Band 44, Heft 10

The effect of epoxidized soybean oil (ESO) on homocrystallization (HC) and stereocomplex (SC) formation behavior of poly( l -lactide) (PLLA) and poly( d -lactide) (PDLA) bends was investigated utilizing differential scanning calorimetry (DSC). Isothermal crystallization was performed on ESO/PLLA/PDLA blends with varying ESO contents (0, 5, 8, and 10 wt%) and temperatures (90 °C, 120 °C, and 150 °C) for a different duration (12.5, 25, and 125 min). It was found that the ESO could effectively inhibit HC crystallization and promote SC crystallization. For the sample without ESO (ESO-0), the isothermal crystallization temperature and duration had little effect on the melting behavior, whereas sample with 5 wt% ESO (ESO-5), HC crystallization decreased while SC crystallization continued to increase with increasing duration. Additionally, at higher crystallization temperatures with constant ESO content, the melting temperature of SC crystals did not significantly change, suggesting that ESO did not degrade PLLA/PDLA blends. These findings imply that ESO modifies crystallization kinetics, suppressing HC formation and enhancing SC formation, which could benefit for specific material properties and applications.

Globally, the development of porous structured materials has been receiving incredible responses for various high-performance engineering applications. Piezoelectric cellular foams have recently attracted the attention of researchers to emerging applications of acoustic sensors, low-frequency hydrophones, and energy-harvesting devices. As pore morphology is closely related to the shape and the size of the pore-foaming agent, it is necessary to address the influence of particle size of the foaming agent on cell morphology to expand their application area. Hence, this research article establishes the impact of particle size of pore foaming agents on pore morphology, hydrophobicity, and acoustic characteristics of open-cell polyvinylidene fluoride (PVDF) based piezoelectric cellular composites. Open-cell PVDF cellular composites have been fabricated using the template removal method with sodium chloride (NaCl) as a sacrificial templating agent in three different particle sizes: larger, medium, and finer. Based on the experimental results, it can be stated that the particle size of the templating agents dramatically influences the pore morphology, hydrophobicity, and acoustics performance of the PVDF foam samples. The PVDF foams possessing medium pore size have exhibited a maximum sound absorption coefficient of 0.89 at a frequency range of 1,000–1,500 Hz, indicating that PVDF foams have great potential for noise-controlling applications.

In this study, lanthanum oxide (La 2 O 3 ) nanoparticles or lanthana were synthesized by the planetary ball milling method and then used as a filler for the preparation of the polypropylene (PP) based nanocomposites by solution mixing method. The PP used in the study was derived from the discarded saline bottles. The structural and the surface morphology of the synthesized lanthanum oxide nanoparticles were characterized by XRD, SEM and FTIR. The thermogravimetric analysis (TGA) study revealed that the thermal stability of the nano lanthana composites increased with the addition of the lanthanum oxide nanoparticles. The mechanical properties, such as Young’s modulus and tensile strength, were also improved by the addition of the lanthanum oxide nanoparticles to the PP matrix. The composites also showed antibacterial activity against Escherichia coli bacteria. This approach not only mitigates medical plastic waste and environmental impact but also paves the way for versatile polymer nanocomposites with extensive industrial applications, especially in biomedical packaging.

Introducing multi-walled carbon nanotubes (MWCNT) and montmorillonite (MMT) simultaneously into a polymer can significantly enhance its properties. Meanwhile, choosing the best technique to homogeneously disperse these nanohybrid particles in polymers, without agglomerates, is still a challenge. In this study, a hybrid MMT/MWCNT, prepared by lyophilization process, is introduced in polylactide (PLA). Morphology of the resulting nanocomposites displays synergistic relationships of the MMT/MWCNT, facilitating dispersion in PLA. The analysis of transmission electron microscopy (TEM) specific particle densities of PLA0.5hyb, PLA1.0hyb, and PLA2.0hyb shows values of 77, 64, and 35 µm⁻ 2 , respectively. This suggests that MMT platelets are significantly more exfoliated in PLA0.5hyb compared to the other nanocomposites. It also indicates that filler aggregation increases as the MMT/MWCNT concentration increases. Compared to neat PLA, elastic modulus of nanocomposites increased by up to 46 %, demonstrating the reinforcing effect of MMT/MWCNT hybrid nanofillers. The nanocomposites exhibit viscosity, plasticity and damage phenomena, which are significantly decreased because of the MMT/MWCNT incorporation, compared to neat PLA. Furthermore, the viscoelastic properties, analyzed by dynamic thermal-mechanical analysis, record about 27 % increase in the storage modulus of the nanocomposites compared to PLA, indicating the effectiveness of the hybrid MMT/MWCNT in increasing the resistance of PLA/MMT/MWCNT nanocomposite against thermomechanical aggression.

A reversible associated copolymer capable of healing at room temperature was constructed using acrylic acid (AA) and hemin as anionic monomers, and methacryloyloxyethyl trimethylammonium chloride (DMC) as the cationic monomer. Through optimization of the synthesis conditions, characterization by 1 HNMR, infrared spectroscopy, ultraviolet-visible spectroscopy, Thermogravimetric analysis, differential scanning calorimetry, and construction of reasonable models for dynamic simulation, the following conclusions were obtained: The introduction of Hemin could convert light energy into heat energy, accelerating the healing of damaged areas; the predicted glass transition temperature value matched well with the experimental value, demonstrating the reliability of the constructed polymer model; the cohesive energy density (CED), dominated by electrostatic interactions, was identified as the key factor in the self-healing mechanism; the study also visually captured the microscopic process of self-healing within the polymer, providing a detailed understanding of the molecular rearrangements that facilitate this process. This work offers valuable insights into the design of reversible associated polymers, contributing to the broader goal of developing functional polymer materials aligned with circular economy principles.

Molecularly imprinted polymers (MIPs) are a diverse class of materials designed for selective molecular recognition. These polymers are synthesized with particular binding sites that are suited to a target molecule or a collection of structurally similar molecules through the use of a process called molecular imprinting. MIPs were synthesized in this work to specifically remove direct violet 51 from occupational leachates and aqueous solutions. Methacrylic acid functioned as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, 2,2-azobisisobutyronitrile (AIBN) as the initiator, and alcohol as a porogenic solvent. To improve the dye removal effectiveness, a number of factors were optimized, including time, pH, analyte concentrations, and MIP/NIP dosages. The findings showed that MIPs had a much greater capacity for direct violet 51 adsorption than nonimprinted polymers (NIPs), with MIP adsorption capacity reaching 42.553 mg g −1 and NIP adsorption capacity reaching 7 mg g −1 . The pseudo 2nd-order model described the adsorption kinetics, and the rate constant ( K 2 ) for MIPs was found to be 0.00251 mg g −1  min. Furthermore, a high rebinding efficiency of 94 % was observed when the selectivity of MIPs for direct violet 51 was assessed against structurally similar templates.

Gelatin methacrylate (GelMA) is a photo-cross-linkable biopolymer. A combination of GelMA with biodegradable polyesters such as PCL (poly‐ε‐caprolactone) and their triblock derivatives improve the mechanical properties of GelMA. PCL-PEG-PCL (PCEC) was synthesized using ring-opening polymerization of ε-caprolactone in the presence of polyethylene glycol (PEG). The GelMA- PCEC was fabricated using freeze-drying and 3D printing and their porosity, mechanical properties, and swelling behavior were investigated. Human dental pulp stem cells were cultured on the scaffolds for a period of 14 days and cell adhesion was evaluated by scanning electron microscopy. Cell viability was analyzed by MTT and osteogenic differentiation was evaluated by Alizarin red S. Results showed that the 3D-printed scaffold had higher water absorption rate, retaining its structure up to a strain of 0.2 %, and a higher Young’s modulus compared to the freeze-dried scaffold. In terms of cell viability, the 3D-printed scaffold outperformed the freeze-dried scaffold with a percentage of 86 % and 63 % viability respectively. Moreover, the 3D-printed scaffold exhibited better osteodifferentiation with calcium deposition. Overall, these findings suggest that the 3D-printed scaffold may have advantages over the freeze-dried scaffold in tissue engineering applications that require high water absorption, elasticity, and cell viability. The fabricated scaffolds provided suitable cell proliferation.

Thermal interface materials (TIMs) are prerequisite components of micro- and nano-electronics, as well as advanced semiconductor applications. A bisphenol-A epoxy-based thermal adhesive amalgamated graphene oxide (GO), reduced graphene oxide (rGO), and modified hexagonal boron nitride (h-BN/mh-BN) are fabricated. The advantages of adhesive TIMs compared to other TIMs encompass lower cost, process savings, reduced component weight, and prevention of vibration loosening the high-end electronics. Additionally, some parts are not suitable for soldering, as they may lack “legs” that go through holes in the PCBs, and adhesive TIMs help prevent short circuits. The thermal conductivity (TC) is measured at 1.653 ± 0.057 W/mK when incorporating 44.5 wt% mh-BN hybrid rGO into the epoxy matrix. However, substituting rGO with GO reduced the TC to 0.81 ± 0.0289 W/mK due to the lower phonon transfer of GO compared to rGO. The binding strength, in terms of lap shear, of the utmost TC composite adhesive was within the range of 6.26 ± 0.48 MPa, which is acceptable for effective end applications. The thermal stability of both optimized composites (mh-BN/rGO and mh-BN/GO) has demonstrated better results beyond 280 °C. The highest TC epoxy nanocomposite, termed mh-BN/rGO4/epoxy, also revealed electrical insulation properties.