Volume 43, Issue 7

In this research, the degradation behaviors of ramie-based cellulose triacetate (CTA) films in alkali or acid solutions at room temperature were assessed. Moreover, the attenuated total reflection infrared (ATR-IR), physicochemical properties testing, scanning electron microscope (SEM), and thermogravimetric analysis/differential scanning calorimeter (TG/DSC) were employed to evaluate the detailed degradation process of the CTA films, which were treated by alkali or acidic aqueous solutions. The research results demonstrated that the dominant reaction of CTA films in NaOH solution with various concentrations is deacetylation. Intriguingly, the degradation behaviors of CTA films in HCl depend on the concentration of acid. The CTA films were almost immune to HCl with the concentration less than 1 mol L −1 . However, films were degraded directly when the concentration of acid was higher than 1 mol L −1 . This study provides a theoretical basis and further understanding for the treatment of dumped CTA films at room temperature.

Polymeric epoxy-based nanocomposites have rapidly developed in high energy density and power industry components. The composite insulation undergoes harsh extreme temperature conditions and a high electric field with varying frequencies. This paper dissects the components of complex permittivity in epoxy/ZnO nano and micro composites that were synthesized using different methods, utilizing dielectric spectroscopy as per ASTM D150. The performance of the composites was studied by analyzing the spectra over a frequency range spanning from 1 mHz to 1 kHz. We presume interfacial polarization arises in the composites due to particle clustering. Furthermore, we evaluated the effect of varying filler concentration at 25, 50, 70, and 90 °C. The real permittivity positions the α-steps at 70 and 90 °C. The real and imaginary permittivities remain largely unpretentious by the synthesis method over the entire frequency range.

We report the preparation and application of ZnO/PVA nanocomposite hydrogel containing diclofenac sodium drug (DS) as a drug delivery system. The purpose of designing the nanocomposite hydrogels is to reduce the frequency of use and its side effects, and increase the effect of the drug. The desired nanocomposite hydrogel were prepared through the freezing–melting cycle. The structure and morphology were determined by FTIR and SEM, respectively. The gel fraction increased with adding the nanoparticles, from 67.49 % to 97.69 %. This amount also reaches 97.97 % by adding the drug. The degree of swelling decreased with increasing the amounts of nanoparticles and DS (998 % for PVA-710 % for 1 wt% DS). Based on the result of antibacterial properties and biocompatibility, the inhibition zones around the sample were about 2 mm for Staphylococcus aureus and for Escherichia coli . The cell viability of hydrogel increased from 66.02 % to 79.84 % with increasing the amount of DS. The biodegradation of PVA, is also higher (5–27.17 %) than ZnO/PVA with (3.8–20.2 %) and without (4–23.53 %) drug. The modeling results showed that Peppas–Korsmeyer is a good model for DS release from ZnO/PVA and the diffusion mechanism of DS is Fickian. In this way, we introduced an effective system for drug delivery.

Most self-healing hydrogels always exhibited poor mechanical property which largely limited the applications in many fields. In this work, g-C 3 N 4 nanosheets were introduced to the PVA-borax hydrogel to reinforce the network without sacrificing the self-healing ability. The obtained hydrogel displayed remarkable tensile strength (0.98 MPa), Young’s modulus (1.54 MPa) and toughness (4.43 MJ m −3 ), of which the self-healing efficiency reached to 99 % in 10 min at room temperature. Overall, the strategy proposed in this work provides a simple, operatable and moderate approach to hydrogel with both excellent mechanical property and self-healing ability.

Microencapsulated phase change material (MPCM) was synthesized by using the in-situ polymerization technique. Dimethyl adipate (DMA) and melamine-formaldehyde were used as core and shell material for polymerization respectively. Sodium laureate sulphate (SLS) is used as a surfactant. The thermal properties were characterized by using a differential scanning calorimeter (DSC) and thermogravimetry analysis (TGA). Fourier transform infrared spectroscopy (FT-IR) was used to confirm the chemical structure. The morphology of microcapsules was studied by using, scanning electron microscopy. DSC result of MPCM has been observed to melt at 10.09 °C with melting latent enthalpy 88 J/g and crystallizes at 4.69 °C with crystallization latent heat 89.50 J/g. TGA analysis confirms increases in the thermal stability of MPCM. The decorative coating was prepared with 0, 5, 10, 15, and 20 % MPCM loading, and the prepared paint was tested for pencil hardness, gloss, and stain resistances. The thermal energy transfer rate was used to measure how much time coated panel took to reach the equilibrium temperature of 25 °C. Coating with 20 % MPCM loading revealed good thermal storage capacity but other general coating properties deteriorate.

In this study, a novel “three-layer sandwich” composite loose nanofiltration (NF) membrane structure by mussel bionic technology was constructed on a porous polyvinylidene fluoride (PVDF) substrate membrane, with a mussel bionic coating as the middle layer and the complex network of polyphenols and metal ions as the top layer. The new composite NF membrane had comprehensive properties such as excellent separation performance, good hydrophilicity and strong antifouling ability. The experimental results showed that the combination of tannic acid (TA) and iron ion (Fe 3+ ) could significantly improve the comprehensive performance of the composite NF membrane, with water flux of more than 3000 L/(m 2 ∙h), and the retention rate of dyes and bovine serum protein (BSA) exceeded 90 %, and contact angle was up to 30°. The combination of TA and copper ion (Cu 2+ ) can greatly enhance the antifouling performance and interception ability of methylene blue. The complexation activity of metal ions and polyphenols was related to the oxidation of metal ions. The PVDF/DA-PEI/TA-M + composite structure scheme of “three-layer sandwich” NF membrane provides a new idea and future development direction for the development of novel NF membranes with excellent comprehensive performance.

Electrospinning is a contemporary and effective technique for producing fine fibers with diameters as small as nanometers by using an electric field. These fibers have numerous industrial applications, including filtration, sensors, composite materials, and membranes. This study provides an overview of the electrospinning process and discusses a few applications of polyvinyl alcohol based electrospun nanofibers in the development of filters and sensors.

In this work, glycidyl methacrylate (GMA) and trimethylol propanetriacrylate (TMPTA) are employed to adjust the branching structure of poly L-lactide acid (PLLA) during reactive extrusion induced by UV irradiation. The reaction of GMA epoxide with terminal carboxyl or hydroxyl groups at PLLA chain end can introduce C=C groups onto PLLA molecular chains. Chain branching reaction occurred via the free-radical grafting reaction of the vinyl group in TMPTA with both PLLA backbone and the C=C group terminated PLLA induced by UV irradiation. As a result, varied branching levels can be obtained by changing the ratio of GMA and TMPTA. The characterizations of rheological properties and size exclusive chromatograph correlated to the chain branches were performed to evaluate the chain branching extent. The increases in shear viscosity and storage modulus at terminal zone, and the reduced branching degree were observed in the branched PLLA samples. The results from 1 H-NMR and FIRT indicate that the grafting reaction of GMA onto PLLA take place successfully. Thus, this study proposes a strategy to adjust LCB-PLA structure using GMA and TMPTA as co-agents, which is of great importance for the industrialization of PLA products.