Application of polyurethane composite antioxidants in the construction of rail transit facilities

Polyurethane composite antioxidants: escort the construction of rail transit

1. Introduction: A battle against time

In the modern industry, the aging problem of materials is like an inevitable competition for time. Whether it is automotive tires, building exterior walls, or plastic parts in electronic equipment, over time, these materials lose their original properties due to oxidation. In rail transit facilities, this aging problem is like a "invisible killer", quietly threatening the safety and stability of train operations.

Polyurethane (PU) as a high-performance polymer material plays an indispensable role in rail transit facilities. From the seats in the car to the shock absorbing pads on the tracks to the waterproof coating in the tunnel, the polyurethane figure is everywhere. However, polyurethane itself is not a "indestructible body". It will also be affected by factors such as oxygen, ultraviolet rays and high temperatures, resulting in performance degradation and even failure. At this time, polyurethane composite antioxidants became the "guardian" in this time competition.

So, what are polyurethane composite antioxidants? How can it play a role in the construction of rail transit facilities? Next, we will explore this mysterious but important field of materials science in an easy-to-understand language. At the same time, we will also unveil the veil of polyurethane composite antioxidants through rich tabular data and domestic and foreign literature references.

2. Polyurethane composite antioxidants: definition and classification

(I) What is polyurethane composite antioxidant?

Polyurethane composite antioxidant is a chemical additive specially designed to protect polyurethane materials from oxidative degradation. Simply put, its task is to delay or prevent the aging caused by exposure to oxygen or other environmental factors during use of polyurethane materials. This is like putting a "protective jacket" on polyurethane, allowing it to maintain its original performance for a longer period of time.

Depending on the mechanism of action, polyurethane composite antioxidants are mainly divided into the following two categories:

Main antioxidant
The main antioxidant acts to directly capture free radicals, thereby interrupting the chain reaction. Common primary antioxidants include amines and phenolic compounds. They are like "fire extinguishers", quickly extinguishing the "flame" caused by oxidation.
Auxiliary antioxidants
Auxiliary antioxidants are responsible for decomposing peroxides and reducing the formation of free radicals. Such antioxidants generally include thioesters and phosphite compounds. If the main antioxidant is a "frontline fighter", then the auxiliary antioxidant is a "logistics support force", and the two can achieve good results by working together.

(II) Advantages of composite antioxidants

Although a single type of antioxidant is effective, it often has limitations. For example, some primary antioxidants may gradually fail due to excessive volatility; while some secondary antioxidants may be sensitive to specific environmental conditions. Therefore, scientists have developed "compound antioxidants" - products that mix multiple antioxidants in a certain proportion. This composite formula not only gives full play to the advantages of each component, but also makes up for each other's shortcomings, thereby achieving longer-lasting and more comprehensive antioxidant protection.

Antioxidant Types	Functional Features	Common Representatives
Main antioxidant	Catch free radicals	BHT, Irganox 1076
Auxiliary Antioxidants	Decomposition of peroxides	DNP, Tinuvin 292

By reasonably matching different types of antioxidants, composite antioxidants can meet the needs of various complex working conditions in rail transit facilities. For example, adding composite antioxidants to polyurethane foam seats used in high-speed train compartments can not only extend their service life, but also ensure that passengers' comfort during riding is not affected.

III. Application of polyurethane composite antioxidants in rail transit

(I) Rail shock absorption system: Make trains more stable

In rail transit, rail shock absorbing systems are a crucial component. It effectively reduces noise and improves passengers' riding experience by absorbing the vibration and impact forces generated when the train is running. Polyurethane elastomers are one of the ideal materials for manufacturing track shock absorbers.

However, due to long-term exposure to outdoor environments, track shock absorbers are susceptible to UV radiation and humid and hot climates, which accelerate the aging process. At this time, polyurethane composite antioxidants are particularly important. It can significantly improve the weather resistance and fatigue resistance of polyurethane elastomers, so that the track shock absorber can maintain a stable working state even under harsh conditions.

Material location	User scenarios	Compound antioxidant effect
Rail shock absorber	High-speed railway	Improving weather resistance and fatigue resistance

(II) Interior of the car: Create a safe and comfortable ride environment

Add to a modern lineYou will find that there are a large number of parts made of polyurethane materials, such as seats, floor coverings and ceiling decorative panels. These components not only need to have good physical and mechanical properties, but also must comply with strict fire and flame retardant standards.

To meet the above requirements, engineers will add an appropriate amount of composite antioxidant to the polyurethane raw material. In this way, even after years of use, the interior of the car can still maintain bright colors and soft feel, while not releasing harmful substances that harm passengers' health.

Application Scenario	Additional range (wt%)	Main effects
Seat Foam	0.3-0.5	Extend life and improve feel
Floor Covering	0.2-0.4	Prevent cracking and enhance wear resistance

(III) Tunnel waterproof coating: resists underground moisture erosion

For underground rail transits such as subways and light rails, tunnel waterproofing is a technical problem that cannot be ignored. Once the waterproof layer is damaged or failed, it will not only cause water seepage problems to affect the normal operation of the train, but may also endanger the safety of the entire tunnel structure.

Polyurethane coatings have become the first choice material in tunnel waterproofing projects due to their excellent adhesion and sealing properties. In order to further improve its durability, construction workers usually add composite antioxidants to the coating formulation. The advantage of this is that even in high humidity and low ventilation environments, the waterproof coating can still maintain good elasticity and toughness, truly achieving "no leakage".

Projects	Using Phase	Antioxidant concentration recommendations
Subway Tunnel	Initial Construction	0.5 wt%
Long-term maintenance	Later fix	0.8 wt%

IV. Domestic and foreign research progress and technical parameters

(I) International Research Trends

In recent years, with the rapid expansion of rail transit networks around the world, scientific research institutions and enterprises in various countries have increased their investment in research on polyurethane composite antioxidants. For example, BASF, Germany, recommendedA new product called Irgastab® PU 28 has been released, designed for polyurethane rigid foam with excellent antioxidant and environmentally friendly properties.

At the same time, DuPont is also actively developing a new generation of multifunctional composite antioxidants. Their goal is to create a new additive that can both delay material aging and enhance mechanical properties. At present, this study has achieved initial results and has been practically applied in some high-end rail transit projects.

(II) Current domestic development status

In my country, the research and development of polyurethane composite antioxidants has also achieved remarkable achievements. A group of scientific research institutions represented by the Institute of Chemistry, Chinese Academy of Sciences have successfully developed a series of high-performance composite antioxidants suitable for the field of rail transit through the optimized combination of different types of antioxidants.

In addition, many well-known domestic companies are also actively participating in technological innovation in this field. For example, the HBA series composite antioxidants launched by Nanjing Hongbaoli Group have won wide recognition in the market for their excellent cost-effectiveness and stable quality.

Company Name	Product Model	Feature Description
BASF	Irgastab® PU 28	High-efficiency, antioxidant, green and environmentally friendly
Nanjing Red Baoli	HBA-200	High cost-effectiveness and strong applicability

(III) Key Performance Indicators

Whether in the international or domestic market, an excellent polyurethane composite antioxidant needs to meet the following performance indicators:

Antioxidation efficiency
Key parameters for measuring whether antioxidants can effectively delay material aging. It is usually evaluated by measuring the thermal weight loss rate of the sample at high temperatures.
Compatibility
Ensure that the antioxidant can be evenly dispersed in the polyurethane matrix without causing problems such as phase separation or surface precipitation.
Migration
Control the speed of antioxidants moving from the inside to the outside of the material to avoid degradation of protection due to excessive loss.
Toxicity and Environmental Protection
While meeting functional requirements, try to chooseSelect low-toxic or even non-toxic raw materials to meet increasingly stringent environmental protection regulations.

Performance metrics	Test Method	Reference value range
Antioxidation efficiency	Thermogravimetric analysis method	≥90%
Compatibility	Microscopy Observation	No obvious stratification
Migration	Simulation Experiment	≤0.1 wt%/year

5. Future development trends and prospects

With the continuous advancement of science and technology, the application prospects of polyurethane composite antioxidants in the field of rail transit will be broader. On the one hand, the emergence of new materials and new processes will promote the continuous innovation of antioxidant technology; on the other hand, the development trend of intelligence and greenness will also bring more opportunities and challenges to this industry.

For example, future composite antioxidants may combine nanotechnology and biobased materials to achieve higher efficiency and lower environmental burden. At the same time, predictive maintenance technology based on big data analysis is also expected to be introduced into rail transit facility management, making the use of antioxidants more accurate and efficient.

In short, polyurethane composite antioxidants, as an important tool to ensure the safe and reliable operation of rail transit facilities, will continue to play an irreplaceable role in future urban development. Let us wait and see and witness the wonderful transformation in this field together!