Polyurethane rigid foam (PU rigid foam) is a high-performance insulation material and is widely used in construction, home appliances, refrigeration equipment and other fields. Its excellent thermal insulation properties, lightweight properties and mechanical strength make it an indispensable and important material in modern industrial and architectural fields. However, with the continuous improvement of the market’s requirements for product quality, traditional polyurethane hard foams have gradually exposed some problems in terms of durability, such as aging, embrittlement, poor dimensional stability, etc. These problems not only affect the service life of the product, but may also lead to safety hazards and economic losses.

In order to improve the durability of polyurethane rigid foam, the selection and optimization of catalysts have become one of the key factors. Catalysts play a crucial role in the polyurethane foaming process. They can control the reaction rate, regulate the foam structure, and ultimately affect the physical properties and chemical stability of the foam. Although traditional catalysts can meet basic foaming needs, they have limitations in improving foam durability. Therefore, the development of new catalysts to improve the durability of polyurethane rigid foam has become a hot topic in research.

Polyurethane delay catalyst 8154 (hereinafter referred to as “8154”) has attracted widespread attention in the polyurethane industry in recent years. Compared with traditional catalysts, 8154 has unique delay characteristics, which can inhibit the reaction rate at the initial stage of foaming and then gradually release the activity, ensuring that the reaction reaches its peak at the right time. This property not only helps to form a more uniform foam structure, but also significantly improves the durability of the foam. This article will discuss in detail the contribution of 8154 catalyst to the durability of polyurethane rigid foam, and analyze its mechanism of action, application effect and future development trends based on new research results at home and abroad.

8154 Basic parameters and characteristics of catalyst

8154 Catalyst is a delay catalyst designed for polyurethane rigid foams with unique chemical composition and physical properties. The following are the main parameters and technical characteristics of the 8154 catalyst:

1. Chemical composition

8154 The main component of the catalyst is organometallic compounds, usually containing metal elements such as tin, bismuth, zinc, etc. These metal ions bind to the organic ligand through coordination bonds to form a stable chelate structure. The specific chemical formula can vary according to different manufacturers and formulas, but common chemical ingredients include:

• organotin compounds: For example, dilaury dibutyltin (DBTDL), has strong catalytic activity and can promote the reaction between isocyanate and polyol.
• Organic bismuth compounds: such as acetylbismuth (Bi(acac)3), which has low toxicity and is suitable for food contact applications.
• organozinc compounds: such as octanol zinc (Zn(OA)2), can provide good delay effect while maintaining high catalytic efficiency.

2. Physical properties

8154 The physical properties of the catalyst are crucial to its performance during the polyurethane foaming process. The following are the main physical parameters of the 8154 catalyst:

3. Delay characteristics

8154 catalyst is characterized by its delay characteristics. Unlike traditional fast catalysts, 8154 can inhibit the reaction rate at the beginning of foaming and avoid premature crosslinking reactions leading to uneven foam structure. Specifically, the delay mechanism of the 8154 catalyst can be divided into two stages:

• Initial delay stage: In the early stage of foaming, the 8154 catalyst has a lower activity and a slow reaction rate. The delay time of this stage is usually 10-30 seconds, depending on the type and amount of other additives in the formula.
• Later acceleration stage: After the initial delay, the 8154 catalyst gradually releases activity, promoting the reaction between isocyanate and polyol, causing the foam to expand and cure rapidly. The reaction rate at this stage is faster, usually within 60-120 seconds.

This delay characteristic allows the 8154 catalyst to better control the reaction rate during the foaming process, avoiding premature or late reactions, thereby forming a more uniform and dense foam structure.

4. Environmental performance

With the increase in environmental awareness, the environmental performance of catalysts has also attracted more and more attention. The 8154 catalyst performs well in this regard and has the following advantages:

• Low Volatility: The 8154 catalyst has extremely low volatility and produces almost no harmful gases. It complies with the EU REACH regulations and the US EPA standards.
• Low toxicity: Compared with traditional organic tin catalysts, the 8154 catalyst has a lower metal ion content and uses safer organic ligands, which reduces the harm to the human body and the environment. .
• Biodegradable: Some organic ligands of catalysts have certain biodegradability,?It can gradually decompose in the natural environment and reduce the long-term impact on the ecosystem.

8154 Mechanism of Action of Catalyst

The 8154 catalyst can play an important role in improving the durability of polyurethane rigid foams mainly due to its unique delay characteristics and precise regulation of reaction kinetics. The following is a detailed analysis of the action mechanism of 8154 catalyst in the polyurethane foaming process:

1. Regulation of reaction rate

In the process of polyurethane foaming, the reaction rate between isocyanate and polyol directly affects the structure and performance of the foam. Traditional fast catalysts will cause too severe reactions, which are prone to problems such as uneven foam expansion and excessive bubble size, which will affect the mechanical strength and durability of the foam. Through its delay characteristics, the 8154 catalyst can suppress the reaction rate in the early stage of foaming and avoid premature crosslinking reactions, thus providing sufficient time for uniform expansion of the foam.

Specifically, the delay mechanism of 8154 catalyst is mainly reflected in the following aspects:

• Initial delay stage: In the early stage of foaming, the 8154 catalyst has a lower activity and a slow reaction rate. At this time, the amount of gas generated in the foam system is small and the foam expansion rate is slow, which is conducive to the formation of a small and uniform bubble structure.
• Later acceleration stage: After the initial delay, the 8154 catalyst gradually releases activity, promoting the reaction between isocyanate and polyol, causing the foam to expand and cure rapidly. The reaction rate at this stage is relatively fast, which can effectively prevent foam from collapsing or over-expansion and ensure the stability and density of the foam structure.

2. Optimization of foam structure

Foam structure is one of the key factors that determine the durability of polyurethane rigid foam. The ideal foam structure should be small, uniform, and high closed cell ratio, which can provide better insulation performance, mechanical strength and dimensional stability. By regulating the reaction rate, the 8154 catalyst can form a more uniform and dense foam structure during the foaming process, thereby improving the durability of the foam.

Study shows that the polyurethane rigid foam prepared using 8154 catalyst has a small average bubble diameter, moderate bubble wall thickness and high cellulose ratio. This not only helps to improve the insulation performance of the foam, but also effectively prevents moisture and air penetration and extends the service life of the foam. In addition, the 8154 catalyst can also reduce microcracks and defects in the foam, further improving the mechanical strength and impact resistance of the foam.

3. Improvement of chemical stability

In addition to the optimization of physical structure, the 8154 catalyst can also improve its durability by improving the chemical stability of the foam. During long-term use, polyurethane hard foam may be affected by factors such as ultraviolet rays, oxygen, moisture, etc., resulting in aging, embrittlement and even decomposition of the material. By regulating the reaction kinetics, the 8154 catalyst can form more stable chemical bonds inside the foam, thereby improving the anti-aging properties of the foam.

Specifically, the 8154 catalyst can promote the cross-linking reaction between isocyanate and polyol, forming more urea and aminomethyl ester bonds. These chemical bonds have high thermal stability and oxidation resistance, which can resist erosion from the external environment to a certain extent and extend the service life of the foam. In addition, the 8154 catalyst can also reduce the occurrence of side reactions and avoid the generation of excessive low molecular weight by-products, thereby improving the overall chemical stability of the foam.

4. Improvement of dimensional stability

Dimensional stability is one of the important indicators for measuring the durability of polyurethane rigid foam. In practical applications, foam materials may be affected by factors such as temperature changes and humidity fluctuations, resulting in changes in size, which in turn affects its performance. 8154 catalyst can improve the dimensional stability of the foam to a certain extent by optimizing the foam structure and chemical stability.

Study shows that the polyurethane rigid foam prepared using 8154 catalyst exhibits good dimensional stability under high temperature and high humidity environment. This is mainly because the 8154 catalyst can promote the formation of a denser crosslinking network inside the foam, reducing the penetration of moisture and gas, thereby preventing the foam from expanding or shrinking in extreme environments. In addition, the 8154 catalyst can also reduce the water absorption rate of the foam, reduce the impact of moisture on the foam structure, and further improve its dimensional stability.

Experimental verification of the durability of 8154 catalyst on polyurethane rigid foam

In order to verify the improvement of the durability of 8154 catalyst on polyurethane rigid foam, many research institutions at home and abroad have conducted a large number of experimental research. The following are some representative experimental results and their analysis.

1. Experimental method

The experiment was conducted using standard polyurethane rigid foam foaming process, and compared tests were performed using 8154 catalyst and traditional catalysts (such as sin cinia). The experimental conditions are as follows:

• Raw Materials: Polyether polyol, MDI (diylmethane diisocyanate), foaming agent (HFC-245fa), surfactant (silicon oil)
• Catalyzer: 8154 catalyst (experimental group), sin cinia (control group)
• Foaming temperature: 60°C
• Foaming time: 120 seconds
• Sample size: 100mm × 100mm × 50mm

After the experiment, several performance tests were performed on the prepared foam samples, includingDensity, compression strength, thermal conductivity, water absorption, dimensional stability, etc.

2. Experimental results

(1)Density and Compression Strength

Table 1 shows the density and compression strength data of polyurethane rigid foam prepared under different catalyst conditions.

It can be seen from Table 1 that the density of the foam samples prepared using the 8154 catalyst is slightly lower than that of the control group, but the compression strength is significantly higher than that of the control group. This shows that the 8154 catalyst can promote the formation of a denser crosslinking network inside the foam, thereby increasing the mechanical strength of the foam.

(2) Thermal conductivity

Table 2 shows the thermal conductivity data of polyurethane rigid foams prepared under different catalyst conditions.

It can be seen from Table 2 that the foam samples prepared with 8154 catalyst have a lower thermal conductivity, which indicates that their thermal insulation performance is better. This is mainly because the 8154 catalyst can promote the formation of a more uniform and tiny bubble structure inside the foam, reducing the heat conduction path.

(3) Water absorption

Table 3 shows the water absorption data of polyurethane rigid foams prepared under different catalyst conditions.

It can be seen from Table 3 that the water absorption rate of foam samples prepared using 8154 catalyst is significantly lower than that of the control group. This shows that the 8154 catalyst can reduce microcracks and defects in the foam, prevent moisture penetration, and thus improve the waterproof performance of the foam.

(4) Dimensional stability

Table 4 shows the dimensional changes of polyurethane rigid foam prepared under different catalyst conditions under high temperature and high humidity environment.

It can be seen from Table 4 that the foam samples prepared using the 8154 catalyst exhibit better dimensional stability under high temperature and high humidity environments, with smaller dimensional changes. This is mainly because the 8154 catalyst can promote the formation of a denser crosslinking network inside the foam, reducing the penetration of moisture and gas, thereby preventing the foam from expanding or shrinking in extreme environments.

3. Results Analysis

Combining the above experimental results, the following conclusions can be drawn:

• 8154 catalyst can significantly enhance the mechanical strength of polyurethane rigid foam, especially in terms of compression strength. This is because the 8154 catalyst can promote the formation of a denser crosslinking network inside the foam, reducing microcracks and defects.
• 8154 catalyst-made foam has better thermal insulation properties and has a lower thermal conductivity. This is mainly because the 8154 catalyst can promote the formation of a more uniform and fine bubble structure inside the foam, reducing the heat conduction path.
• 8154 catalyst can significantly reduce the water absorption rate of foam and improve its waterproof performance. This is because the 8154 catalyst can reduce microcracks and defects in the foam and prevent moisture from penetration.
• 8154 Catalyst foams have better dimensional stability in high temperature and high humidity environments, and have smaller dimensional changes. This is because the 8154 catalyst can promote the formation of a denser crosslinking network inside the foam, reducing moisture and gas penetration.