What is the Roughly Difference in the Role of Foam Stabilizers

Aug 12, 2021

In recent years, in the production of polyurethane products, stabilizers have been proven to be one of the key components in foam production. They make the pores fine and uniform. When the system is in the low viscosity stage, it stabilizes the pore wall/the pores can grow to a thickness suitable for the opening, creating conditions for the final opening. The type of foam is different, the type of stabilizer used is also: the same, its main function is to nucleate and emulsify each component in the formula. The compatibility of the various components in the foam formulation is not good, so a stabilizer with a strong emulsifying ability is needed to emulsify and mix them uniformly. The soft foam is made of water as a blowing agent, which accounts for 3% to 5% of the weight of the polyether in the formula. The reaction rate of water and isocyanate is higher than that of isocyanate and polyol, so there are a lot of solids in the initial stage of foaming. Polyurea is formed, which is a defoaming agent that can help open and blast holes. Opening and popping are the stages when soft foam foaming must occur, otherwise, closed cells will appear, resulting in a decrease in foam performance. However, opening and puncturing and popping must occur when the foaming reaction and the gel reaction are basically completed and reach equilibrium. That is, when the foam rises to the highest point and the strength of the foam can support its own weight, otherwise it will cause the foam to collapse. Therefore, another important function of the soft steam stabilizer is that it can dissolve the polyurea formed by the reaction in the early stage of foaming and it can help to open and burst holes in the late stage of foaming. According to this principle, the following aspects should be considered when choosing a soft foam stabilizer.
① Activity of stabilizer;
②The relationship between the operating range of the stabilizer and the range of tin dosage
③The influence of various raw materials constituting the stabilizer on the operating range.

Stabilizers with high activity are generally less used in the formulation and are economically cost-effective. Nephew is that the operating range of the high-activity stabilizer is narrow, which is likely to cause foam quality problems, so special attention should be paid when choosing. -Generally speaking; if the polyether has low activity, or is propylene oxide polyether, a high-activity stabilizer can be used to prolong the dissolution time of polyurea. If the polyether is a copolymer of propylene oxide and ethylene oxide, the polyether has a strong ability to dissolve polyurea due to the presence of ethoxy groups, so it is appropriate to use a stabilizer of medium activity. In some special high-density foams, such as 40-50kg/cm3, low-activity stabilizers are required.

The situation of hard foam is different from that of soft foam. It has a higher degree of cross-linking and the bubbles are easy to stabilize. Rigid foam is mostly used for molded products or foamed in a restricted cavity, so the fluidity of the material is an extremely important process parameter. Poor fluidity will cause vacancies and affect the insulation performance; so the rigid foam stabilizer The requirements are as follows. .

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 raw materials required for rigid foams are often supplied in the form of combined materials, so the storage performance is relatively high. During the effective storage period, silico-carbon stabilizers that are not easily hydrolyzed are used steadily. In the high resilience foam system, raw materials such as polymer polyols are used, and there are many solid particles, so special attention should be paid. It is not advisable to use a general foam stabilizer, but a special 0 foam agent. Foam stabilizers can be dissolved in most solvents. Because the molecular structure contains Wei polyether, it also has a certain solubility in water. This solubility can be regarded as a kind of hydration, that is, water and the oxygen atoms in the polyether associate through hydrogen bonds IU. The small publication called Xieganlan degree will make the stabilizer have different viscosity. However, the association weakens as the temperature rises, so when the temperature rises, the stabilizer will separate from the water. The cloud point of the stabilizer used is 25-40°C, and the rigid bubble is 95C. Therefore, the stabilizer should not be stored at high temperature. The stabilizer is relatively stable in the amine catalyst. Someone once did an experiment where the amine catalyst and stabilizer were mixed and stored, and there was no change in two weeks. After three weeks, the density of the foam increased slightly. The rise time of foaming is reduced very little, and the porosity is improved. After 4 weeks, the change was obvious, but there was no difficulty in foaming. TDI destroys the stabilizer within a few hours. However, MDI and foam stabilizers can be very beneficial in the production of isocyanurate foam within a few weeks. The stabilizer can be dissolved well in Freon and is relatively stable, but in the presence of certain metal ions, a small amount of monofluorotrichloromethane will decompose, and the decomposition product itself will affect the stabilizing effect of the stabilizer.

The organotin catalyst will destroy the stabilizer, making it a defoamer. Therefore, stabilizers cannot be placed in tinned containers. Copper metal also has an adverse effect on the stabilizer, so avoid contact. Such as storage tank pipelines, pumps, valves, couplings and other components.