Rheological and Multifunctional Properties of PBAT/CNT Nanocomposites With Diverse CNT Dispersion Quality Tuned by the Processing Parameters

This study investigates the effect of processing parameters on the dispersion quality of carbon nanotube (CNT) within poly(butylene adipate-co-terephthalate) (PBAT) matrix and the corresponding rheological behavior, electrical conductivity, dielectric properties, and electromagnetic interference shielding effectiveness (EMI-SE). Neat PBAT and nanocomposites containing 1, 3, and 5 wt% CNT were prepared using an internal melt mixer with varying processing temperatures and screw speeds. Small amplitude oscillatory shear rheological analysis revealed that an increase in processing temperature resulted in a more significant increase in complex viscosity and storage modulus at low frequencies reflecting a better CNT dispersion and the formation of a stronger network. Higher mixing speeds also facilitated CNT dispersion more effectively; although further increases could cause the mechanical degradation of PBAT molecules and CNTs breakage. Scanning electron microscopy analysis confirmed the better and more uniform CNT dispersion when the nanocomposites were processed at higher temperatures and mixing speeds. The changes in electrical conductivity, dielectric permittivity, and EMI-SE of the nanocomposites were consistent with the melt rheological results confirming a symbiotic correlation between these characteristics. Nanocomposites with 5 wt% CNT revealed DC conductivity and EMI-SE values of about 10⁻⁷ S/cm and 35–38 dB, respectively, when processed at 150°C and 100 rpm. These values, however, reached about 10⁻³ S/cm and 44–50 dB, respectively, when nanocomposites were prepared at 190°C and 200 rpm. Under this preparation condition, the onset of rheological and electrical conductivity percolation thresholds was estimated at CNT contents of about 0.18 and 0.45 wt%, respectively. A higher processing temperature (190°C) and increased mixing speed (200 rpm) were found to be critical in achieving uniform CNT dispersion and enhancing the multifunctional properties of the nanocomposites.