Abstract
Polyaniline (PANI) has recently gained great attention due to its outstanding electrical properties and ease of processability; these characteristics make it ideal for the manufacturing of polymer blends. In this study, the processing and piezoresistive characterization of polymer composites resulting from the blend of PANI with ultra-high molecular weight polyethylene (UHMWPE) in different weight percentages (wt %) is reported. The PANI/UHMWPE composites were uniformly homogenized by mechanical mixing and the pellets were manufactured by compression molding. A total of four pellets were manufactured, with PANI percentages of 20, 25, 30 and 35 wt %. Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to confirm the effective distribution of PANI and UHMWPE particles in the pellets. A piezoresistive characterization was performed on the basis of compressive forces at different voltages; it was found that the error metrics of hysteresis and drift were influenced by the operating voltage. In general, larger voltages lowered the error metrics, but a reduction in sensor sensitivity came along with voltage increments. In an attempt to explain such a phenomenon, the authors developed a microscopic model for the piezoresistive response of PANI composites, aiming towards a broader usage of PANI composites in strain/stress sensing applications as an alternative to carbonaceous materials.
Highlights
Polyaniline (PANI) has been positioned as a relevant material in recent decades due to its outstanding electromechanical characteristics and attractive processing properties
Costa et al [20] and Andreatta et al [60] experimentally determined the percolation threshold to be around 10 wt % for PANI composites, and the prepared pellets in our study were operating under the percolation regime
The Fourier-transform infrared (FTIR) spectrum of the PANI and the composites show the characteristic bands of the conducting emeraldine salt phase in the region between 1560 and 1530 cm−1 attributed to the stretching vibration of N=Q=N bonds of quinoid diamine ring (Q) and the C–C aromatic ring stretching vibration of the benzenoid diamine in 1460 cm−1 [66]
Summary
Polyaniline (PANI) has been positioned as a relevant material in recent decades due to its outstanding electromechanical characteristics and attractive processing properties. Despite being discovered in the nineteenth century, the usage of PANI remained rather scarce until the 1980s when highly conductive PANI was synthesized for the first time [1,2]. The conductivity of PANI can be trimmed through grafting or irradiation [3,4] while exhibiting environmental stability to external agents [5,6]. PANI is a low-cost polymer with multiple ways of preparation [7]. PANI is commonly synthesized by polymerization of aniline in an aqueous acidic medium, prioritizing the formation of the most conductive form of PANI, the emeraldine salt (ES). The properties of Polymers 2020, 12, 1164; doi:10.3390/polym12051164 www.mdpi.com/journal/polymers
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