Foam stabilizer: also known as foam stabilizer. The foam stabilizer currently used is mostly a polysiloxane surfactant, which is the key auxiliary agent for the production of polyurethane foam.
It is mainly used as a foam stabilizer to mix the raw materials evenly during the foaming process, reduce the surface tension of the system to promote nucleation and support the foam, and avoid the occurrence of undesirable phenomena such as slump, coarse pores, and cracking.
Types and Functions of Foam Stabilizers
Foam stabilizers are divided into soft foam stabilizers and hard foam stabilizers. Its main functions are as follows:
Emulsification: The compatibility of each component in the foam formulation is poor. The foam stabilizer has a lipophilic and hydrophilic molecular structure, which can emulsify the foaming raw materials and improve the compatibility state of the materials before and during the reaction, so as to make the foam The foaming reaction and the cross-linking reaction proceeded smoothly.
Nucleation and foam stabilization: The foam stabilizer reduces the surface tension of the material, and helps the mixed air to form a bubble nucleus during stirring, and the gas generated by the reaction enters the bubble nucleus and causes the bubble to grow continuously. During the foaming process, the foam stabilizer stabilizes the thinned cell wall by reducing the stress in the cell wall and prevents the collapse of the rapidly growing foam until the cell wall has sufficient strength and can be self-supporting.
Open-cell/closed-cell effect: The cells of the polyurethane flexible foam must be open-celled to make the product soft and elastic. Due to the action of the foam stabilizer, when the foaming system is at a low viscosity, the cell wall is stable and the bubbles grow to a certain extent, the cell wall is thinned, and the cell ruptures under the combined action of the catalyst and the foam stabilizer, that is, "open cell". ". The foam stabilizer can control the foam opening time, eliminate defects such as foam cracking and closed cells, and endow the foam with good air permeability and comfort performance.
For rigid polyurethane foam, closed cells can make the foam products have good thermal insulation effect and sufficient mechanical strength. 95% foam to ensure foam insulation performance.
Raw Material of Foam Stabilizer
Polyurethane foam stabilizer is prepared by hydrosilation reaction of allyl polyether and polysiloxane under the action of catalyst.
Its main manufacturing raw materials include: octamethylcyclotetrasiloxane (abbreviation: D4), hexamethyldisiloxane (abbreviation: MM), polymethyl hydrogen siloxane (abbreviation: high H), epoxy resin Ethane, propylene oxide, chloroplatinic acid, etc.
Production Process of Foam Stabilizer
There are three main chemical reactions in the synthesis process of foam stabilizer: the synthesis of allyl polyether with special structure, the synthesis of polysiloxane, and the hydrosilation reaction of polyether and polysiloxane. Finally, the use of formula design technology , by adding certain additives, to prepare foam stabilizer products that meet different performance requirements.
Requirements for The Selection of Foam Stabilizers
Selection requirements for soft foam stabilizers
Soft foam stabilizer is a polyurea that can dissolve and react in the initial stage of foaming, and can help open and burst cells in the later stage of foaming. According to this principle, the selection of soft foam stabilizer should consider:
① Activity of foam stabilizer
②The relationship between the operating range of the foam stabilizer and the range of the amount of tin
③ The influence of various raw materials constituting the foam stabilizer on the operating range
Selection requirements for rigid foam stabilizers
Rigid foam has a high degree of cross-linking and is easy to stabilize. Rigid foam is mostly used for molding products or foaming in a restricted cavity, so the fluidity of the material is a very important process parameter. Cause vacancies and affect thermal insulation performance. Therefore, when choosing a rigid foam stabilizer, you should consider:
①Strong ability to emulsify raw material components
②It has a strong effect of controlling the size of the cells
③Make the material have better fluidity and uniform density distribution
The difference between the selection of rigid foam and soft foam stabilizer
Foam homogenizers not only play the role of homogenizing foam, but also affect the specific gravity, elasticity and tension of the foam. Different types of foam stabilizers are required for different active raw materials, different use conditions and different foaming forms.
The raw materials required for rigid foamed plastics are often supplied in the form of combined materials, so silicon-carbon stabilizers that are not easily hydrolyzed are often used during the storage period.
In the high-resilience foam system, raw materials such as polymer polyols are used, and there are many solid particles, so it is not appropriate to use a general foam stabilizer but a special foam stabilizer.
Compared with the two, the soft foam type foam stabilizer has higher technical content, and its market share is mainly occupied by foreign manufacturers.
The Future Market of Foam Stabilizers
The diversification and high performance of polyurethane materials are inseparable from additives. From the perspective of dosage, flame retardants take the first place in polyurethane foam additives, foam stabilizers (foam stabilizers) take the second place, and polyurethane foam plastics take the second place. The rapid development of the technology has led to the development of foam stabilizers.
With the development of the polyurethane foam industry in the direction of low carbon, energy saving, environmental protection and safety, the continuous development of new foaming raw materials and multi-performance foams, and the need for new foam stabilizers to match them, the future foam stabilizers will be more special. The development and application of new quality are more diversified.
