Search Results (65)

Poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) stands out as a renowned commercial conducting polymer composite, boasting extensive and promising applications in the realm of film electronics. In this study, we have made a concerted effort to overcome the inherent drawbacks of PEDOT:PSS films (especially, high moisture absorption, mechanical damage vulnerability, insufficient substrate adhesion ability, etc.) by uniformly blending them with polydimethylsiloxane polyurea (PDMS-PUa) and silica (SiO₂) nanoparticles through a feasible mechanical stirring process, which effectively harnesses the intermolecular interactions, as well as the morphological and structural characteristics, among the various components. The Si−O bonds within PDMS-PUa and the −CH₃ groups attached to Si atoms significantly enhance the hydrophobicity of the composite film (as evidenced by a water contact angle of 132.89° under optimized component ratios). Meanwhile, SiO₂ microscopically modifies the surface morphology, resulting in increased surface roughness. This composite film not only maintains high conductivity (1.21 S/cm, in contrast to 0.83 S/cm for the PEDOT:PSS film) but also preserves its hydrophobicity and electrical properties under rigorous conditions, including high-temperature exposure (60–200 °C), ultraviolet (UV) aging (365.0 nm, 1.32 mW/cm²), and abradability testing (2000 CW abrasive paper, drag force of approximately 0.98 N, 40 cycles). Furthermore, the film demonstrates enhanced resistance to both acidic (1 mol/L, 24 h) and alkaline (1 mol/L, 24 h) environments, along with excellent self-cleaning and de-icing capabilities (−6 °C), and satisfactory adhesion (Level 2). Notably, the dried composite film can be re-dispersed into a solution with the aid of isopropanol through simple magnetic stirring, and the sequentially coated films also exhibit good surface hydrophobicity (136.49°), equivalent to that of the pristine film. This research aims to overcome the intrinsic performance drawbacks of PEDOT:PSS-based materials, enabling them to meet the demands of complex application scenarios in the field of organic electronics while endowing them with multifunctionality. Full article

The imperative for high-performance protective materials has catalyzed the rapid evolution of polyurea (PUA) coatings, widely recognized for their mechanical robustness, chemical resistance, and rapid-curing properties. However, their inherent flammability and harmful combustion byproducts pose significant challenges for safe use in applications where fire safety is a critical concern. In response, significant efforts focus on improving the fire resistance of PUA materials through chemical modifications and the use of functional additives. The review highlights progress in developing flame-retardant approaches for PUA coatings, placing particular emphasis on the underlying combustion mechanisms and the combined action of condensed-phase, gas-phase, and interrupted heat feedback pathways. Particular emphasis is placed on phosphorus-based, intumescent, and nano-enabled flame retardants, as well as hybrid systems incorporating two-dimensional nanomaterials and metal–organic frameworks, with a focus on exploring their synergistic effects in enhancing thermal stability, reducing smoke production, and maintaining mechanical integrity. By evaluating current strategies and recent progress, this work identifies key challenges and outlines future directions for the development of high-performance and fire-safe PUA coatings. These insights aim to guide the design of next-generation protective materials that meet the growing demand for safety and sustainability in advanced engineering applications. Full article

The aim of the current study is to investigate the mechanical properties and ballistic performance of HARDOX 450 steel for defense applications in different conditions: uncoated, alumina-coated, and LINE X polyurea-coated. Tensile tests and Vickers microhardness measurements were conducted, along with fracture surface analysis using stereomicroscopy, scanning electron microscopy, and computed tomography. Experimental results showed that uncoated HARDOX 450 steel exhibited the highest strength and hardness, with ductile fracture features. Polyurea-coated HARDOX 450 steel samples retained good mechanical properties and demonstrated effective ballistic protection, including the containment of fragments. In contrast, alumina-coated HARDOX 450 steel samples exhibited reduced strength and ballistic resistance, attributed to the microstructural changes in HARDOX 450 steel caused by the high-temperature deposition process of alumina. Numerical simulations performed with the 5.56 × 45 mm bullet used in the simulation, along with its ballistic impact interaction with the Hardox 450 target model, aligned well with experimental ballistic impact results for all the samples. Overall, LINE X polyurea coating on HARDOX 450 steel proved to be the more suitable coating for applications requiring a balance of mechanical strength and ballistic impact resistance. Full article

This study investigated the erosive wear of a polyurea coating with a hardness of 95 ShA and a thickness of 3 mm applied to a 3 mm thick plate made of S235 steel. The process of erosive wear was carried out using a stream of compressed air containing abrasive grains of aluminum oxide (Al₂O₃). The erosive wear was studied using different incidence angles (45°, 60° and 90°) and erosive grain sizes. Thus, the effects of the incidence angle and erosive grain size on the erosive wear of the polyurea coating were analyzed. Erosive wear was determined as linear wear: the depth of the wear trace was measured using an optical profilometer. This study showed a non-linear correlation between erosive wear, incidence angle and erosive particle size. In addition, a qualitative study of the surface of the coating after a wear test was carried out using a scanning electron microscope, which made it possible to describe the mechanisms of erosive wear of the polyurea coating. Full article

Polyurea failures in reinforced concrete tanks, such as swimming pools and sewage treatment plants, require a thorough analysis of the causes of failures during renovation. Urban agglomerations are increasingly relying on these facilities for maintaining city functioning, and the increasing concentration of pollutants in these facilities necessitates urgent repairs due to frequent failures. More thorough analysis should be given to repeated failures on the same object or “twin” objects within a short period, causing high renovation costs and long shutdowns. The causes of failures can be found not only as a result of insufficient knowledge but also in a limited analysis of the entire project from the assumption phase to completion. The article analyzed water and sewage tanks on which failures of applied polyurea coatings occurred many times. The posteriori uses of the risk management analysis with the assessment of the impact and probability of occurrence of the planned activities that failed allows it to be applied a priori and treated as a necessary analysis. For this purpose, in selected repairs, those activities that had the greatest impact on failure and a relatively high probability of occurrence during implementation were distinguished from the entire project. Based on the risk management analysis, it was shown that the basic cause of the failure was the poor knowledge and insufficient experience of the entities performing the repairs, and the errors that occurred could be minimized by conducting good diagnostics of the facility, selecting professional designers and contractors, and constant monitoring of each important activity. Full article

In this study, a solvent-free, slow-curing, inherently flame-retardant polyurea coating was successfully developed through an optimized formulation. The novel polyurea was synthesized using mixed Schiff base latent curing agents derived from terminal polyether amines with different-number average molecular weights (D2000 and D400), methyl isobutyl ketone, and polyethyl phosphate glycol ester (OP550). Subsequently, polyurea/meta-aramid (PUA/AF) composite fabrics were fabricated via a scraping coating technique. Thermogravimetric analysis revealed enhanced char formation and reduced decomposition temperatures due to the incorporation of OP550. Comprehensive flame retardant performance was demonstrated through vertical flame testing, limiting oxygen index, and micro-scale combustion calorimetry, with results showing significantly reduced heat release rates, lower total heat release, and increased residual char. Mechanical evaluations indicated marked improvements in tearing, tensile, single-yarn tensile, and bursting forces, attributed to strong fiber–polyurea interfacial interactions, as confirmed by detailed SEM morphological analyses. Moreover, the PUA/AF composites exhibited excellent static puncture resistance and effective self-healing capability. Collectively, these advancements highlight the potential of PUA/AF composite fabrics as promising candidates for advanced protective textiles, integrating superior flame retardancy, mechanical strength, puncture resistance, and self-repairing functionality. Full article

Polyurea spraying is a new temporary support technology that can significantly enhance the mechanical properties of coal. However, the mechanism of interactions between the polymer coating and coal is unclear. In this study, the No. 4 non-stick coal from Mengcun Coal Mine and polyurea material were used to conduct experiments and numerical simulations. The tests and simulations were used to examine the role of the sprayed coating in the formation of residual strength and the unloading and rebound mechanism after brittle failure of the coal. The results showed that the presence of the polyurea coating had a significant impact on the mechanical behavior of the coal. The specimens sprayed with polyurea were affected by the confining pressure applied by the coating and the internal friction of the coal; consequently, the specimens exhibited certain plastic characteristics and maintained their residual strength after experiencing brittle failure. The polyurea coating not only effectively prevents the loosening and slippage of the coal but also improves the stability of the coal by altering its mechanical behavior during the loading process. This study lays the foundation for popularizing and applying polyurea spraying technology in coal mine support while providing rich data to support further theoretical research. Full article

Urea groups appear in many biomolecules and polymers. They have a significant impact on the properties of the materials because of their inherent strength and for their ability to participate in hydrogen bonds. Typically, in classical urea-based polymer materials, the urea groups occur in their N,N′-disubstituted state. Recently, bis-aspartates have been introduced as a novel type of hindered amine resins providing, upon crosslinking with (poly)isocyanates, the polyurea–polyaspartate thermosets (PU-ASPE) for coatings, sealants, polyelectrolytes, and other applications. These materials contain N,N′N′-trisubstituted urea linkages in their structures. However, the infrared (IR) characterization of trisubstituted urea groups has not been documented in sufficient detail. Consequently, studies on the structure of aspartate-based polyurea materials often rely on data from N,N′-disubstituted ureas, which can lead to inaccurate conclusions. This study presents a detailed evaluation of the possible urea H-bonding states, focusing on the difference between the di- and trisubstituted species. Particularly, the attributions of the IR spectra to urea-based hydrogen bonding states are presented both in neat materials and their solutions. To systematize this study, we initially focus on a simple trisubstituted urea model system, tributyl urea (3BUA), and compare its spectral response with disubstituted N-butyl-N′-cyclohexyl urea (1B1CHUA) and trisubstituted N-butyl-N′,N′-dicyclohexyl urea (1B2CHUA), to elucidate their hydrogen-bonding fingerprints. This research provides a thorough understanding of the IR response of the di- and trisubstituted urea species and their structural characteristics in urea-containing materials. Full article

In recent years, polyurea (PUA) systems have drawn considerable attention in the coatings industry for their superior performance. Among these systems, polyaspartate ester-based polyurea (PAE-PUA) stands out for its excellent comprehensive properties, and the structure of the diamines used in polyaspartate ester (PAE) significantly influences key performance attributes, such as gel time, mechanical properties, and thermal stability. To investigate the influence of diamine structures on PAE-PUA properties, this study synthesized PAEs through ester exchange reactions involving diamines and monohydric alcohols with varied chain lengths and structural types (linear or cyclic). The effects of four diamines (D230, DMH, IPDA, PACM) and four monohydric alcohols (CA, DDA, OD, CHOL) on polyurea coating properties were systematically examined. The results demonstrated that adjusting the structural regularity of PAEs via ester exchange reactions effectively regulated their viscosity, maintaining it below 1500 mPa·s. These reactions also enabled simultaneous regulation of surface-drying time, mechanical properties, and thermal performance. Notably, introducing 1-octadecanol (OD) significantly improved surface-drying time and thermal stability, whereas cyclic structures in diamines or alcohols resulted in higher glass transition temperatures (T_g). Additionally, the mechanical properties and reaction rates of modified PAEs can be tailored to meet specific application requirements, offering an effective strategy for developing polyurea materials optimized for the coatings industry. Full article

The protective effect of polyurea (PU) coatings on polymer matrix composite (PMC) panels subjected to high-velocity ballistic impacts, particularly as a potential replacement material for large power transformer (LPT) tanks, has not been extensively reported in the literature. This study addresses the gap by presenting a numerical investigation into the ballistic performance of PMC panels with PU coatings. Due to the complex nature and high cost of experimental testing, this research relies on finite element modeling to predict the panels’ responses under impact. Glass fiber/epoxy and carbon fiber/epoxy composite panels were tested individually and in hybrid configurations while being subjected to simulated 400 m/s steel projectile impacts. This study first investigates the impact damage evolution in uncoated panels, analyzing the arrest depth as a function of the panel thickness. It then evaluates the effect of PU coatings on the ballistic response. The results demonstrate that PU coatings are three times more effective in protecting both glass and carbon fiber panels from penetration compared to simply increasing the panel thickness. Additionally, the utilization of PU coatings led to a reduction in cost, mass, and thickness while still preventing penetration of the projectile in the models. Full article

Polyurea (PUR) has been widely used as a protective coating in recent years. In order to complete the understanding of the relationship between PUR microstructure and its energy absorption capabilities, the mechanical and dynamic performance of PURs containing various macrodiol structural units were compared using material characterization techniques and molecular dynamic simulation. The results showed that the PUR polycarbonate diols formed as energy absorbing materials showed high tensile strength, high toughness, and excellent loss factor distribution based on the comparison of stress–strain tensile curves, glass transition temperatures, phase images, and dynamic storage loss modulus. External energy from simple shear deformation was absorbed to convert non-bond energy, in particular, based on fractional free volume, interaction energy, and total energy and hydrogen bond number change from the molecular dynamic simulation. Hydrogen bonds formed between soft segments and hard segments in the PURs have been proven to play a significant role in determining their mechanical and dynamic performance. The mechanical and dynamic properties of PURs characterized and tested using experimental techniques were quantified effectively using molecular dynamic simulation. This is believed to be an innovative theoretical guidance for the structural design of PURs at the molecular level for the optimization of energy absorption capabilities. Full article

To enhance the corrosion resistance of underground pipelines made of low carbon steel, nano-TiO₂-modified polyurea was applied to their surface. The anti-corrosion performance of these nano-TiO₂-modified coatings was tested by immersing them in a NACE (5 wt.% NaCl + 0.5 wt.% CH3COOH) solution under high temperatures and high CO₂ pressures. The mass variation, SEM morphology, and open-circuit potential were determined. EIS tests, neutral salt spray tests, and contact angle measurements were carried out to analyze the effect of nanoparticles on corrosion resistance. Within the same pressure range, the polyurea coating shows the highest corrosion resistance when 5% TiO₂ nanoparticles were added compared to that of polyurea coatings with 0%, 10%, and 15% TiO₂ added. Coatings with 5% TiO₂ nanoparticles showed rapid diffusion after being immersed for 96 h, indicating that the anti-corrosion performance of the coating weakened. Full article

This study addresses a practical and efficient approach to evaluating the load-bearing capacity of severely degraded concrete manholes. Concrete deterioration, often advanced and highly irregular, can be captured accurately through surface scanning to create a detailed model of the damaged structure and also to build a simplified modeling to enable rapid engineering-level assessment, filling a critical gap in infrastructure maintenance. The repair strategy involves applying an internal polyurea layer, a variable-thickness polyurethane foam layer depending on the degree of localized degradation, and an external polyurea layer to restore the original shape of the manhole. However, these repairs do not fully restore the manhole’s original load-bearing capacity. A full 3D model, encompassing millions of finite elements, would provide a detailed analysis of strength reductions but is impractical for engineering applications due to computational demands. An alternative approach utilizing sectional homogenization is proposed, where sectional properties are sequentially averaged to calculate effective parameters. This approach enables the use of only a few hundred shell elements, each representing thousands of elements from the detailed 3D model, thus providing a rapid, engineering-level assessment of load-bearing reductions in degraded manholes. The study finds that while the repair method restores up to 76% of bending stiffness in heavily corroded sections, it does not fully recover the original load-bearing capacity. Full article

With the rapid development of marine engineering, effective antifouling and anti-corrosion technologies are essential for ensuring the safety and longevity of marine facilities. This review synthesizes current research on various coating technologies designed to combat marine biological fouling and corrosion. It analyzes the causes of marine biological fouling and corrosion, discusses their potential impacts on the safety of ships and marine structures, and emphasizes the need for effective protective systems. The review covers current antifouling coating technologies, including the preparation of low-surface-energy coatings, conductive coatings, biomimetic coatings, polysiloxane coatings, polyurea coatings, epoxy coatings, polyurethane coatings, and high-entropy alloy coatings. Anti-corrosion coatings are also discussed, with a focus on the characteristics of epoxy, polyurethane, and polyurea coatings, as well as metal-based coatings, alongside their corrosion resistance in marine environments. Based on existing research, the review summarizes ongoing challenges in marine antifouling and anti-corrosion coating technologies, and offers perspectives on future research directions and technological developments. Full article

The main objective of this study is to analyze the impact resistance of aluminum foam composites containing fillers and coatings and to investigate the effect of different thickness ratios of the composites on this capability. We prepared composites using aluminum foam and polyurea and performed impact tests and numerical simulations. A comparison of the results shows that the Abaqus simulation results are in general agreement with the test results. The results show that the polyurea filler material and polyurea coating can significantly improve the impact resistance of the aluminum foam, and the best impact resistance of the aluminum foam composite with polyurea coating on the back. An extended study of the composites was carried out using a numerical model validated by the test results. For the energy absorption effect of the aluminum foam composites in the impact resistance process, there is an optimum value for the thickness ratio of the aluminum foam/polyurea composite, which is 3:1. The remaining kinetic energy of cylindrical fragments in the 3-1-1-2 composite material decreased by 13.26%, in the 4-1-1-2 composite material decreased by 11.91%, in the 2-1-1-2 composite material decreased by 11.78%, and in the 1-1-1-2 composite material increased by 2.7% when compared to the remaining kinetic energy of cylindrical fragments in the control group. The energy absorption efficiency of the aluminum foam composite increases as the residual kinetic energy of the cylindrical fragments decreases. The 3-1-1-2 composite can significantly improve the energy absorption effect, which can be used as a reference for the design of impact-resistant composites in the future. Full article