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In the lining of water conveyance tunnels, the expansion joint is susceptible to leakage issues, significantly impacting the long-term safety of tunnel operations. Polyurea is a type of protective coating commonly used on concrete surfaces, offering multiple advantages such as resistance to seepage, erosion, and wear. Polyurea coatings are applied by spraying them onto the surfaces of concrete linings in water conveyance tunnels to seal the expansion joint. These coatings endure prolonged exposure to environmental elements such as water flow erosion, internal and external water pressure, and temperature variations. However, the mechanism of polyurea coating's long-term leakage prevention failure in tunnel operations remains unclear. This study is a field investigation to assess the anti-seepage performance of polyurea coating in a water conveyance tunnel project located in Henan Province, China. The testing apparatus can replicate the anti-seepage conditions experienced in water conveyance tunnels. An indoor accelerated aging test plan was formulated to investigate the degradation regular pattern of the cohesive strength between polyurea coating and concrete substrates. This study specifically examines the combined impacts of temperature, water flow, and water pressure on the performance of cohesive strength. The cohesive strength serves as the metric for predicting the service lifetime based on laboratory aging test data. This analysis aims to evaluate the polyurea coating's cohesive strength on the tunnel lining surface after five years of operation. [ABSTRACT FROM AUTHOR]

The growing interest in modern polymer materials has targeted research on complex plastic coatings and the possibilities of modifying their features and properties during manufacturing. Today's modern coatings, including polyurea and polyurethane, are among the most modern developed resins. Compared to other polymer coatings, they are distinguished by their versatility, strength, and durability. They undoubtedly represent the next step in the evolution of coatings. Advances in coating technology have also led to the development of spray, injection, and roto-cast application equipment, improving polyurea-based elastomers' performance. For many years, there has been much interest in increasing the flame resistance of polymers. This is dictated by safety considerations and the increasing requirements for the flammability of plastics, the area of application of which is growing every year. This text attempts to provide an overview of current research on flame retardant composites. Particular attention was paid to polyurea (PU) and polyurea-based hybrids and the application areas of polyurea coatings. The paper defines flame retardants, discusses how they work, and presents the types of flame retardants and the current trends of their usage in the production of plastics. [ABSTRACT FROM AUTHOR]

Polyurea coatings are well recognized for their remarkable protective properties, making them highly appropriate for practical use in the field of concrete building. The use of polyurea coatings in the concrete building business is currently constrained, despite its prevalent application in industrialized nations. The limited use may be ascribed to ambiguities about the determinants of effective implementation in this particular setting, as well as the dearth of extensive study in the realm of new building materials. The primary objective of this research is to assess and conceptualize the key determinants linked to the use of polyurea coatings in concrete building endeavors. Utilizing a quantitative research approach, a comprehensive literature analysis was conducted to identify a total of 21 probable success variables. The reliability of the questionnaire was established by the administration of a pilot survey, and afterwards, an exploratory factor analysis (EFA) was performed to enhance the clarity and precision of the underlying components. The researchers used structural modeling (SEM) approaches to develop a robust model using the primary data obtained from the questionnaire survey. The EFA revealed the presence of five unique constructs that have an impact on the effectiveness of polyurea coatings in concrete building projects. These constructions comprise several characteristics, including environmental considerations, functional requirements, protective properties, execution processes, and creative elements. The significance and relevance of this research are shown by the validation of the study's results using SEM. The study makes a valuable contribution towards the progression of polyurea coating use within the concrete building sector.

In the lining of water conveyance tunnels, the expansion joint is susceptible to leakage issues, significantly impacting the long-term safety of tunnel operations. Polyurea is a type of protective coating commonly used on concrete surfaces, offering multiple advantages such as resistance to seepage, erosion, and wear. Polyurea coatings are applied by spraying them onto the surfaces of concrete linings in water conveyance tunnels to seal the expansion joint. These coatings endure prolonged exposure to environmental elements such as water flow erosion, internal and external water pressure, and temperature variations. However, the mechanism of polyurea coating’s long-term leakage prevention failure in tunnel operations remains unclear. This study is a field investigation to assess the anti-seepage performance of polyurea coating in a water conveyance tunnel project located in Henan Province, China. The testing apparatus can replicate the anti-seepage conditions experienced in water conveyance tunnels. An indoor accelerated aging test plan was formulated to investigate the degradation regular pattern of the cohesive strength between polyurea coating and concrete substrates. This study specifically examines the combined impacts of temperature, water flow, and water pressure on the performance of cohesive strength. The cohesive strength serves as the metric for predicting the service lifetime based on laboratory aging test data. This analysis aims to evaluate the polyurea coating’s cohesive strength on the tunnel lining surface after five years of operation.

The growing interest in modern polymer materials has targeted research on complex plastic coatings and the possibilities of modifying their features and properties during manufacturing. Today’s modern coatings, including polyurea and polyurethane, are among the most modern developed resins. Compared to other polymer coatings, they are distinguished by their versatility, strength, and durability. They undoubtedly represent the next step in the evolution of coatings. Advances in coating technology have also led to the development of spray, injection, and roto-cast application equipment, improving polyurea-based elastomers’ performance. For many years, there has been much interest in increasing the flame resistance of polymers. This is dictated by safety considerations and the increasing requirements for the flammability of plastics, the area of application of which is growing every year. This text attempts to provide an overview of current research on flame retardant composites. Particular attention was paid to polyurea (PU) and polyurea-based hybrids and the application areas of polyurea coatings. The paper defines flame retardants, discusses how they work, and presents the types of flame retardants and the current trends of their usage in the production of plastics.

Nowadays, the mitigation of damage to a ship caused by the underwater explosion attracts more and more attention from the modern ship designers. In this study, two kinds of scale tests were conducted to investigate the effects of polyurea coatings on the blast resistance of hulls subjected to underwater explosion. Firstly, small-scale model tests with different polyurea coatings were carried out. Results indicate that polyurea has a better blast resistance performance when coated on the front face, which can effectively reduce the maximum deflection of the steel plate by more than 20% and reduce the deformation energy by 35.7%–45.4%. Next, a full-scale ship (approximately 50 m × 9 m) under loadings produced by the detonation of 33 kg of spherical TNT charges was tested, where a part of the ship was coated with polyurea on the front face (8 mm + 24 mm) and not on the contrast area. Damage characteristics on the bottom were statistically analyzed based on a 3D scanning technology, indicating that polyurea contributes to enhancing the blast protection of the ship. However, damage results of this test were different from those of the small-scale tests. Moreover, the deformation area of the bottom with polyurea was greatly increased by 40.1% to disperse explosion energy, a conclusion that cannot be drown from the small-scale tests.

Polyurea is widely used in marine anti-corrosion engineering because it has the physical advantages of high tensile strength, strong adhesion, excellent waterproof and anti-corrosion performance as well as mature construction technology. In this paper, the origin, characteristics and development direction of polyurea coating technology were first introduced, and then the applications of polyurea coating in the fields of concrete protection and metal protection in marine atmospheric environment and seawater environment in recent years were summarized, respectively. Aiming at the problems of coating performance degradation and failure caused by complex environmental factors such as temperature, corrosive medium erosion and collision during service, the research progress of new polyurea coatings was discussed, including the research on improving the performance of coatings such as corrosion resistance, wetting and hardness with organic and inorganic nanoparticles as fillers, and the research on new polyurea microcapsule coatings that could respond intelligently and repair microcracks independently, and the research on the processing and preparation technology of new self-healing materials such as electrospinning. Finally, the shortcomings and challenges of the current research on polyurea coating were pointed out, and the future research trend of polyurea coating in marine environment was prospected.

Today, polyurea is known as one of the most famous and widely used protective coatings in the world. The unique properties of polyurea are at such a high level that it is possible to use this coating in a wide range of applications. Although polyurea is generally made from the reaction between two types of precursors (diisocyanate and diamine), it is challenging to choose the right precursor pair for producing a coating with a specific application due to the great variety of introduced diisocyanate and diamine precursors. On the other hand, the experimental synthesis of the formulations and the study of their performance is also very costly and time‐consuming. In this study and by examining a series of commercially available precursors for polyurea coatings synthesis, well‐known materials have been introduced and classified. Then, a representative of each formulation family is simulated by a molecular dynamics and mechanical approach using a three‐step method on atomic, meso, and continuum scales, and the mechanical properties of the formulations are extracted. Then, by examining the response of each formulation to the three types of dynamic load (earthquake, projectile impact, and air blast), the protective capabilities of these formulations have been compared, and the optimal formulation for each application has been introduced. [ABSTRACT FROM AUTHOR]

Polyurea coatings are well recognized for their remarkable protective properties, making them highly appropriate for practical use in the field of concrete building. The use of polyurea coatings in the concrete building business is currently constrained, despite its prevalent application in industrialized nations. The limited use may be ascribed to ambiguities about the determinants of effective implementation in this particular setting, as well as the dearth of extensive study in the realm of new building materials. The primary objective of this research is to assess and conceptualize the key determinants linked to the use of polyurea coatings in concrete building endeavors. Utilizing a quantitative research approach, a comprehensive literature analysis was conducted to identify a total of 21 probable success variables. The reliability of the questionnaire was established by the administration of a pilot survey, and afterwards, an exploratory factor analysis (EFA) was performed to enhance the clarity and precision of the underlying components. The researchers used structural modeling (SEM) approaches to develop a robust model using the primary data obtained from the questionnaire survey. The EFA revealed the presence of five unique constructs that have an impact on the effectiveness of polyurea coatings in concrete building projects. These constructions comprise several characteristics, including environmental considerations, functional requirements, protective properties, execution processes, and creative elements. The significance and relevance of this research are shown by the validation of the study's results using SEM. The study makes a valuable contribution towards the progression of polyurea coating use within the concrete building sector., Competing Interests: The authors declare that they do not have any conflict of interest., (© 2024 Published by Elsevier Ltd.)

Abstract The response of composite cylinders to near field underwater explosive (UNDEX) loading, including the effects of polyurea coatings, have been studied through experiments with corresponding computational simulations. Experiments were conducted on woven E-glass/epoxy roll wrapped cylinders in three unique configurations: (1) base composite, (2) base composite with a thin (100% composite thickness) coating, and (3) base composite with a thick (200% composite thickness) coating. Each cylinder configuration was subjected to near field underwater explosive loading in a large diameter test tank at charge standoff distances of 2.54 cm and 5.08 cm. The response of the cylinders on the non-loaded side was evaluated through high speed photography coupled with three-dimensional Digital Image Correlation (DIC). Transient deformation and Post-mortem damage comparisons were made to evaluate the effects of the applied coatings. The LS-Dyna finite element code has been utilized to conduct corresponding computational simulations of the experiments to allow for additional evaluations of the cylinder response. The simulations are shown to provide high correlation to the experiments in terms of pressure loading and final damage mechanisms. Results for the internal / kinetic energy levels and the material strains as determined through the simulations are presented. The experimental and numerical results show that the application of a polyurea coating is effective for significantly reducing damage in the cylinders. It is also shown that there is in increase in both material internal energies as well as overall strains with increasing coating thickness. [ABSTRACT FROM AUTHOR]

• The driving power of osmosis under the polyurea coating. • The relationship between the chemical resistance of a material and its flexibility. • The relationship between the thickness of the polyurea coating and its tightness. • Defects in polyurea applications. • The reasons for the loss of polyurea coatings adhesion to the concrete. The article discusses the use of one of coatings protecting and strengthening concrete surfaces. It is polyurea coatings to strengthen waterproofing in tanks for water and other related liquids. Details of polyurea application technologies for specific tank structures and preparatory works that must be performed before the application of spray polyurea coatings have been discussed, as well as essential points related to minor and major cracks, cover reprofiling, type of coating used in chemically aggressive environments, causes and examples of structures where destructive corrosion processes of concrete surfaces and, consequently, the polyurea coatings covering them have been activated. The presented examples of failures in the application of polyurea coatings arise due to insufficient knowledge about the coatings themselves and the substrate on which the coatings are applied, but above all in failing to follow the strict procedure for their application. [ABSTRACT FROM AUTHOR]

The mitigation of damage to ship hulls due to underwater explosions (UNDEX) has attracted more and more attention. Spraying polyurea on steel plates has been proven to be an effective method. This study investigated the best thickness ratio of polyurea and steel and the ability to absorb energy of polyurea-steel and bare metal by using theoretical analysis. When the Young's modulus of polyurea was in the range of 80 MPa–160 MPa, the best thickness ratio increased from 2.2 to 4.6. Air-backed plate tests were conducted to investigate the influence of spraying thickness and methods of polyurea on the blast resistance, and results were statistically analysed using 3D scanning technology. The final plastic deformation of steel, which had polyurea coated on the front face, was the least out of the three spraying methods. Furthermore, the best protective effect at the smallest areal density was observed when the polyurea sprayed on the front face was three times the thickness of the substrate. This reduced the deformation experimentally and theoretically by 54.5% and 47.4%, respectively. Additionally, the blast resistance of polyurea-steel was not as good as that of bare steel under the same areal density. Finally, a full-scale ship with 8 mm-thickness of bottom steel with a 24 mm-thick polyurea layer was subjected to UNDEX with 33 kg spherical TNT charges. The ability of polyurea to reduce the final plastic deformation of steel is lesser than that in air-backed plate tests. However, the deformation area of the bottom steel with polyurea increased by 40.1% compared to bare metal. • The blast resistance of polyurea-steel plate subjected to underwater explosion is studied. • Blast resistance mechanism of delaying metal necking is proposed for polyurea. • The strength, thickness and spraying method have an impact on the blast resistance. • The capacity of blast resistance of polyurea-steel is lower than that of bare metal. • Differences in performance of polyurea in full ship and laboratory scale tests are evaluated. [ABSTRACT FROM AUTHOR]

An experimental study on the underwater collapse of composite tubes with polymeric coatings is conducted in an attempt to mitigate the implosion pressure pulse released. Experiments are performed in a pressure vessel designed to provide constant hydrostatic pressure during collapse. Filament-wound carbon-fiber/epoxy tubes are studied with polyurea coatings of different thicknesses on the interior and exterior of the tube to explore the effects of these configurations on implosion pulse mitigation. 3-D Digital Image Correlation (DIC) technique is used to capture the full-field deformation and velocities during the implosion event. Local pressure fields generated by the implosion event are measured using dynamic pressure transducers to evaluate the strength of the emitted pressure pulses. Local pressure data and DIC results are used to obtain a measure of normalized energy released during implosion. Results show that thick interior coatings significantly reduce the energy released in the pressure pulse by slowing the collapse and softening the initial wall-to-wall contact. In contrast, thick exterior coatings increase this energy by suppressing damage, thereby reducing the energy absorption capacity of the structure. [ABSTRACT FROM AUTHOR]

An experimental study with corresponding numerical simulations has been conducted to evaluate the response of E-Glass / Epoxy composite plates, including polyurea coating effects, subjected to near field underwater explosion (UNDEX) loading. Experiments are performed in a water filled blast tank in which the including transient plate response during the UNDEX loading is measured utilizing high speed photography coupled with Digital Image Correlation. The experimental results show that the transient response of the plate is improved through the use of a thicker plate or through the application of a polyurea coating, although there is a weight penalty associated with the additional material which should be considered. Corresponding computational models of the experiments have been conducted with the commercial finite element code LS-Dyna. The simulations are shown to have a high level of correlation to the experimental data. [ABSTRACT FROM AUTHOR]

An experimental and numerical study has been conducted to evaluate the underwater blast response of E-Glass/epoxy composite plates with polyurea coatings. The goal of the study is to determine the effects of these elastomeric coatings on the dynamic response of the plates, specifically the influence of coating thickness, location, and plate natural frequency. The composite material is a 0°/90° biaxial layup and the coatings are applied to either the loaded or non-loaded faces. A conical shock tube facility which produces shock loading conditions representative of the underwater detonation of an explosive charge is used to impart the shock loading to the plates during the experiments. The transient response of the plates is recorded using a three-dimensional (3D) digital image correlation system, consisting of high-speed photography and specialized post processing software. Computational models of the experiments are developed using the LS-DYNA finite element code. The simulations are shown to have a high level of correlation to the experimental data in terms of center point displacements and full field deformation profiles. Additional parametric studies using the correlated model show that the transient response of the composite plates is improved with increasing coating thickness, and that polyurea coatings located on the back face of the panels provide better performance than when located on the loaded surface. [ABSTRACT FROM PUBLISHER]

Polyurea is a polymeric material that can be used to provide environmental protection and structural enhancement. In this study, a low modulus polyurea coating, having high elongation, high energy absorption capacities, and a fast gel time, was sprayed under field conditions onto the surfaces of high-performance cementitious composites (). Flexure tests were conducted to measure toughness so that predictions could be made regarding the impact performance of two uncoated and coated matrices, one containing polyvinyl butyral (PVB) as the only aggregate, the other with polyvinyl alcohol (PVA) fibers added for reinforcement. Results from the flexure tests showed that encapsulation by plain polyurea increased the flexural strength of specimens by at least 60%. Results from drop-weight tests showed that the PVA fibers helped to improve impact resistance. A visible reduction in damage was seen when polyurea was applied to one surface, more so by coating the tension side opposite the striker. Coating both surfaces further increased impact resistance. [ABSTRACT FROM AUTHOR]

Abstract: Polyurea is a polymeric material that can be used to provide environmental protection and structural enhancement. In this study, a low modulus polyurea coating, having high elongation and energy absorption capacities and a fast gel time, was sprayed under field conditions onto the surfaces of cementitious materials. Compression tests were conducted to establish the wet–dry performance of uncoated and circumferentially coated cylinders fabricated from a high-performance matrix constructed with Poly(vinyl butyral) (PVB) as the only aggregate. Results showed that the coating increased the compressive strength of specimens exposed to both fresh and sea water environments. Similar results were obtained when a lightweight matrix containing sand was subjected to the same sea water environment. Flexure tests were conducted on uncoated and fully encapsulated plates kept under normal operating conditions to establish the stress–strain behavior of these two matrices, as well as a PVB matrix with Poly(vinyl alcohol) (PVA) fibers added as reinforcement. Results showed that the addition of the fibers and the coating increased the ultimate flexural strength, decreased the stiffness, allowed the structure to sustain higher strains prior to failure, and increased the fracture toughness. Comparisons are made between the performance of lightweight and high-performance concretes. [Copyright &y& Elsevier]

Polyurea is a polymeric material that can be used to provide environmental protection and structural enhancement. In this study, a low modulus polyurea coating, having high elongation, high energy absorption capacities, and a fast gel time, was sprayed under field conditions onto the surfaces of high-performance cementitious composites (). Flexure tests were conducted to measure toughness so that predictions could be made regarding the impact performance of two uncoated and coated matrices, one containing polyvinyl butyral (PVB) as the only aggregate, the other with polyvinyl alcohol (PVA) fibers added for reinforcement. Results from the flexure tests showed that encapsulation by plain polyurea increased the flexural strength of specimens by at least 60%. Results from drop-weight tests showed that the PVA fibers helped to improve impact resistance. A visible reduction in damage was seen when polyurea was applied to one surface, more so by coating the tension side opposite the striker. Coating both surfaces further increased impact resistance. [ABSTRACT FROM AUTHOR]

Michael addition reactions were utilized to form AB2 type monomers and esterified to form polyaspartate esters (PASPE). FTIR and NMR spectroscopic methods indicate that a relatively linear architecture was produced that contrasts with an expected hyperbranched (HB) structure. Linear chains formed due to a reactivity difference between the hydrogen bonded (H-bonded) and non-H-bonded esters. The esterification reaction was directed toward the H-bonded ester as shown by 2D NMR correlation spectroscopy. A model is proposed to explain the observed increase in reactivity of the H-bonded ester. Hydrogen bonding (H-bonding) in both the monomeric and polymeric aspartate (ASP) esters was analyzed by 2D NMR spectroscopy. The difference in chemical shifts of the methylene protons before and after reaction was attributed to the geometrical effects of the five-membered ring formed from H-bonding. Monomeric aspartate esters (ASPE) were found to have the greatest difference in chemical shift, while the in-chain H-bonded protons of the PASPE were observed to have the least difference in chemical environments. Internal H-bonding in the ASPE affected its reaction with an aliphatic isocyanate (NCO) due to varying reactivities of the primary hydroxyl (OH) compared to the secondary amine (NH). Internal hydrogen bonding of the OH groups with the amine may also explain unexpected relative reactivities with isocyanates. Both NMR and FTIR spectroscopy indicated that the OH group was exclusively consumed with no NH reaction product detected. A lack of hydantoin ring formation upon further heating the NCO/ASPE reaction product proved that the OH group was more reactive. In an equimolar reaction of ASPE with cyclohexyl isocyanate, NMR and FTIR measurements showed quantitative formation of the urethane adduct instead of the expected urea. [ABSTRACT FROM AUTHOR]

New polyurea coatings were synthesized using aromatic diphenylmethane diisocyanate, large molecular weight amino-terminated polyether, and appropriate additives. Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy were used to examine the effects of γ-ray irradiation with different dose rates and cumulative doses on the microstructure of the new polyurea coatings. The variations of mechanical properties of the polyurea coatings before and after irradiation were studied using an electronic universal testing machine and a split Hopkinson compression bar. FTIR spectroscopy showed that the raw materials for preparing polyurea coatings had reacted completely, and polyurea had been synthesized. An analysis of the mechanical properties showed that the mechanical behavior of the new polyurea changed gradually from rubbery under a quasi-static load to glassy under a dynamic load, showing excellent impact resistance. The characteristic absorption peaks of the FTIR spectrum of polyurea did not change significantly before and after irradiation. However, the color of the polyurea changed from light yellow to dark red with decreasing dose rate or increasing cumulative dose, which is related to the radiation oxidation time. Some white fragments appeared after the polyurea was irradiated with γ-rays. The number of white fragments increased with decreasing dose rate or increasing cumulative dose, which may be caused by the soft segment embrittlement of polyurea under radiation oxidation. A comparison of the mechanical properties under different γ-ray irradiation conditions found that the newly synthesized polyurea coatings had good resistance to γ-ray radiation. Moreover, their performance was improved to a certain extent after irradiation. The performance of irradiated polyurea was optimum when the irradiation dose rate was 2 KGy/h, and the cumulative dose was 220 KGy. • The impact-resistant and irradiation-resistant polyurea is synthesized. • Quasi-static and dynamic mechanical properties of polyurea are studied. • Effect of γ-ray irradiation on microstructure morphology of polyurea is discussed. • Influence of γ-ray irradiation on the mechanical behavior of polyurea is analyzed. • Optimal irradiation condition for irradiation modification of polyurea is obtained. [ABSTRACT FROM AUTHOR]

Lignin‐containing polyurea coating with good ultraviolet (UV) resistance is prepared by partially substituting polyetheramine with enzymatic hydrolysis lignin. Lignin is first grafted by polyetheramine chains via Mannich reaction, which improves its interfacial compatibility with polyurea matrix. The influences of the modified lignin on the chemical and corrosion resistance, UV‐aging property, and thermal stability of the polyurea coatings are studied. It is demonstrated that lignin‐containing polyurea coatings exhibit excellent UV‐aging properties. Aminating lignin with polyetheramine improves its dispersion in the polymer matrix. This work offers a novel method for the high‐value utilization of biomass lignin in anti‐UV polyurea coatings. [ABSTRACT FROM AUTHOR]