Thermoplastic Electromagnetic Shielding Materials from the Integral Recycling of Waste from Electronic Equipment.

The European Green Deal's goals are anticipated to be fulfilled in large part thanks to the New Circular Economy Action Plan. It is believed that recycling materials will have a significant positive impact on the environment, particularly in terms of reducing greenhouse gas emissions and the impacts this will have on preventing climate change. Due to the complexity of the issue and its significant practical ramifications, the activity of Waste Electrical and Electronic Equipment (WEEE) collection networks is a subject of interest for researchers and managers, in accordance with the principles that recent laws have addressed in a large number of industrialized countries. The goal of this paper is to characterize and obtain composite materials using an injection process with a matrix of LDPE, PP, and HDPE, with up to a 10% addition of nonmetallic powders from PCBs and electronic parts from an integrated process of WEEE recycling. The composites present relevant thermal, electrical, and mechanical properties. Such composite materials, due to their relevant dielectric properties, may be further tested for applications in electromagnetic shielding at frequencies above 1 kHz, or for electromagnetic interference/electromagnetic compatibility (EMI/EMC and ESD) applications at lower frequencies due to their superior dielectric loss factor values, associated with relevant behaviors around exploitation temperatures, mainly for the electric, electronic, or automotive industries.

Special Packaging Materials from Recycled PET and Metallic Nano-Powders.

The European methodology for plastics, as a feature of the EU's circular economy activity plan, ought to support the decrease in plastic waste. The improvement of recycled plastics' economics and quality is one important part of this action plan. Additionally, achieving the requirement that all plastic packaging sold in the EU by 2030 be recyclable or reusable is an important objective. This means that food packaging materials should be recycled in a closed loop at the end. One of the most significant engineering polymers is polyethylene terephthalate (PET), which is widely used. Due to its numerous crucial qualities, it has a wide variety of applications, from packaging to fibers. The thermoplastic polyolefin, primarily polyethylene and polypropylene (PP), is a popular choice utilized globally in a wide range of applications. In the first phase of the current experiment, the materials were obtained by hot pressing with the press machine. The reinforcer is made of Al nanopowder 800 nm and Fe nanopowder 790 nm and the quality of the recycled polymer was examined using Fourier transform infrared spectroscopy (FTIR), a scanning electron microscope (SEM), and differential scanning calorimetry (DSC). From DSC variation curves as a function of temperature, the values from the transformation processes (glass transition, crystallization, and melting) are obtained. SEM measurements revealed that the polymer composites with Al have smooth spherical particles while the ones with Fe have bigger rough spherical particles.

Chitosan Membranes Containing Plant Extracts: Preparation, Characterization and Antimicrobial Properties.

The main strategy of this study was to combine the traditional perspective of using medicinal extracts with polymeric scaffolds manufactured by an engineering approach to fabricate a potential dressing product with antimicrobial properties. Thus, chitosan-based membranes containing S. officinalis and H. perforatum extracts were developed and their suitability as novel dressing materials was investigated. The morphology of the chitosan-based films was assessed by scanning electron microscopy (SEM) and the chemical structure characterization was performed via Fourier transform infrared spectroscopy (FTIR). The addition of the plant extracts increased the sorption capacity of the studied fluids, mainly at the membrane with S. officinalis extract. The membranes with 4% chitosan embedded with both plant extracts maintained their integrity after being immersed for 14 days in incubation media, especially in PBS. The antibacterial activities were determined by the modified Kirby-Bauer disk diffusion method for Gram-positive (S. aureus ATCC 25923, MRSA ATCC 43300) and Gram-negative (E. coli ATCC 25922, P. aeruginosa ATCC 27853) microorganisms. The antibacterial property was enhanced by incorporating the plant extracts into chitosan films. The outcome of the study reveals that the obtained chitosan-based membranes are promising candidates to be used as a wound dressing due to their good physico-chemical and antimicrobial properties.

Fabrication of Poly(vinyl alcohol)/Chitosan Composite Films Strengthened with Titanium Dioxide and Polyphosphonate Additives for Packaging Applications.

Eco-innovation through the development of intelligent materials for food packaging is evolving, and it still has huge potential to improve food product safety, quality, and control. The design of such materials by the combination of biodegradable semi-synthetic polymers with natural ones and with some additives, which may improve certain functionalities in the targeted material, is continuing to attract attention of researchers. To fabricate composite films via casting from solution, followed by drying in atmospheric conditions, certain mass ratios of poly(vinyl alcohol) and chitosan were used as polymeric matrix, whereas TiO2 nanoparticles and a polyphosphonate were used as reinforcing additives. The structural confirmation, surface properties, swelling behavior, and morphology of the xerogel composite films have been studied. The results confirmed the presence of all ingredients in the prepared fabrics, the contact angle of the formulation containing poly(vinyl alcohol), chitosan, and titanium dioxide in its composition exhibited the smallest value (87.67°), whereas the profilometry and scanning electron microscopy enlightened the good dispersion of the ingredients and the quality of all the composite films. Antimicrobial assay established successful antimicrobial potential of the poly(vinyl alcoohol)/chitosan-reinforced composites films against Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. Cytotoxicity tests have revealed that the studied films are non-toxic, presented good compatibility, and they are attractive candidates for packaging applications.

Surface Functionalities of Polymers for Biomaterial Applications.

Changes of a material biointerface allow for specialized cell signaling and diverse biological responses. Biomaterials incorporating immobilized bioactive ligands have been widely introduced and used for tissue engineering and regenerative medicine applications in order to develop biomaterials with improved functionality. Furthermore, a variety of physical and chemical techniques have been utilized to improve biomaterial functionality, particularly at the material interface. At the interface level, the interactions between materials and cells are described. The importance of surface features in cell function is then examined, with new strategies for surface modification being highlighted in detail.

Composite Materials Based on Gelatin and Iron Oxide Nanoparticles for MRI Accuracy.

The majority of recent studies have focused on obtaining MRI materials for internal use. However, this study focuses on a straightforward method for preparing gelatin-based materials with iron oxide nanoparticles (G-Fe2O3 and G-Fe3O4) for external use. The newly obtained materials must be precisely tuned to match the requirements and usage situation because they will be in close touch with human/animal skin. The biocompatible structures formed by gelatin, tannic acid, and iron oxide nanoparticles were investigated by using FTIR spectroscopy, SEM-EDAX analysis, and contact angle methods. The physico-chemical properties were obtained by using mechanical investigations, dynamic vapor sorption analysis, and bulk magnetic determination. The size and shape of iron oxide nanoparticles dictates the magnetic behavior of the gelatin-based samples. The magnetization curves revealed a typical S-shaped superparamagnetic behavior which is evidence of improved MRI image accuracy. In addition, the MTT assay was used to demonstrate the non-toxicity of the samples, and the antibacterial test confirmed satisfactory findings for all G-based materials.

Poly(vinyl alcohol)/Plant Extracts Films: Preparation, Surface Characterization and Antibacterial Studies against Gram Positive and Gram Negative Bacteria.

In this study, we aim to obtain biomaterials with antibacterial properties by combining poly(vinyl alcohol) with the extracts obtained from various selected plants from Romania. Natural herbal extracts of freshly picked flowers of the lavender plant (Lavandula angustifolia) and leaves of the peppermint plant (Mentha piperita), hemp plant (Cannabis sativa L.), verbena plant (Verbena officinalis) and sage plant (Salvia officinalis folium) were selected after an intensive analyzing of diverse medicinal plants often used as antibacterial and healing agents from the country flora. The plant extracts were characterized by different methods such as totals of phenols and flavonoids content and UV-is spectroscopy. The highest amounts of the total phenolic and flavonoid contents, respectively, were recorded for Salvia officinalis. Moreover, the obtained films of poly(vinyl alcohol) (PVA) loaded with plant extracts were studied concerning the surface properties and their antibacterial or cytotoxicity activity. The Attenuated Total Reflection Fourier Transform Infrared analysis described the successfully incorporation of each plant extract in the poly(vinyl alcohol) matrix, while the profilometry demonstrated the enhanced surface properties. The results showed that the plant extracts conferred significant antibacterial effects to films toward Staphylococcus aureus and Escherichia coli and are not toxic against fibroblastic cells from the rabbit.

Characteristics of Composite Materials of the Type: TPU/PP/BaTiO3 Powder for 3D Printing Applications.

Composite materials are materials with anisotropic properties that are created by combining several different components in a way that allows the best qualities of each component to be used. In this paper, raw materials were used to obtain composite materials of the type TPU/PP/BaTiO3 powder. The thermogravimetric analysis, dynamic differential calorimetry, and scanning electron microscopy were carried out. The preliminary tests for making specific filaments for 3D printing with a diameter of 1.75 mm were carried out on a laboratory extruder. The purpose of the experiment was to develop the optimal extrusion temperatures and the speed of drawing the filament to make filaments with rigorously constant dimensions, and the variation in diameter had a maximum of 10%.

Composite Materials Based on Iron Oxide Nanoparticles and Polyurethane for Improving the Quality of MRI.

Polyether urethane (PU)-based magnetic composite materials, containing different types and concentrations of iron oxide nanostructures (Fe2O3 and Fe3O4), were prepared and investigated as a novel composite platform that could be explored in different applications, especially for the improvement of the image quality of MRI investigations. Firstly, the PU structure was synthetized by means of a polyaddition reaction and then hematite (Fe2O3) and magnetite (Fe3O4) nanoparticles were added to the PU matrices to prepare magnetic nanocomposites. The type and amount of iron oxide nanoparticles influenced its structural, morphological, mechanical, dielectric, and magnetic properties. Thus, the morphology and wettability of the PU nanocomposites surfaces presented different behaviours depending on the amount of the iron oxide nanoparticles embedded in the matrices. Mechanical, dielectric, and magnetic properties were enhanced in the composites' samples when compared with pristine PU matrix. In addition, the investigation of in vitro cytocompatibility of prepared PU nanocomposites showed that these samples are good candidates for biomedical applications, with cell viability levels in the range of 80-90%. Considering all the investigations, we can conclude that the addition of magnetic particles introduced additional properties to the composite, which could significantly expand the functionality of the materials developed in this work.

Electrospun Polyvinyl Alcohol Loaded with Phytotherapeutic Agents for Wound Healing Applications.

In this paper, hydroalcoholic solutions of Thymus vulgaris, Salvia officinalis folium, and Hyperici herba were used in combination with poly (vinyl alcohol) with the aim of developing novel poly (vinyl alcohol)-based nanofiber mats loaded with phytotherapeutic agents via the electrospinning technique. The chemical structure and morphology of the polymeric nanofibers were investigated using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The addition of Thymus vulgaris, Salvia officinalis folium, and Hyperici herba extracts to the pure polyvinyl alcohol fibers led to changes in the morphology of the fibers and a reduction in the fibers' diameter, from 0.1798 µm in the case of pure polyvinyl alcohol to 0.1672, 0.1425, and 0.1369 µm in the case of polyvinyl alcohol loaded with Thymus vulgaris, Salvia officinalis folium, and Hyperici herba, respectively. The adapted Folin-Ciocalteu (FC) method, which was used to determine the total phenolic contents, revealed that the samples of PVA-Hyperici herba and PVA-Thymus vulgaris had the highest phenol contents, at 13.25 µgGAE/mL and 12.66 µgGAE/mL, respectively. Dynamic water vapor measurements were used in order to investigate the moisture sorption and desorption behavior of the developed electrospun materials. The antimicrobial behavior of these products was also evaluated. Disk diffusion assay studies with Escherichia coli, Staphylococcus aureus, and Methicillin-resistant Staphylococcus aureus were conducted on the developed nanofibers in order to quantify their phytotherapeutic potential.

Synthesis of Poly(Ethylene Brassylate-Co-squaric Acid) as Potential Essential Oil Carrier.

Bio-based compounds are a leading direction in the context of the increased demand for these materials due to the numerous advantages associated with their use over conventional materials, which hardly degrade in the environment. At the same time, the use of essential oils and their components is generated mainly by finding alternative solutions to antibiotics and synthetic preservatives due to their bioactive characteristics, but also to their synergistic capacity during the manifestation of different biological properties. The present study is devoted to poly(ethylene brassylate-co-squaric acid) (PEBSA), synthesis and its use for thymol encapsulation and antibacterial system formation. The synthesized copolymer, performed through ethylene brassylate macrolactone ring-opening and copolymerization with squaric acid, was physicochemical characterized. Its amphiphilic character allowed the entrapment of thymol (Ty), a natural monoterpenoid phenol found in oil of thyme, a compound with strong antiseptic properties. The copolymer chemical structure was confirmed by spectroscopic analyses. Thermal analysis evidenced a good thermal stability for the copolymer. Additionally, the antimicrobial activity of PEBSA_Ty complex was investigated against eight different reference strains namely: bacterial strains-Staphylococcus aureus ATCC25923, Escherichia coli ATCC25922, Enterococcus faecalis ATCC 29212, Klebsiella pneumonie ATCC 10031 and Salmonella typhimurium ATCC 14028, yeast strains represented by Candida albicans ATCC10231 and Candida glabrata ATCC 2001, and the fungal strain Aspergillus brasiliensis ATCC9642.

Smart Nanomaterials for Biomedical Applications-A Review.

Recent advances in nanotechnology have forced the obtaining of new materials with multiple functionalities. Due to their reduced dimensions, nanomaterials exhibit outstanding physio-chemical functionalities: increased absorption and reactivity, higher surface area, molar extinction coefficients, tunable plasmonic properties, quantum effects, and magnetic and photo properties. However, in the biomedical field, it is still difficult to use tools made of nanomaterials for better therapeutics due to their limitations (including non-biocompatible, poor photostabilities, low targeting capacity, rapid renal clearance, side effects on other organs, insufficient cellular uptake, and small blood retention), so other types with controlled abilities must be developed, called "smart" nanomaterials. In this context, the modern scientific community developed a kind of nanomaterial which undergoes large reversible changes in its physical, chemical, or biological properties as a consequence of small environmental variations. This systematic mini-review is intended to provide an overview of the newest research on nanosized materials responding to various stimuli, including their up-to-date application in the biomedical field.

Preparation and Characterization of Electrospun Collagen Based Composites for Biomedical Applications.

Electrospinning is a widely used technology for obtaining nanofibers from synthetic and natural polymers. In this study, electrospun mats from collagen (C), polyethylene terephthalate (PET) and a blend of the two (C-PET) were prepared and stabilized through a cross-linking process. The aim of this research was to prepare and characterize the nanofiber structure by Fourier-transform infrared with attenuated total reflectance spectroscopy (FTIR-ATR) in close correlation with dynamic vapor sorption (DVS). The studies indicated that C-PET nanofibrous mats shows improved mechanical properties compared to collagen samples. A correlation between morphological, structural and cytotoxic proprieties of the studied samples were emphasized and the results suggest that the prepared nanofiber mats could be a promising candidate for tissue-engineering applications, especially dermal applications.

Preparation and Evaluation of Nanofibrous Hydroxypropyl Cellulose and ß-Cyclodextrin Polyurethane Composite Mats.

A series of nanofibrous composite mats based on polyurethane urea siloxane (PUUS), hydroxypropyl cellulose (HPC) and ß-cyclodextrin (ß-CD) was prepared using electrospinning technique. PUUS was synthesized by two steps solution polymerization procedure from polytetramethylene ether glycol (PTMEG), dimethylol propionic acid (DMPA), 4,4'-diphenylmethane diisocyanate (MDI) and 1,3-bis-(3-aminopropyl) tetramethyldisiloxane (BATD) as chain extender. Then, the composites were prepared by blending PUUS with HPC or ßCD in a ratio of 9:1 (w/w), in 15% dimethylformamide (DMF). The PUUS and PUUS based composite solutions were used for preparation of nanofibrous mats. In order to identify the potential applications, different techniques were used to evaluate the chemical structure (Fourier transform infrared-attenuated total reflectance spectroscopy-FTIR-ATR), morphological structure (Scanning electron microscopy-SEM and Atomic force microscopy-AFM), surface properties (contact angle, dynamic vapors sorption-DVS), mechanical characteristics (tensile tests), thermal (differential scanning calorimetry-DSC) and some preliminary tests for biocompatibility and microbial adhesion.

Functional Polyimide-Based Electrospun Fibers for Biomedical Application.

The current study focuses on the application of cytotoxicity tests upon one membrane matrix based on electrospun polyimide fibers, appealing for biomedical application, such as scaffolds for cell growth, patches or meshes for wound healing, etc. Assays were performed in order to determine the viability and proliferation of L929 murine fibroblasts after they were kept in direct contact with the studied electrospun polyimide fibers. Increased cell viability and proliferation were detected for cells seeded on electrospun polyimide fibers membrane, in comparison with the control system, either after two or six days of evaluation. The number of live cells was higher on the studied material compared to the control, after two and six days of cell seeding. The tendency of the cells to proliferate on the electrospun polyimide fibers was revealed by confocal microscopy. The morphological stability of electrospun polyimide membrane was evaluated by SEM observation, after immersion of the samples in phosphate buffer saline solution (PBS, 7.4 at 37 °C) at various time intervals. Additionally, the easy production of electrospun polyimide fibers can facilitate the development of these types of matrices into specific biomedical applications in the future.

Biocompatibility of Polyimides: A Mini-Review.

Polyimides (PIs) represent a benchmark for high-performance polymers on the basis of a remarkable collection of valuable traits and accessible production pathways and therefore have incited serious attention from the ever-demanding medical field. Their characteristics make them suitable for service in hostile environments and purification or sterilization by robust methods, as requested by most biomedical applications. Even if PIs are generally regarded as "biocompatible", proper analysis and understanding of their biocompatibility and safe use in biological systems deeply needed. This mini-review is designed to encompass some of the most robust available research on the biocompatibility of various commercial or noncommercial PIs and to comprehend their potential in the biomedical area. Therefore, it considers (i) the newest concepts in the field, (ii) the chemical, (iii) physical, or (iv) manufacturing elements of PIs that could affect the subsequent biocompatibility, and, last but not least, (v) in vitro and in vivo biocompatibility assessment and (vi) reachable clinical trials involving defined polyimide structures. The main conclusion is that various PIs have the capacity to accommodate in vivo conditions in which they are able to function for a long time and can be judiciously certified as biocompatible.

Pullulan/Poly(Vinyl Alcohol) Composite Hydrogels for Adipose Tissue Engineering.

Composite hydrogels based on pullulan (HP) and poly(vinyl alcohol) (PVA) were both prepared by simple chemical crosslinking with sodium trimethaphosphate (STMP) or by dual crosslinking (simultaneously chemical crosslinking with STMP and physical crosslinking by freeze-thaw technique). The resulting hydrogels and cryogels were designed for tissue engineering applications. PVA, with two different molecular weights (47,000 and 125,000 g/mol; PVA47 and PVA125, respectively), as well as different P/PVA weight ratios were tested. The physico-chemical characterization of the hydrogels was performed by FTIR spectroscopy and scanning electron microscopy (SEM). The swelling kinetics, dissolution behavior, and degradation profiles in simulated physiological conditions (phosphate buffer at pH 7.4) were investigated. Pullulan concentration and the crosslinking method had significant effects on the pore size, swelling ratio, and degradation profiles. Cryogels exhibit lower swelling capacities than the conventional hydrogels but have better stability against hydrolitic degradation. Biocompatibility of the hydrogels was also investigated by both MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and LDH (lactaten dehydrogenase) assay. The MTT and LDH assays proved that dual crosslinked HP/PVA125 (75:25, w/w) scaffolds are more biocompatible and promote to a greater extent the adhesion and proliferation of L929 murine fibroblast cells than chemically crosslinked HP/PVA47 (50/50, w/w) scaffolds. Moreover, the HP/PVA125 cryogel had the best ability for the adipogenic differentiation of cells. The overall results demonstrated that the HP/PVA composite hydrogels or cryogels are suitable biomaterials for tissue engineering applications.

Anisotropy of Thin Foils Obtained from Microwave-Irradiated Poly(Vinyl Alcohol) Aqueous Solutions.

In this paper, poly(vinyl alcohol) (PVA) foils of comparable thickness were obtained by using 10 wt % PVA aqueous solutions exposed to microwave (MW) radiations for different times. The main goal of this paper is to identify the effects of MW irradiation on the induced optical birefringence of PVA stretched foils, since it is known that the changes in the chemical and physical properties of polymers induced by radiations can influence the asymmetry of their molecular structures from which the birefringence of polymers derives. The efficiency of the MW oven was estimated, and the contribution of sensible and latent heat and heat loss to the absorbed energy was discussed. The effects of MW irradiation, in terms of absorbed energy, were evidenced by using FTIR spectra analysis, contact angle measurements, scanning electron microscopy (SEM) images, and induced optical birefringence. The dehydration (cross-linking) of PVA in aqueous solution and the dependence of the anisotropy on the absorbed MW energy, stretching ratio, and the type of hydrogen bonds formed are discussed in this study.

Eco-Friendly Method for Tailoring Biocompatible and Antimicrobial Surfaces of Poly-L-Lactic Acid.

In this study, a facile, eco-friendly route, in two steps, for obtaining of poly-L-lactic acid/chitosan-silver nanoparticles scaffolds under quiescent conditions was presented. The method consists of plasma treatment and then wet chemical treatment of poly-L-lactic acid (PLLA) films in a chitosan based-silver nanoparticles solution (Cs/AgNp). The changes of the physical and chemical surface proprieties were studied using scanning electron microscopy (SEM), small angle X-Ray scattering (SAXS), Fourier transform infrared spectroscopy (FTIR) and profilometry methods. A certain combination of plasma treatment and chitosan-based silver nanoparticles solution increased the biocompatibility of PLLA films in combination with cell line seeding as well as the antimicrobial activity for gram-positive and gram-negative bacteria. The sample that demonstrated from Energy Dispersive Spectroscopy (EDAX) to have the highest amount of nitrogen and the smallest amount of Ag, proved to have the highest value for cell viability, demonstrating better biocompatibility and very good antimicrobial proprieties.

Functional silsesquioxane-based hierarchical assemblies for antibacterial/antifungal coatings.

This paper reports the first study on functional silsesquioxane-based hierarchical assemblies containing an ordered distribution of silver nanoparticles with a large number of {111} facets, obtained through sol-gel reaction, intended for antibacterial/antifungal coatings.