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Application of soft foam auxiliaries

Time:2018-07-19  Edit by Sirui Machinery

The production of polyurethane foam needs to balance two main chemical reactions: A polyether polyol and isocyanate binding reaction (catalyzed by stannous octanate catalyst) the gas reaction between B water and isocyanate (catalyzed by TERT amine catalyst). The two reactions should be carried out smoothly at the same time, and the balance should be achieved when the reaction is completed, so as to produce high-quality foam.

When foaming reaction is carried out, viscosity control is the key. The speed of viscosity growth is the speed of chain growth. When the viscosity increases too fast, the bubbles are solidified before the foaming reaction is completed, which increases the density of the foam and reduces the performance of the compression setting; the viscosity increases too slowly, and the bubbles escape before the foaming reaction is completed, which will lead to collapse and other phenomena, and affect the strength and tear properties of the foam.

From the performance requirements of the foam, these two main reactions must be balanced: when the foaming reaction is completed, the growth of the chain to the foam network is enough to reach the extent that the bubble is trapped.
Soft foam additives include catalysts, stabilizers, foaming agents and flame retardants.
1, amine catalyst (main gas reaction)
2, tin catalyst (mainly gelatin reaction)

3. Silicone surfactant (mainly stabilizing)

Some unusual phenomena and treatment methods in foaming process are introduced:
1) defect: bubble rise to a certain height and collapse
Possible reasons: a deterioration or insufficient dosage, B tin deterioration or insufficient dosage.
Solution: check both quality and output pump output

2) defect: foam top skin has pimples: top skin is full of stomata.

Possible reasons: too much tin, too short gel, too fast, so that the bubble is too solid, part of CO2 can not break through the bubble wall, especially in the top of the skin is very obvious, showing pimples.
A fast foaming reaction speed increase of amine catalyst
B reduces the rate of gel reaction and reduces the amount of tin


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