Electromagnetic Interference Shielding Effectiveness of Interlayered Systems Containing Metal-Oxide, Conducting Polymer and Carbon Nanotube Reinforced Polymeric Composites

The Electromagnetic Interference (EMI) Shielding Effectiveness (SE) has become one of the important requirements for the devices associated with telecommunication systems consisting of large frequency bands. The degradation of the quality of transmitting signal influenced by frequencies emitting from external sources can be reduced by covering the circuits of the devices by EMI Shielding materials like polymer composites, metal-based nanofiber mats, the metal of oxide films, etc. The investigation strives for the attenuation of EMI by introducing two composite mats from conducting polymer-based, multiwalled carbon nanotubes (MWCNTs) coated Nylon 6 nanofiber composites. Two other composite mats are also developed by the Forcespinning® method using sol solution of functionalized multiwalled carbon nanotubes (f-MWCNTs) and magnetite (Fe3O4) into as-prepared polyacrylonitrile (PAN) which is then carbonized at elevated temperature to convert it into carbon nanofiber (CNF). A total of four layers of mats are stacked and compression molded together to develop one multilayered composite (MLC 1). The Fe3O4 has higher magnetic properties which may provide a good magnetic loss effect. The focus is to investigate the synergistic effects between higher magnetic Fe3O4, conductive MWCNTs nanofillers with the dielectric CNF, conducting polymer, and functionalized MWCNTs coated nanofiber composite which can provide information about the dominating mechanism. (Absorption, reflection, or multiple reflections) for EMI SE. The multilayered composite (MLC 2) consisting 8 layers (repeating the stacking sequence again) has given the highest obtained value more than 40 dB EMI SE in the frequency range from 300–500 MHz. The results will bring some findings of optimized materials yielding good EMI SE in lightweight applications

Effect of color on scratch and mar visibility of polymers

Polymer scratch mechanics has been widely studied. However, the physics behind scratch visibility is still not well understood. Scratch deformation mechanisms certainly affect visibility but also other material properties, such as roughness, color or gloss. This work relates to methods to quantitatively evaluate the effect of sample color on polymer scratch and mar induced visibility, aiming at linking scratch behavior with the underlying physics. A custom-built black box was utilized for the analysis of samples possessing different colors and surface finishing. Automatic image analysis was performed through a commercial software to quantify the onset of visibility in terms of a critical load above which the scratch becomes visible. Trained surveyors visually quantified said critical load. White color was shown to delay the onset of visibility by reducing the contrast between the damaged and undamaged area. For instance, the critical load for the onset of visibility for a white polycarbonate copolymer was nearly twice the value reported for its black variant. Consistent results were obtained for all tested samples. Similar findings were reported for the mar phenomenon, highlighting how white color can also mask a different type of damage. The usefulness of the present work and some future perspectives are discussed

Recent Advances in Centrifugal Spinning and Their Applications in Tissue Engineering

Over the last decade, researchers have investigated the potential of nano and microfiber scaffolds to promote wound healing, tissue regeneration, and skin protection. The centrifugal spinning technique is favored over others due to its relatively straightforward mechanism for producing large quantities of fiber. Many polymeric materials have yet to be investigated in search of those with multifunctional properties that would make them attractive in tissue applications. This literature presents the fundamental process of fiber generation, and the effects of fabrication parameters (machine, solution) on the morphologies such as fiber diameter, distribution, alignment, porous features, and mechanical properties. Additionally, a brief discussion is presented on the underlying physics of beaded morphology and continuous fiber formation. Consequently, the study provides an overview of the current advancements in centrifugally spun polymeric fiber-based materials and their morphological features, performance, and characteristics for tissue engineering applications

High Dielectric Breakdown Strength Nanoplatelet‐Based Multilayer Thin Films

Abstract Dielectric materials that can withstand high voltages are of great interest due to the growing need for high‐performance insulation systems in electronics. Polymer nanocomposites have gained popularity as electrical insulators due to their processability, high operating voltage, and tortuous paths for current flow created by the nanoparticles in the polymer matrix. The dielectric breakdown strength of a relatively thick multilayer thin film containing polyethylenimine (PEI) and vermiculite clay (VMT), thickened with tris(hydroxymethyl)aminomethane (tris), is evaluated as a function of bilayers (BL) deposited. The resulting nanobrick wall structure of this clay‐based assembly is ideal for protective insulation. An 8 BL PEI+tris/VMT film achieves a dielectric breakdown strength of 245 kV mm−1, with a thickness of 5 µm. With increasing bilayers, the breakdown strength gradually decreases, but 20 BL of PEI+tris/VMT achieves a breakdown voltage of 2.36 kV. This nanoplatelet‐based system is the first “thick growing” layer‐by‐layer deposited film to be used as an insulating layer. Its unusually high breakdown strength can be useful for the protection of various high voltage electronics