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Polyurethane foaming machine Causes of cavitation during operation and its solutions

1. Strictly control the ratio and injection amount of the original liquid

Control the ratio of black material, combination polyether and cyclopentane. Under the condition that the total injection volume remains unchanged, a large proportion of black material will lead to cavitation, a large proportion of white material will lead to soft bubbles, a large proportion of cyclopentane will lead to swelling bubbles, and a small proportion will lead to cavitation. The proportion of black and white material is maladjusted, there will be uneven mixing, foam shrinkage phenomenon.

The amount of injection should be based on the process requirements. When the injection amount is lower than the required amount, the molding density and strength of the foam body will be low, and even the filling of the cavity will not be dense. Injection amount higher than the process requirements will appear bubble and leakage bubble phenomenon, box (door) deformation

2. Temperature control of polyurethane foaming machine is a key to solve cavitation

The reaction is hard to control when the temperature is too high. It is easy to see uneven performance of the bubble solution injected into the larger box. Chemical reaction has occurred in the bubble solution injected at the beginning, and the viscosity increases rapidly, but the bubble solution injected later has not reacted. As a result, the injected foam cannot push the injected foam to the front of the foaming process of the box body, resulting in partial cavitation of the box body

Black and white materials should be treated at a constant temperature before foaming, and the foaming temperature should be controlled at 18~25℃. The preheating furnace temperature of foam equipment should be controlled at 30~50℃, and the temperature of foam mold should be controlled at 35~45℃

When the temperature of foam mold is too low, the foam liquid system has poor fluidity, long curing time, incomplete reaction and cavitation. When the temperature of foam mold is too high, the plastic liner is heated and deformed. Therefore, the temperature of foam mold and the ambient temperature of foam furnace must be strictly controlled.

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

3、Polyurethane foaming machine pressure control

The pressure of foaming machine is too low and the mixture of black and white materials and cyclopentane is uneven, which is manifested as uneven density of polyurethane foam, local large bubbles, foam cracking and local softening of foam: white, yellow or black streaks appear on the foam, and the foam shrinks. The injection pressure of the foaming machine is 13~16MPa