3 - Biopolymer Composites With High Dielectric Performance: Interface Engineering
Abstract
In recent years, there is a growing interest in studying the dielectric behavior of biopolymer composites due to their potential application as a dielectric material in various electronic devices such as microchips, transformers, and circuit boards. Conducting electroactive polymer composites have also been investigated for various potential applications which include biological, biomedical, flexible electrodes, display devices, biosensors, and cells for tissue engineering. In this chapter, the preparation and dielectric behavior of various biopolymer composites is presented. These biopolymer composites generally consist of nanoscale metal nanoparticles and carbon-based nanofillers such as carbon nanotubes, graphene, graphene oxide (GO), etc., dispersed into the polymer matrix. The physical and chemical properties of these fillers and their interactions with polymers have a significant effect on the microstructure and the final properties of nanocomposites. The biopolymer composites with excellent dielectric properties show great promise as an energy storage dielectric layer in high-performance capacitor applications such as embedded capacitors. This chapter highlights some of the examples of such biopolymer composites; their processing and dielectric behavior will be discussed in detail.
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Anthocyanins extracted from Jamelon fruits (Syzygium cumini L.): Effect of microencapsulation on the properties and bioaccessibility
2024, South African Journal of BotanyThe purpose of this research was to produce and encapsulate anthocyanins obtained from Jamelon fruit using β-cyclodextrin and maltodextrin as wall materials and evaluate the effects of this process on their physico-chemical properties and bioaccessibility. The capsules were produced from the anthocyanins extract with the wall materials, obtaining the samples synthesized with β-cyclodextrin (MβCD) and maltodextrin (MMD). MβCD and MMD had their structure evaluated, as well as their phenolic content, antioxidant activity and percentage of bioaccessible anthocyanins. The microphotographs obtained through SEM indicated the existence of whole capsules, without cracks or leaked material and, alongside the data from the FT-IR, they indicate an association between the anthocyanin molecules and the wall material. MβCD presented higher resistance to thermal degradation at 300 ºC, while MMD had higher encapsulation efficiency (93.01 %). The content of anthocyanins varied between 2.29 and 47.04 mg.mL−1 among samples and no significant differences were observed regarding phenolic content and antioxidant activity of MβCD (37.98 EAG/100 g and 8.93 µM TEAC/g, respectively) and MMD (39.17 mg EAG/100 g and 8.93 µM TEAC/g, respectively). It was noted higher preservation of the anthocyanins content in MMD, which after simulated digestion showed a bioaccessible percentage of 26.22 %. According to the data obtained through this research, maltodextrin is indicated as the ideal wall material for jamelon anthocyanins encapsulation, being able to offer protection for its biological properties, represented by the considerable values of antioxidant activity and stability after simulated digestion.
Advances in implant for surface modification to enhance the interfacial bonding of shape memory alloy wires in composite resins
2024, Progress in Organic CoatingsShape memory alloys (SMAs) are gaining traction in aerospace, automotive, and energy sectors due to their roles as actuators, sensors, and energy converters at high temperatures. Their unique benefits have led to widespread commercial use, supported by extensive research. However, engineered metallics often face deformation and strength issues. Efforts are underway to bolster the bond between SMA wires and composite resins through advanced surface modifications. This review delves into recent surface modification techniques, challenges in SMA composite adhesion, and analytical tools like X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The study concludes with insights on promising modification strategies and the future of enhanced bonding in SMA composites.
3D-printing for the rehabilitation and health monitoring of structures with FBG: Experimental tests
2024, Construction and Building MaterialsNowadays 3D-printing technology is part of many construction processes in different engineering fields, thanks to the possibility of precisely reproducing the shape of complex elements and the availability of different printing materials. In this context, the paper presents the results of tensile experimental tests on samples 3D-printed in PLA (PolyLactic acid), and analyse the effect of the printing process and aging test. Referring to the interest in producing smart components, some samples were printed with an embedded single-mode fiber optic with acrylate coating, commonly used for FOSs (fiber optic sensor). In particular, some samples were produced with pristine optical fiber to test the procedure, while others were produced with the FBG (Fiber Bragg Grating) sensor. The results are discussed in terms of strength and stiffness in both pre-peak stage and post-peak one (ductility and softening), and the functionality of the embedded FBG sensors in operating as strain sensors is reported.
A novel designed nanofibrous mat based on hydroxypropyl methyl cellulose incorporating mango peel extract for potential use in wound care system
2024, International Journal of Biological MacromoleculesSkin tissue is damaged by factors such as burns, physical injuries and diseases namely diabetes. Infection and non-healing of burn wounds and lack of angiogenesis in diabetic wounds lead to extensive injuries and death. Therefore, the design of wound dressings with antibacterial and restorative capabilities is very important. In this study, nanofibers (NFs) including polyurethane (PU) and hydroxypropyl methyl cellulose (HPMC) were prepared with different ratios and Mango peel extract (MPE) loaded into NFs by electrospinning method. The morphology, chemical structure, porosity, degradation, water vapor permeability, mechanical properties, wettability, antioxidant activity and some cell studies and evaluation of their antibacterial properties were investigated. The optimal mat (PU90/HPMC10) had a defect-free morphology with homogeneous NFs. Furthermore, it showed improved biodegradability, water vapor permeability and porosity compared to other Mats. All NFs were non-toxic with hydrophilic behavior in the cellular environment and had acceptable hemocompatibility. The PU90/HPMC10/20 % optimal scaffold had significantly higher cell viability and proliferation than other samples and also had a higher antibacterial ability against pathogenic bacteria S. aureus (17 mm) and E. coli (11 mm). All these findings confirm that the produced NF mats, especially those loaded with MPE, have a high potential to be used as an effective wound dressing.
This research paper introduces an innovative method for tailoring polylactic acid/graphite (PLA/GPT) filament, specifically designed for 3D printing applications. The main achievement is the seamless incorporation of 30 % graphite without the need for a reflux system, elevated temperatures, or additional additives. The filament is thoroughly characterized through Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The electrochemical performance of 3D-printed electrodes is assessed using cyclic voltammetry and a dual-stage activation process, while surface properties are analyzed via roughness examination. The results highlight the successful fabrication of a PLA/GPT filament with uniformly dispersed graphite within the PLA matrix. Additionally, the study confirms the presence of graphite on the surface of the printed electrode, underscoring the vital role and effectiveness of the activation process in enhancing electrochemical responses. These findings have the potential to significantly impact materials in the fields of 3D printing and electrochemistry, offering new possibilities for advanced technological applications.
Interactions of humic acid with pristine poly (lactic acid) microplastics in aqueous solution
2024, Science of the Total EnvironmentMicroplastics and natural organic matter are present in the aquatic environment and their reciprocal interaction plays important roles in the transport and behavior of nutrients and contaminants. Nevertheless, we lack mechanistic understanding on these interactions, especially in the case of biodegradable plastics. Here we investigate the adsorption of a commercial humic acid onto poly (lactic acid) (PLA) microplastics in aqueous solution. While the pseudo-second order kinetic model provided a more accurate representation of the adsorption kinetics, the Elovich model also produced a good fit, suggesting that chemisorption may be the rate-limiting step. The equilibrium data was better fit by the Langmuir model, that provided a maximum adsorption capacity of 0.118 ± 0.006 mg·g−1. The obtained values for the separation factor (RL) and free energy (E) suggest that adsorption of humic acid onto PLA is controlled by physisorption. We studied the effects of pH, ionic strength, and PLA concentration on the adsorption of humic acid onto PLA and demonstrated that electrostatic interactions and aggregation are important. The humic acid was characterized by Fourier-transform infrared (FTIR) spectroscopy, excitation-emission matrix (EEM) fluorescence spectroscopy, and parallel factor analysis (PARAFAC), before and after interacting with PLA. This set of analyses demonstrated that PLA caused alterations in the molecular structure of humic acid, primarily attributed to modifications in hydrogen bonding and hydrophobic interactions. Therefore, we hypothesize that the carboxylic groups of humic acid formed dimers in contact with PLA. This study provides new insights into the interactions between organic matter and a biodegradable microplastic in aqueous systems.