Hydrophobic, flexible electromagnetic interference shielding films derived from hydrolysate of waste leather scraps

Ultralight Flexible Collagen Fiber Based Aerogels Derived from Leather Solid Waste for High Electromagnetic Interference Shielding

Designing and developing high-performance shielding materials against electromagnetic interference is of utmost importance due to the rapid advancement of wireless telecommunication technologies. Such materials hold both fundamental and technological significance. A three-stage process is presented for creating ultralight, flexible aerogels from biomass to shield against electromagnetic interference. Collagen fibers sourced from leather solid waste are used for: (i) freeze-drying preparation of collagen fibers/poly(vinyl alcohol) (PVA) aerogels, (ii) adsorption of silver nanowires (AgNWs) onto collagen fiber/PVA aerogels, and (iii) Hydrophobic modification of collagen fiber/PVA/AgNWs aerogels with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (POTS). Scanning electron microscopy studies reveal that an interweaving of AgNWs and collagen fiber/PVA porous network has formed a conductive network, exhibiting an electrical conductivity of 103 S·m-1. The electromagnetic interference shielding effectiveness reached more than 62 dB, while the density was merely 5.8 mg/cm3. The collagen fiber/PVA/AgNWs/POTS aerogel displayed an even better electromagnetic shielding efficiency of 73 dB and water contact angle of 147°. The study results emphasize the distinctive capacity of leather solid waste to generate cost-effective, ecofriendly, and highly efficient electromagnetic interference shielding materials.

Production and Characterization of Flame Retardant Leather Waste Filled Thermoplastic Polyurethane

Discovering new applications for discarded materials, such as leather waste (LW), has proven to be an effective approach to an ecofriendly and sustainable production. The manufacture of halogen-free flame retardant LW containing thermoplastic polyurethane (TPU)-based samples containing an organic phosphinate (OP)-based flame retardant additive would represent an advance in this area. The effects of LW and OP levels on the thermal, flame retardant, and tensile properties of the samples using thermal gravimetric analysis (TGA), limiting oxygen index (LOI), vertical UL-94 (UL-94 V), mass loss calorimetry, and tensile tests have been assessed. OP is highly effective in LW-filled TPU. The highest UL-94 V rating of V0, LOI value of 31.4%, the lowest peak heat release rate (93 ± 3 kW/m2), and total heat evolved (49 ± 2 MJ/m2) values are obtained with the use of 20 wt % OP. OP is primarily promoted through the creation of a compact intumescent residue structure in the condensed phase. LW exhibits an adjuvant effect by producing nonflammable gases in the gas phase and raising the residual yield in the condensed phase. The most remarkable effect of the LW presence is observed in fire performance index (FPI) and fire growth rate (FIGRA) values. The highest FPI value of 0.49 sm2/kW and the lowest FIGRA value of 0.91 kW/m2s are observed with the use of 20 wt % LW.

Robust, ultrathin and flexible electromagnetic interference shielding paper designed with all-polysaccharide hydrogel and MXene

An effective strategy was demonstrated to design an electromagnetic interference (EMI) shielding paper via a facile surface treatment on paper. TEMPO-oxidized cellulose nanofibers (TOCN) were first integrated with Ti3C2Tx MXene, and subsequently cast onto a filter paper with cationic guar gum (CGG) in a sequential way. TOCN and CGG generated a self-assembling hydrogel and formed a MXene-containing hydrogel film on top of the filter paper. The hydrogel film enhanced the tensile strength (9.49 MPa) of composite paper, and resulted in a 17 % increase as compared to the control. The composite paper containing 80 mg MXene (namely, 2.07 mg·cm-2) showed a conductivity of 3843 S·m-1 and EMI shielding effectiveness (EMI SE) of 49.37 dB. Furthermore, the 2-layer assembled TC-M 80 hydrogel composite paper achieved an EMI SE of 73.99 dB. Importantly, this composite paper showed higher EMI SE and lower thickness than a lot of reported materials. The presence of TOCN and CGG also protected MXene against several solvents and the incorporation of polydimethylsiloxane (PDMS) further improved the durability of the composite paper. This work provides a novel and simple strategy to design robust, ultrathin and flexible EMI shielding materials, and it might also inspire other work in paper-based functional materials.

Increasing Functionality of Fish Leather by Chemical Surface Modifications

Fish skin is a by-product of the fishing industry, which has become a significant environmental pollutant in recent years. Therefore, there is an emerging interest in developing novel technologies to utilize fish skin as a versatile raw material for the clothing and biomedical industries. Most research on finishing procedures is conducted on cattle leather, and practically very limited information on fish leather finishing is found in the literature. We have developed three functional surface finishing treatments on chromium (CL)- and vegetable (VL)- tanned salmon leather. These treatments include hydrophobic, oil repellent, and electro-conductive ones. The hydroxyl functional groups present on the surface of the leather were covalently grafted with bi-functional aliphatic small molecule, 10-undecenoylchloride (UC), by esterification reaction forming hydrophobic coating. The surface hydrophobicity was further increased via covalent binding of perfluorodecanethiol (PFDT) to the double bond end-groups of the UC-modified leather via thiol-ene click chemistry conditions. The oleophobic coating was successfully developed using synthesized fluorinated silica nanoparticles (FSN) and polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), showing oil repellency with a contact angle of about 100° for soybean oil and n-hexadecane. The electrically conductive coating was realized by the incorporation of conjugated polymer, polyaniline (PANI), via in situ polymerization method. The treated leather exhibited surface resistivity of about 5.2 (Log (Ω/square)), much lower than untreated leather with a resistivity of 11.4 (Log (Ω/square)).

Asymmetric and Flexible Ag-MXene/ANFs Composite Papers for Electromagnetic Shielding and Thermal Management

Lightweight, flexible, and electrically conductive thin films with high electromagnetic interference (EMI) shielding effectiveness and excellent thermal management capability are ideal for portable and flexible electronic devices. Herein, the asymmetric and multilayered structure Ag-MXene/ANFs composite papers (AMAGM) were fabricated based on Ag-MXene hybrids and aramid nanofibers (ANFs) via a self-reduction and alternating vacuum-assisted filtration process. The resultant AMAGM composite papers exhibit high electrical conductivity of 248,120 S m-1, excellent mechanical properties with tensile strength of 124.21 MPa and fracture strain of 4.98%, superior EMI shielding effectiveness (62 dB), ultra-high EMI SE/t (11,923 dB cm2 g-1) and outstanding EMI SE reliability as high as 96.1% even after 5000 cycles of bending deformation benefiting from the unique structure and the 3D network at a thickness of 34 μm. Asymmetric structures play an important role in regulating reflection and absorption of electromagnetic waves. In addition, the multifunctional nanocomposite papers reveal outstanding thermal management performances such as ultrafast thermal response, high heating temperatures at low operation voltage, and high heating stability. The results indicate that the AMAGM composite papers have excellent potential for high-integration electromagnetic shielding, wearable electronics, artificial intelligence, and high-performance heating devices.

Transferring and Retaining of Different Polyaniline Nanofeatures via Electrophoretic Deposition for Enhanced Sensing Performance

Nanofeatured polyaniline (PANI) electrodes have demonstrated impressive sensing performance due to the enhanced electrolyte diffusion and ion transport. However, the retaining of these nanostructures on substrates via electrophoretic deposition (EPD) faces an insurmountable challenge from the involved dedoping process. Here, camphorsulfonic acid is utilized with high steric effects to dope PANI (PANI-CSA) that can be directly used EPD without involving a dedoping process. Five different nanofeatures (sea cucumber-like, nanofiber, amorphous, nanotube, and nanorod) are synthesized, and they have been all successfully transferred onto indium tin oxide substrate in a formic acid/acetonitrile system, namely a morphology memory effect. The mechanism of retaining these nanofeatures is revealed, which is realized via the processes of dissolution of PANI-CSA, codoping and solvation, and reassembly of basic units into the original nanofeature. The enhanced protonation level by the codoping of formic acid and solvation of acetonitrile plays the key role in retaining these nanofeatures. This method is also applicable to transfer PANI/gold nanorod composites (PANI-CSA/AuNRs). The PANI-CSA/AuNRs electrode as an ascorbic acid sensor has shown an excellent sensing performance with a sensitivity up to 872.7 µA mm^-1 cm^-2 and a detection limit of as low as 0.18 × 10^-6 m.

Sandwich-Structured Surface Coating of a Silver-Decorated Electrospun Thermoplastic Polyurethane Fibrous Film for Excellent Electromagnetic Interference Shielding with Low Reflectivity and Favorable Durability

Nowadays, high efficiency and low reflection electromagnetic interference (EMI) shielding materials have a wide potential application of electronic fields. However, it is still challenging to achieve long-term durability under external mechanical deformations or other harsh conditions. Herein, sandwich-structured surface coatings with a mixture of polydimethylsiloxane (PDMS)/carboxylated multiwalled carbon nanotube and magnetic ferriferous oxide nanoparticle hybrid fillers (MWCNTs-COOH/Fe₃O₄, MFs) are introduced onto a silver-decorated electrospun thermoplastic polyurethane (TPU) fibrous film to achieve both outstanding low reflective EMI shielding and favorable durability. The surface coatings not only act as an effective absorbing layer but also provide a micro-nano hierarchical superhydrophobic surface. The resultant film shows a remarkable conductivity (361.0 S/cm), an excellent EMI shielding effectiveness (SE) approaching 85.4 dB, and a low reflection coefficient value of 0.61. Interestingly, the obtained film still maintains an excellent EMI SE even after mechanical deformations or being immersed in strong acidic solution, alkaline solution, and organic solvents for 6 h. This work opens a new avenue for the design of low reflective EMI shielding films under harsh environments.

Absorption-Dominant, Low-Reflection Multifunctional Electromagnetic Shielding Material Derived from Hydrolysate of Waste Leather Scraps

High-performance flexible conductive films are highly promising for the development of wearable devices, artificial intelligence, medical care, etc. Herein, a three-step procedure was developed to produce electromagnetic interference (EMI) shielding, Joule heating, and a hydrophobic nanofiber film based on hydrolysate of waste leather scraps (HWLS): (i) electrospinning preparation of the HWLS/polyacrylonitrile (PAN)/zeolitic imidazolate framework-67 (ZIF-67) nanofiber film, (ii) carbonization of the HWLS/PAN/ZIF-67 nanofiber film, and (iii) coating of the carbon nanofiber@cobalt (Co@CNF) nanofiber film with perfluorooctyltriethoxysilane (POTS). The X-ray diffraction results showed that metal nanoparticles and amorphous carbon had obvious peaks. The micromorphology results showed that metal nanoparticles were coated with carbon nanofibers. The conductivity and shielding efficiency of the carbon nanofiber film with 250 μm thickness could reach 45 S/m and 49 dB, respectively, and absorption values (A > 0.5) were higher than reflection (R) values for the Co@CNF nanofiber film, which indicated that the contribution of absorption loss was more significant than that of reflection loss. Ultrafast electrothermal response performances were also achieved, which could guarantee the normal functioning of films in cold conditions. The water contact angle of the Co@CNF@POTS nanofiber film was ∼151.3°, which displayed a self-cleaning property with water-proofing and antifouling. Absorption-dominant and low-reflection EMI shielding and electrothermal films not only showed broad application potential in flexible wearable electronic devices but also provided new avenues for the utilization of leather solid waste.