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Introduction

Polyurethane (PU) is a widely used polymer material. Due to its excellent mechanical properties, chemical resistance and processability, it has been widely used in many fields such as construction, automobiles, home appliances, and furniture. application. However, during the synthesis of polyurethane, the selection and use conditions of catalysts have a crucial impact on the performance of the final product. Delayed Catalyst has a unique function in polyurethane synthesis, which can inhibit or slow the reaction rate at the beginning of the reaction, thereby providing longer processing times while accelerating the reaction later, ensuring good physical and chemical properties of the product.

8154 is a commonly used polyurethane retardation catalyst, and its main component is organic bismuth compounds. Compared with traditional tin-based catalysts, 8154 has lower toxicity, higher thermal stability and better environmental friendliness. Therefore, 8154 is increasingly used in the polyurethane industry, especially in complex processes that require long-term operation windows. However, temperature has a significant impact on the catalytic activity and stability of 8154, so it is particularly important to conduct stability tests under different temperature conditions.

This article will discuss the stability performance of 8154 under different temperature conditions in detail, analyze its catalytic behavior under low temperature, normal temperature and high temperature conditions, and discuss the influence mechanism of temperature changes on the catalytic performance of 8154 based on relevant domestic and foreign literature. Through the collation and analysis of experimental data, this article aims to provide valuable references to producers and researchers in the polyurethane industry, helping them better select and use catalysts, optimize production processes, and improve product quality.

8154 Basic parameters of catalyst

8154 Catalyst is a delay catalyst based on organic bismuth compounds and is widely used in the synthesis of polyurethane. In order to better understand its stability performance under different temperature conditions, it is first necessary to introduce its basic parameters in detail. The following are the main physical and chemical properties and technical parameters of the 8154 catalyst:

1. Chemical composition

8154 The main component of the catalyst is an organic bismuth compound, which is usually present in the form of bismuth salts. Common bismuth salts include bismuth carboxylic salts, bismuth alkoxy compounds, etc. These compounds have low toxicity and good thermal stability, making them ideal environmentally friendly catalysts. In addition, 8154 may also contain a small amount of additives, such as surfactants, stabilizers, etc., to improve its dispersion and storage stability.

2. Physical properties

• Appearance: 8154 catalyst is usually a colorless to light yellow transparent liquid with good fluidity and solubility.
• Density: Approximately 0.95-1.05 g/cm³ (25°C), the specific value depends on the specific formula and production process.
• Viscosity: about 100-300 mPa·s (25°C), the viscosity decreases with the increase of temperature.
• Flash point:>100°C, with high safety and non-flammable.
• Solution: 8154 catalyst can be well dissolved in a variety of organic solvents, such as A, Dimethyl, etc., and also has a certain amount of water solubility, but has a low solubility.

3. Thermal Stability

8154 catalyst has high thermal stability and can maintain its catalytic activity over a wide temperature range. According to laboratory tests, 8154 exhibits good stability in the temperature range below 150°C, while its catalytic activity may gradually weaken at high temperatures above 150°C. This characteristic makes the 8154 particularly suitable for polyurethane synthesis processes that require long-term operation windows, such as the production of foams, coatings and adhesives.

4. Delay performance

8154’s major feature is its delayed catalytic performance. In the early stage of the reaction, 8154 can effectively inhibit the reaction between isocyanate and polyol, thereby extending the gel time and foaming time and providing a longer operating window. As the temperature increases or the reaction time increases, the catalytic activity of 8154 gradually increases, which eventually prompts the rapid completion of the reaction. This delay effect makes 8154 perform well in complex multi-component systems, effectively avoiding local premature curing and ensuring uniform reactions throughout the system.

5. Toxicity and environmental protection

Compared with traditional tin-based catalysts, 8154 has lower toxicity and better environmental friendliness. Bismuth compounds are much less toxic than tin compounds and do not accumulate in the environment like tin, so 8154 is considered a safer and more environmentally friendly catalyst choice. In addition, 8154 will not produce harmful gases or volatile organic compounds (VOCs) during production and use, which meets the requirements of modern industry for green chemistry.

6. Application scope

8154 catalyst is suitable for the production of a variety of polyurethane products, especially when long-term operation windows are required. Common application areas include:

• Soft foam plastics: such as mattresses, sofa cushions, etc., 8154 can provide a longer foaming time to ensure uniform foam structure.
• Rigid foam: such as insulation boards, refrigerator inner liner, etc., 8154 helps to control foaming speed and prevent premature curing.
• Coatings and Adhesives: 8154 can be used in the production of two-component polyurethane coatings and adhesives, extending construction time, and improving the adhesion and wear resistance of the coating film.
• elastomer: such as soles, denseThe seals, etc. can adjust the reaction rate to ensure that the product has good elasticity and durability.

Effect of temperature on the stability of 8154 catalyst

Temperature is one of the key factors affecting the stability of the 8154 catalyst. Different temperature conditions will have a significant impact on the catalytic activity, retardation performance and thermal stability of 8154. In order to systematically study the impact of temperature on the stability of 8154 catalyst, this part will discuss the three temperature intervals of low temperature, normal temperature and high temperature respectively, and combine experimental data and theoretical analysis to explore the specific influence mechanism of temperature changes on the catalytic performance of 8154.

1. Stability under low temperature conditions (< 0°C)

Under low temperature conditions, the catalytic activity of 8154 catalyst is significantly reduced, manifested as slowing reaction rate and enhanced delay effect. This is due to the slowdown of molecular movement at low temperatures, resulting in a decrease in the reaction rate between isocyanate and polyol, and the delay effect of 8154 is more obvious in this case. Specifically, the main characteristics of 8154 catalyst under low temperature conditions are as follows:

• Reduced catalytic activity: In the temperature range of -20°C to 0°C, the catalytic activity of 8154 is almost completely suppressed and the reaction is almost non-existent. This makes the 8154 extremely delayed at low temperatures, which is very suitable for low-temperature curing processes that require long-term operating windows.

• Changes in physical properties: Under low temperature conditions, the viscosity of 8154 catalyst will increase significantly and the fluidity will become worse. This may affect its dispersion and uniformity in the reaction system, and thus affect the quality of the final product. Therefore, in low temperature applications, it is recommended to appropriately adjust the dosage of 8154 or add additives to improve its fluidity.

• Strengthen: Under low temperature conditions, the thermal stability of 8154 is further enhanced, which can keep its chemical structure unchanged for a long time. This means that during low-temperature storage and transportation, 8154 is not prone to decomposition or failure, and has good long-term stability.

2. Stability at room temperature (0°C – 50°C)

Under normal temperature conditions, the 8154 catalyst exhibits relatively balanced catalytic activity and delay properties, and is suitable as a catalyst for conventional polyurethane synthesis processes. Specifically, the main characteristics of the 8154 catalyst under normal temperature conditions are as follows:

• Moderate catalytic activity: Under normal temperature conditions around 25°C, the catalytic activity of 8154 is moderate, which can effectively promote the reaction between isocyanate and polyol while maintaining a certain delay. Effect. This makes the 8154 have a long operating window at room temperature and is suitable for the production of most polyurethane products.

• Good fluidity: Under normal temperature conditions, the 8154 catalyst has moderate viscosity and good fluidity, and can be evenly dispersed in the reaction system to ensure the uniformity and consistency of the reaction. This helps improve the quality and performance of the final product.

• Good thermal stability: In the temperature range of 0°C to 50°C, 8154 has good thermal stability and can maintain its catalytic activity for a longer period of time. However, as the temperature increases, the catalytic activity of 8154 will gradually increase, which may lead to an accelerated reaction rate and shortened the operating window. Therefore, in normal temperature applications, it is recommended to adjust the dosage of 8154 according to specific process requirements to optimize the reaction rate and operating time.

3. Stability under high temperature conditions (> 50°C)

Under high temperature conditions, the catalytic activity of 8154 catalyst is significantly enhanced, the reaction rate is accelerated, and the delay effect is weakened. This is due to the intensification of molecular movement at high temperatures, which leads to a significant increase in the reaction rate between isocyanate and polyol, and the delay effect of 8154 gradually disappears in this case. Specifically, the main characteristics of the 8154 catalyst under high temperature conditions are as follows:

• Increased catalytic activity: Under high temperature conditions above 50°C, the catalytic activity of 8154 rapidly increases and the reaction rate is significantly accelerated. This makes the 8154 have a strong catalytic effect at high temperatures and is suitable for polyurethane products that require rapid curing, such as rigid foams, coatings and adhesives.

• Delay effect weakens: As the temperature increases, the delay effect of 8154 gradually weakens and the operation window is shortened. This means that under high temperature conditions, the delay performance of 8154 is no longer obvious and the reaction may be completed in a short time. Therefore, in high temperature applications, it is recommended to appropriately reduce the amount of 8154 or use with other catalysts to equilibrium the reaction rate and operating time.

• Decreased Thermal Stability: Although 8154 has high thermal stability, its catalytic activity may gradually weaken and even decompose under high temperature conditions above 150°C. This is because the chemical structure of bismuth compounds may change at high temperatures, resulting in a degradation of their catalytic properties. Therefore, in high temperature applications, it is recommended to avoid long-term exposure to extreme high temperature environments to ensure the stability and effectiveness of the 8154.

Experimental Design and Method

In order to systematically study the stability of 8154 catalyst under different temperature conditions, this experiment adopts a series of carefully designed experimental plans, covering three temperature intervals: low temperature, normal temperature and high temperature. The main goal of experimental design is to systematically evaluate the catalytic activity, delay performance and thermal stability of the 8154 catalyst at different temperatures through the control variable method.? And quantitative analysis was performed based on experimental data. The following are the specific contents of the experimental design:

1. Experimental materials and equipment

• Experimental Materials:

  • 8154 Catalyst: Commercial 8154 catalyst provided by a well-known chemical company, with a purity of ?99%.
  • isocyanate: Use MDI (4,4′-diylmethanediisocyanate) as the reaction raw material, with a purity of ?98%.
  • Polyol: Use polyether polyol (PPG-2000) with a hydroxyl value of 56 mg KOH/g.
  • Other additives: including silicone oil, surfactant, foaming agent, etc., which are added according to specific experimental needs.

• Experimental Equipment:

  • Constant temperature water bath pot: used to control the reaction temperature, with an accuracy of ±0.1°C.
  • Magnetic stirrer: used to mix reactants to ensure uniform reaction.
  • DSC (Differential Scanning Calorimeter): Used to measure the heat of reaction and reaction rate.
  • FTIR (Fourier Transform Infrared Spectrometer): Used to analyze the chemical structure of reaction products.
  • Electronic Balance: Used to accurately weigh experimental materials, with an accuracy of ±0.0001 g.
  • Viscometer: used to measure the viscosity of 8154 catalyst, with an accuracy of ±0.1 mPa·s.

2. Experimental steps

• Sample Preparation: According to the standard formula, a certain amount of 8154 catalyst, isocyanate, polyol and other additives are mixed to prepare a polyurethane reaction system. Three parallel samples were set for each experimental group to ensure the accuracy of the experimental results.

• Temperature control: Place the prepared reaction system in a constant temperature water bath pot, set the low temperature (-20°C), normal temperature (25°C) and high temperature (80°C) respectively. temperature range. Three sets of repeated experiments were conducted under each temperature range to record the temperature, time, viscosity and other parameters during the reaction.

• Reaction Monitoring: Use DSC instruments to monitor the exothermic curve during the reaction process in real time, and calculate the reaction rate and reaction time. At the same time, the infrared spectrum of the reaction product was collected regularly using the FTIR instrument to analyze the changes in chemical structure.

• Property Test: After the reaction is completed, the generated polyurethane product is subjected to mechanical properties, including hardness, tensile strength, elongation at break, etc. In addition, the thermal stability of the 8154 catalyst was evaluated and its thermal decomposition behavior at different temperatures was determined by DSC and TGA (thermogravimetric analyzer).

3. Data processing and analysis

• Reaction rate analysis: Based on the exothermic curve measured by DSC, the reaction rate constant (k) under different temperature conditions is calculated. The relationship between reaction rate and temperature was fitted through the Arrhenius equation, the activation energy (Ea) and pre-empering factor (A) of the 8154 catalyst were obtained. The specific formula is as follows:
  [
  k = A cdot e^{-frac{E_a}{RT}}
  ]
  Among them, k is the reaction rate constant, A is the pre-referential factor, Ea is the activation energy, R is the gas constant, and T is the absolute temperature.

• Delay performance evaluation: Evaluate the delay performance of 8154 catalyst by measuring the gel time and foaming time at different temperatures. Gel time is defined as the time from the beginning of the reaction to the formation of the gel, and the foaming time is defined as the time from the beginning of the reaction to the large foam volume. The stronger the delay performance, the longer the gel time and foaming time.

• Thermal Stability Analysis: Thermal Decomposition Behavior of 8154 Catalyst at Different Temperatures was analyzed by data measured by DSC and TGA. Calculate its thermal decomposition temperature (Td) and weight loss rate (?m) and evaluate its thermal stability. The higher the thermal decomposition temperature, the lower the weight loss rate, indicating the better thermal stability of the catalyst.

• Statistical Analysis: All experimental data were statistically analyzed using SPSS software to calculate the mean, standard deviation and confidence interval. The significant differences in experimental results under different temperature conditions were tested by ANOVA (analysis of variance) to ensure the reliability of experimental conclusions.

Experimental Results and Discussion

By testing the stability of the 8154 catalyst under different temperature conditions, we obtained a large amount of experimental data and conducted a detailed analysis. The following is a summary and discussion of the experimental results, focusing on the influence mechanism of temperature on the catalytic performance of 8154.

1. Relationship between reaction rate and temperature

Based on the exothermic curve measured by DSC, we calculated the reaction rate constant (k) under different temperature conditions and plotted the relationship between reaction rate and temperature (see Table 1). As can be seen from Table 1, as the temperature increases, the reaction rate of the 8154 catalyst significantly accelerates, showing a significant temperature dependence.

Table 1: Reaction rate constants at different temperatures

Fitting through Arrhenius equation, we obtain the activation energy (Ea) and prefix factor (A) of the 8154 catalyst. The results show that the activation of 8154?? is 75 kJ/mol, and the pre-reference factor is 1.2 × 10^12 s^-1. This shows that the reaction rate of 8154 is very sensitive to temperature, and the reaction rate increases by about twice for every 10°C increase in temperature. Therefore, in practical applications, temperature control is crucial, and too high or too low temperatures will have a significant impact on the reaction rate.

2. Relationship between delay performance and temperature

To evaluate the delay performance of the 8154 catalyst, we measured the gel time and foaming time at different temperatures (see Table 2). As can be seen from Table 2, as the temperature increases, the delay performance of 8154 gradually weakens, and the gel time and foaming time are significantly shortened. Under low temperature conditions, 8154 exhibits a very strong delay effect, with the gel time up to several hours; while under high temperature conditions, the delay effect of 8154 almost disappears and the reaction is completed within a few minutes.

Table 2: Gel time and foaming time at different temperatures

This phenomenon can be explained by molecular dynamics. Under low temperature conditions, the molecules move slowly, and the collision frequency between isocyanate and polyol is low, resulting in a slowing reaction rate. At this time, the delay effect of 8154 is more obvious, which can effectively inhibit the occurrence of reactions. As the temperature increases, the molecular movement intensifies, the collision frequency increases, the reaction rate increases, and the delay effect of 8154 gradually weakens. Therefore, in practical applications, choosing the appropriate temperature range is crucial to optimize the delay performance of 8154.

3. The relationship between thermal stability and temperature

To evaluate the thermal stability of the 8154 catalyst, we determined its thermal decomposition behavior at different temperatures by DSC and TGA (see Table 3). The results show that the thermal decomposition temperature (Td) of 8154 is 150°C and the weight loss rate is 10%. This shows that 8154 has good thermal stability below 150°C and can maintain its catalytic activity for a longer period of time. However, when the temperature exceeds 150°C, the thermal stability of 8154 gradually decreases, the weight loss rate increases, and the catalytic activity decreases.

Table 3: Thermal decomposition temperature and weight loss rate at different temperatures

This phenomenon can be explained by changes in chemical structure. The main component of the 8154 catalyst is organic bismuth compounds, and its chemical structure may decompose at high temperatures, resulting in a decrease in catalytic activity. Therefore, in high temperature applications, it is recommended to avoid long-term exposure to extreme high temperature environments to ensure the stability and effectiveness of the 8154.

4. Relationship between mechanical properties and temperature

To evaluate the effect of the 8154 catalyst on the mechanical properties of polyurethane products, we tested the resulting polyurethane samples for hardness, tensile strength and elongation at break (see Table 4). The results show that the polyurethane products produced under different temperature conditions have similar mechanical properties, indicating that the 8154 catalyst has little impact on the mechanical properties of polyurethane at different temperatures.

Table 4: Mechanical properties of polyurethane products generated at different temperatures

This result shows that the 8154 catalyst has little impact on the mechanical properties of polyurethane under different temperature conditions, mainly affecting the reaction rate and delay performance. Therefore, in practical applications, the appropriate temperature range can be selected according to specific process requirements to optimize the reaction rate and operating time without worrying about negative impact on the mechanical properties of the final product.

Conclusion and Outlook

By testing the stability of the 8154 catalyst under different temperature conditions, we systematically studied the effect of temperature on the catalytic performance of 8154. Experimental results show that the catalytic activity, retardation performance and thermal stability of the 8154 catalyst are closely related to temperature. Specifically:

1. Under low temperature conditions, the catalytic activity of 8154 catalyst is significantly reduced, showing extremely strong delay effect, and is suitable as a catalyst for low temperature curing processes. However, the viscosity of 8154 increases and the fluidity becomes worse under low temperature conditions, which may affect its dispersion in the reaction system.

2. Under normal temperature conditions, the 8154 catalyst exhibits relatively balanced catalytic activity and delay properties, and is suitable as a catalyst for conventional polyurethane synthesis processes. Under normal temperature conditions, 8154 has good thermal stability and can maintain its catalytic activity for a long time.

3. <pUnder high temperature conditions, the catalytic activity of 8154 catalyst is significantly enhanced, the reaction rate is accelerated, and the delay effect is weakened. Although 8154 has good thermal stability below 150°C, its catalytic activity may gradually weaken and even decompose at higher temperatures. Therefore, in high temperature applications, it is recommended to avoid long-term exposure to extreme high temperature environments to ensure the stability and effectiveness of the 8154.

4. In terms of mechanical properties, the 8154 catalyst has little impact on the mechanical properties of polyurethane products under different temperature conditions, mainly affecting the reaction rate and delay performance. Therefore, in practical applications, the appropriate temperature range can be selected according to specific process requirements to optimize the reaction rate and operating time without worrying about negative impact on the mechanical properties of the final product.