efficient and Scalable In Situ Exfoliation of Expanded Graphite for Preparation of Multifunctional Polybutylene Adipate Terephthalate Nanocomposite

Low cost expanded graphite (EG) can endow polymers with multifunctionality. However, achieving excellent in situ exfoliation, dispersion, and distribution of EG on a large scale is a challenge. This article first uses a novel dual‐speed non‐twin screw extruder (NTSE) for in situ pre‐exfoliating of EG, and then uses supercritical fluid extrusion foaming (SFEF) for further in situ exfoliating, successfully preparing a high‐performance multifunctional PBAT/EG composite. Experimental comparisons were conducted on composites with varying EG contents and processed using different methods. The results revealed that the implementation of NTSE resulted in superior exfoliation, dispersion, and distribution of EG compared with those prepared solely by SFEF, whereas a synergistic enhancement was observed with the combined NTSE and SFEF. The thermal conductivity and dielectric constant of composites produced through the integrated approach were 0.70 ± 0.04 W K −1 m −1 and 798.6 ± 4.5 F/m, respectively, representing enhancements of 21% and 150% over those prepared using SFEF alone. Moreover, the PBAT/EG composites fabricated through the combined techniques exhibited improved electromagnetic absorption properties, attaining a minimum reflection loss value of −60.7 dB at a thickness of 6.9 mm, coupled with excellent impedance matching characteristics. This research introduces a novel fabrication method for producing multifunctional polymer/EG composites through the efficient in situ exfoliation of EG using melt extrusion.