Preparation of Silver-Plated Para-Aramid Fiber by Employing Low-Temperature Oxygen Plasma Treatment and Dopamine Functionalization

Construction of an Interfacial Layer of Aramid Fibers Grafted with Glycidyl POSS Assisted by Heat Treatment and Evaluation of Interfacial Adhesion Properties with Epoxy Resin

The surface of para-aramid fibers (AFs) was modified via air-assisted heat pretreatment and solution impregnation by varying the glycidyl polyhedral oligomeric silsesquioxane (POSS) content. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy showed an ester group, confirming the graft reaction between glycidyl POSS and oxidized AFs. The mechanical properties of AFs could be altered by varying the glycidyl POSS content. The modified AFs exhibited an optimal tensile strength after embedding 5 wt % glycidyl POSS on the fiber surface. The thermal stability of the modified fibers decreased; however, no obvious changes in crystallinity were observed by varying the glycidyl POSS content. Moreover, the tensile strength of monofilament increased from 23.8 to 25.8 cN·dtex-1, the thickness of the grafted layer on the fiber surface was above 30-40 nm after the graft modification with 5 wt % glycidyl POSS, and the interfacial shear strength (IFSS) increased by 62.55% to 26.22 MPa. Thus, the modified glycidyl AFs can be used for the reinforcement of composite materials.

Fabrication of highly conductive, flexible, and hydrophobic Kevlar®@Ni-P-B@Cu@CS fabric with excellent self-cleaning performance for electromagnetic interference shielding

In this work, a simple and cost-effective method was proposed and developed to prepare a novel multilayer-structured Kevlar®@nickel-phosphorus-boron@copper@copper stearate (Kevlar®@Ni-P-B@Cu@CS) composite fabric with high conductivity, high flexibility, high hydrophobicity, and high durability to effectively shield electromagnetic interference (EMI). In this method, an amorphous Ni-P-B alloy nanolayer was initially deposited onto a Kevlar® fabric via electroless plating. Afterward, a crystalline Cu nanolayer was deposited as the second layer via electroplating. Finally, a monolayer of copper stearate was innovatively self-assembled as the outermost protective layer. The Cu deposition was effectively adjusted and designed by controlling the plating current and plating time. The electrical resistance and contact angle of the optimized Kevlar®@Ni-P-B@Cu@CS composite fabric were as low as 3.2 mΩ sq-1 and as high as 115.39°, respectively, indicating that the fabric could withstand bending, tape-off, corrosion, and accelerated environmental tests. The average EMI-shielding efficiency of the durable composite fabric was 93.9 dB in the frequency range of 8.2-12.4 GHz, which was mainly attributed to the absorption loss. Thus, the proposed material configuration has promise for applications in aviation, aerospace, telecommunication, wearable devices, and military industries.

Conductive Aramid Fibers from Electroless Silver Plating of Crosslinked HPAMAM-Modified PPTA: Preparation and Properties

Conductive aramid (PPTA) fibers are highly needed for making flexible conductive materials, antistatic materials, and electromagnetic shielding materials. In this work, silver-plated conductive PPTA fibers with high conductivity and excellent mechanical properties were prepared by the electroless plating of PPTA fibers modified with crosslinked hyperbranched polyamide-amine (HPAMAM). The crosslinked HPAMAM creates a stable interface between the PPTA fibers and the silver plating. The morphology and physicochemical properties of the modified and the silver-plated fibers were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Three epoxy crosslinking agents with different chain lengths were used to crosslink HPAMAM, and the effects of HPAMAM concentration, crosslinking agent dosage, and crosslinking time on the resistance of the fibers were studied. The long chain crosslinking agent appears to be beneficial to silver plating. The lowest resistance (0.067 Ω/cm) was attained when HPAMAM was modified by diethylene glycol diglycidyl ether (1:1 molar ratio), and 20 g/L HPAMAM was used to modify the PPTA fibers. The tensile strength of the original PPTA fibers decreased by only 3% or less after silver plating.

Silver Nanowires and Silanes in Hybrid Functionalization of Aramid Fabrics

New functionalization methods of meta- and para-aramid fabrics with silver nanowires (AgNWs) and two silanes (3-aminopropyltriethoxysilane (APTES)) and diethoxydimethylsilane (DEDMS) were developed: a one-step method (mixture) with AgNWs dispersed in the silane mixture and a two-step method (layer-by-layer) in which the silanes mixture was applied to the previously deposited AgNWs layer. The fabrics were pre-treated in a low-pressure air radio frequency (RF) plasma and subsequently coated with polydopamine. The modified fabrics acquired hydrophobic properties (contact angle ΘW of 112-125°). The surface free energy for both modified fabrics was approximately 29 mJ/m2, while for reference, meta- and para-aramid fabrics have a free energy of 53 mJ/m2 and 40 mJ/m2, respectively. The electrical surface resistance (Rs) was on the order of 102 Ω and 104 Ω for the two-step and one-step method, respectively. The electrical volume resistance (Rv) for both modified fabrics was on the order of 102 Ω. After UV irradiation, the Rs did not change for the two-step method, and for the one-step method, it increased to the order of 1010 Ω. The specific strength values were higher by 71% and 63% for the meta-aramid fabric and by 102% and 110% for the para-aramid fabric for the two-step and one-step method, respectively, compared to the unmodified fabrics after UV radiation.

Application of Fragrance Microcapsules onto Cotton Fabric after Treatment with Oxygen and Nitrogen Plasma

Cotton fabric was exposed to low-pressure capacitively coupled plasma to enhance the adsorption and adhesion of fragrance microcapsules (FCM). Two plasma-forming gases, namely oxygen (O2) and nitrogen (N2), were investigated. The untreated and plasma-treated samples were investigated for their morphological changes by scanning electron microscopy (SEM), mechanical properties (breaking force, elongation, and flexural rigidity), and wicking properties. The cotton samples were functionalized with FCM and the effect of plasma pretreatment on the adsorption and adhesion of FCM was evaluated using SEM, air permeability, fragrance intensity of unwashed and washed cotton fabrics, and Fourier transform infrared spectroscopy (FTIR). The results show that the plasma containing either of the two gases increased the wicking of the cotton fabric and that the O2 plasma caused a slight etching of the fibers, which increased the tensile strength of the cotton fabric. Both plasma gases caused changes that allowed higher adsorption of FCM. However, the adhesion of FCM was higher on the cotton treated with N2 plasma, as evidenced by a strong fragrance of the functionalized fabric after repeated washing.