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Microplastics (MPs) and nanoplastics (NPs) have emerged as significant environmental pollutants with potential detrimental effects on ecosystems and human health. Several studies indicate their interaction with enzymes; this topic represents a multifaceted research field encompassing several areas of interest from the toxicological and ecotoxicological impact of MPs and NPs on humans and wildlife to the biodegradation of plastics by microbial enzymes. This review aims to provide a critical analysis of the state-of-the-art knowledge of the interaction of MPs and NPs on the enzyme carbonic anhydrase (CA), providing recent insights, analyzing the knowledge gaps in the field, and drawing future perspectives of the research and its application. CA is a widespread and crucial enzyme in various organisms; it is critical for various physiological processes in animals, plants, and bacteria. It catalyzes the reversible hydration of CO2, which is essential for respiration, acid–base balance, pH homeostasis, ion transport, calcification, and photosynthesis. Studies demonstrate that MPs and NPs can inhibit CA activity with mechanisms including adsorption to the enzyme surface and subsequent conformational changes. In vitro and in silico studies highlight the role of electrostatic and hydrophobic interactions in these processes. In vivo studies present mixed results, which are influenced by factors like particle type, size, concentration, and organism type. Moreover, the potentiality of the esterase activity of CA for plastic degradation is discussed. The complexity of the interaction between CA and MPs/NPs underscores the need for further research to fully understand the ecological and health impacts of MPs and NPs on CA activity and expression and glimpses of the potentiality and perspectives in this field. [ABSTRACT FROM AUTHOR]

The adsorption studies of contaminants on microplastics (MPs) collected from the marine environment are very hard to carry out mainly due to the difficulties associated with both to filtration of MPs and separation from biofilm and organic matrices. In this work, MPs were produced by a top-down protocol from polyethylene terephthalate (PET) bottles collected on the beach, thus already aged in the natural environment, and compared with engineered MPs obtained from PET pellets. Both types of MPs (size < 150 μm) were used to study the adsorption of amoxicillin, which is one of the most widely consumed antibiotics in the world and is found unchanged in the aquatic environment. The results of sorption kinetics and isotherm tests indicated that aged MPs absorbed a higher antibiotic content than unaged ones since the two kinds of microplastics had different specific surface areas. The experimental results were explained by analysing the thermodynamic affinity among amoxicillin and PET MPs and comparing it with several pharmaceuticals and other microplastics by evaluating Hansen's solubility parameters (HSPs), which account for dispersive, polarizable and hydrogen bonding contributions to the overall cohesive energy of a compound. The possible interaction mechanism among amoxicillin and PET MPs, based on hydrogen bond interactions among the antibiotic and the ester groups of the polymer, was hypothesised. The results of adsorption tests demonstrated that PET MPs can be pollutant carriers with potential long-range transport in the aquatic environment. [ABSTRACT FROM AUTHOR]

Liquid composite molding (LCM) is a class of fast and cheap processes suitable for the fabrication of large parts with good geometrical and mechanical properties. One of the main steps in an LCM process is represented by the filling stage, during which a reinforcing fiber preform is impregnated with a low-viscosity resin. Darcy's permeability is the key property for the filling stage, not usually available and depending on several factors. Permeability is also essential in computational modeling to reduce costly trial-and-error procedures during composite manufacturing. This review aims to present the most used and recent methods for permeability measurement. Several solutions, introduced to monitor resin flow within the preform and to calculate the in-plane and out-of-plane permeability, will be presented. Finally, the new trends toward reliable methods based mainly on non-invasive and possibly integrated sensors will be described. [ABSTRACT FROM AUTHOR]

Fish collagen garnered significant academic and commercial focus in the last decades featuring prospective applications in a variety of health-related industries, including food, medicine, pharmaceutics, and cosmetics. Due to its distinct advantages over mammalian-based collagen, including the reduced zoonosis transmission risk, the absence of cultural-religious limitations, the cost-effectiveness of manufacturing process, and its superior bioavailability, the use of collagen derived from fish wastes (i.e., skin, scales) quickly expanded. Moreover, by-products are low cost and the need to minimize fish industry waste's environmental impact paved the way for the use of discards in the development of collagen-based products with remarkable added value. This review summarizes the recent advances in the valorization of fish industry wastes for the extraction of collagen used in several applications. Issues related to processing and characterization of collagen were presented. Moreover, an overview of the most relevant applications in food industry, nutraceutical, cosmetics, tissue engineering, and food packaging of the last three years was introduced. Lastly, the fish-collagen market and the open technological challenges to a reliable recovery and exploitation of this biopolymer were discussed. [ABSTRACT FROM AUTHOR]

In this work, a general method to predict the stiffness tensor of short‐fiber composites as a function of the fabric tensor (i.e. the tensor describing the architectural anisotropy of the micro‐structure), determined by X‐ray computed tomography, is presented. The proposed method does not depend on the type of fabric tensor used to characterize the symmetry properties of the composite. The experimental data used for method validation were obtained from thermoplastic composite matrices reinforced with short carbon and basalt fibers. The components of the stiffness tensor were calculated using the Mori‐Tanaka model and the Halpin‐Tsai equation for the stiffness of aligned short‐fiber composites, but other micromechanics models could be used as well. The statistical alignment of the fibers in each portion of the sample was measured by determining the principal axes of the fabric tensor. The average properties calculated on sub‐volumes provided moduli values in very good agreement with those determined experimentally. This approach is very general and easy to implement and does not need any numerical analysis tools. [ABSTRACT FROM AUTHOR]

In recent decades, extensive research has been performed on the friction stir welding of flat-shaped materials while pipe welding, particularly polymer pipes, still encounters challenging issues. This work presents a feasible route for joining high-density polyethylene (HDPE) pipes using an orbital friction stir welding (OFSW) set-up properly designed with a retractable pin tool. Fully consolidated joints were achieved using a portable heating-assisted OFSW system suited for on-site pipeline welding. The obtained joined pipes were characterized by a high-quality weld surface and a lack of defects arising from the tool-pin hole. The samples welded with the optimum parameters presented comparable properties with the base materials and even a slight increase in the tensile strength. The highest tensile and impact strengths were 14.4 MPa and 2.45 kJ/m2, respectively, which is 105% and 89% of those of the base material. XRD, FTIR, and SEM were also applied to assess the property changes in the HDPE pipes after the FSW process. The morphological analysis evidenced that the crystalline structure of the welded sample was similar to that of the base material, proving the effectiveness of the proposed technology. [ABSTRACT FROM AUTHOR]

This work contributes to fill one of the gaps regarding nanoplastic interactions with biological systems by producing polyethylene terephthalate (PET) model nanoplastics, similar to those found in the marine environment, by means of a fast top-down approach based on mechanical fragmentation. Their size distribution and morphology were characterized by laser diffraction and atomic force microscopy (AFM). Their autofluorescence was studied by spectrofluorimetry and fluorescence imaging, being a key property for the evaluation of their interaction with biota. The emission spectra of label-free nanoplastics were comparable with those of PET nanoplastics labeled with Nile red. Finally, the suitability of label-free nanoplastics for biological studies was assessed by in vitro exposure with Mytilus galloprovincialis hemolymphatic cells in a time interval up to 6 h. The nanoplastic internalization into these cells, known to be provided with phagocytic activity, was assessed by fluorescence microscopy. The obtained results underlined that the autofluorescence of the model PET nanoplastics produced in the laboratory was adequate for biological studies having the potential to overcome the disadvantages commonly associated with several fluorescent dyes, such as the tendency to also stain other organic materials different from plastics, to form aggregates due to intermolecular interactions at high concentrations with a consequent decrease in fluorescence intensity, and to dye desorption from nanoparticles. The results of the autofluorescence study provide an innovative approach for plastic risk assessment. [ABSTRACT FROM AUTHOR]

On the other hand, in the case of polymer matrices, biodegradable polymers such as cellulose, polylactic acid (PLA), and chitosan have relevance in the packaging and biomedical sectors. Polymer-based nanocomposites have received considerable interest in research for the last three decades. Figure 2 shows the most used nanofillers and polymer matrices in the last decade to prepare polymer nanocomposites among the different application fields. [Extracted from the article]

Figure 2 shows the most used nanofillers and polymer matrices in the last decade to prepare polymer nanocomposites among the different application fields. Polymer-based nanocomposites have received considerable interest in research for the last three decades. On the other hand, in the case of polymer matrices, biodegradable polymers such as cellulose, polylactic acid (PLA), and chitosan have relevance in the packaging and biomedical sectors. [Extracted from the article]

Carbon fiber-epoxy thin laminates, manufactured adopting a [0/90] non-symmetric lay-up, are characterized by two stable curved shapes, so being bistable. These composite thin laminates are attracting great interest for their potential application as novel morphing structures and power harvesting devices in many engineering fields. The curvature changes of rectangular bistable plates were monitored at room temperature by a laser scanner system over a time span of 10 d. These changes were ascribed to the relaxation of thermal stresses over time. Anisotropic stress relaxation behavior was then studied looking at the matrix dominated properties, such as the transverse modulus in accelerated high temperature experiments and the moisture absorption. Then, a simple viscoelastic model was proposed together with a finite element analysis of the distortion arising from laminate cooling at the end of high temperature cure process. The experimental and numerical results showed that the transverse elastic modulus and the hygroscopic effect are the main factors affecting the shape relaxation of bistable laminates. [ABSTRACT FROM AUTHOR]

During autoclave processing of composites for high-performance applications, it is mandatory to limit the porosities, which mainly depend on the hydrostatic pressure in the resin. This pressure, which is not constant during heating being affected either by resin flow either by elastic stress in the fiber stack, can be significantly different from the autoclave pressure. Modeling of resin flow and stress in the fiber stack is a key issue for prediction of the resin hydrostatic pressure, which can be related to void development. Also, the viscosity of the thermosetting matrix is a relevant parameter since it is not constant but evolves during curing going through a minimum and then increasing to an infinite value at gel point. In this work, a viscoelastic model is adopted to calculate the evolution of resin pressure during an autoclave cycle up to gelation, accounting for viscosity and degree of reaction changes. Therefore, the model includes a kinetic and rheological model whose input parameters have been experimentally determined by Differential Scanning Calorimetry and rheological analysis. The predicted resin pressure for three case studies associated to different composite and bleeder thicknesses and reinforcement materials have been discussed. POLYM. ENG. SCI., 57:631-637, 2017. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A simple procedure for the alignment of graphene nanoplatelets (GNPs) in a thermosetting matrix is presented. First, the alignment of GNPs in thermoplastic fibers of amorphous polyetylene terephthalate (aPET) is achieved by a fiber spinning process. The nanocomposite fibers, obtained with a very high filler content (10 wt%), are then transferred into a reactive epoxy resin. After dissolution of aPET, the nanofillers remained oriented in the thermosetting matrix. The characterization of the obtained nanocomposites has been carried by means of different experimental techniques which provided complementary results. The proposed method has the potential to be used in the manufacturing of hierarchical composites, by introducing nanofilled microfibers into continuous fibers reinforced composites. [ABSTRACT FROM PUBLISHER]

The need for new measurement techniques able to assess the nanofiller dispersion is still receiving great consideration when nanocomposites are developed. This occurs since different routes to disperse nanostructures generate molecular changes in polymer matrices that promote complex polymer–polymer and polymer–nanofiller interactions, which make difficult a suitable estimation of the dispersion. In this paper, ultrasonic waves at different frequencies and power were used for preparing nanocomposite samples and for evaluating the nanofiller dispersion. First, a patented method was used to disperse multiwall carbon nanotubes (MWCNTs) in polyamide 12 through extrusion assisted by low-frequency and high power ultrasound (with frequency ranging between 20 and 50 kHz). This “green” processing method was able to induce different states of dispersion of the nanofillers, as well as chemical modifications to polymer chains promoting branching reactions. Then, ultrasonic dynamic mechanical analysis (UDMA with ultrasound frequency in the megahertz range) was used to estimate the dispersion of the different nanocomposite samples. Compared to rheological measurement methods, UDMA provided a better estimation of the quality of dispersion, being sensitive both to the complex molecular architectures in polymer matrices and to the scattering due to MWCNT agglomerates. [ABSTRACT FROM PUBLISHER]

ABSTRACT A nanostructured epoxy-silica hybrid based on epoxy systems with interpenetrating silica domains was designed for a possible use as a structural adhesive for civil engineering applications. Silica domains were obtained in situ during the curing of the thermosetting matrix by means of the sol-gel process, which was able to chemically bind the organic phase with the inorganic one. To assess the ability of the developed epoxy-silica hybrid system of overcoming some of the well known deficiencies of conventional epoxy adhesives used in civil engineering field, the environmental effects on the adhesion properties of these novel systems were investigated. First, flexural tests were undertaken on cast epoxy-silica specimens to determine the mechanical properties of the nanostructured adhesive when exposed to different environmental conditions, that is, moderate temperature or immersion in water. For comparison purposes, a control sample of epoxy resin, representative of a commercially available adhesive, was tested after the same exposure regimes. In order to assess their durability in service, concrete/concrete joints, bonded or with the hybrid epoxy-silica or with the control epoxy adhesive, were exposed to the same environmental conditions and subjected to adhesion tests according to the 'slant shear test.' The results obtained on both cast specimens and concrete/concrete adhesive joints proved the significantly better retention of properties of the nanostructured organic-inorganic adhesive compared to the control resin after exposure to moderate temperature or immersion in water. This constitutes a distinct advantage of the hybrid system over the corresponding conventional epoxy resins cured at ambient temperature for civil engineering applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42514. [ABSTRACT FROM AUTHOR]

The engineering aspects, which are associated with the development of nanocomposites, involve in either final properties or processability of nanocomposites. Both are affected by the distribution of nanofiller in the matrix and by the aspect ratio of the nanofiller. A nanofilled thermosetting resin can be exploited as a matrix for continuous fibers when the alignment of a high aspect ratio nanofiller is achieved, and in this case, a hierarchical composite is obtained. In this study, a new procedure for the alignment of nanofillers in a thermosetting matrix is proposed. The two-step approach is based on (i) the alignment of nanofillers (carbon nanotubes, graphene, etc.) in thermoplastic fibers by a fiber spinning process and (ii) the use of these nanocomposite fibers as a carrier to bring aligned nanofillers into a reactive thermosetting resin. These fibers, soluble in the thermosetting resin, release the nanofillers orientated according to the direction in which fibers are positioned, even after the curing of the matrix. The proof of concept is demonstrated by producing melt spun polyethylene terephtalate (PETg) fibers filled with graphene nanoplatelets (GNP) and multiwall carbon nanotubes (MWCNT) with a very high filler content (up to 10 wt%) in view of producing a hierarchical composite. POLYM. COMPOS., 36:1096-1103, 2015. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The article investigates the effects of long term environmental aging on thermal and mechanical properties of epoxy-silica hybrids. These nanostructured materials, prepared by non-aqueous sol-gel process and in situ generation of nanosilica during epoxy curing at room temperature, present the potential to be used as cold-cured adhesives for civil engineering and Cultural Heritage applications. A specifically developed conditioning procedure for these cold-cured nanostructured materials was applied before moisture/water absorption tests. The work evidenced the superior durability of the studied epoxy-silica hybrid, which kept its performances in severe, but realistic, environmental conditions with respect to traditional epoxy adhesives. The reduction in the glass transition temperature and mechanical properties of the studied epoxy-silica hybrid, observed in the first weeks of environmental aging, was followed by a significant recovery. This was attributed to two concomitant phenomena: the reactivation of the incomplete curing reactions in the epoxy domains and the continuation of the condensation reactions in the siloxane domains activated by the absorbed water. Finally, the Fickian behavior, presented by the studied epoxy-silica hybrid, was used as an indirect indication of the homogeneity of achieved microstructure, with well dispersed silica nanostructures in the epoxy network. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40093. [ABSTRACT FROM AUTHOR]

The propagation of low intensity ultrasound in a curing resin, acting as a high frequency oscillatory excitation, has been recently proposed as an ultrasonic dynamic mechanical analysis (UDMA) for cure monitoring. The technique measures sound velocity and attenuation, which are very sensitive to changes in the viscoelastic characteristics of the curing resin, since the velocity is related to the resin storage modulus and density, while the attenuation is related to the energy dissipation and scattering in the curing resin. The paper reviews the results obtained by the authors' research group in the last decade by means of in-house made ultrasonic set-ups for both contact and air-coupled ultrasonic experiments. The basics of the ultrasonic wave propagation in polymers and examples of measurements of the time-evolution of ultrasonic longitudinal modulus and chemical conversion of different thermosetting resins are presented. The effect of temperature on the cure kinetics, the comparison with rheological, low frequency dynamic mechanical and calorimetric results, and the correlation between ultrasonic modulus and crosslinking density will be also discussed. The paper highlights the reliability of ultrasonic wave propagation for monitoring the physical changes taking place during curing and the potential for online monitoring during polymer and polymer matrix composite processing. [ABSTRACT FROM AUTHOR]

An overview of the current state of art of the ultrasonic treatment technology applied to polymer melts is presented. The research and technological advancements of the ultrasonic treatment as applied to development of polymeric materials are discussed. An analysis of the technological progress shows that the mechanism of the effects of ultrasound on polymer melts is not fully understood at present. Such lack in fully understanding the mechanism could limit the use of this versatile technology in future applications. Based on the critical analysis of the research progress to date, some key issues for a deeper understanding of the chemical and physical effects of ultrasound on polymer melts are identified. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E582-E602, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21303 [ABSTRACT FROM AUTHOR]

The degree of crystallinity of cellulose was used for assessing the degradation level of coated and uncoated samples of pine wood after weathering. X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy measured the changes in the surface crystallinity of cellulose resulting from weathering, both natural and artificial. Both techniques revealed an increase in the crystallinity index (CI) of cellulose when wood was subjected to weathering. An increase in the size of crystallites was also observed by XRD measurements. These results were related to the reduction of the amorphous fractions of wood, and, consequently, to the enrichment of the relative crystalline content. Thanks to FT-IR analysis, the degradation of hemicellulose was observed for uncoated samples after exposure to artificial weathering. The effect of weathering was less evident on coated samples because of the protective action of the coating. A good correlation between the crystallinity indexes obtained from FT-IR and XRD was found. The experimental results proved that the proposed method may be a very useful tool for a rapid and accurate estimation of the degradation level of wood exposed to weathering. This methodology can find application in the field of conservation and restoration of wooden objects or in the industry of wood coatings [ABSTRACT FROM AUTHOR]

The use of polyether polyols is common in polyurethane industry, particularly in soft PU applications. In particular, viscoelastic foams, characterized by slow recovery after compression, are obtained using poly(ethylene oxide) (PEO) polyols. Nanofilled polyols can be used for the production of viscoelastic foams with improved fire resistance properties. The high polarity of polyether polyols is responsible of a poor affinity with the organic modifiers used in commercial organically modified montmorillonite (omMMT). In this work, organically modified montmorillonites were prepared, having an improved affinity with the polyether polyols used for the production of soft PU foams. The montmorillonite was modified by using polyetheramines with different ethyleneoxide/propyleneoxide amounts. A strongly intercalated/exfoliated structure was obtained after mixing the polyol with the omMMT. The viscosity increased by three orders of magnitude and the diffraction angles of the MMT measured by x-ray analysis decreased to values lower than 1.5°. The intercalated structure was preserved after the curing stage, when the isocyanate was added to the polyol/omMMT. The resulting polyurethane had an irregular open cell structure, and was characterized by a mechanical properties comparable to those of unfilled polyurethane. Copyright © 2009 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The article presents information on a study which investigated the mechanical behavior of flexible polyurethane foams used in cushioning applications. It highlights the differences between slow recovery (SR) and fast recovery (FR) foams. It describes the characteristics of flexible polyurethane foams, creep and hysteresis tests performed at different strain rate, stress levels, and temperatures. It compares creep compliance at different stress levels with a Voigt-Kelvin model. it also compares stress-strain loading curves with a phenomenological model originally modified to account for the strain rate dependence.

In this work, a potentially economic and environmentally friendly method for the synthesis of bacterial cellulose (BC) by Gluconacetobacter xylinus from a biomass containing orange peel extract was evaluated. Orange peel extract was used as a culture medium without any hydrolysis treatment, thus speeding up the synthesis procedure. The efficacy of orange peel as a carbon source was compared with that of sucrose. The orange peel extract formed thicker cellulose gels than those formed using sucrose. X-ray diffraction (XRD) revealed both a high crystallinity index and crystallite size of BC nanofibers in samples obtained from orange peel (BC_Orange). Field emission scanning electron microscopy (FE-SEM) revealed a highly densely packed nanofibrous structure (50 nm in diameter). BC_Orange presented a two-fold increase in water holding capacity (WHC), and dynamic mechanical analysis (DMA) showed a 44% increase in storage modulus compared to sucrose derived BC. These results showed that the naturally available carbon sources derived from orange peel extract can be effectively used for BC production. The orange-based culture medium can be considered a profitable alternative to the generation of high-value products in a virtuous circular economy model. [ABSTRACT FROM AUTHOR]

Fish industry waste is attracting growing interest for the production of environmentally friendly materials for several different applications, due to the potential for reduced environmental impact and increased socioeconomic benefits. Recently, the application of fish industry waste for the synthesis of value-added materials and energy storage systems represents a feasible route to strengthen the overall sustainability of energy storage product lines. This review focused on an in-depth outlook on the advances in fish byproduct-derived materials for energy storage devices, including lithium-ion batteries (LIBs), sodium-ion (NIBs) batteries, lithium-sulfur batteries (LSBs), supercapacitors and protein batteries. For each of these, the latest applications were presented together with approaches to improve the electrochemical performance of the obtained materials. By analyzing the recent literature on this topic, this review aimed to contribute to further advances in the sustainability of energy storage devices. [ABSTRACT FROM AUTHOR]

A custom-made, air-coupled ultrasonic device was applied to cure monitoring of thick samples (7-10 mm) of unsaturated polyester resin at room temperature. A key point was the optimization of the experimental setup in order to propagate compression waves during the overall curing reaction by suitable placement of the noncontact transducers, placed on the same side of the test material, in the so-called pitch-catch configuration. The progress of polymerization was monitored through the variation of the time of flight of the propagating longitudinal waves. The exothermic character of the polymerization was taken into account by correcting the measured value of time of flight with that one in air, obtained by sampling the air velocity during the experiment. The air-coupled ultrasonic results were compared with those obtained from conventional contact ultrasonic measurements. The good agreement between the air-coupled ultrasonic results and those obtained by the rheological analysis demonstrated the reliability of air-coupled ultrasound in monitoring the changes of viscoelastic properties at gelation and vitrification. The position of the transducers on the same side of the sample makes this technique suitable for on-line cure monitoring during several composite manufacturing technologies. [ABSTRACT FROM AUTHOR]

Microplastic (MP) pollution represents one of the biggest environmental problems that is further exacerbated by the continuous degradation in the marine environment of MPs to nanoplastics (NPs). The most diffuse plastics in oceans are commodity polymers, mainly thermoplastics widely used for packaging, such as polyethylene terephthalate (PET). However, the huge interest in the chemical vector role of micro/nanoplastics, their fate and negative effects on the environment and human health is still under discussion and the research is still sparse due also to the difficulties of sampling MPs and NPs from the environment or producing NPs in laboratory. Moreover, the research on MPs and NPs pollution relies on the availability of engineered nanoparticles similar to those present in the marine environment for toxicological, transport and adsorption studies in biological tissues as well as for wastewater remediation studies. This work aims to develop an easy, fast and scalable procedure for the production of representative model nanoplastics from PET pellets. The proposed method, based on a simple and economic milling process, has been optimized considering the peculiarities of the polymer. The results demonstrated the reliability of the method for preparing particle suspensions for aquatic microplastic research, with evident advantages compared to the present literature procedures, such as low cost, the absence of liquid nitrogen, the short production time, the high yield of the process, stability, reproducibility and polydisperse size distribution of the produced water dispersed nanometric PET. [ABSTRACT FROM AUTHOR]

The Special Issue I Carbon Fiber Reinforced Polymers i collects 31 papers, 3 reviews and 28 research papers, with the aim to present recent advances in carbon fiber reinforced polymers, focusing on emerging trends in matrix development, composite manufacturing technologies and joining methods and mechanical behavior modeling. Moreover, the diffusion of a multi-material design, where metallic and non-metallic materials are used together to fabricate the same component, has driven the research towards efficient joining technologies of metals to carbon fiber reinforced composites. The current demand for lightweight and high-performance structures leads to increasing applications of carbon fiber reinforced polymers, which is also made possible by novel production methods, automation with repeatable quality, the reduced cost of carbon fibers, out of autoclave processes such as resin transfer molding and resin infusion technologies, the re-use of waste fibers, development in preform technology, high-performance, fast-curing resins, etc. [[1]]. [Extracted from the article]

Fish waste is attracting growing interest as a new raw material for biopolymer production in different application fields, mainly in food packaging, with significant economic and environmental advantages. This review paper summarizes the recent advances in the valorization of fish waste for the preparation of biopolymers for food packaging applications. The issues related to fishery industry waste and fish by-catch and the potential for re-using these by-products in a circular economy approach have been presented in detail. Then, all the biopolymer typologies derived from fish waste with potential applications in food packaging, such as muscle proteins, collagen, gelatin, chitin/chitosan, have been described. For each of them, the recent applications in food packaging, in the last five years, have been overviewed with an emphasis on smart packaging applications. Despite the huge industrial potential of fish industry by-products, most of the reviewed applications are still at lab-scale. Therefore, the technological challenges for a reliable exploitation and recovery of several potentially valuable molecules and the strategies to improve the barrier, mechanical and thermal performance of each kind of biopolymer have been analyzed. [ABSTRACT FROM AUTHOR]

Ultrasonic waves are nowadays used for multiple purposes in many different fields from the non-destructive inspection of materials to sonochemical synthesis of materials and welding. The aim is to generate a focused ultrasound field by plane transducer using axicon lens, which can be suitable for focused ultrasound through human skull bone. Ryuzono et al. [[9]] in the paper entitled " I Topology optimization-based damage identification using visualized ultrasonic wave propagation i " present a new damage identification method in structures based on topology optimization in combination with visualized ultrasonic wave propagation. Then, it describes the individual physical mechanisms leading to different shapes of the ultrasound intensity curves, and provides measurements confirming that the measured ultrasound intensity is linked to the liquid penetration regime into the structure. [Extracted from the article]

Most biomaterials and tissues are viscoelastic; thus, evaluating viscoelastic properties is important for numerous biomedical applications. Compressional viscoelastography is an ultrasound imaging technique used for measuring the viscoelastic properties of biomaterials and tissues. It analyzes the creep behavior of a material under an external mechanical compression. The aim of this study is to use finite element analysis to investigate how loading conditions (the distribution of the applied compressional pressure on the surface of the sample) and boundary conditions (the fixation method used to stabilize the sample) can affect the measurement accuracy of compressional viscoelastography. The results show that loading and boundary conditions in computational simulations of compressional viscoelastography can severely affect the measurement accuracy of the viscoelastic properties of materials. The measurement can only be accurate if the compressional pressure is exerted on the entire top surface of the sample, as well as if the bottom of the sample is fixed only along the vertical direction. These findings imply that, in an experimental validation study, the phantom design should take into account that the surface area of the pressure plate must be equal to or larger than that of the top surface of the sample, and the sample should be placed directly on the testing platform without any fixation (such as a sample container). The findings indicate that when applying compressional viscoelastography to real tissues in vivo, consideration should be given to the representative loading and boundary conditions. The findings of the present simulation study will provide a reference for experimental phantom designs regarding loading and boundary conditions, as well as guidance towards validating the experimental results of compressional viscoelastography. [ABSTRACT FROM AUTHOR]

This manuscript explores the disassembly potential of ultrasonically welded thermoplastic composite joints for reuse or recycling through resistance heating via a nanocomposite film located at the welded interface. Nanocomposite films containing multi-walled carbon nanotubes (MWCNTs) were characterized for thermo-electrical behavior to assess self-heating. It was generally observed that maximum temperature increased with MWCNT and film thickness. To demonstrate potential for disassembly, glass fiber/polypropylene adherends were welded with nanocomposite films. Shear stress during disassembly was measured for three initial adherend's surface temperatures. It was found that the required tensile load decreased by over 90% at the highest temperatures, effectively demonstrating the potential for disassembly via electrically conductive films. Fracture surfaces suggested that disassembly was facilitated through a combination of nanocomposite and matrix melting and weakened fiber–matrix interface. Limitations, such as slow heating rates and the loss of contact at the interface, imply that the method could be more suited for recycling, instead of repair and reuse, as the heat-affected zone extended through the adherends' thickness at the overlap during heating. [ABSTRACT FROM AUTHOR]

The rheometer curing curves of neat natural rubber (NR) and neat chloroprene rubber (CR) with maleide F (MF) exhibit considerable crosslinking torque at 180 °C. This indicates that MF can crosslink both these rubbers via Alder-ene reactions. Based on this knowledge, MF has been introduced as a co-crosslinking agent for a 50/50 blend of NR and CR in conjunction with accelerated sulfur. The delta (Δ) torque obtained from the curing curves of a blend with the addition of 1 phr MF was around 62% higher than those without MF. As the content of MF increased to 3 phr, the Δ torque was further raised to 236%. Moreover, the mechanical properties, particularly the tensile strength of the blend with the addition of 1 phr MF in conjunction with the accelerated sulfur, was around 201% higher than the blend without MF. The overall tensile properties of the blends cured with MF were almost retained even after ageing the samples at 70 °C for 72 h. This significant improvement in the curing torque and the tensile properties of the blends indicates that MF can co-crosslink between NR and CR via the Diels–Alder reaction. [ABSTRACT FROM AUTHOR]

Marine pollution is one of the biggest environmental problems, mainly due to single-use or disposable plastic waste fragmenting into microplastics (MPs) and nanoplastics (NPs) and entering oceans from the coasts together with human-made MPs. A rapidly growing worry concerning environmental and human safety has stimulated research interest in the potential risks induced by the chemicals associated with MPs/NPs. In this framework, the present review analyzes the recent advances in adsorption and desorption studies of different contaminants species, both organic and metallic, on MPs made of Poly(Ethylene terephthalate). The choice of PET is motivated by its great diffusion among plastic items and, unfortunately, also in marine plastic pollution. Due to the ubiquitous presence of PET MPS/NPs, the interest in its role as a vector of contaminants has abruptly increased in the last three years, as demonstrated by the very high number of recent papers on sorption studies in different environments. The present review relies on a chemical engineering approach aimed at providing a deeper overview of both the sorption mechanisms of organic and metal contaminants to PET MPs/NPs and the most used adsorption kinetic models to predict the mass transfer process from the liquid phase to the solid adsorbent. [ABSTRACT FROM AUTHOR]

Ultrasonically welded hybrid aluminum/fiber-reinforced PEEK joints were analyzed non-destructively with an X-ray microscope. The potential and limitations of the technology as a non-destructive testing method were investigated. For a quantitative evaluation, joints with suitable and unsuitable parameters were compared. For a further comparison, geometric modifications of the joining partners were made, and the influence on the structure and process variation of the resulting hybrid joints was examined on a microscopic level. By using a tool for 3D segmentation of the composition of the joining zone, quantitative information on volume-specific proportions could be obtained and compared in relation to each other. [ABSTRACT FROM AUTHOR]

Functionalized hypercrosslinked polymers (HCPs) with surface areas between 213 and 1124 m2/g based on a range of monomers containing different chemical moieties were evaluated for CO2 capture using a pressure swing adsorption (PSA) methodology under humid conditions and elevated temperatures. The networks demonstrated rapid CO2 uptake reaching maximum uptakes in under 60 s. The most promising networks demonstrating the best selectivity and highest uptakes were applied to a pressure swing setup using simulated flue gas streams. The carbazole, triphenylmethanol and triphenylamine networks were found to be capable of converting a dilute CO2 stream (>20%) into a concentrated stream (>85%) after only two pressure swing cycles from 20 bar (adsorption) to 1 bar (desorption). This work demonstrates the ease with which readily synthesized functional porous materials can be successfully applied to a pressure swing methodology and used to separate CO2 from N2 from industrially applicable simulated gas streams under more realistic conditions. [ABSTRACT FROM AUTHOR]

Phenylethynyl-terminated aromatic polyimides meet requirements of resin transfer molding (RTM) and exhibits high glass transition temperature (Tg) were prepared. Moreover, the relationship between the polyimide backbones structure and their melting stability was investigated. The phenylethynyl-terminated polyimides were based on 4,4′-(hexafluorosiopropylidene)-diphthalic anhydride (6FDA) and different diamines of 3,4′-oxydianiline (3,4′-ODA), m-phenylenediamine (m-PDA) and 2,2′-bis(trifluoromethyl)benzidine (TFDB) were prepared. These oligoimides exhibit excellent melting flowability with wide processing temperature window and low minimum melt viscosities (<1 Pa·s). Two of the oligoimides display good melting stability at 280–290 °C, which meet the requirements of resin transfer molding (RTM) process. After thermally cured, all resins show high glass transition temperatures (Tgs, 363–391 °C) and good tensile strength (51–66 MPa). The cure kinetics studied by the differential scanning calorimetry (DSC), 13C nuclear magnetic resonance (13C NMR) characterization and density functional theory (DFT) definitely confirmed that the electron-withdrawing ability of oligoimide backbone can tremendously affect the curing reactivity of terminated phenylethynyl groups. The replacement of 3,4′-ODA units by m-PDA or TFDB units increase the electron-withdrawing ability of the backbone, which increase the curing rate of terminated phenylethynyl groups at processing temperatures, hence results in the worse melting stability. [ABSTRACT FROM AUTHOR]

We have performed a systematical investigation on the glass transition behavior of amorphous polymers with different solvent concentrations. Acrylate-based amorphous polymers are synthesized and treated by isopropyl alcohol to obtain specimens with a homogenous solvent distribution. The small strain dynamic mechanical tests are then performed to obtain the glass transition behaviors. The results show that the wet polymers even with a solvent concentration of more than 60 wt.% still exhibit a glass transition behavior, with the glass transition region shifting to lower temperatures with increasing solvent concentrations. A master curve of modulus as a function of frequency can be constructed for all the polymer–solvent systems via the time–temperature superposition principle. The relaxation time and the breadth of the relaxation spectrum are then obtained through fitting the master curve using a fractional Zener model. The results indicate that the breadth of the relaxation spectrum has been greatly expanded in the presence of solvents, which has been rarely reported in the literature. Thus, this work can potentially advance the fundamental understanding of the effects of solvent on the glass transition behaviors of amorphous polymers. [ABSTRACT FROM AUTHOR]

Characterizing early-age properties is very important for the quality control and durability of cementitious materials. In this paper, an approach using embedded guided waves was adopted to monitor the changes in the mechanical proprieties of mortar and concrete during setting, and embedded thin rods with low-cost piezoelectric sensors mounted on top were used for guide wave monitoring. Through continuous attenuation monitoring of the guided waves, the evolution of mortar and concrete properties was characterized. Four different kinds of metallic rods were tested at the same time to find out the optimal setup. Meanwhile, shear wave velocities of the mortar and concrete samples were monitored and correlated to the attenuation, and setting time tests were also performed on these samples. Experimental results demonstrate that the proposed approach could monitor the evolution of the setting of cementitious materials quantitatively, and time of the initial setting could be determined by this technique as well. In addition, it is found that the attenuations of fundamental longitudinal guided wave mode are almost the same in concrete samples and mortar samples sieved from concrete, indicating that this technique is able to eliminate the effects of coarse aggregates, which makes it of great potential for in-situ monitoring of early age concrete. [ABSTRACT FROM AUTHOR]

Liquid resin infusion processes are becoming attractive for aeronautic applications as an alternative to conventional autoclave-based processes. They still present several challenges, which can be faced only with an accurate simulation able to optimize the process parameters and to replace traditional time-consuming trial-and-error procedures. This paper presents an experimentally validated model to simulate the resin infusion process of an aeronautical component by accounting for the anisotropic permeability of the reinforcement and the chemophysical and rheological changes in the crosslinking resin. The input parameters of the model have been experimentally determined. The experimental work has been devoted to the study of the curing kinetics and chemorheological behavior of the thermosetting epoxy matrix and to the determination of both the in-plane and out-of-plane permeability of two carbon fiber preforms using an ultrasonic-based method, recently developed by the authors. The numerical simulation of the resin infusion process involved the modeling of the resin flow through the reinforcement, the heat exchange in the part and within the mold, and the crosslinking reaction of the resin. The time necessary to fill the component has been measured by an optical fiber-based equipment and compared with the simulation results. [ABSTRACT FROM AUTHOR]

Out-of-plane permeability of reinforcement preforms is of crucial importance in the infusion of large and thick composite panels, but so far, there are no standard experimental methods for its determination. In this work, an experimental set-up for the measurement of unsaturated through thickness permeability based on the ultrasonic wave propagation in pulse echo mode is presented. A single ultrasonic transducer, working both as emitter and receiver of ultrasonic waves, was used to monitor the through thickness flow front during a vacuum assisted resin infusion experiment. The set-up was tested on three thick carbon fiber preforms, obtained by stacking thermal bonding of balanced or unidirectional plies either by automated fiber placement either by hand lay-up of unidirectional plies. The ultrasonic data were used to calculate unsaturated out-of-plane permeability using Darcy's law. The permeability results were compared with saturated out-of-plane permeability, determined by a traditional gravimetric method, and validated by some analytical models. The results demonstrated the feasibility and potential of the proposed set-up for permeability measurements thanks to its noninvasive character and the one-side access. [ABSTRACT FROM AUTHOR]

Different hybrid epoxy formulations were produced and cold-cured, monitoring the properties development during low temperature curing and aging. All systems were based on silane functionalized bis-phenol A (DGEBA) resins (Part A), cured at ambient temperature with two amine hardeners (Part B). The different components of the formulations were selected on their potential capability to bring about enhancements in the glass transition temperature. The durability of the produced hybrids was probed in comparison to the corresponding neat epoxies by monitoring changes in glass transition temperature (Tg) and flexural mechanical properties after exposure to different levels of humidity and immersion in water and at temperatures slightly higher than the local ambient temperature, in order to simulate the conditions encountered during summer seasons in very humid environments. The thermal degradation resistance of the hybrid systems was also evaluated by thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

In this research, a simple experimental apparatus based on a bipolar electrode (BPE) configuration was set up, in order to tackle erosion-corrosion problems of materials of interest in the oil and gas field. As a case study, the resistance to erosion and corrosion of carbon steel samples coated by Electroless Nickel Plating and by thermo-sprayed coating with the high velocity oxy fuel (HVOF) process was investigated. The main objective was to demonstrate if this simple, contactless technique could be applied to effectively discriminate the erosion-corrosion behavior of different materials in a vast range of experimental conditions. In fact, by means of polarization curves, visual inspection and morphological analysis by scanning electron microscope (SEM), the effects due to erosion-corrosion by solid particles, by fluid and those due to simple erosion were evaluated. [ABSTRACT FROM AUTHOR]

A novel, green route for pre-exfoliation of graphite based on a biodegradable polymer and high-power ultrasound is presented. Candelilla wax (CW), derived from the leaves of the candelilla plant, has been used for the first time as a natural non aqueous medium to induce the pre-exfoliation of expanded graphite (EG) under ultrasonic irradiation in an economical way. The proposed method uses also D-limonene as a natural organic solvent for reducing viscosity and increasing the affinity between the polar groups of EG and candelilla wax, thus improving the intercalation/exfoliation of EG. The quality of dispersion of the nanofiller in the natural wax matrix has been evaluated using multiple techniques. The addition of EG to wax and use of ultrasonic treatment leads to a reduced crystallinity, probably due to restrictions of the molecular movements, improved thermal stability of wax, and to an increased shear thinning exponent, which are all indicative of a high degree of EG dispersion. The ultrasonic dynamic mechanical results suggest a reduction in the cluster size and a better filler dispersion in the wax matrix promoted by polar or chemical reactions between the CW fractions and the graphite stacks, which was observed by XPS analysis. The results were compared to those obtained with paraffin, a synthetic wax, and confirmed the dispersion improvement obtained by using natural wax as a pre-exfoliating medium. [ABSTRACT FROM AUTHOR]

The development of improved cold-cured resins, to be used as either adhesives or matrices for FRP (fiber reinforced polymer) composites employed in the construction industry, has become the focus of several academic and industrial research projects. It is expected that the use of nano-structured organic–inorganic hybrid materials could represent a realistic alternative to commercial epoxy-based resins due to their superior properties, especially in terms of higher durability against: moisture, temperatures, harsh environments, and fire. In this context, organic–inorganic epoxy hybrids were synthesized by a modified sol–gel method without the addition of water. The experimental formulations were prepared starting from a mixture of a silane-functionalized epoxy resin, alkoxysilane components and a deep eutectic solvent (DES) based on a blend of choline chloride and urea. The latter was added in two different loads in order to analyze in depth its effect as a promoter for an effective dispersion of silica nano-phases, formed through hydrolysis and condensation reactions, into the cross-linked epoxy network. The produced formulations were cold-cured for different time spans in the presence of two hardeners, both suitable for a curing process at ambient temperature. In this first part of a wider experimental program, several analyses were carried out on the liquid (rheological and calorimetric) and cold-cured (calorimetric, thermogravimetric, dynamic-mechanical, flexural mechanical, and morphological) systems to evaluate and quantify the improvement in properties brought about by the presence of two different phases (organic and inorganic) in the same epoxy-based hybrid system. [ABSTRACT FROM AUTHOR]