All issues / Volume 15 (2021) / Issue 11 (November)
This is an editorial article. It has no abstract.
Scalable preparation of flexible, porous, and microstructure membrane for triboelectric nanogenerators (TENGs) with controllable thickness and high contact surface area using cost-effective methods is still a great challenge. Herein, we developed a novel, cost-effective, and scalable fabrication procedure for the preparation of a lightweight, flexible, thin, and porous polyurethane (PU) membrane for a TENG device. Importantly, the thickness and pore size of the PU membrane can be tuned easily. The PU-based TENG device fabricated with a porous PU membrane of 5 μm thickness and 15 μm pore size (PU-5-15) generated a maximum peak to peak output voltage was 58.5 V with a corresponding peak to peak current was 1.37 μA at 4 N and power density of 9.7 mW/m2. The device was systematically used to energize 24 green commercial lightemitting diodes (LEDs) in brighter condition connected in series and to turn on the LCD of a portable timer clock within 51 s and glow for 1 s after 187 taps. The developed TENG device also exhibited stable cyclic charging and discharging property that is very important for real applications. Furthermore, the energy-harvesting performance of the device was also tested with human body movements. The developed industrially compatible method is very easy and convenient, and mass production is possible. Compared to other studies, in this novel study, we achieved a higher electrical performance at the desired lower thickness for the porous PU membrane-based TENG device. The developed fabrication method will pave the way for the facile and scalable industrial processing of PU membranes for energy-harvesting applications.
In this paper, toluene-diisocyanate-trimer (TDI-T) was utilized to manufacture a new type of epoxy resin with high toughness via the co-polymerization method. In the procedure of preparing bisphenol A epoxy resin, before the reaction between bisphenol A (BPA) and epichlorohydrin (ECH), TDI-T was introduced to react with BPA for embedding flexible segments into the chain of epoxy resin, and obtaining the prepolymers, which are easy to form spatial interweaving network structures, then modified epoxy resin (TDI-T/EP) was manufactured. Mechanical properties, thermomechanical properties, and corrosion resistance of the cured TDI-T/EP were tested and characterized. Due to flexible segments and partial molecular network structure, the material presents high mechanical properties, especially the toughness, and the results show that the maximum tensile strength of cured TDI-T/EP reaches 30.3 MPa, and the maximum fracture elongation reaches 48.02%, at the same time the compressive strength arrives at 57.5 MPa. Compared with cured E-51, the toughness, strength, and fracture elongation are all strikingly enhanced. At the same time, the cured TDI-T/EP also has an excellent heat resistance and corrosion resistance, which avoided worries at home for its application. This work provides a new method for manufacturing high-toughness epoxy resins.
Lapatinib-loaded polyvinylpyrrolidone-based nanofibrous solid dispersions were prepared by electrospinning in order to enhance the aqueous solubility and dissolution rate of the anticancer drug. The prepared nanofibers were characterized by smooth-surfaced, homogenous filaments with average diameters of 462±160 nm determined by scanning electron microscopy. The crystalline to amorphous transition of the active ingredient was confirmed by differential scanning calorimetry, while Raman spectroscopy showed that amorphous lapatinib was uniformly distributed in the fibrous structures. Gas chromatographic analyses revealed that residual solvents in the nanofiber mats were below the ICH Guideline Q3C recommended limits, namely ethanol 10.9±2.3 ppm (recommended limit 5000 ppm) and dimethyl formamide 780±56 ppm (recommended limit 880 ppm). Determination of drug content and in vitro dissolution studies were performed in order to observe the influence of electrospinning on the drug release characteristics of the product obtained. The lapatinib content in the nanofibers were measured to be 16.76±0.11 w/w%, whereas the dissolution study at pH 6.8 indicated a rapid disintegration of the nanofibrous mats, releasing ~70% of the drug loading under 5 minutes compared to the ~0.05% dissolution of the neat lapatinib ditosylate. The results confirm the applicability of electrospinning for the improvement of physicochemical characteristics of the poorly bioavailable anticancer agent.
Preparation and properties of semi-alicyclic colorless polyimide films and light-colored sheets with low dielectric features for potential applications in optoelectronic integrated circuits
X. X. Zhi, Y. Zhang, X. M. Zhang, H. L. Wang, L. Wu, Y. C. An, X. Y. Wei, J. G. Liu
Vol. 15., No.11., Pages 1051-1062, 2021
Vol. 15., No.11., Pages 1051-1062, 2021
Colorless and transparent polymer films and sheets with good high-temperature resistance and low dielectric constant (low-Dk) and low dissipation factors (low-Df) features are highly desired in advanced optoelectronic integrated circuits (OEIC) fabrications. In the current work, a series of semi-alicyclic polyimide (PI) powders were first prepared by the onestep high-temperature polycondensation of an alicyclic dianhydride, hydrogenated 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (HBPDA) and aromatic diamines which were beneficial for endowing the derived PI films with low-Dk features, including 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) for PI-1, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (BDAF) for PI-2, and 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene (BAOFL) for PI-3. Then, the derived PI powders were fabricated into colorless films and light-colored sheets, respectively. The freestanding flexible and tough PI films showed excellent optical transparency with the ultraviolet (UV) cutoff wavelength (λcut) lower than 300 nm, the optical transmittance higher than 85% at the wavelength of 400 nm, yellow indices (b*) lower than 1.0, and haze values lower than 1.2%. The hot-processed PI sheets also exhibited light colors. The PI films and sheets showed good thermal stability with the glass transition temperatures (Tg) higher than 220 °C. More importantly, the derived semi-alicyclic PI sheets showed Dk and Df values as low as 2.56 and 0.008 at 1 MHz, respectively.
Separators are one of the most critically important components of lithium-ion batteries to ensure the safe performance of the battery. Commercial polyolefin separators have high thermal shrinkage and low electrolyte uptake, which confines the application of the battery. By using the thermally induced phase separation (TIPS) method, we successfully prepared HDPE/sepiolite nanocomposite separators with high thermal stability and electrolyte wettability. The sepiolite nanofibers are modified with the Vinyltriethoxysilane (VTES) as a coupling agent for better dispersion and interaction in the HDPE matrix. The purpose of fabricating this separator is to decrease the thermal shrinkage and increasing electrolyte uptake of the HDPE separator. The separator electrolyte uptake increased from 86% for pure HDPE separator to 120% for HDPE/sepiolite separator. The thermal shrinkage results indicated that the sample with 3 wt% of sepiolite after remaining for 30 min at 150 °C had only 5% shrinkage compared with 93% of pure HDPE. The results of electrochemical performance showed that the ion conductivity of the separator increased from 0.36・10–3 S・cm–1 for the pure HDPE to 0.9・10–3 S・cm–1 for the nanocomposite separator. The results of cyclability and rate performance showed that the cell assembled with a separator having 3 wt% modified sepiolite has a higher discharge capacity than the cell assembled with a pure HDPE separator.
Disinfectant natural rubber films filled with modified zinc oxide nanoparticles: Synergetic effect of mechanical and antibacterial properties
A. Krainoi, K. Poomputsa, E. Kalkornsurapranee, J. Johns, L. Songtipya, R. L. Nip, Y. Nakaramontri
Vol. 15., No.11., Pages 1081-1100, 2021
Vol. 15., No.11., Pages 1081-1100, 2021
Disinfectant natural rubber (NR) film filled with nano-zinc oxide (ZnOnp) was prepared via latex processes. In addition, modification of ZnOnp was done by coating calcium carbonate (CaCO3) at the ratios of 90:10 and 60:40 (ZnOnp-Ca10 and ZnOnp-Ca40). Mechanical and thermo-mechanical properties, together with the unique anti-microbial activity of the resulting NR film products, were studied in detail. It was found that the nature of ZnO dispersion plays an important role in the improvement of the properties of NR films. Enhancement in the properties of NR was noticed for the films by the addition of ZnOnp-Ca10 and a reduction in properties was observed in the case of unmodified ZnOnp. Van-der Waals force of attraction among the ZnOnp particles and the improved degree of crosslinking of NR molecules are the reasons for the property enhancement. The results are well correlated with qualitative and quantitative determinations against gram-negative E. coli anti-microbial studies. Usage of modified-ZnOnp effectively kills bacteria through the formation of ROS and Zn++, which transfer across the NR molecules via electrostatic forces. Hence, it can be effectively used in the dipping process to develop gloves, condoms, clothes etc.
The processing method of a polymer composite plays an important role in determining the filler morphology inside the polymer matrix, which in turn influences the overall properties of the composite. In the present work, colloidal nano-silica was mixed with natural rubber (NR) latex, and the nanocomposites were made by two distinct processes. The first method was simple film casting, which helped to generate a segregated filler network by arranging nano-silica along the outskirts of the rubber latex circles on drying. The second method involved latex co-coagulation with nano-silica, followed by melt mixing in an internal mixer which shattered the segregated network and yielded a random distribution of nano-silica in the NR matrix. The study revealed that irrespective of the processing method and filler morphology, incorporation of nano-silica in NR significantly improved the mechanical and solvent resistance properties in both cases without affecting thermal stability.