Improved sensitivity of liquid sensing melt-spun polymer fibers filled with carbon nanoparticles by considering solvent-polymer solubility parameters

Abstract

The Hansen Solubility Parameters (HSPs) and the Relative Energy Differences (REDs) were used to select suitable polymers to perform sensing experiments of electrically conductive nanocomposites against different solvents to employ such materials for sensor applications. From the solvent-polymer HSPs and their REDs, it was determined that polycarbonate (PC) is a polymer with potential towards high liquid sensitivity for different organic solvents. Furthermore, PC is spinnable and sensing fibers of different diameters can be easily produced. In order to get electrically conductive materials, PC was melt-mixed with carbon nanoparticles such as Multi-walled Carbon Nanotubes (MW) and Carbon Black (CB). The materials were then spun into fibers via melt-spinning and evaluated for liquid sensing. It was found that combining MW and CB (50/50 wt%) improved the fiber spinnability and their sensing range in comparison to fibers made of PC and only MW. Liquid sensing evaluations showed that knowing the REDs in advance allows predictions on the ability of nanocomposite fibers to be highly sensitive to specific solvents. From the sensing evaluations it was found that fibers made with hybrid fillers of CB+MW, drawing down ratios of 4 to 12 and filler contents between 3 and 6 wt% showed the best liquid sensing abilities. Depending on the composition and the conditions of fiber production, the maximum values of relative resistance change for fibers with CB+MW were always higher than for fibers containing MW only. Testing for instance butyl acetate as solvent, the fibers with MW+CB achieved values between 600%–3200% for long immersion times, while values between 390 and 1200% were obtained for the fibers with only MW. Testing a selected fiber under a simulated leakage scenario and as sheath/core bi-component fiber showed the effectiveness of these fibers working as liquid detector as well as potential for applications beyond single component fiber sensors.

Keywords

• polymer nanocomposite sensors
• melt-spinning
• liquid sensing
• carbon hybrid fillers