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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]

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%e45.4%. 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 þ 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. [ABSTRACT FROM AUTHOR]

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]

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]

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]