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How to prevent foaming in polyurethane foaming machine

How to prevent foaming in polyurethane foaming machine

1。 Strictly control the ratio and injection volume of the stock solution

Control the ratio of black material, combined polyether and cyclopentane. When the total injection amount is constant, if the proportion of black material is too large, voids will appear. If the ratio of white material is too large, soft foam will appear. If the proportion of cyclopentane is too large, foaming will occur. If the ratio is too small, vacuoles will appear. The proportion of black and white materials is out of balance, and uneven mixing will occur, and the foam will shrink.

The amount of injection should be based on process requirements. When the injection amount is lower than the required amount of the process, the foam molding density is low, the strength is low, and even the filling is not dense and vacuol. When the injection volume is higher than the process requirements, the foaming and bubble leakage will occur, and the casing (door) will be deformed.

2, polyurethane foaming machine temperature control is a key to solving air bubbles

When the temperature is too high, the reaction is drastic and difficult to control. It is easy to appear that the foaming liquid injected into the larger tank is not uniform, the chemical reaction has begun to occur in the foaming liquid that has begun to be injected, the viscosity is rapidly increased, and the bubble liquid injected later has not reacted. The bubble liquid that causes the post injection cannot push the first injected bubble liquid to the forefront of the foaming process of the box, and the local cavity is bubbled.

The black and white material should be thermostatically treated before foaming, and the foaming temperature is controlled at 18~25 °C. The temperature of the preheating furnace of the foaming equipment should be controlled at 30~50 °C, and the temperature of the foaming mold should be controlled between 35~45 °C.

When the temperature of the foaming mold is too low, the fluidity of the foaming system is poor, the curing time is long, the reaction is not thorough, and voids appear; when the temperature of the foaming mold is too high, the plastic liner is thermally deformed, and the foaming system reacts violently。 Therefore, the temperature of the foaming mold and the ambient temperature of the foaming furnace must be strictly controlled。

Especially in winter, it is necessary to preheat the foaming mold, preheating furnace, foaming furnace, cabinet and door body for more than 30 minutes every morning. The foaming system must be cooled and cooled after a period of foaming in the summer.

 

Polyurethane foaming machine pressure control

The pressure of the foaming machine is too low。 The mixing of black, white and cyclopentane is uneven, which is characterized by uneven density of polyurethane foam, large local bubbles, foam cracking and soft foam: white, yellow or black stripes appear on the foam。 The bubble is shrinking。 The injection pressure of the foaming machine is 13~16MPa


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