2022.08.12
According to the physical properties of the plastic, the softness and hardness of the foam texture can be divided into three categories. Polystyrene foam, phenolic foam, epoxy resin foam, and some polyurethane foams are all rigid foams; while rubber, elastic polyurethane and some polyolefin foams are flexible foams.
Expandable polystyrene resin is a liquid foaming agent with a low boiling point added to polystyrene beads, which penetrates into the polystyrene beads under the condition of heating and pressure to make them swell to make expandable polystyrene beads. Polystyrene resin (beads).
In the case of heating, polystyrene softens and low-boiling alkanes volatilize, causing polystyrene particles to expand. Using this principle, expandable poly Styrene products.
1. The bubble formation stage of the foam: the synthetic resin is added 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 saturation limit in the melt or solution, it forms a When the solution is saturated, gas will escape from the melt to form bubbles. At a certain temperature and pressure, the decrease in the solubility coefficient will cause the dissolved gas concentration to decrease, and the excess gas released will form bubbles.
2. The growth of the bubble nucleus of the foam: During the foaming process, the growth rate of the cell is determined by the growth rate of the internal pressure of the cell and the deformation ability of the cell ratio. After the bubble is formed, since the pressure of the gas in the bubble is inversely proportional to the radius, the larger the bubble, the higher the internal pressure, and the number of bubbles is increased through nucleation, and the expansion of the bubble expands the growth of the bubble. The factors that promote the growth of foam are mainly the increase of dissolved gas, the increase of temperature, the expansion of gas and the merger of bubbles.
3. Stable curing of the foam: Of course, if the cell growth process is not interrupted at a certain stage, some cells can grow to be very large, so that the material forming the cell wall reaches the material rupture limit, and finally all cells will be Collusion with each other 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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