Search Results (40)

This review article focuses on providing an accumulated knowledge on state-of-the-art composite polymer coating technologies that are studied for corrosion protection. A specific focus has been given to epoxy resin-based composite systems, considering their wide use due to remarkable chemical resistance, excellent adhesion to substrate, thermal stability, and mechanical strength. The addition of various functional polymers to the epoxy matrix has spurred significant advancements in the prevention of corrosion. Light has been shed on the epoxy resin composite systems that are produced by blending with functional polymers like conductive polymers, hydrophobic polymers, etc., and nanofillers. In many cases, the formation of a passive layer at the metal/polymer interface was aided by the addition of such a functional polymer and nanofiller to the epoxy matrix. As a result, corrosive ions are prevented from penetrating by the physical barrier that composite coatings provide. Comparable blends of epoxy and polyamide, epoxy and polyester, and epoxy/poly(vinyl alcohol) and epoxy/polyurethane have superior adhesion, wear, barrier, and anticorrosion properties due to the fine dispersion of nanocarbon and inorganic nanoparticles. The several strategies used to prevent metals from corroding are covered in this review article. Full article

The creation of heat-resistant polymers represents one of the most significant challenges and priorities in contemporary scientific research. The incorporation of a filler of analogous nature and content into disparate types of resins will facilitate the identification of the relationship between properties and the structure of macromolecular chains in synthetic resins that function as composite matrices. The objective of this study was to ascertain the impact of lignin at 5 and 15% by weight on the thermal degradation of two resin-based composites with disparate structural compositions. The thermal decomposition products of the composites were determined by the method of temperature-programmed desorption mass spectroscopy (TPD MS). The thermal oxidative degradation patterns of polymer composites were investigated through derivatography (Q–1500D). It was demonstrated that the incorporation of lignin in modest quantities has a negligible impact on the thermal stability of the composites. Notably, the temperature at which the composites undergo thermal decomposition during thermal oxidation degradation exhibits a variation of over 10 °C, suggesting that the utilisation of lignin holds promise for the development of environmentally benign and cost-effective materials for diverse industrial applications. Full article

The acoustic product development process, crucial for effective noise control, emphasises efficient testing and validation of materials for sound absorption in the R&D phase. Balancing cost-effectiveness, speed, and sustainability, the focus is on minimising excess materials. While strides have been made in reducing sample sizes for estimating random-incident absorption, challenges persist, particularly in establishing validity thresholds for smaller samples with increasing thickness, susceptible to potential overestimation due to edge effects. This study delves into analysing the absorption coefficients of widely used acoustic absorber types—polyester, fibreglass, and open-cell foam—in a full-scale reverberation chamber at Ventac, Blessington, and Wicklow. Demonstrating significant absorption above 500 Hz, these porous absorbers exhibit diminished effectiveness at lower frequencies. The strategic combination of these absorbers with different facings enhances their theoretical broadband absorption characteristics in practical applications. Moreover, the study assesses the validity threshold for reduced sample sizes, employing statistical analysis against ISO 354:2003 standard control samples of the absorber types. Analysis of Variance (ANOVA) on material groups underscores the significant influence of frequency components and sample sizes on the absorption coefficient. The determined validity threshold for 12.8 sqm ISO 354 standard control size is 7.7 sqm for the 25 mm open-cell foam. Similarly, the validity threshold of the 12 sqm ISO 354 standard control size is 9.6 sqm for the 20 mm 800 gsm polyester, 7.2 sqm for the 25 mm fibreglass, and the vinyl black on 25 mm fibreglass. Full article

The study investigated the effect of Vinnex^® (vinyl acetate polymer) and Joncryl^® (epoxy-based copolymer) as compatibilizers on the mechanical properties of thermoplastic starch (TPS) and polybutylene adipate-co-terephthalate (PBAT) and polybutylene succinate-co-adipate (PBSA) films. Due to TPS’s hydrophilicity and brittleness, blending it with biodegradable polyesters like PBAT enhances its properties but may introduce compatibility challenges. This research evaluated three formulations (TPS/PBAT with Vinnex, TPS/PBAT with Joncryl, and TPS/PBAT with both additives) along with the inclusion of a polybutadiene succinate-co-adipate (PBSA) matrix to further improve performance. Mechanical testing (tensile strength, elongation at break, Young’s modulus) reveals that Vinnex and Joncryl enhance plasticization and polymer compatibility, positively impacting TPS/PBAT’s mechanical properties. The introduction of the PBSA matrix further improves tensile strength and elongation. Scanning electron microscopy (SEM) confirms better additive dispersion and interfacial adhesion within the blend. Complementary analysis includes melt flow index, melt density, DSC, and TGA, providing a comprehensive understanding of how these additives optimize TPS/PBAT compounds for sustainable applications. Mechanically, the compatibilized blends showed improved performance: Vinnex mainly enhanced stiffness, Joncryl primarily improved elongation, and a synergistic effect was observed with their combination. Full article

Polyesters (PEs) are sustainable alternatives for conventional polymers owing to their potential degradability, recyclability, and the wide availability of bio-based monomers for their synthesis. Herein, we used a one-pot, one-step self-switchable polymerization linking the ring-opening alternating copolymerization (ROAC) of epoxides/cyclic anhydrides with the ring-opening polymerization (ROP) of L-lactide (LLA) to synthesize PE-based hot-melt adhesives with a high bio-based content. In the cesium pivalate-catalyzed self-switchable polymerization of glutaric anhydride (GA), butylene oxide (BO), and LLA using a diol initiator, the ROAC of GA and BO proceeded whereas the ROP of LLA simultaneously proceeded very slowly, resulting in a copolyester consisting of poly(GA-alt-BO) and poly(L-lactide) (PLLA) segments with tapered regions, that is, PLLA-tapered block-poly(GA-alt-BO)-tapered block-PLLA (PLLA-tb-poly(GA-alt-BO)-tb-PLLA). Additionally, a series of tapered-block or real-block copolyesters consisting of poly(anhydride-alt-epoxide) (A segment) and PLLA (B segment) with AB-, BAB-, (AB)₃-, and (AB)₄-type architectures of different compositions and molecular weights were synthesized by varying the monomer combinations, alcohol initiators, and initial feed ratios. The lap shear tests of these copolyesters revealed an excellent relationship between the adhesive strength and polymer structural parameters. The (AB)₄-type star-block copolyester (poly(GA-alt-BO)-tb-PLLA)₄ exhibited the best adhesive strength (6.74 ± 0.64 MPa), comparable to that of commercial products, such as PE-based and poly(vinyl acetate)-based hot-melt adhesives. Full article

This overview provides insights into organic and metal–organic polymer (OMOP) catalysts aimed at processes carried out in the liquid phase. Various types of polymers are discussed, including vinyl (various functional poly(styrene-co-divinylbenzene) and perfluorinated functionalized hydrocarbons, e.g., Nafion), condensation (polyesters, -amides, -anilines, -imides), and additional (polyurethanes, and polyureas, polybenzimidazoles, polyporphyrins), prepared from organometal monomers. Covalent organic frameworks (COFs), metal–organic frameworks (MOFs), and their composites represent a significant class of OMOP catalysts. Following this, the preparation, characterization, and application of dispersed metal catalysts are discussed. Key catalytic processes such as alkylation—used in large-scale applications like the production of alkyl-tert-butyl ether and bisphenol A—as well as reduction, oxidation, and other reactions, are highlighted. The versatile properties of COFs and MOFs, including well-defined nanometer-scale pores, large surface areas, and excellent chemisorption capabilities, make them highly promising for chemical, electrochemical, and photocatalytic applications. Particular emphasis is placed on their potential for CO₂ treatment. However, a notable drawback of COF- and MOF-based catalysts is their relatively low stability in both alkaline and acidic environments, as well as their high cost. A special part is devoted to deactivation and the disposal of the used/deactivated catalysts, emphasizing the importance of separating heavy metals from catalysts. The conclusion provides guidance on selecting and developing OMOP-based catalysts. Full article

The aim of this study was to analyze the influence of different packaging materials on the composition of the headspace (CO₂ and O₂) of rennet cheeses packed in unit packaging under different modified atmosphere (MAP) conditions during a storage period of 90 days at 2 °C and 8 °C. The packaging materials comprised different combinations of BOPP—biaxially oriented polypropylene; PET—polyester; PE—polyethylene; PP—polypropylene; EVOH—ethylene–vinyl alcohol copolymer; PET—polyethylene terephthalate; and PA—polyamide. As the properties of the packaging material (foil) affect the gas conditions inside the packaging, it is important to study whether the modifications, i.e., properties and thickness, of the foils will result in significant differences in the composition of the headspace of packed cheeses. The CO₂ content in the headspace of Gouda cheese packages ranged from 35% to 45%, while for Maasdamer and Sielski Klasyczny cheese, it varied between 55% and 65%. Throughout the storage period, the O₂ content in the headspace of cheeses packaged in tested foils (1–5) did not exceed 0.5%. The type of foil used did not influence the modified atmosphere packaging (MAP) conditions. Full article

In general, the majority of fiber-reinforced polymer composites (FRPs) used in structural applications comprise carbon, glass, and aramid fibers reinforced with epoxy resin, with the occasional utilization of polyester and vinyl ester resins. This study aims to assess the feasibility of utilizing recyclable and sustainable materials to create a resilient composite suitable for structural applications, particularly in scenarios involving low-velocity and high-velocity impact (LVI, HVI) loading. The paper presents a comparative analysis of the performance of E-glass, aramid, and eco-friendly basalt-reinforcing fabrics as reinforcement fibers in both thermosetting (epoxy) and recyclable thermoplastic (Elium^©) resins. Given the limited research on Elium composites, especially those incorporating basalt-reinforcing fiber, there is an urgent need to expand the databases of fundamental mechanical properties for these diverse composites. This necessity is exacerbated by the scarcity of the literature regarding their performance under low- and high-velocity impact loadings. The results of this study will demonstrate the potential of basalt-reinforced Elium composite as an effective recyclable and environmentally friendly structural material system for both static and dynamic loading conditions. Full article

Natural and synthetic polymers are a versatile platform for developing biomaterials in the biomedical and environmental fields. Natural polymers are organic compounds that are found in nature. The most common natural polymers include polysaccharides, such as alginate, hyaluronic acid, and starch, proteins, e.g., collagen, silk, and fibrin, and bacterial polyesters. Natural polymers have already been applied in numerous sectors, such as carriers for drug delivery, tissue engineering, stem cell morphogenesis, wound healing, regenerative medicine, food packaging, etc. Various synthetic polymers, including poly(lactic acid), poly(acrylic acid), poly(vinyl alcohol), polyethylene glycol, etc., are biocompatible and biodegradable; therefore, they are studied and applied in controlled drug release systems, nano-carriers, tissue engineering, dispersion of bacterial biofilms, gene delivery systems, bio-ink in 3D-printing, textiles in medicine, agriculture, heavy metals removal, and food packaging. In the following review, recent advancements in polymer chemistry, which enable the imparting of specific biomedical functions of polymers, will be discussed in detail, including antiviral, anticancer, and antimicrobial activities. This work contains the authors’ experimental contributions to biomedical and environmental polymer applications. This review is a vast overview of natural and synthetic polymers used in biomedical and environmental fields, polymer synthesis, and isolation methods, critically assessessing their advantages, limitations, and prospects. Full article

Currently, fiber-reinforced polymer composites (FRPs) used for demanding structural applications predominantly utilize carbon, glass, and aramid fibers embedded in epoxy resin, albeit occasionally polyester and vinyl ester resins are also used. This study investigates the feasibility of employing recyclable and sustainable materials to formulate a composite suitable for load-bearing structural applications, particularly in scenarios involving low-velocity and high-velocity impacts (LVIs and HVIs, respectively). The paper presents a comparative analysis of the performance of basalt–Elium, a fully recyclable, sustainable, and environmentally friendly composite, with an epoxy-based counterpart. Moreover, an accurate and reliable numerical model has been developed and introduced through which the response of these composites can be examined efficiently and accurately under various loading states. The results of this investigation demonstrate the viability of the basalt–elium composite as a fully recyclable and sustainable material for crafting efficient and lightweight composites. Additionally, the accurately developed finite element model presented here can be used to assess the influence of several parameters on the composite, thereby optimizing it for a given situation. Full article

In order to investigate the durability of two kinds of fiber-reinforced composite materials, and obtain the degradation mechanism and failure model in a hygrothermal environment, E-glass- fiber-reinforced composite materials, glass fiber-reinforced epoxy vinyl ester and glass fiber-reinforced unsaturated polyester (named GF/VE and GF/UP, respectively) were chosen to suffer rigorous hygrothermal aging. Their mechanical performance was monitored during the aging process to evaluate their durability. The cause of deterioration of the composite was comprehensively analyzed. Based on the analysis results of attenuated total-reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), the change mechanism of chain structure of the resin molecule was proposed. SEM (scanning electron microscopy), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to analyze the microstructure and degradation mechanism of the fiber and the interface between fiber and matrix. The degradation mechanism of the composite system, including the resin, the fiber and the interface, was obtained, and it was found that the deterioration of the matrix resin caused by the hygrothermal environment was the main factor leading to the decline in composites performance. Full article

The emission of chlorinated pollutants is one of the main problems when recovering copper (Cu) via pyrolysis from waste enameled wires. This is mainly attributed to other wastes which possess high poly(vinyl chloride) content, such as electrical wires and cables, which are often recycled together with enameled copper wires. In this research, to control the chlorinated pollutants, copper(II) oxide (CuO) was chosen and demonstrated to be an efficient dechlorinating agent, and CuO did not introduce any impurities that influence the quality of the recovered Cu. The pyrolysis and co-pyrolysis of polyester enameled wires, PVC, and CuO were investigated, and special attention was paid to chlorinated compounds in released pyrolytic products. In particular, the co-pyrolysis of this ternary mixture was studied for the first time, and some new pyrolysis behaviors were discovered. For example, the results of Py-GC/MS analyses showed that the addition of CuO removed about 75% of the chloro-organic products, the main types of which were chloroaromatic compounds rather than the more toxic chloroesters. Moreover, pyrolysis gases were collected and characterized via ion chromatography, and the results showed that the chlorine content in the pyrolysis gases decreased by about 71%. TG analysis indicated that CuO only minimally affected the pyrolysis of polyester paint. However, through the chlorine fixation effect, CuO influenced the dechlorination and dehydrochlorination of PVC, as well as secondary reactions between HCl and pyrolysis products of polyester paint, therefore changing the products and behaviors of co-pyrolysis. Mechanism of reducing chlorine-containing pollutants and reaction mechanism of forming typical pyrolysis products closely correlated to the effects of CuO were also proposed, providing theoretical guidance for the recycling of waste enameled wires. Full article

Genome mining of Streptomyces exfoliatus DSMZ 41693 has allowed us to identify four different lipase-encoding sequences, and one of them (SeLipC) has been successfully cloned and extracellularly expressed using Rhodococcus sp. T104 as a host. SeLipC was purified by one-step hydrophobic interaction chromatography. The enzyme is a monomeric protein of 27.6 kDa, which belongs to subfamily I.7 of lipolytic enzymes according to its phylogenetic analysis and biochemical characterization. The purified enzyme shows the highest activity at 60 °C and an optimum pH of 8.5, whereas thermal stability is significantly improved when protein concentration is increased, as confirmed by thermal deactivation kinetics, circular dichroism, and differential scanning calorimetry. Enzyme hydrolytic activity using p-nitrophenyl palmitate (pNPP) as substrate can be modulated by different water-miscible organic cosolvents, detergents, and metal ions. Likewise, kinetic parameters for pNPP are: K_M = 49.6 µM, k_cat = 57 s⁻¹, and k_cat/K_M = 1.15 × 10⁶ s⁻¹·M⁻¹. SeLipC is also able to hydrolyze olive oil and degrade several polyester-type polymers such as poly(butylene succinate) (PBS), poly(butylene succinate)-co-(butylene adipate) (PBSA), and poly(ε-caprolactone) (PCL). Moreover, SeLipC can catalyze the synthesis of different sugar fatty acid esters by transesterification using vinyl laurate as an acyl donor, demonstrating its interest in different biotechnological applications. Full article

In this work, a comprehensive shrinkage and tensile strength characterization of unsaturated polyester (UPE-8340) and vinyl ester (VE-922) epoxy matrices and composites reinforced with multiwall carbon nanotubes (MWCNTs) was conducted. The aspect ratio of UPE and VE with methyl ethyl ketone peroxide (MEKP) was kept at 1:16.6; however, the weight of the MWCNTs was varied from 0.03 to 0.3 gm for the doping of the reinforced nanocomposites. Using a dumbbell-shaped mold, samples of the epoxy matrix without MWCNTs and with reinforced UPE/MWCNT and VE/MWCNT nanocomposites were made. The samples were then cured in a typical ambient chamber with air and an inner gas (carbon dioxide). The effect of the MWCNTs on UPE- and VE-reinforced composites was studied by observing the curing kinetics, shrinkage, and tensile properties, as well as the surface free energy of each reinforced sample in confined saline water. The CO₂ curing results reveal that the absence of O₂ shows a significantly lower shrinkage rate and higher tensile strength and flexural modulus of UPE- and VE-reinforced nanocomposite samples compared with air-cured reinforced nanocomposites. The construction that was air- and CO₂-cured produced results in the shape of a dumbbell, and a flawless surface was seen. The results also show that smaller quantities of MWCNTs made the UPET- and VE-reinforced nanocomposites more stable when they were absorbed and adsorbed in concentrated salt water. Perhaps, compared to air-cured nanocomposites, CO₂-cured UPE and VE nanocomposites were better at reducing shrinkage, having important mechanical properties, absorbing water, and being resistant to seawater. Full article

Recently, there has been a growing interest in polymer insulating materials that incorporate nanoscale inorganic additives, as they have shown significantly improved dielectric, thermal, and mechanical properties, making them highly suitable for application in high-voltage insulating materials for electrical machines. This study aims to improve the dielectric and thermal properties of a commercial polyester varnish by incorporating different concentrations of titanium dioxide nanoparticles (TiO₂) with proper surface functionalization. Permafil 9637 dipping varnish is the varnish used for this investigation, and vinyl silane is the coupling agent used in the surface functionalization of TiO₂ nanoparticles. First, nanoparticles are characterized through Fourier transform infrared spectroscopy to validate the success of their surface functionalization. Then, varnish nanocomposites are characterized through field emission scanning electron microscopy to validate the dispersion and morphology of nanoparticles within the varnish matrix. Following characterization, varnish nanocomposites are evaluated for thermal and dielectric properties. Regarding thermal properties, the thermal conductivity of the prepared nanocomposites is assessed. Regarding dielectric properties, both permittivity and dielectric losses are evaluated over a wide frequency range, starting from 20 Hz up to 2 MHz. Moreover, the AC breakdown voltage is measured for varnish nanocomposites, and the obtained data are incorporated into a finite element method to obtain the dielectric breakdown strength. Finally, the physical mechanisms behind the obtained results are discussed, considering the role of nanoparticle loading and surface functionalization. Full article