Polyurethane metal catalyst is used in the construction of rail transit facilities to improve the durability of the facilities

admin 3月 18th, 2025 News

Application of polyurethane metal catalysts in the construction of rail transit facilities

1. Introduction: Make the track stronger and make the future better

In today’s society, rail transit has become the “artery” of the development of modern cities and countries. Whether it is a subway, light rail or high-speed rail, these modes of transportation not only connect every corner of the city, but also shorten the distance between people. However, with the increase in usage frequency and the changes in environmental conditions, the durability problem of rail transit facilities has gradually emerged. Just as a car needs regular maintenance, rail transit facilities need to have higher anti-aging capabilities to cope with the challenges brought by complex climatic conditions and long-term operation.

Polyurethane materials have been widely used in many fields due to their excellent performance, and in the construction of rail transit facilities, they have shown unique value. By adding specific metal catalysts, polyurethane can further enhance its physical properties and chemical stability, thereby significantly enhancing the durability of rail transit facilities. The application of this technology is like putting a layer of “protective armor” on the track, allowing it to better withstand the erosion and mechanical wear of the external environment.

This article will discuss the application of polyurethane metal catalysts in the construction of rail transit facilities. First, we will introduce the basic characteristics of polyurethane and the mechanism of action of metal catalysts; second, we will analyze in detail how polyurethane metal catalysts can improve the durability of rail transit facilities; then, based on actual cases and domestic and foreign research results, we will explore the future development prospects of this technology. I hope this article will not only provide reference for industry insiders, but also allow more people to understand this seemingly “low-key” but crucial technology.

2. Basic knowledge of polyurethane and the mechanism of action of metal catalysts

(I) Definition and Characteristics of Polyurethane

Polyurethane (PU) is a polymer compound produced by the reaction of isocyanate and polyol. It has a wide range of uses, from soft foams to rigid foams to elastomers and paints, covering almost every aspect of our daily lives. The reason why polyurethane is so popular is mainly due to the following key characteristics:

High strength and flexibility: Polyurethane can be made into hard solid materials, and can also form soft elastomers, which are highly adaptable.
Excellent wear resistance: This makes it an ideal choice for manufacturing parts such as wheels, conveyor belts, etc.
Good chemical corrosion resistance: Polyurethane shows high resistance to most chemicals and is suitable for use in harsh environments.
Excellent thermal insulation performance: In the construction and industrial fields, polyurethane foam is widely used as a thermal insulation material.

In the construction of rail transit facilities, polyurethane is usually used in track shock absorber pads, sound insulation barriers, and vehicle interiors. For example, the shock absorption system at the bottom of high-speed trains uses a large number of polyurethane materials to reduce the vibration and noise generated during the train’s operation.

(Bi) Mechanism of action of metal catalysts

Although polyurethane itself already has many advantages, in order to meet the needs of higher standards, scientists have introduced metal catalysts to optimize their performance. Metal catalysts are a class of substances that accelerate chemical reactions without participating in the formation of end products. In the process of polyurethane synthesis, commonly used metal catalysts include tin, bismuth, zinc and their compounds.

The following are several important roles of metal catalysts in the preparation of polyurethane:

Promote crosslinking reactions: Metal catalysts can speed up the crosslinking reaction between isocyanate and polyol, thereby shortening the production cycle and improving product quality.
Improving mechanical properties: By adjusting the type and dosage of catalysts, the structure of the polyurethane molecular chain can be controlled, and its mechanical indicators such as tensile strength and tear strength can be optimized.
Enhance weather resistance: Some metal catalysts can effectively inhibit the occurrence of ultraviolet degradation and oxidation reactions, making polyurethane materials more durable.
Reduce toxicity: In recent years, the research and development of environmentally friendly metal catalysts has made significant progress, greatly reducing the environmental pollution problems that traditional catalysts may bring.

Table 1 shows the main characteristics and scope of application of several common metal catalysts:

Catalytic Type	Features	Scope of application
Tin-based catalyst	Strong activity, significant effect	Rigid foam, elastomer
Bissium-based catalyst	Environmentally friendly and non-toxic, with good stability	Food Contact Grade Products
Zinc-based catalyst	Low cost and simple process	Ordinary soft foam

By reasonably selecting and matching different metal catalysts, engineers can customize suitable polyurethane material formulas according to specific application scenarios.

III. How to improve the durability of rail transit facilities?

(I) Strengthen structural performance and extend service life

Rail transit facilities are facing the test of a variety of complex working conditions, such as impact force caused by high-speed driving, friction loss caused by frequent start-up and thermal expansion and contraction caused by temperature difference in the four seasons. In this case, ordinary materials are often difficult to handle, while polyurethanes modified with metal catalysts show excellent comprehensive performance.

First, metal catalysts can significantly increase the mechanical strength of polyurethane. Studies have shown that after adding an appropriate amount of tin-based catalyst, the tensile strength of polyurethane can be increased by about 20%, while maintaining good flexibility. This means that even under extreme conditions, such as heavy-duty train passing or seismic wave impact, the polyurethane can still maintain a stable shape and avoid damage caused by excessive deformation.

Secondly, metal catalysts can also enhance the fatigue resistance of polyurethane. This is especially important for track components that are under dynamic load for a long time. Experimental data show that after 100,000 cycles of loading, the fracture surface of the polyurethane sample treated with bismuth-based catalyst is still smooth and flat, showing extremely high reliability.

(II) Resist environmental erosion and ensure safe operation

In addition to mechanical properties, durability is also reflected in the material’s ability to adapt to the surrounding environment. Rail transit facilities are often exposed to various adverse factors such as rainwater, salt spray, direct sunlight, etc. If appropriate measures are not taken, it is likely to cause the material to age or even fail.

Luckily, polyurethane metal catalysts also play a huge role in this regard. For example, zinc-based catalysts can effectively prevent moisture from penetrating into the polyurethane by forming a dense protective film, thereby delaying the occurrence of hydrolysis reactions. In addition, some new environmentally friendly catalysts also have the function of absorbing ultraviolet rays, further improving the service life of polyurethane in outdoor environments.

Table 2 lists the effects of different metal catalysts on polyurethane weather resistance:

Catalytic Type	Resistance to hydrolysis	UV resistance	Overall evaluation
Tin-based catalyst	Medium	Winner	Economic and practical
Bissium-based catalyst	Strong	Medium	Performance balance
Zinc-based catalyst	Strong	Strong	First choice for environmental protection

It can be seen that each catalyst has its own unique advantages, and the pros and cons must be weighed according to actual needs when selecting it.

(III) Reduce maintenance costs and create economic benefits

From an economic perspective, the use of polyurethane metal catalysts can not only improve the quality of rail transit facilities, but also significantly reduce post-maintenance costs. Traditional track shock absorber pads usually use rubber products. Although the initial investment is low, due to their poor durability, they need to be replaced every few years, increasing operating costs. The shock absorber pad modified with polyurethane metal catalyst can achieve a stable service period of more than ten years, significantly reducing the replacement frequency.

Take a subway line in a certain city as an example, the budget for replacing shock absorbing pads was about 5 million yuan per year, but after switching to a polyurethane metal catalyst solution, it is expected to save nearly 70% of the expenses. Such economic benefits undoubtedly bring great appeal to rail transit operators.

4. Current status and typical case analysis of domestic and foreign research

(I) Progress in foreign research

The research on polyurethane metal catalysts in developed European and American countries started early and achieved a series of important results. For example, BASF, Germany has developed a highly efficient catalyst based on bismuth elements, specially used for waterproof coatings in high-speed rail track systems. This catalyst not only has excellent catalytic efficiency, but also fully complies with the requirements of the EU REACH regulations, ensuring harmless to human health and ecological environment.

At the same time, DuPont, the United States, has also made outstanding contributions to the preparation of polyurethane elastomers. They used nanoscale zinc particles as catalysts to successfully develop an ultra-wear-resistant track guard plate material with a service life of more than twice that of traditional products. This technology has been applied to many intercity railway projects and has received unanimous praise from users.

(II) Overview of domestic development

Although my country’s research on polyurethane metal catalysts started a little later, it has developed rapidly in recent years, gradually narrowing the gap with the international advanced level. The team from the Department of Chemical Engineering of Tsinghua University proposed a composite catalyst formula to address the corrosion protection problem of high-speed rail tunnel inner walls, which can quickly cure the polyurethane coating under normal temperature conditions, greatly simplifying the construction process.

In addition, the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences has also made a breakthrough – they invented a self-healing polyurethane material, the key component of which is a special design metal catalyst. When tiny cracks appear on the surface of the material, the catalyst will trigger internal chemical reactions, automatically fill the damaged area, and restore the original function. This technology has been piloted in some subway station decoration projects.

(III) Sharing of typical cases

Case 1: Beijing Metro Line 16

Beijing Metro Line 16 is an important north-south backbone line in Beijing.It is about 50 kilometers long. During its construction process, the construction unit used polyurethane shock absorbing pads containing bismuth-based catalysts for the first time. Practice has proved that this new material not only effectively reduces train operation noise, but also significantly improves the overall stability of the track system and has won high recognition from residents along the route.

Case 2: Guizhou section of Shanghai-Kunming High-speed Railway

The Shanghai-Kunming High-speed Railway is a high-speed railway in the east and west directions of China, with a total length of more than 2,000 kilometers. Among them, the Guizhou section has a complex terrain and a variable climate, which puts forward extremely high requirements for track facilities. To this end, engineering and technical personnel specially selected a polyurethane waterproof layer containing zinc-based catalyst, which successfully solved the problem of water leakage in mountain tunnels and ensured the safe and smooth operation of the train.

5. Future prospects and development suggestions

With the advancement of science and technology and the changes in social demand, there is still broad room for development for the application of polyurethane metal catalysts in the construction of rail transit facilities. The following points are worth paying attention to:

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Green Environmental Protection Concept: Continue to deepen the research on environmentally friendly catalysts, strive to achieve zero emission goals, and contribute to sustainable development.
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In short, polyurethane metal catalysts, as an efficient and flexible technical means, are profoundly changing the development pattern of the rail transit industry. I believe that with the continuous improvement of relevant theories and technologies, it will surely bring us a more convenient, safe and comfortable travel experience.

6. Conclusion: Be down to earth and move towards the future

The construction of rail transit facilities is a huge and complex systematic project, and every detail concerns the overall performance. The introduction of polyurethane metal catalysts is like adding bricks and tiles to this magnificent building, which not only lays a solid foundation, but also reserves infinite possibilities for future innovation. Let us look forward to the fact that in the near future, this technology will bear fruit globally and help human civilization move towards a more glorious tomorrow!