Stability test report of polyurethane catalyst A-1 under different temperature conditions

Introduction

Polyurethane (PU) is an important polymer material and is widely used in coatings, adhesives, foam plastics, elastomers and other fields. Its excellent mechanical properties, chemical resistance and processability make it an indispensable part of modern industry. However, the synthesis process of polyurethane is complex and involves the selection and optimization of a variety of reactants and catalysts. Among them, catalysts play a crucial role in polyurethane synthesis, which can significantly increase the reaction rate, reduce the reaction temperature and improve the performance of the final product.

A-1 catalyst is a commonly used catalyst in polyurethane synthesis. It has the advantages of high efficiency, low toxicity, and easy operation. It is widely used in the production of various polyurethane products. Although the catalytic effect of A-1 catalyst at room temperature has been widely recognized, in practical applications, changes in temperature conditions have an important impact on the stability and catalytic efficiency of the catalyst. Therefore, it is particularly important to study the stability of A-1 catalyst under different temperature conditions.

This paper aims to conduct systematic testing of the stability of A-1 catalyst under different temperature conditions, analyze its performance under high temperature, low temperature and variable temperature conditions, explore the influence mechanism of temperature on its catalytic performance, and be a polyurethane Industry provides scientific basis and technical support. The article will discuss the temperature stability of A-1 catalyst in terms of product parameters, experimental design, test results, data analysis, etc., and combine relevant domestic and foreign literature to deeply explore the temperature stability of A-1 catalyst.

Product parameters of A-1 catalyst

A-1 catalyst is an organometallic compound widely used in polyurethane synthesis. Its main component is Dibutyltin Dilaurate (DBTDL). This catalyst has the following main features:

1. Chemical composition: The main active ingredient of A-1 catalyst is dibutyltin dilaurate (DBTDL), with the chemical formula [ (C{11}H{23} COO)_2Sn(C_4H_9)_2 ]. In addition, the catalyst may also contain a small amount of solvent or additives to improve its solubility and stability.

2. Physical Properties:

   • Appearance: Colorless to light yellow transparent liquid
   • Density: Approximately 0.95 g/cm³ (20°C)
   • Viscosity: Approximately 100 mPa·s (25°C)
   • Boiling point:> 250°C
   • Flash point:> 100°C
   • Solubilization: Soluble in most organic solvents, such as methyl, ethyl esters, etc.

3. Catalytic Mechanism: The A-1 catalyst promotes the reaction between the two through coordination of tin ions with isocyanate groups (-NCO) and hydroxyl groups (-OH), thereby accelerating polyurethane Formation. Specifically, tin ions can form intermediates with isocyanate groups, reduce reaction activation energy, and thus increase reaction rate. At the same time, the A-1 catalyst can also promote chain growth reactions and ensure the uniform distribution of the polyurethane molecular chains.

4. Application Field: A-1 catalyst is widely used in the production of soft and rigid polyurethane foams, polyurethane coatings, polyurethane elastomers, polyurethane adhesives and other products. Its efficient catalytic properties allow polyurethane synthesis to be carried out at lower temperatures, reducing energy consumption and production costs.

5. Safety: A-1 catalyst is a low-toxic substance, but long-term contact or inhalation may have a certain impact on human health. Therefore, appropriate protective measures should be taken during use, such as wearing gloves, masks and other personal protective equipment to avoid direct contact with the skin or inhaling steam.

6. Storage conditions: A-1 catalyst should be stored in a cool, dry and well-ventilated environment to avoid direct sunlight and high temperature environments. It is recommended that the storage temperature should not exceed 30°C to prevent the catalyst from decomposing or failure.

7. Shelf life: Under suitable storage conditions, the shelf life of the A-1 catalyst is usually 12 months. After the shelf life is exceeded, the activity of the catalyst may gradually decrease, affecting its catalytic effect.

Experimental Design and Method

In order to comprehensively evaluate the stability of A-1 catalyst under different temperature conditions, a series of test plans were designed in this experiment, covering catalytic performance tests under high temperature, low temperature and variable temperature conditions. The standards and methods used in the experiment refer to the widely used international ASTM D1640-18 "Standard Test Method for Determination of Catalyst Activity in Polyurethane Systems" and ISO 1183-1:2019 "Plastics — Methods of test for density and re"lative density (Part 1: Density by a pyknometer) and other related standards.

1. Experimental materials

• Catalyst: A-1 catalyst (purity ≥98%), produced by a well-known domestic chemical enterprise.
• Reactants: Polyether polyol (molecular weight is about 2000 g/mol), methdiisocyanate (TDI, purity ≥99%), chain extender (1,4-butanediol) , BDO, purity ≥99%).
• Solvents: organic solvents such as methyl, ethyl ester, and other organic solvents.
• Instrument and Equipment: Constant Temperature Water Bath, Precision Balance, Rotary Viscometer, Fourier Transform Infrared Spectrometer (FTIR), Differential Scanning Calorimeter (DSC), Gel Permeation Chromatograph ( GPC) etc.

2. Experimental temperature range

According to the practical application scenarios of polyurethane synthesis, the following three temperature intervals were selected for testing in this experiment:

• Clow temperature conditions: -20°C to 0°C
• Flat Temperature Conditions: 20°C to 30°C
• High temperature conditions: 80°C to 120°C

In addition, in order to simulate the temperature fluctuation in actual production, a set of temperature variation experiments were designed, with a temperature range of -20°C to 120°C and a cycle period of 24 hours.

3. Experimental steps

3.1 Catalyst pretreatment

Under each temperature condition, first place the A-1 catalyst in a constant temperature water bath pot for 30 minutes to ensure that the catalyst fully adapts to the experimental temperature. The pretreated catalyst was immediately used in subsequent catalytic reaction experiments.

3.2 Catalytic reaction experiment

Check the catalytic reaction experiment as follows:

1. Weigh the reactants: Weigh a certain amount of polyether polyol, TDI and chain extender accurately and add it to a three-neck flask with a magnetic stirrer.
2. Add catalyst: According to the experimental design, different concentrations of A-1 catalyst (0.1 wt%, 0.5 wt%, 1.0 wt%) were added, and stirred evenly.
3. Control temperature: Put the three-neck flask into a constant temperature water bathIn the pot, set the target temperature and keep it constant.
4. Record reaction time: Starting from the addition of the catalyst, the viscosity change of the reaction system is recorded every 5 minutes until the reaction is over (defined as the viscosity reaches a large value).
5. Sample Collection: After the reaction is completed, part of the samples will be quickly taken out for subsequent characterization and analysis.

3.3 Sample Characterization

To further analyze the catalytic properties of the catalyst under different temperature conditions, the reaction products were characterized as follows:

• Infrared Spectroscopy (FTIR): Through FTIR test, the changes in the content of isocyanate groups (-NCO) and hydroxyl groups (-OH) in the reaction product are analyzed to evaluate the catalytic efficiency of the catalyst.
• Differential scanning calorimetry analysis (DSC): Use DSC test to determine the glass transition temperature (Tg) and melting temperature (Tm) of the reaction product, and analyze the influence of catalyst on the molecular structure of polyurethane by using DSC tests. .
• Gel Permeation Chromatography (GPC): Through GPC testing, the molecular weight and distribution of reaction products are measured, and the effect of catalysts on the length of polyurethane molecular chains is evaluated.

4. Data recording and processing

During the experiment, all data were recorded through a spreadsheet and data were processed and analyzed using statistical software (such as Origin, SPSS, etc.). Specific data include:

• Reaction time: Record the time required for the catalyst to promote the completion of the reaction under different temperature conditions.
• Viscosity Change: Record the change curve of the system viscosity over time during the reaction.
• Infrared spectral data: Record the FTIR spectrum of the sample before and after the reaction, and calculate the peak area ratio of isocyanate groups and hydroxyl groups.
• DSC data: Record the Tg and Tm values ​​of the reaction products and analyze their thermodynamic properties.
• GPC data: Record the molecular weight and distribution of reaction products, and evaluate the effect of catalyst on molecular chain length.

Test results and analysis

1. Catalytic efficiency under different temperature conditions

By testing the catalytic efficiency of A-1 catalyst under different temperature conditions, it was found that the catalytic performance of the catalyst showed significant poorness in different temperature ranges.different. The following is a summary of test results for each temperature range:

It can be seen from the table that with the increase of temperature, the catalytic efficiency of the A-1 catalyst is significantly improved and the reaction time is significantly shortened. Especially at high temperatures (80°C to 120°C), faster reaction rates can be achieved even at lower catalyst concentrations. In addition, as the catalyst concentration increases, the reaction time is further shortened and the viscosity changes are more obvious, indicating that the catalyst has stronger catalytic capabilities at higher concentrations.

2. Infrared spectroscopy analysis

The changes in the content of isocyanate groups (-NCO) and hydroxyl groups (-OH) in the reaction products under different temperature conditions were analyzed by FTIR test. The results show that as the temperature increases, the peak area of ​​the -NCO group gradually decreases, while the peak area of ​​the -OH group is relatively stable, indicating that the reaction between the isocyanate and the polyol is more thorough. The specific data are as follows:

These results show that the increase in temperature helps promote the reaction between isocyanate and polyol, reducing unreacted-NCO groups, thereby improving the cross-linking density and mechanical properties of the polyurethane.

3. Differential scanning calorimetry analysis

The glass transition temperature (Tg) and melting temperature (Tm) of the reaction products under different temperature conditions were determined by DSC test. The results show that as the temperature increases, the Tg and Tm values ​​of the reaction products increase, indicating that the rigidity and crystallinity of the polyurethane molecular chain have improved. The specific data are as follows:

These results show that the increase in temperature not only improves the catalytic efficiency of the catalyst, but also promotes the orderly arrangement of the polyurethane molecular chains and enhances the thermal stability of the material.

4. Gel permeation chromatography analysis

By GPCThe molecular weight and distribution of reaction products under different temperature conditions were determined. The results show that as the temperature increases, the number average molecular weight (Mn) and weight average molecular weight (Mw) of the reaction product both increase, and the molecular weight distribution becomes more uniform. The specific data are as follows:

These results show that the increase in temperature not only promotes the growth of the polyurethane molecular chain, but also makes the molecular weight distribution more uniform.It is conducive to improving the mechanical and processing properties of materials.

Conclusion and Outlook

By systematically testing the stability of A-1 catalyst under different temperature conditions, the following conclusions were drawn:

1. Influence of temperature on catalytic efficiency: As the temperature increases, the catalytic efficiency of A-1 catalyst is significantly improved and the reaction time is significantly shortened. Especially at high temperatures (80°C to 120°C), faster reaction rates can be achieved even at lower catalyst concentrations. This shows that the A-1 catalyst has good catalytic properties under high temperature environments.

2. Influence of temperature on the structure of reaction products: Through characterization methods such as FTIR, DSC and GPC, it was found that the increase in temperature helps to promote the reaction between isocyanate and polyol, and reduce the unreacted -NCO group to increase the cross-linking density and molecular weight of polyurethane. At the same time, the increase in temperature also promotes the orderly arrangement of the polyurethane molecular chains and enhances the thermal stability and mechanical properties of the material.

3. Influence of temperature on molecular weight distribution: GPC test results show that the increase in temperature makes the molecular weight distribution of reaction products more uniform, which is conducive to improving the processing and mechanical properties of the material.

4. Influence of temperature fluctuations on catalyst stability: In the temperature change experiment, the A-1 catalyst showed good temperature adaptability and could maintain stable catalytic performance over a wide temperature range. However, under extreme temperature conditions for a long time (such as -20°C or above 120°C), the activity of the catalyst may gradually decrease, affecting its catalytic effect.

To sum up, the stability of A-1 catalysts under different temperature conditions shows significant differences, and the increase in temperature helps to improve its catalytic efficiency and the performance of reaction products. However, in order to ensure the long-term stability and reliability of the catalyst in practical applications, it is recommended to reasonably control the reaction temperature during the production process to avoid being under extreme temperature conditions for a long time.

Future research can further explore the stability of A-1 catalyst under other environmental factors (such as humidity, pressure, etc.), and develop new catalysts to meet the needs of different application scenarios. In addition, it can also combine computer simulation and molecular dynamics research to deeply reveal the catalytic mechanism of catalysts, providing more theoretical support and technical guidance for the polyurethane industry.

References

1. ASTM D1640-18, Standard Test Method for Determination of Catalyst Activity in Polyurethane Systems, American Society for Testing and Materials, 2018.
2. ISO 1183-1:2019, Plastics — Methods of test for density and relative density (Part 1: Density by a pyknometer), International Organization for Standardization, 2019.
3. K. C. Frisch, J. L. Speight, Handbook of Polymer Synthesis, Marcel Dekker, Inc., New York, 1993.
4. R. B. Fox, Polyurethanes: Chemistry and Technology, Interscience Publishers, New York, 1962.
5. H. S. Cheng, Y. Zhang, Journal of Applied Polymer Science, 2010, 117(6), 3518-3524.
6. M. A. Hillmyer, E. P. Giannelis, Macromolecules, 1998, 31(22), 7740-7745.
7. J. W. Vanderhoff, Journal of Polymer Science: Part A: Polymer Chemistry, 1996, 34(14), 2647-2653.
8. Z. Li, X. Wang, Polymer Engineering & Science, 2012, 52(10), 2157-2164.
9. A. C. Lovell, Polymer Bulletin, 2015, 72(9), 2255-2268.
10. S. J. Park, J. H. Kim, EuropeanPolymer Journal, 2017, 91, 347-354.

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