Polyether polyol functionality on its performance?

Polyether polyol is an important polyurethane raw material, which is widely used in coatings, adhesives, foams and other fields. Its performance characteristics are closely related to its chemical structure, and functionality (that is, the number of hydroxyl groups in the molecule) is one of the key factors affecting its performance. In this paper, the influence of the functionality of polyether polyol on its performance will be analyzed in detail from the aspects of molecular structure, physical properties and chemical properties.

1. The effect of functionality on the molecular structure of polyether polyols

The functionality of polyether polyols directly determines the complexity of their molecular structure. In general, the higher the functionality, the greater the number of hydroxyl groups in the molecular chain and the stronger the intermolecular hydrogen bonding. This hydrogen bonding can increase the cohesion of the material, thereby affecting the physical and chemical properties of the material.

For example, a polyether polyol having a functionality of 2, such as polypropylene glycol, has a simple molecular structure, weak intermolecular forces, and exhibits low viscosity and reactivity. However, polyether polyols with a functionality of 4 or 6 (such as polytetrapropylene glycol or polyhexapropylene glycol) exhibit higher viscosity and stronger crosslinking ability due to their complex molecular structure.

The functionality also affects the molecular weight and molecular chain flexibility of the polyether polyol. High functionality polyether polyols typically have a higher molecular weight, giving the material better mechanical strength and durability.

2. Effect of functionality on physical properties of polyether polyols

The functionality of polyether polyols has a significant effect on their physical properties. Here are a few key aspects:

2.1 viscosity

The higher the functionality, the stronger the intermolecular hydrogen bonding of polyether polyol, the more complex the molecular structure, resulting in the increase of its viscosity. For example, a polyether polyol having a functionality of 6 typically has a higher viscosity at room temperature than a comparable product having a functionality of 2. This change in viscosity has an important effect on the processability and reactivity of the material.

2.2 reactivity

During the preparation of polyurethanes, the hydroxyl groups of polyether polyols react with isocyanates to form urea linkages. The higher the functionality, the more hydroxyl groups that can participate in the reaction process, thereby increasing the crosslinking density of the material. Too high a functionality may result in too rapid a reaction, making it difficult to control the reaction process, and may even initiate side reactions.

2.3 mechanical properties

The functionality of the polyether polyol affects the mechanical properties of the polyurethane material from which it is formed. Polyether polyols with high functionality can form a denser cross-linked network, thereby improving the hardness, strength and wear resistance of the material. However, too high a functionality may also cause the material to become brittle, affecting its toughness.

3. Effect of functionality on chemical properties of polyether polyols

The functionality also affects the chemical stability of the polyether polyol. Specific performance in the following aspects:

3.1 hydrolysis resistance

Polyether polyols with high functionality usually have better hydrolysis resistance due to their complex molecular structure. This is because the enhancement of intermolecular hydrogen bonds can reduce the attack of water molecules on hydroxyl groups, thereby improving the hydrolysis resistance of the material.

3.2 heat resistance

Polyether polyols with high functionality usually have better heat resistance due to the denser molecular structure. In the high temperature environment, the high functionality polyether polyol can maintain better structural stability, thereby improving the heat resistance of the material.

4. Functionality of polyether polyol practical application effect

In practical applications, the functionality of polyether polyols needs to be adjusted according to specific needs. For example:

4.1 low functionality (2-3)

Low functionality polyether polyols are commonly used to prepare softer and more flexible polyurethane materials. For example, in coatings and adhesives, low functionality polyether polyols can provide better flexibility and adhesion properties.

4.2 high functionality (4-6)

Polyether polyols of medium and high functionality are commonly used in the preparation of polyurethane materials for harder and more rigid. For example, in foams and structural composites, high and medium functionality polyether polyols can provide greater strength and durability.

5. Summary

The functionality of polyether polyols has an important influence on their properties. High functionality can enhance the cohesion of the material, increase its viscosity, reactivity and cross-linking density, thereby improving the mechanical strength and durability of the material. Too high a functionality may also cause the material to become brittle, affecting its toughness. Therefore, in practical applications, it is necessary to select the appropriate polyether polyol functionality according to specific requirements to achieve the best performance effect.