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Polyurethane adhesives are an important component of polyurethane resins, which are seeing rapid development at present. They possess excellent properties and are widely used in many areas; they are one of the eight major types of synthetic adhesives. Polyurethane adhesives exhibit excellent shear strength and impact resistance, making them suitable for various structural bonding applications. They also possess outstanding flexibility. Polyurethane adhesives possess excellent rubber-like properties, enabling them to bond substrates with different coefficients of thermal expansion. They form a soft-to-hard transition layer between substrates; this not only ensures strong adhesion but also provides superior cushioning and shock-absorbing capabilities. The low-temperature and ultra-low-temperature performance of polyurethane adhesives exceeds that of all other types of adhesives. Water-based polyurethane adhesives feature low VOC content, low or no environmental pollution, and non-flammability, making them a key development direction for polyurethane adhesives. The diversity of polyurethane adhesives provides solutions to many bonding challenges, and they are particularly suitable for applications where other types of adhesives cannot bond or have difficulty bonding. In addition, polyurethane adhesives also possess characteristics such as adjustable toughness, simple bonding process, excellent low-temperature resistance, and good stability. It is precisely because of the excellent adhesive properties of polyurethane adhesives and their adaptability to bonding various substrates that their application areas continue to expand. In recent years, they have become the fastest-growing type of adhesive both domestically and internationally. 1. Polyurethane adhesives for automobiles: The use of large amounts of lightweight metals, composite materials, and plastics in new automobile designs has led to a continuous increase in the demand for adhesives and sealants used in vehicles. The polyurethane adhesives most widely used in automobiles include single-component, moisture-curing polyurethane sealants for assembling windshields; structural adhesives for bonding glass fiber reinforced plastics and sheet molding composites, two-component polyurethane adhesives for interior components, as well as water-based polyurethane adhesives. Automotive interior components are also a sector where the use of adhesives is increasing. For a fairly long period in the past, China’s automotive industry relied on importing polyurethane windshield adhesive from abroad. It wasn’t until the Eighth Five-Year Plan period that the research and development of this adhesive was included as a **key scientific and technological project**. Aqueous polyurethane adhesives, which are widely used in automobiles, refer to adhesives formed by dissolving or dispersing polyurethane in water. Most water-based polyurethanes are linear thermoplastic polyurethanes; due to the lack of cross-linking in their film layers and their low molecular weight, they exhibit poor properties such as water resistance, solvent resistance, and film strength. Therefore, it is necessary to modify them in order to improve their performance. Automobile repair varnishes prepared using hybrid dispersions of polyester and acrylic along with uretdiones and isocyanurates require no high-speed mixing equipment; they mix easily together and possess good adhesion properties. 2. Polyurethane adhesives for wood: With the rapid decline of global forest resources and the implementation of projects aimed at protecting natural forests in China, when small pieces of wood are combined to form larger boards, it is necessary that the adhesives possess bonding strength as well as durability and resistance to weathering that are superior to those of the wood itself. The amount of adhesive used has become an indicator of the technological development level of the wood industry. In the past, the wood adhesives used were mainly urea-formaldehyde resins based on formaldehyde, phenol-formaldehyde resins, and melamine-formaldehyde resins. However, due to the presence of free formaldehyde, these products would gradually release formaldehyde gas into the surrounding environment over time, causing environmental pollution. The wood processing industry has begun to turn its attention to the new, environmentally friendly adhesive polyurethane, in an effort to reduce environmental pollution. The single-component moisture-curing polyurethane adhesives used in the woodworking industry are liquid and are used at room temperature. It generally has high adhesion strength, good flexibility and water resistance, and can bond with many non-wood substrates (such as textile fibers, metals, plastics, rubber, etc.). The dry and wet strengths exhibited by the one-component polyurethane adhesive in the tests were both better than those of the phenolic adhesive. Applying a hydroxymethylresorcinol (HMR) coupling agent to the surface of the substrate before bonding can improve the bonding strength; HMR can enhance the bonding strength of all thermosetting wood adhesives. When the wood surface is pre-coated with an HMR coupling agent, the strength and durability of one-component polyurethane adhesives can meet most stringent testing requirements. 3. Polyurethane adhesives for shoes: China is a major shoe-manufacturing country. After three generations of development, the growing global awareness of environmental protection and the worsening oil crisis have led to the emergence of the fourth generation of eco-friendly, solvent-free and water-based adhesives for shoes. In recent years, the production process of water-based polyurethanes has become increasingly mature. For bonding some low-polarity shoe materials such as SBS, the peel strength of polyurethane adhesives does not meet the required standards. By modifying them with tackifying resins and other materials, polyurethane adhesives for shoes can be developed that exhibit high crystallinity, fast crystallization speed, high cohesive strength, and satisfactory peel strength. 4. Polyurethane adhesives for packaging. Soft packaging, also known as soft cans, has surpassed hard packaging such as plastic bottles and glass jars due to its unique comprehensive advantages, including light weight and convenience, long shelf life, hygiene, ease of storage and transportation, simplicity in opening, reduced waste generation, and good shelf effect. Due to their excellent properties, polyurethane adhesives can bond film materials with different properties together to produce composite films for flexible packaging that possess various characteristics such as cold resistance, oil resistance, chemical resistance, transparency, and wear resistance. Currently, in both domestic and international markets, polyurethane adhesives have become the primary adhesives used in the processing of composite films for flexible packaging. In the domestic adhesive market, within the manufacturing industry of packaging composite films, polyurethane adhesives are used in the second highest volume, after those used in the shoe-making industry. There are a wide variety of polyurethane adhesives used for packaging, such as water-based polyurethane adhesives, hot-melt polyurethane adhesives, solvent-based polyurethane adhesives, and solvent-free polyurethane adhesives. The commonly used polyurethane hot-melt adhesives can be further divided into 2 categories: 1) thermoplastic polyurethane elastomer hot-melt adhesives; 2) reactive hot-melt adhesives. The main drawback of thermoplastic hot melt adhesives is their high viscosity, which has a significant impact on the apparent quality of the coating. Reactive polyurethane hot-melt adhesives are a new type of adhesive developed on the basis of traditional hot-melts. They not only possess the advantages of traditional hot-melts, such as good initial adhesion and excellent post-curing properties, but also benefit from the versatility of polyurethane’s structural composition and its wide range of adjustable properties, enabling them to provide strong bonding strength to a variety of substrates. Furthermore, in terms of water-based polyurethane adhesives used for packaging, their water resistance is reduced due to the use of emulsifiers or the introduction of hydrophilic ionic groups in their molecules; as a result, research aimed at improving their water resistance has become a focus in recent years. At the same time, due to water’s high heat capacity, finding ways to increase its solid content in order to speed up the drying process is also one of the pressing issues that need to be addressed. 5. Polyurethane adhesives for construction: In addition to being non-toxic, pollution-free, and easy to use, polyurethane adhesives possess advantages that other adhesives cannot match, namely excellent resistance to low temperatures, solvents, aging, ozone, and bacteria. They play an important role in the application of construction flooring materials. It is widely used in elastic rubber mats, rigid rubber tiles, and sports fields with plastic running tracks. The new two-component polyurethane adhesive overcomes the contradiction between shear strength and peel strength associated with traditional adhesives, enabling both properties to reach high levels simultaneously. It exhibits excellent performance in bonding steel plates used in construction, providing strong adhesion without causing deformation. Moreover, its curing speed can be adjusted at room temperature, making this polyurethane adhesive easy to use and suitable for a wide range of applications. Polyurethane adhesives are widely used in bonding PVC materials for construction, in the production of sandwich panels, and in building waterproof coatings. 6. Polyurethane adhesives for inks: Water-based inks are considered the preferred choice for environmentally friendly printing. Water-based polyurethane adhesives that cure at room temperature can be used to produce single-component water-based polyurethane inks suitable for gravure printing. These inks are resistant to water in high-gloss areas, offer strong adhesion, allow for adjustable drying times, have vibrant colors and clear color gradients, are non-toxic and non-flammable, weather-resistant, and have a consistency that is easy to control. Compared with other water-based inks, they exhibit broad compatibility with various substrate materials. As a binder in water-based inks, polyurethane-polyacrylate combines the properties of polyurethane adhesives and polyacrylates; the emulsion obtained through this modification also exhibits good adhesion to films during the drying process of ink-coated films. The base films used in the color printing industry mainly include polyester film, nylon film, polypropylene film, polyethylene film, etc. The key to choosing ink is that it must have good adhesion to all these types of base films. A new type of polyurethane adhesive can be prepared by reacting a vinyl chloride-hydroxyethyl acrylate copolymer containing hydroxyl groups with macromolecular diols, small molecular chain extenders, and toluene diisocyanate; this adhesive can effectively improve the quality of color printing inks. 7. Polyurethane adhesives for book binding: Over the past 20 years, the use of hot-melt adhesives in book binding has seen rapid development. The main reason is the astonishing growth in the production of low-cost paperback books; simultaneously, a binding process without covers was developed. Due to its excellent adhesion and elasticity, EVA hot melt adhesive is currently used in the vast majority of book bindings in the domestic market. However, EVA hot melt adhesives are expensive, and they have drawbacks such as memory effect. Polyurethane hot-melt adhesives can overcome the aforementioned shortcomings. These adhesives have a simple production process and low costs; they possess good elasticity and toughness, as well as high bonding strength. They can be melted and reused repeatedly, resulting in high product utilization rates, and thus they offer broader application prospects. 8. Applications in railway construction: For the installation of ballastless tracks (the development direction of high-speed rail technology), domestic polyurethane adhesives will be used primarily. A convex retaining block is inserted every 5 meters along the monorail track; approximately 17.8 kg of polyurethane adhesive is required on each side of each retaining block. For the construction of one kilometer of ballastless dual-track railway, more than 7 tons of polyurethane adhesive are needed. In addition to railway construction, the production of high-speed trains has also **increased the demand for polyurethane adhesives. Polyurethane plays various essential roles in trains, such as bonding glass, securing floors, filling gaps, and providing waterproofing. In EMUs based on the CRH3 model, each car uses approximately 84.07 liters of polyurethane adhesive, which is equivalent to around 109.3 kg; this adhesive is mainly used for sealing window glass and for sealing certain filler areas. 9. Others: Due to their excellent bonding properties, polyurethane adhesives are playing an increasingly important role in areas such as the bonding of aerospace components, the preservation and restoration of cultural artifacts, the military industry, stationery, and healthcare. Polyurethane adhesives are widely used in various fields due to their excellent properties, and are increasingly becoming important synthetic materials in human life. Currently, the global polyurethane adhesive industry is evolving to meet requirements related to environmental protection, safety and hygiene, as well as resource recycling. China’s polyurethane adhesive industry has also shown rapid growth, with significant progress being made in technology development. With the gradual expansion of polyurethane’s applications and the growing environmental awareness among humans.