The application of molecular sieves in the drying and dehydration of polyurethane polyol materials is a key step, which is crucial for improving the quality and stability of polyurethane products. The following is a detailed analysis of molecular sieves in this application:

1. Moisture problem in polyurethane polyol materials

Polyurethane polyol materials are highly prone to adsorbing moisture. When the moisture content in the material exceeds 0.05%, bubbles will form in the material, seriously affecting its molding and performance. Therefore, controlling the moisture content in polyol materials is the key to avoiding the generation of bubbles.

2. Limitations of traditional dehydration methods

The traditional dehydration method mainly involves heating and reducing the pressure of polyol components, such as dehydrating oligomeric polyols under high vacuum at 100-120 ℃ for 1-2 hours. However, although this method can remove most of the moisture from the material, experiments have shown that bubbles can still be generated with changes in environmental humidity and temperature.

3. Application advantages of molecular sieves

1) Deep drying: Molecular sieves have strong hydrophilic properties and can adsorb trace amounts of water in materials, achieving deep drying. By adding a small amount of molecular sieve, polyurethane material can be maintained in an anhydrous and dry state for a long time, thereby avoiding the generation of bubbles.

2) Improving product quality: The addition of molecular sieves can not only eliminate bubbles, but also enhance the physical properties of polyurethane products, such as tear resistance, elongation at break, and tensile strength. At the same time, it can also lower the glass transition temperature of the material and broaden its application range.

3) Simplified production process: Compared with traditional methods of temperature and pressure reduction dehydration, adding molecular sieves can simplify the production process and reduce production costs. In addition, the addition of molecular sieves can reduce bubble problems caused by changes in environmental humidity and temperature, and improve the stability and controllability of production.

4. Precautions

1) Selection of molecular sieves: When choosing molecular sieves, factors such as model, particle size, and water absorption should be considered. Different types of molecular sieves have different water absorption properties and applicable ranges, so the selection needs to be based on specific application scenarios.

2) Control of addition amount: The addition amount of molecular sieve needs to be controlled within a certain range. Excessive addition may increase production costs and may affect the synthesis reaction speed and curing time of polyurethane. Therefore, in practical applications, it is necessary to determine the optimal amount of addition through experiments.

3) The quality stability of molecular sieves: If the molecular sieves added to polyurethane elastomers have unstable quality, it may cause impurities and bubbles in some batches of products produced. When the finished material is subjected to external forces, it is easy to crack from the position of bubbles and impurities, seriously affecting the performance and quality of the product. Therefore, it is necessary to ensure the quality stability of molecular sieves to guarantee the quality of polyurethane products.

In summary, the application of molecular sieves in the drying and dehydration of polyurethane polyol materials has significant advantages, which can improve the quality and stability of polyurethane products, simplify production processes, and reduce production costs. However, in practical applications, attention should be paid to the selection of molecular sieves, control of the amount added, and quality stability.