2022.11.11
There are many ways to stabilize the foam, which can reduce the surface tension, reduce the gas diffusion effect, and stabilize the foam. For example, in the foaming process, the viscosity of the plastic liquid can be increased through the cooling of the material or the cross-linking of the resin, so as to achieve the purpose of stable foam.
Stage 1: The formation of the bubble core of the foam: the synthetic resin is ginseng foamed with a chemical foaming agent or gas. When the temperature is heated or depressurized, a gas will be generated to form a foam. When the gas exceeds its capacity in the melt or solution. When the saturation limit is reached to form a supersaturated solution, the gas will escape from the melt to form bubbles. At a certain temperature and pressure, the decrease of the solubility coefficient will cause the concentration of dissolved gas to decrease, and the excess gas released will form bubbles.
Stage 2: Foam nucleus addition: In the foaming process, the cell addition rate is determined by the addition rate of the internal pressure of the cell and the deformation of the cell ratio. After the bubbles are formed, since the pressure of the gas in the bubbles is inversely proportional to the radius, the smaller the bubbles, the higher the internal pressure, and the number of bubbles is increased through the nucleation effect, and the expansion of the bubbles expands the foam. The factors that promote the addition of foam are mainly the addition of dissolved gas, the increase of temperature, the expansion of gas and the merger of bubbles.
Stage 3: Stability of the foam: Of course, if the cell addition process is not interrupted at a certain stage, some cells can be added to a very large size, so that the material constituting the cell wall reaches the breaking limit, and all the cells behind will meet each other. Collusion will make the whole foam structure collapse, or all the gas will slowly diffuse into the atmosphere from the cells, and the pressure of the gas in the foam will gradually attenuate, so the cells will gradually become smaller and disappear.
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