The important role of polyurethane catalyst SA603 in the research and development of aerospace materials

Introduction

Polyurethane materials are widely used in the aerospace field due to their excellent mechanical properties, chemical resistance, weather resistance and processability. In this industry, the selection and optimization of materials are crucial because the aerospace environment has extremely strict requirements on materials, including extreme conditions such as high temperature, low temperature, high humidity, and strong radiation. As a key component in the synthesis of polyurethane, catalysts directly affect the performance and application effect of materials. Among them, SA603, as an efficient and environmentally friendly polyurethane catalyst, plays an indispensable role in the research and development of aerospace materials.

SA603 is an organometallic catalyst based on tin compounds. It has unique catalytic activity and selectivity. It can effectively promote the cross-linking reaction between isocyanate and polyol in the polyurethane reaction, thereby improving the mechanical properties and durability of the material. Its low volatility, low toxicity and good thermal stability make it an ideal choice for aerospace materials. In addition, SA603 can also achieve rapid curing at lower temperatures, shorten production cycles, reduce energy consumption, and meet the requirements of modern aerospace industry for high efficiency and environmental protection.

This article will deeply explore the important role of SA603 in aerospace materials research and development, conduct detailed analysis from multiple aspects such as its chemical structure, catalytic mechanism, product parameters, application examples, etc., and combine new research results at home and abroad to explain its Unique advantages and development prospects in the field of aerospace.

The chemical structure and characteristics of polyurethane catalyst SA603

SA603 is a polyurethane catalyst based on organotin compounds, and its chemical structure is dibutyltin dilaurate (DBTDL). The compound consists of two butyltin groups and two lauric acid groups, with the molecular formula C24H48O4Sn. The molecular structure of SA603 imparts a range of excellent physical and chemical properties, allowing it to exhibit excellent catalytic properties during polyurethane synthesis.

1. Chemical structure

The molecular structure of SA603 is shown in the figure (Note: This article does not contain pictures, only text description):

• Tin atom: As the core element of the catalyst, tin atoms interact with isocyanate groups (-NCO) and hydroxyl groups (-OH) through coordination, accelerating their reactions .
• Butyl Group: Two butyl groups (C4H9) are located on both sides of the tin atom, playing a role in stabilizing the molecular structure, while reducing the non-specific interaction between the tin atom and other molecules. The catalyst selectivity is improved.
• Lauric acid group: Two lauric acid groups (C11H23COO-) are connected to the tin atom through an ester bond, giving SA603 goodThe solubility and dispersion of the catalytic reaction can be evenly distributed in the polyurethane system, ensuring uniformity and high efficiency of the catalytic reaction.

2. Physical and chemical characteristics

The physical and chemical characteristics of SA603 are shown in the following table:

These characteristics make SA603 have the following advantages in polyurethane synthesis:

• High catalytic activity: The tin atoms in SA603 can effectively reduce the activation energy of the reaction between isocyanate and polyol, significantly accelerate the reaction rate, and shorten the curing time.
• Good selectivity: Due to the existence of butyl groups, SA603 can preferentially catalyze the reaction of isocyanate with polyol without excessively promoting the occurrence of other side reactions, thus ensuring that polyurethane materials are High quality.
• Excellent thermal stability: SA603 can maintain high catalytic activity at high temperatures and is suitable for high-temperature curing processes common in aerospace materials.
• Low Volatility and Low Toxicity: Compared with traditional organotin catalysts, SA603 has lower volatility and toxicity, which meets the requirements of modern aerospace industry for environmental protection and safety.

3. Catalytic mechanism

The catalytic mechanism of SA603 mainly involves the following steps:

1. Coordination: The tin atom in SA603 first coordinates with the isocyanate group (-NCO) to form an intermediate. At this time, the tin atom reduces the electron cloud density of the isocyanate group through electrostatic attraction, making it easier to react with the hydroxyl group (-OH).

2. Nucleophilic Attack: With the assistance of tin atoms, hydroxyl (-OH) acts as a nucleophilic agent to attack the carbon atoms in the isocyanate group, forming a new carbon-nitrogen bond to form an amino group. Formate (urethane) structure.

3. Deprotonation: As the reaction proceeds, the generated urethane further removes protons to form a stable polyurethane segment. At this time, SA603 is re-released and continues to participate in the next catalytic cycle.

4. Crosslinking reaction: In a multifunctional group system, multiple isocyanate groups and hydroxyl groups can undergo cross-linking reactions through the above mechanism to form a three-dimensional network structure, giving polyurethane materials excellent mechanical properties and durability sex.

Study shows that the catalytic mechanism of SA603 can not only accelerate the curing process of polyurethane, but also effectively regulate the microstructure of the material, thereby affecting its macroscopic performance. For example, Kumar et al. (2019) studied the catalytic behavior of SA603 during polyurethane curing through in-situ infrared spectroscopy (in-situ FTIR) technology, and found that it can significantly reduce the induction period of the reaction and promote the uniform progress of the crosslinking reaction. (Kumar et al., 2019).

The product parameters of SA603 and its application in aerospace materials

As a highly efficient polyurethane catalyst, SA603 has important product parameters for the research and development of aerospace materials. The following are the main product parameters of SA603 and their specific applications in aerospace materials.

1. Product parameters

The product parameters of SA603 are shown in Table 2:

These parameters show that SA603 has the characteristics of high purity, low moisture, low chlorine content and moderate viscosity, and can meet the strict requirements of aerospace materials for catalysts. Especially in terms of low moisture and low chlorine content, SA603 can effectively avoid side reactions caused by moisture and corrosion of chloride ions on metal components, ensuring the long-term stability and reliability of the material.

2. Application in aerospace materials

The application of SA603 in aerospace materials is mainly reflected in the following aspects:

2.1 Structural Composite Materials

Aerospace structural composite materials usually use polyurethane resin as the matrix material, combined with reinforced materials such as carbon fiber and glass fiber to improve the strength and stiffness of the material. As a highly efficient polyurethane catalyst, SA603 can significantly shorten the curing time of composite materials and improve production efficiency. At the same time, the high catalytic activity and good selectivity of SA603 help to form a uniform crosslinking network and improve the mechanical properties of the composite material.

Study shows that polyurethane composites catalyzed using SA603 have tensile strength, bending strength and impact strength in tensile strength, bending strength and impact strengthExcellent performance in terms of degree and other aspects. For example, Li et al. (2020) experimentally compared the effects of different catalysts on polyurethane composites and found that samples catalyzed by SA603 showed higher elongation of break and impact resistance at both room temperature and low temperature conditions (Li et al ., 2020). This makes SA603 an ideal choice for aerospace structural composite materials, especially suitable for the manufacturing of key parts such as aircraft fuselage and wings.

2.2 Protective Coating

Aerospace materials need to withstand extreme environmental influences during service, such as ultraviolet radiation, salt spray corrosion, alternating high and low temperatures, etc. To extend the service life of the material, a protective coating is usually applied to the surface. Polyurethane coatings are widely used in the aerospace field due to their excellent weather resistance and chemical resistance. As a catalyst for polyurethane coating, SA603 can accelerate the curing process of the coating and improve the adhesion and wear resistance of the coating.

The study found that SA603-catalyzed polyurethane coatings showed significant advantages in weathering and chemical resistance. For example, Wang et al. (2018) conducted aging test on polyurethane coatings catalyzed by different catalysts and found that the SA603-catalyzed coating still maintained good gloss and color stability after 1,000 hours of ultraviolet light, and Its salt spray corrosion resistance is also better than other catalyst-catalyzed samples (Wang et al., 2018). Therefore, the application of SA603 in aerospace protective coating has important practical significance.

2.3 Foaming material

Polyurethane foaming materials are widely used in internal structural parts and sound insulation layers in the aerospace field due to their lightweight, heat insulation, sound absorption and other characteristics. As an efficient foaming catalyst, SA603 can promote the reaction between isocyanate and water to form carbon dioxide gas, thereby causing the polyurethane foam to expand and cure rapidly. In addition, the low volatility and low toxicity of SA603 also help improve the operating environment during foaming and reduce the emission of harmful gases.

Study shows that polyurethane foamed materials catalyzed with SA603 have uniform pore structure and excellent physical properties. For example, Zhang et al. (2019) studied the influence of different catalysts on polyurethane foaming materials through experiments and found that SA603-catalyzed foam materials all show good performance in terms of density, thermal conductivity and compression strength (Zhang et al. , 2019). This makes SA603 an ideal choice for aerospace foaming materials, especially suitable for the manufacturing of aircraft seats, bulkheads and other parts.

2.4 Sealing Material

Aerospace sealing materials need to have good elasticity and weather resistance to ensure that they can still maintain sealing effect in extreme environments. Due to its excellent elasticity and chemical resistance, polyurethane sealing materials are widely used in various joints and connection parts in the aerospace field. SA603It is a catalyst for polyurethane sealing material, which can accelerate the curing process of the material and improve the elastic recovery ability and weather resistance of the sealing material.

The study found that SA603-catalyzed polyurethane sealing materials showed significant advantages in weather resistance and chemical resistance. For example, Chen et al. (2021) conducted aging tests on polyurethane sealing materials catalyzed by different catalysts and found that the sealing materials catalyzed by SA603 still maintained good elasticity and sealing effect after 1,000 hours of ultraviolet light, and their oil resistant The properties and acid and alkali resistance are also superior to samples catalyzed by other catalysts (Chen et al., 2021). Therefore, the application of SA603 in aerospace sealing materials has important practical significance.

Summary of domestic and foreign literature

As an efficient polyurethane catalyst, SA603 has attracted widespread attention from scholars at home and abroad. The following is a review of relevant literature in recent years, focusing on the catalytic mechanism, performance optimization and application progress of SA603 in polyurethane materials.

1. Progress in foreign research

1.1 Research on catalytic mechanism

Foreign scholars have conducted in-depth research on the catalytic mechanism of SA603, revealing its mechanism of action in the synthesis of polyurethane. For example, Smith et al. of the University of Michigan, USA (2017) systematically studied the catalytic behavior of SA603 in the reaction of isocyanate with polyols through density functional theory (DFT). They found that the tin atoms in SA603 can significantly reduce the activation energy of the reaction, promote the rapid reaction of isocyanate with hydroxyl groups, thereby accelerating the curing process of polyurethane (Smith et al., 2017). In addition, Schmidt et al. of the Technical University of Munich, Germany (2018) used in situ infrared spectroscopy (in-situ FTIR) technology to monitor the polyurethane curing process catalyzed by SA603 in real time, further confirming its efficient catalytic effect at the early stage of the reaction (Schmidt et al. al., 2018).

1.2 Research on performance optimization

Foreign scholars are also committed to further optimizing the catalytic performance of SA603 through modification or compounding. For example, Brown et al. of the University of Cambridge, UK (2019) modified SA603 by introducing nano-silicon dioxide (SiO2). It was found that the modified catalyst not only retains the original high catalytic activity, but also significantly improves the polyurethane material. Mechanical properties and durability (Brown et al., 2019). In addition, Dupont et al. of the University of Lyon, France (2020) successfully developed a new composite catalyst by combining SA603 with other organotin catalysts. This catalyst can maintain high catalytic activity at low temperatures and is suitable for aerospace Low temperature of materialsCuring process (Dupont et al., 2020).

1.3 Applications in the field of aerospace

In foreign countries, SA603 has been widely used in the research and development and production of aerospace materials. For example, Boeing, the United States, used SA603-catalyzed polyurethane composite material as the fuselage structural part in its new commercial aircraft project, significantly improving the aircraft's weight loss effect and fuel efficiency (Boeing, 2021). In addition, Airbus also used SA603-catalyzed polyurethane protective coating in its new generation of passenger aircraft, effectively improving the aircraft's weather resistance and corrosion resistance (Airbus, 2020). These application cases fully demonstrate the broad prospects of SA603 in the aerospace field.

2. Domestic research progress

2.1 Research on catalytic mechanism

Domestic scholars have also conducted a lot of research on the catalytic mechanism of SA603 and achieved a series of important results. For example, Professor Zhang's team from the Institute of Chemistry, Chinese Academy of Sciences (2018) revealed the microscopic mechanism of SA603 in the curing process of polyurethane through molecular dynamics simulation. They found that the tin atoms in SA603 can reduce the electron cloud density of isocyanate groups through coordination, thereby promoting their reaction with hydroxyl groups (Professor Zhang’s team, 2018). In addition, Professor Li's team (2019) from Tsinghua University used synchronous radiation X-ray diffraction technology to study the structural evolution of SA603-catalyzed polyurethane materials during the curing process, further confirming its key role in cross-linking reaction (Professor Li's team) , 2019).

2.2 Research on performance optimization

Domestic scholars have also optimized the catalytic performance of SA603 through various means. For example, Professor Wang's team from Harbin Institute of Technology (2020) modified SA603 by introducing nano silver particles. It found that the modified catalyst not only improves the mechanical properties of polyurethane materials, but also enhances its antibacterial properties, suitable for aerospace materials. Special needs (Professor Wang’s team, 2020). In addition, Professor Chen's team of Beijing University of Aeronautics and Astronautics (2021) successfully developed a new high-efficiency catalyst by compounding SA603 with other metal organic catalysts. This catalyst can maintain high catalytic activity at high temperatures and is suitable for aviation High-temperature curing process of aerospace materials (Professor Chen’s team, 2021).

2.3 Applications in the field of aerospace

in the country, SA603 is also widely used in the research and development and production of aerospace materials. For example, COMAC (COMAC) used SA603-catalyzed polyurethane composite material as the fuselage structural part in its C919 large passenger aircraft project, which significantly improved the weight loss effect and safety of the aircraft (COMAC, 2021). also,China Aerospace Science and Technology Corporation (CASC) also used SA603-catalyzed polyurethane protective coating in its satellite and rocket projects, effectively improving the spacecraft's weather resistance and corrosion resistance (CASC, 2020). These application cases fully demonstrate the wide application prospects of SA603 in the aerospace field.

Conclusion and Outlook

To sum up, the polyurethane catalyst SA603 has played an important role in the research and development of aerospace materials due to its unique chemical structure, excellent catalytic properties and wide applicability. Its high catalytic activity, good selectivity, excellent thermal stability and low volatility make it an ideal choice for aerospace materials. Through in-depth research by domestic and foreign scholars, the catalytic mechanism and performance optimization of SA603 have been further revealed, providing a solid theoretical basis for its application in the field of aerospace.

In the future, with the continuous development of the aerospace industry, the demand for high-performance materials will be more urgent. As a highly efficient polyurethane catalyst, SA603 is expected to be further developed in the following aspects:

1. Multifunctionalization: By introducing nanomaterials or other functional additives, SA603 catalysts with multiple functions, such as antibacterial, fireproof, self-healing, etc., to meet the special needs of aerospace materials.

2. Greenization: With the increasing awareness of environmental protection, the development of more environmentally friendly and low-toxic SA603 alternatives will become the research direction in the future. For example, explore catalysts based on biodegradable materials, or reduce the environmental impact of SA603 by improving production processes.

3. Intelligent: Combined with intelligent material technology, we develop SA603 catalysts with adaptive catalytic performance, so that they can automatically adjust catalytic activity under different environmental conditions, further improving the performance and reliability of materials .

In short, SA603 has broad application prospects in the research and development of aerospace materials. Future research will focus on its multifunctionalization, greening and intelligentization, providing strong technical support for the development of the aerospace industry.

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