Polymers, Volume 15, Issue 22 (November-2 2023) – 130 articles

As a light-weight solution for electromagnetic shielding, this paper aims to investigate the development of electrically conductive composites that shield from electromagnetic radiation while providing sustainability by using recycled fibers in the structure of nonwoven reinforcement materials. The main novelty of this research is the conversion of waste fabrics into functional composites via a fast and inexpensive method. For this purpose, waste fabrics were recycled into fibers, and the recycled fibers were processed into needle-punched nonwovens to be used as reinforcement materials for electromagnetic shielding composites. Electrically conductive composite structures were obtained by adding copper (II) sulfate and graphite conductive particles with different ratios to polyester resin. The hand lay-up method was used for the production of composites. Electromagnetic shielding, electrical resistivity, and some mechanical properties of the composites were investigated. The results were analyzed statistically using IBM SPSS software version 18. The results have shown that up to 31.43 dB of electromagnetic shielding effectiveness was obtained in the 1–6 GHz frequency range. This result corresponds to a very good grade for general use and a moderate grade for professional use, according to FTTS-FA-003, exceeding the acceptable range for industrial and commercial applications of 20 dB. The composites developed in this research are good candidates to be used in various general and professional applications, such as plastic parts in household applications, electronic industry, building and construction industries, and other applications where light weight shielding materials are needed. Full article

In this paper, the damage initiation/propagation mechanisms and failure modes of open-hole carbon fiber-reinforced thermoplastic composites and thermosetting composites with tension, compression, and bearing loads are investigated, respectively, by experiments and finite element simulations. The experimental evaluations are performed on the specimens using the Combined Loading Compression (CLC) test method, the tensile test method, and the single-shear test method. The differences in macroscopic damage initiation, evolution mode, and damage characteristics between thermoplastic composite materials and thermosetting composite material open-hole structures are obtained and analyzed under compressive load. Based on scanning electron microscope SEM images, a comparative analysis is conducted on the micro-failure modes of fibers, matrices, and fiber/matrix interfaces in the open-hole structures of thermoplastic and thermosetting composites under compressive load. The differences between thermoplastic and thermosetting composites were analyzed from the micro-failure mechanism. Finally, based on continuum damage mechanics (CDM), a damage model is also developed for predicting the initiation and propagation of damage in thermoplastic composites. The model, which can capture fiber breakage and matrix crack, as well as the nonlinear response, is used to conduct virtual compression tests, tensile test, and single-shear test, respectively. Numerical simulation results are compared with the extracted experimental results. The displacement-load curve and failure modes match the experimental result, which indicates that the finite element model has good reliability. Full article

The particle size distribution (PSD) in emulsion polymerization (EP) has been modeled in the past using either the pseudo bulk (PB) or the 0-1/0-1-2 approaches. There is some controversy on the proper type of model to be used to simulate the experimental PSDs, which are apparently broader than the theoretical ones. Additionally, the numerical technique employed to solve the model equations, involving hyperbolic partial differential equations (PDEs) with moving and possibly steep fronts, has to be precise and robust, which is not a trivial matter. A deterministic kinetic model for the PSD evolution of ab initio EP of vinyl monomers was developed to investigate these issues. The model considers three phases, micellar nucleation, and particles that can contain $n\ge 0$ radicals. Finite volume (FV) and weighted-residual methods are used to solve the system of PDEs and compared; their limitations are also identified. The model was validated by comparing predictions with data of monomer conversion and PSD for the batch emulsion homopolymerization of styrene (Sty) and methyl methacrylate (MMA) using sodium dodecyl sulfate (SDS)/potassium persulfate (KPS) at 60 °C, as well as the copolymerization of Sty-MMA (50/50; mol/mol) at 50 and 60 °C. It is concluded that the PB model has a structural problem when attempting to adequately represent PSDs with steep fronts, so its use is discouraged. On the other hand, there is no generalized evidence of the need to add a stochastic term to enhance the PSD prediction of EP deterministic models. Full article

Glaucoma has become the world’s leading cause of irreversible blindness, and one of its main characteristics is high intraocular pressure. Currently, the non-surgical drug treatment scheme to reduce intraocular pressure is a priority method for glaucoma treatment. However, the complex and special structure of the eye poses significant challenges to the treatment effect and safety adherence of this drug treatment approach. To address these challenges, the application of polymer-based self-assembled drug delivery systems in glaucoma treatment has emerged. This review focuses on the utilization of polymer-based self-assembled structures or materials as important functional and intelligent carriers for drug delivery in glaucoma treatment. Various drug delivery systems, such as eye drops, hydrogels, and contact lenses, are discussed. Additionally, the review primarily summarizes the design strategies and methods used to enhance the treatment effect and safety compliance of these polymer-based drug delivery systems. Finally, the discussion delves into the new challenges and prospects of employing polymer-based self-assembled drug delivery systems for the treatment of glaucoma. Full article

Paper is one of the most significant inventions in human civilization, which considerably advanced global cultural development. Pulping is a key step in the conversion of fiber raw materials into paper. Since its inception, pulping has rapidly evolved, continually adapting to technological advancements. Researchers are constantly investigating various types of raw materials for pulping. In this review, some of the materials employed in pulping are outlined, and the fiber content, pulping method, as well as the strength of wood and non-wood crop straw as pulping raw materials are analyzed and discussed. In addition, this review explores the effects of different materials under various pulping conditions and assesses the future trends in raw material selection for pulping while considering the current global environmental pressures. Full article

Novel core–shell magnetic molecularly imprinted polymers (MMIPs) were synthesized using the sol–gel method for the adsorption of cefixime (CFX). Fe₃O₄@SiO₂ is the core, and molecularly imprinted polymers (MIPs) are the shell, which can selectively interact with CFX. The preparation conditions, adsorption kinetics, adsorption isotherms, selective adsorption ability, and reutilization performance of the MMIPs were investigated. The adsorption capacity of MMIPs for CFX was 111.38 mg/g, which was about 3.5 times that of MNIPs. The adsorption equilibrium time was 180 min. The dynamic adsorption experiments showed that the adsorption process of MMIPs to CFX conformed to the pseudo-second-order model. Through static adsorption study, the Scatchard analysis showed that MMIPs had two types of binding sites—the high-affinity binding sites and the low-affinity binding sites—while the Langmuir model fit the adsorption isotherms well (R² = 0.9962). Cefepime and ceftiofur were selected as the structural analogs of CFX for selective adsorption studies; the adsorption of CFX by MMIPs was higher than that of other structural analogs; and the imprinting factors of CFX, cefepime, and ceftiofur were 3.5, 1.7, and 1.4, respectively. Furthermore, the MMIPs also showed excellent reusable performance. Full article

Biodegradable plastics are attracting attention as a solution to the problems caused by plastic waste. Among biodegradable plastics, polylactide (PLA) and poly (butylene succinate) (PBS) are particularly noteworthy because of their excellent biodegradability. However, the drawbacks of their mechanical properties prompts the need to compound them to achieve the desired strength. The characteristics of the interface of the composite material determine the realization of its final performance. The study of the interface and microstructure of composites is essential for the development of products from degradable polymers. The morphology evolution and microcrystal structure of spin-casted fully biodegradable (PLA/PBS) blend films were investigated using atomic force microscopy (AFM)-based nanomechanical mapping. Results show that intact blend films present an obvious phase separation, where the PBS phase is uniformly dispersed in the PLA phase in the form of pores. Furthermore, the size and number of the PBS phase have a power exponential relationship and linear relationship with PBS loading, respectively. Intriguingly, after annealing at 80 °C for 30 min, the PLA phase formed an orderly petal-like microcrystalline structure centered on the PBS phase. Moreover, the microcrystalline morphology changed from a “daisy type” to a “sunflower type” with the increased size of the PBS phase. Since the size of the PBS phase is controllable, a new method for preparing microscopic patterns using fully biodegradable polymers is proposed. Full article

This research investigates the quantitative impact of incorporating epoxy resin and crumb rubber powder (CRP) into cement asphalt mortar (CAM) for railway track stabilization. The study reveals significant improvements in various key parameters compared to conventional CAM. The modified CAM exhibits a 12.7% reduction in flow time, indicative of enhanced flowability, and a substantial 62.4% decrease in the mixing stability gap, demonstrating superior mixing stability. Additionally, the modified CAM displays remarkable early-age compressive strength, with increases of up to 15.3% compared to traditional CAM formulations. Importantly, the modified CAM showcases robust resistance to challenging environmental conditions, with only a 6.7% strength reduction after exposure to sulfuric acid, highlighting its acid resistance, and exceptional freeze–thaw resistance, with a mere 1.5% strength reduction after undergoing six cycles. In a mock-up test simulating real-world conditions, the modified CAM effectively prevents ballast layer settlement, underscoring its potential to enhance the durability of railway track infrastructure. These quantitative findings not only endorse the practical feasibility of epoxy resin and CRP-enhanced CAM but also suggest its potential to contribute significantly to railway track longevity, reduce maintenance expenditures, and ensure operational reliability. Full article

In this work, a 3D printed biocompatible micro-optofluidic (MoF) device for two-phase flow monitoring is presented. Both an air–water bi-phase flow and a two-phase mixture composed of micrometric cells suspended on a liquid solution were successfully controlled and monitored through its use. To manufacture the MoF device, a highly innovative microprecision 3D printing technique was used named Projection Microstereolithography (P$\mu$SL) in combination with the use of a novel 3D printable photocurable resin suitable for biological and biomedical applications. The concentration monitoring of biological fluids relies on the absorption phenomenon. More precisely, the nature of the transmission of the light strictly depends on the cell concentration: the higher the cell concentration, the lower the optical acquired signal. To achieve this, the microfluidic T-junction device was designed with two micrometric slots for the optical fibers’ insertion, needed to acquire the light signal. In fact, both the micro-optical and the microfluidic components were integrated within the developed device. To assess the suitability of the selected biocompatible transparent resin for optical detection relying on the selected working principle (absorption phenomenon), a comparison between a two-phase flow process detected inside a previously fully characterized micro-optofluidic device made of a nonbiocompatible high-performance resin (HTL resin) and the same made of the biocompatible one (BIO resin) was carried out. In this way, it was possible to highlight the main differences between the two different resin grades, which were further justified with proper chemical analysis of the used resins and their hydrophilic/hydrophobic nature via static water contact angle measurements. A wide experimental campaign was performed for the biocompatible device manufactured through the P$\mu$SL technique in different operative conditions, i.e., different concentrations of eukaryotic yeast cells of Saccharomyces cerevisiae (with a diameter of 5 $\mathsf{\mu }$m) suspended on a PBS (phosphate-buffered saline) solution. The performed analyses revealed that the selected photocurable transparent biocompatible resin for the manufactured device can be used for cell concentration monitoring by using ad hoc 3D printed micro-optofluidic devices. In fact, by means of an optical detection system and using the optimized operating conditions, i.e., the optimal values of the flow rate $FR=0.1$ mL/min and laser input power $P\in \{1,3\}$ mW, we were able to discriminate between biological fluids with different concentrations of suspended cells with a robust working ability $R^2=0.9874$ and $R_{adj}^2=0.9811$. Full article

Ionenes are poly(ionic liquids) (PILs) comprising a polymer backbone with ionic groups along the structure. Ionenes as solid–solid phase change materials are a recent research field, and some studies have demonstrated their potential in thermal dissipation into electronic devices. Eight ionenes obtained through Menshutkin reactions were synthesized and characterized. The analysis of the thermal tests allowed understanding of how the thermal properties of the polymers depend on the aliphatic nature of the dihalogenated monomer and the carbon chain length. The TGA studies concluded that the ionenes were thermally stable with T_10% above 420 °C. The DSC tests showed that the prepared ionenes presented solid–solid transitions, and no melting temperature was appreciated, which rules out the possibility of solid–liquid transitions. All ionenes were soluble in common polar aprotic solvents. The hydrophilicity of the synthesized ionenes was studied by the contact angle method, and their total surface energy was calculated. Self-healing behavior was preliminarily explored using a selected sample. Our studies show that the prepared ionenes exhibit properties that make them potential candidates for applications as solid–solid phase change materials. Full article

With the increasing demand for lightweight and high-performance materials in the automotive and aerospace industries, full-thermoplastic hybrid composites have emerged as a pivotal solution, offering enhanced mechanical properties and design flexibility. This work aims to numerically model the fracture strength in full-thermoplastic hybrid composites made by forming and overmolding organosheets. The mode I fracture was investigated by modeling the behavior of T-joint specimens under a tensile test following the cohesive zone modeling (CZM) approach. The sample was designed to replicate the connection between the laminate and the overmolded part. Double cantilever beam (DCB) specimens were manufactured with organosheets and tested to mode I opening to determine the interlaminar fracture toughness. The fracture toughness out of the mode I test with DCB specimens was used to define the CZM parameters that describe the traction-separation law. Later, due to the particular geometry of the T-join specimens that under tensile load work close to pure mode I, the cohesive parameters were determined by inverse analysis, i.e., calibrating the theoretical models to match experimental results. The fracture resistance T-joint specimens appeared dependent on the fiber-bridging phenomenon during the delamination. In particular, the presence of fiber-bridging visible from the experimental results has been replicated by virtual analyses, and it is observed that it leads to a higher energy value before the interface’s complete breakage. Moreover, a correspondence between the mode I fracture toughness of the DCB specimen and T-joint specimens was observed. Full article

Although the behavior of the confined semi-dilute solutions of self-assembling copolymers represents an important topic of basic and applied research, it has eluded the interest of scientists. Extensive series of dissipative particle dynamics simulations have been performed on semi-dilute solutions of A₅B₅ chains in a selective solvent for A in slits using a DL-MESO simulation package. Simulations of corresponding bulk systems were performed for comparison. This study shows that the associates in the semi-dilute bulk solutions are partly structurally organized. Mild steric constraints in slits with non-attractive walls hardly affect the size of the associates, but they promote their structural arrangement in layers parallel to the slit walls. Attractive walls noticeably affect the association process. In slits with mildly attractive walls, the adsorption competes with the association process. At elevated concentrations, the associates start to form in wide slits when the walls are sparsely covered by separated associates, and the association process prevents the full coverage of the surface. In slits with strongly attractive walls, adsorption is the dominant behavior. The associates form in wide slits at elevated concentrations only after the walls are completely and continuously covered by the adsorbed chains. Full article

Renewable and biodegradable polysaccharides have attracted interest for their wide applicability, among them their use as sorbents for heavy metal ions. Their high sorption capacity is due mainly to the acidic groups that populate the polysaccharide backbone, for example, carboxylic groups in alginate and sulfate ester groups in the iota and lambda carrageenans. In this study, these three polysaccharides were employed, alone or in different mixtures, to recover different heavy metal ions from aqueous solutions. All three polysaccharides were capable of adsorbing Eu³⁺, Sm³⁺, Er³⁺, or UO₂²⁺ and their mixtures, findings that were also confirmed using XPS, TGA, and FTIR analyses. In addition, the highest sorption yields of all the metal ions were obtained using alginate, alone or in mixtures. While the alginate with carboxylic and hydroxyl groups adsorbed different ions with the same selectivity, carrageenans with sulfate ester and hydroxyl groups exhibited higher adsorption selectivity for lanthanides than for uranyl, indicating that the activity of the sulfate ester groups toward trivalent and smaller ions was higher. Full article

Several polyurethane-formulated films with curcumin and/or chitosan additives for food packaging have been previously obtained. The study examines the effect of the additives on the film’s morphological, mechanical, barrier, and migration properties. Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), water contact angle, thermogravimetric and differential thermal analysis (TGA and DTGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), oxygen transmission rate (OTR), water vapor transmission rate (WVTR), and the overall and specific migration tests were conducted. The results show that the presence of chitosan significantly increased the overall migration and mechanical properties, such as the elongation at break, tensile strength, and Young’s modulus of most polyurethane formulations, while curcumin had a minor influence on the mechanical performance. Based on the results, formulations with curcumin but without chitosan are suitable for food packaging. Full article

The UN 2030 Agenda for Sustainable Development established the goal of cutting the use of pesticides in the EU by 50% by 2030. However, a ban on pesticides could seriously affect the productivity of agriculture, resulting in severe issues due to global hunger and food deficiency. Controlled release (CR) of bioactive chemicals could play a valid alternative in this context. To this aim, two biodegradable polymers, namely sodium alginate (AL) and sodium carboxymethylcellulose (CMC), were employed to obtain crosslinked hydrogel beads for the encapsulation and CR of glycoalkaloids extracted from tomato and potato leaves to be used as biocompatible disinfectants for agricultural soils. The physico-chemical characterization of the controlled-release systems was carried out by means of Attenuated Total Reflectance–Fourier Transform Infrared (ATR-FTIR) spectroscopy, Scanning Electron Microscopy (SEM), thermogravimetry (TGA), differential scanning calorimetry (DSC) (FWI > 80%) and drying kinetics. The plant extracts and the encapsulation efficiency (~84%) were, respectively, characterized and evaluated by High-performance Liquid Chromatography–Mass Spectrometry (HPLC-MS). Finally, preliminary microbiological tests were conducted to test the efficacy of the most promising systems as biocidal formulations both in the lab and on a model soil, and interesting results were obtained in the reduction of bacterial and fungal load, which could lead to sustainable perspectives in the field. Full article

In this study, cotton fabric-reinforced phenolic resin (CPF) composites were modified by adding four two-dimensional fillers: graphitic carbon nitride (g-C₃N₄), graphite (Gr), molybdenum disulfide (MoS₂), and hexagonal boron nitride (h-BN). The tribological properties of these modified materials were investigated under dry friction and water lubrication conditions. The CPF/Gr composite exhibits significantly better tribological performance than the other three filler-modified CPF composites under dry friction, with a 24% reduction in friction coefficient and a 78% reduction in wear rate compared to the unmodified CPF composite. Under water lubrication conditions, all four fillers did not significantly alter the friction coefficient of the CPF composites. However, except for an excessive amount of Gr, the other three fillers can reduce the wear rate. Particularly in the case of 10% MoS₂ content, the wear rate decreased by 56%. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed for the analysis of the morphology and composition of the transfer films. Additionally, molecular dynamics (MD) simulations were conducted to investigate the adsorption effects of CPF/Gr and CPF/MoS₂ composites on the counterpart surface under both dry friction and water lubrication conditions. The difference in the adsorption capacity of CPF/Gr and CPF/MoS₂ composites on the counterpart, as well as the resulting formation of transfer films, accounts for the variation in tribological behavior between CPF/Gr and CPF/MoS₂ composites. By combining the lubrication properties of MoS₂ and Gr under dry friction and water lubrication conditions and using them as co-fillers, we can achieve a synergistic lubrication effect. Full article

We investigated the effect of nanoscale curvature on the structure of thermally equilibrated poly-3-hexylthiophene (P3HT) ultrathin films. The curvature-induced effects were investigated with synchrotron grazing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). Our results demonstrate that nanoscale curvature reduces the polymer crystalline fraction and the crystal length. The first effect is strongest for the lowest curvature and results in a decrease in the out-of-plane thickness of the polymer crystals. On the other hand, the crystal in-plane length decreases with the increase in substrate curvature. Finally, the semi-quantitative analysis of crystal anisotropy shows a marked dependence on the substrate curvature characterized by a minimum at curvatures between 0.00851 nm⁻¹ and 0.0140 nm⁻¹. The results are discussed in terms of a curvature-dependent polymer fraction, which fills the interstices between neighboring particles and cannot crystallize due to extreme space confinement. This fraction, whose thickness is highest at the lowest curvatures, inhibits the crystal nucleation and the out-of-plane crystal growth. Moreover, because of the adhesion to the curved portion of the substrates, crystals adopt a random orientation. By increasing the substrate curvature, the amorphous fraction is reduced, leading to polymer films with higher crystallinity. Finally, when the thickness of the film exceeds the particle diameter, the curvature no longer affects the crystal orientation, which, similarly to the flat case, is predominantly edge on. Full article

Additive manufacturing of components using the material extrusion (MEX) of thermoplastics enables the integration of multiple materials into a single part. This can include functional structures, such as electrically conductive ones. The resulting functional structure properties depend on the process parameters along the entire manufacturing chain. The aim of this investigation is to determine the influence of process parameters in filament production and additive manufacturing on resistivity. Filament is produced from a commercially available composite of polylactide (PLA) with carbon nanotubes (CNT) and carbon black (CB), while the temperature profile and screw speed were varied. MEX specimens were produced using a full-factorial variation in extrusion temperature, layer height and deposition speed from the most and least conductive in-house-produced filament and the commercially available filament from the same composite. The results show that the temperature profile during filament production influences the resistivity. The commercially available filament has a lower conductivity than the in-house-produced filament, even though the starting feedstock is the same. The process parameters during filament production are the main factors influencing the resistivity of an additively manufactured structure. The MEX process parameters have a minimal influence on the resistivity of the used PLA/CNT/CB composite. Full article

Temperature-sensitive carboxylated cellulose nanocrystals/N-isopropyl acrylamide aerogels (CCNC-NIPAMs) were developed as novel pesticide-controlled release formulas. Ammonium persulfate (APS) one-step oxidation was used to prepare bagasse-based CCNCs, and then the monomer N-isopropyl acrylamide (NIPAM) was successfully introduced and constructed into the temperature-sensitive CCNC-NIPAMs through polymerization. The results of the zeta potential measurement and Fourier infrared transform spectrum (FTIR) show that the average particle size of the CCNCs was 120.9 nm, the average surface potential of the CCNCs was −34.8 mV, and the crystallinity was 62.8%. The primary hydroxyl group on the surface of the CCNCs was replaced by the carboxyl group during oxidation. The morphology and structure of CCNC-NIPAMs were characterized via electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), compression performance, porosity analysis, and thermogravimetric (TG) analysis. The results demonstrate that CCNC-NIPAM has a high porosity and low density, as well as good thermal stability, which is conducive to loading and releasing pesticides. In the swelling, drug loading, and controlled release process, the CCNC-NIPAM exhibited significant temperature sensitivity. Under the same NIPAM reaction amount, the equilibrium swelling rate of the CCNC-NIPAM first increased and then decreased with increasing temperature, and the cumulative drug release ratio of the CCNC-NIPAM at 39 °C was significantly higher than that at 25 °C. The loading efficiency of the CCNC-NIPAM on the model drug thiamethoxam (TXM) was up to 23 wt%, and the first-order model and Korsmyer–Peppas model could be well-fitted in the drug release curves. The study provides a new method for the effective utilization of biomass and pesticides. Full article

Composite phase change materials commonly exhibit drawbacks, such as low thermal conductivity, flammability, and potential leakage. This study focuses on the development of a novel flame-retardant phase change material (RPCM). The material’s characteristics and its application in the thermal management of lithium-ion batteries are investigated. Polyethylene glycol (PEG) serves as the medium for phase change; expanded graphite (EG) and multi-walled carbon nanotubes (MWCNT) are incorporated. Moreover, an intumescent flame retardant (IFR) system based on ammonium polyphosphate (APP) is constructed, aided by the inclusion of bio-based flame-retardant chitosan (CS) and barium phytate (PA-Ba), which can improve the flame retardancy of the material. Experimental results demonstrate that the RPCM, containing 15% IFR content, exhibits outstanding flame retardancy, achieving a V-0 flame retardant rating in vertical combustion tests. Moreover, the material exhibits excellent thermomechanical properties and thermal stability. Notably, the material’s thermal conductivity is 558% higher than that of pure PEG. After 2C and 3C high-rate discharge cycles, the highest temperature reached by the battery module cooled with RPCM is 18.71 °C lower than that of natural air-cooling; the material significantly reduces the temperature difference within the module by 62.7%, which achieves efficient and safe thermal management. Full article

When it comes to grouting in coal mines, polyurethane (PU) is often utilized. However, it is of vital importance to consistently improve the mineral PU, considering the significant amount of environmental deterioration to which it is prone. Laboratory experiments were used to model various coal mine conditions. Additionally, a workable technique for PU strengthening using ultrasonic waves was proposed. Compression tests and scanning electron microscopy (SEM) were used to describe the PU–gangue material’s induration characteristics. The results showed that ultrasound has a positive impact on PU’s mechanical strength. The final strength of the PU was significantly impacted by the size of the coal gangue particles, the amount of dust, and the amount of water. The induration made of gangue and PU with the same mass but differing particle sizes was noticeably different in its compressive strength. The strengthening mechanism showed that the average size of the rigid foam after the ultrasound treatment was smaller, and the ‘honeycomb’-structured space in the inner section was more compact, resulting in the rigid PU foam having a higher compressive strength after ultrasound treatment. Furthermore, the dust content and water content of coal mines need to be controlled within a specific range to ensure the effective use of PU grouting materials. Full article

Epoxy matrix composites reinforced with high-performance fibers, such as carbon, Kevlar, and glass, exhibit excellent specific stiffness and strength in many mechanical applications. However, these composites are disappointingly non-recyclable and are usually disposed of in landfill sites, with no realistic prospect for biodegradation in a reasonable time. In contrast, moldable composites with carbonized elastomeric matrices developed in the last decades possess attractive mechanical properties in final net-shape products and can also be incinerated or recycled. Many carbon and inorganic fillers have recently been evaluated to adjust the properties of carbonized elastomeric composites. Renewable organic fillers, such as human or animal hair, offer an attractive fibrous material with substantial potential for reinforcing composites with elastomeric matrices. Samples of unidirectional fiber composites (with hair volume fractions up to 7%) and quasi-isotropic short fiber composites (with hair volume fractions up to 20%) of human hair-reinforced nitrile butadiene rubbers (HH-NBRs) were produced in the peroxide-cured and carbonized states. The samples were characterized using scanning electron microscopy (SEM), Raman spectroscopy, and photoacoustic microscopy. Mechanical tests were performed under tension using a miniature universal testing machine. The expected effect of fiber reinforcement on the overall mechanical performance was demonstrated for both cured and carbonized composites. Considerable enhancement of the elastic modulus (up to ten times), ultimate tensile strength (up to three times), and damage tolerance was achieved. The evidence of satisfactory interfacial bonding between hair and rubber was confirmed via SEM imaging of fracture surfaces. The suitability of photoacoustic microscopy was assessed for 3D reconstructions of the fiber sub-system’s spatial distribution and non-destructive testing. Full article

The need for sustainable alternatives to conventional plastic mulches in agriculture has led to the development of various types of biodegradable mulches made from natural fibres and biopolymers to reduce environmental pollution and mitigate soil pollution caused by conventional plastic mulch usage. Degradation, impact on soil temperature and humidity, and weed suppression properties of needle-punched nonwoven mulches of different mass per unit area, made of jute, hemp, viscose, and PLA biopolymer, are investigated. Their biodegradation is determined by changes in the mulch properties (mass per unit area, thickness, air permeability, tensile properties, microscopic images, and FTIR analyses) during 300 days of exposure to the environmental conditions in the period from May 2022 to February 2023. The change in mass per unit area, thickness, air permeability, and tensile properties of nonwoven mulches did not show a tendency to degrade during exposure to environmental conditions. The microscopic and FTIR analysis showed the degradation of the fibres from the mulches during the exposure time to a certain extent. The environmental conditions influence the change in the dimensions of the mulches (shrinkage and expansion)—which impact periodically tested mass results per unit area—as well as their thickness and air permeability. The nonwoven mulches provide higher temperatures compared to bare soil, though not as high as those observed beneath traditional agricultural foil. When comparing the humidity in bare soil and soil covered by mulches during the plant growth period (June to October), it was found that soil humidity was higher beneath all mulches. The nonwoven mulches provide superior soil moisture retention compared to conventionally used agrofoil. Almost all nonwoven mulches effectively suppressed weed growth, except hemp mulches. The newly produced mulches have the potential to replace traditional agrofoil, offering improved conditions for plant growth, effective weed control, and faster degradation without causing harm to the environment. Full article

For different manufacturing processes, porosity occurs in parts made using selective laser sintering (SLS) technology, representing one of the weakest points of materials produced with these processes. Even though there are different studies involving many polymeric materials employed via SLS, and different manuscripts in the literature that discuss the porosity occurrence in pure or blended polymers, to date, no researcher has reported a systematic and exhaustive comparison of the porosity percentage. A direct comparison of the available data may prove pivotal in advancing our understanding within the field of additively manufactured polymers. This work aims to collect and compare the results obtained by researchers who have studied SLS’s applicability to different amorphous or semi-crystalline polymers and pure or blended materials. In particular, the porosity values obtained by different researchers are compared, and tables are provided that show, for each material, the process parameters and the measured porosity values. Full article

The synthesis of biocompatible and bioresorbable composite materials, such as a “polymer matrix-mineral constituent,” stimulating the natural growth of living tissues and the restoration of damaged parts of the body, is one of the challenging problems in regenerative medicine and materials science. Composite films of bioresorbable polymer of polyvinylpyrrolidone (PVP) and hydroxyapatite (HA) were obtained. HA was synthesized in situ in the polymer solution. We applied electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) approaches to study the composite films’ properties. The application of EPR in two frequency ranges allowed us to derive spectroscopic parameters of the nitrogen-based light and radiation-induced paramagnetic centers in HA, PVP and PVP-HA with high accuracy. It was shown that PVP did not significantly affect the EPR spectral and relaxation parameters of the radiation-induced paramagnetic centers in HA, while light-induced centers were detected only in PVP. Magic angle spinning (MAS) ¹H NMR showed the presence of two signals at 4.7 ppm and −2.15 ppm, attributed to “free” water and hydroxyl groups, while the single line was attributed to ³¹P. NMR relaxation measurements for ¹H and ³¹P showed that the relaxation decays were multicomponent processes that can be described by three components of the transverse relaxation times. The obtained results demonstrated that the applied magnetic resonance methods can be used for the quality control of PVP-HA composites and, potentially, for the development of analytical tools to follow the processes of sample treatment, resorption, and degradation. Full article

Vinyl-addition polynorbornenes are of great interest as versatile templates for the targeted design of polymer materials with desired properties. These polymers possess rigid and saturated backbones, which provide them with high thermal and chemical stability as well as high glass transition temperatures. Vinyl-addition polymers from norbornenes with bromoalkyl groups are widely used as precursors of anion exchange membranes; however, high-molecular-weight homopolymers from such monomers are often difficult to prepare. Herein, we report the systematic study of vinyl-addition polymerization of norbornenes with various bromoalkyl groups on Pd-catalysts bearing N-heterocyclic carbene ligands ((NHC)Pd-systems). Norbornenes with different lengths of hydrocarbon linker (one, two, and four CH₂ groups) between the bicyclic norbornene moiety and the bromine atom were used as model monomers, while single- and three-component (NHC)Pd-systems were applied as catalysts. In vinyl-addition polymerization, the reactivity of the investigated monomers varied substantially. The relative reactivity of these monomers was assessed in copolymerization experiments, which showed that the closer the bromine is to the norbornene double-bond, the lower the monomer’s reactivity. The most reactive monomer was the norbornene derivative with the largest substituent (with the longest linker). Tuning the catalyst’s nature and the conditions of polymerization, we succeeded in synthesizing high-molecular-weight homopolymers from norbornenes with bromoalkyl groups (M_n up to 1.4 × 10⁶). The basic physico-chemical properties of the prepared polymers were studied and considered together with the results of vinyl-addition polymerization. Full article

Huge energy consumption and running out of fossil fuels has led to the advancement of renewable sources of power, including solar, wind, and tide. Among them, solar cells have been well developed with the significant achievement of silicon solar panels, which are popularly used as windows, rooftops, public lights, etc. In order to advance the application of solar cells, a flexible type is highly required, such as layered casting solar cells (LCSCs). Organic solar cells (OSCs), perovskite solar cells (PSCs), or dye-sensitive solar cells (DSSCs) are promising LCSCs for broadening the application of solar energy to many types of surfaces. LCSCs would be cost-effective, enable large-scale production, are highly efficient, and stable. Each layer of an LCSC is important for building the complete structure of a solar cell. Within the cell structure (active material, charge carrier transport layer, electrodes), hole transport layers (HTLs) play an important role in transporting holes to the anode. Recently, diverse HTLs from inorganic, organic, and organometallic materials have emerged to have a great impact on the stability, lifetime, and performance of OSC, PSC, or DSSC devices. This review summarizes the recent advances in the development of inorganic, organic, and organometallic HTLs for solar cells. Perspectives and challenges for HTL development and improvement are also highlighted. Full article

The use of mixed matrix membranes (MMMs) comprising metal–organic frameworks (MOFs) for the separation of CO₂ from flue gas has gained recognition as an effective strategy for enhancing gas separation efficiency. When incorporating porous materials like MOFs into a polymeric matrix to create MMMs, the combined characteristics of each constituent typically manifest. Nevertheless, the inadequate dispersion of an inorganic MOF filler within an organic polymer matrix can compromise the compatibility between the filler and matrix. In this context, the aspiration is to develop an MMM that not only exhibits optimal interfacial compatibility between the polymer and filler but also delivers superior gas separation performance, specifically in the efficient extraction of CO₂ from flue gas. In this study, we introduce a modification technique involving the grafting of poly(ethylene glycol) diglycidyl ether (PEGDE) onto a UiO-66-NH₂ MOF filler (referred to as PEG-MOF), aimed at enhancing its compatibility with the 6FDA-durene matrix. Moreover, the inherent CO₂-philic nature of PEGDE is anticipated to enhance the selectivity of CO₂ over N₂ and CH₄. The resultant MMM, incorporating 10 wt% of PEG-MOF loading, exhibits a CO₂ permeability of 1671.00 Barrer and a CO₂/CH₄ selectivity of 22.40. Notably, these values surpass the upper bound reported by Robeson in 2008. Full article

Oil well cement is prone to corrosion and damage in carbon dioxide (CO₂) acidic gas wells. In order to improve the anti-corrosion ability of oil well cement, polymer resin was used as the anti-corrosion material. The effect of polymer resin on the mechanical and corrosion properties of oil well cement was studied. The corrosion law of polymer anti-corrosion cement in an acidic gas environment was studied. The long-term corrosion degree of polymer anti-corrosion cement was evaluated using an improved neural network model. The cluster particle algorithm (PSO) was used to improve the accuracy of the neural network model. The results indicate that in acidic gas environments, the compressive strength of polymer anti-corrosion cement was reduced under the effect of CO₂, and the corrosion depth was increased. The R² of the prediction model PSO-BPNN3 is 0.9970, and the test error is 0.0136. When corroded for 365 days at 50 °C and 25 MPa pressure of CO₂, the corrosion degree of the polymer anti-corrosion cement was 43.6%. The corrosion depth of uncorroded cement stone is 76.69%, which is relatively reduced by 33.09%. The corrosion resistance of cement can be effectively improved by using polymer resin. Using the PSO-BP neural network to evaluate the long-term corrosion changes of polymer anti-corrosion cement under complex acidic gas conditions guides the evaluation of its corrosion resistance. Full article

The thermal decomposition product of magnesium hydroxide (MH) is magnesium oxide (MgO), which serves as the foundational material for fireproof layer construction in the condensed phase. However, the weak interaction force between particles of MgO generated by thermal decomposition leads to the insufficient strength and poor adhesion ability of the fireproof layer. The fireproof layer was easily damaged and detached in this study, resulting in the low flame-retardant efficiency of MH. In this work, polycarbosilane (PCS) and divinyl benzene (DVB) were used to modify MH, and EVA/MH/PCS/DVB composites were made via melt blending. The flame-retardant properties of EVA/MH/PCS/DVB were evaluated using the limiting oxygen index (LOI), vertical combustion (UL-94), and a cone calorimeter (CONE). The thermal stability of the composites and flame retardants was analyzed using a thermogravimetric analyzer. The char layer structure was observed and analyzed using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The results indicate that the LOI of the EVA/MH/PCS/DVB with 50 wt.% flame retardants in total was as high as 65.1, which increased by 160% in comparison with EVA/MH. Furthermore, the total smoke production (TSP) of the EVA/MH/PCS/DVB composite decreased by 22.7% compared to EVA/MH/PCS; the thermal stability of the MH/PCS/DVB and EVA/MH/PCS/DVB improved to some extent; and the compact residual char after the combustion of EVA/MH/PCS/DVB had fewer cracks due to the adhesive effect induced by PCS/DVB. Full article