Highly Ordered Thermoplastic Polyurethane/Aramid Nanofiber Conductive Foams Modulated by Kevlar Polyanion for Piezoresistive Sensing and Electromagnetic Interference Shielding

Abstract

Highly ordered and uniformly porous structure of conductive foams is a vital issue for various functional purposes such as piezoresistive sensing and electromagnetic interference (EMI) shielding. With the aids of Kevlar polyanionic chains, thermoplastic polyurethane (TPU) foams reinforced by aramid nanofibers (ANF) with adjustable pore-size distribution were successfully obtained via a non-solvent-induced phase separation. In this regard, the most outstanding result is the in situ formation of ANF in TPU foams after protonation of Kevlar polyanion during the NIPS process. Furthermore, in situ growth of copper nanoparticles (Cu NPs) on TPU/ANF foams was performed according to the electroless deposition by using the tiny amount of pre-blended Ti3C2Tx MXene as reducing agents. Particularly, the existence of Cu NPs layers significantly promoted the storage modulus in 2,932% increments, and the well-designed TPU/ANF/Ti3C2Tx MXene (PAM-Cu) composite foams showed distinguished compressive cycle stability. Taking virtues of the highly ordered and elastic porous architectures, the PAM-Cu foams were utilized as piezoresistive sensor exhibiting board compressive interval of 0–344.5 kPa (50% strain) with good sensitivity at 0.46 kPa−1. Meanwhile, the PAM-Cu foams displayed remarkable EMI shielding effectiveness at 79.09 dB in X band. This work provides an ideal strategy to fabricate highly ordered TPU foams with outstanding elastic recovery and excellent EMI shielding performance, which can be used as a promising candidate in integration of satisfactory piezoresistive sensor and EMI shielding applications for human–machine interfaces. Graphical Abstract

Dopant Engineering of Flexible MNPs/TPU/PPy Core–Shell Films for Controllable Electromagnetic Interference Shielding

“…With a sufficiently high modulus and excellent abrasion resistance, the flexibility and tensile properties of the TPU framework guarantee outstanding mechanical properties of the films. Moreover, as shown in the FT-IR spectrum (Figure a), a broad band is located in the 3500–3400 cm –1 frequency region of the spectrum, attributed to a strong hydrogen bonding interaction formed between the isocyanate bonds (−NCO) in hard segments as well as the polyol structure in soft segments of TPU and the secondary amine groups (−NH) on PPy. , The PPy coating layer was tightly coated on the TPU fibers because of this strong interfacial bonding between the particles and the TPU surface. However, the inherently rigid nature of the polymer chains makes pure PPy intractable and brittle .…”

Multifunctional Wearable Device Based on an Antibacterial and Hydrophobic Silver Nanoparticles/Ti3C2Tx MXene/Thermoplastic Polyurethane Fibrous Membrane for Electromagnetic Shielding and Strain Sensing

“…To address these problems, AgNPs, as zero-dimensional (0D) nanomaterials, are usually used in combination with 1D or 2D nanomaterials, thus having advantages over 1D or 2D nanomaterials. − MXene 2D nanosheets have metal-like conductivity and negatively charged hydrophilic groups on the surface, which is conducive to uniform dispersion in aqueous solution and bonding with polymer substrates. − Compared with water-insoluble graphene and CNTs, which only have covalent bonds and thus are difficult to complex directly with other materials, MXene has the advantage of having covalent, metallic, and ionic bonds, allowing it easily to be compounded with other materials without pre-processing. TPU is widely used as substrates for devices that achieve high electromagnetic shielding performance due to excellent tensile and resilient properties. − However, the inherent hydrophobicity of TPU itself does not facilitate subsequent surface modification of TPU in aqueous solution. Attaching MXene to a TPU fibrous membrane in the first step greatly facilitates the subsequent treatment of the TPU fibrous membrane in aqueous solutions.…”

Flexible Basalt Fiber/Aramid Nanofiber/Carbon Nanotube Electromagnetic Shielding Paper with Outstanding Environmental Stability and Joule Heating Performance

“…Metallic substrate materials have been favored for their high conductivity and convenient assembly processes, yet their disadvantages, such as high density and poor corrosion resistance, limited their applications. − In contrast, conductive polymer composites (CPCs) have gained increasing attention in recent years due to their advantages, including low density, good processability, corrosion resistance, and tunable electromagnetic shielding performance. ,− Importantly, EMI shielding performance can be further enhanced through the flexible design of CPCs with special structures, such as porous structures, ,− isolation structures, , and multilayer structures. − …”