There are many small pores in the plastic foam, which is very light in weight and versatile. Soft foam can be used for car seats and sofas; hard foam can be used as packaging material, and it can be used around the TV to prevent damage when the TV is transported; lining the foam in the wall of the house is like wearing it for buildings Putting on cotton clothes makes the house warm in winter and cool in summer.
So how are these small pores formed? The principle is similar to that of making steamed buns. Put some fresh yeast in the flour when you bake. After steaming, many small pores will form in the steamed buns, making the buns soft. When making foamed plastics, we also put in something called foaming agent to make it evenly mixed with plastics, and then self-heating. This plastic will melt into a very sticky material, and the blowing agent will decompose, producing nitrogen, carbon dioxide and other gases. Because the molten plastic is very sticky, these gases cannot escape from the plastic. When the plastic cools, these small pores are wrapped in the plastic.
In addition to adding a blowing agent, sometimes it is also possible to add some liquids that are easily volatile, such as butane used in lighters, which is absorbed into the plastic (in small particles of polystyrene) under pressure. When these small particles are heated to soften, the absorbed butane vaporizes and generates pressure, and the small particles immediately swell into a foam with many small bubbles. The principle is the same as popcorn. In addition, some foam plastics can also be mechanically stirred by adding substances like soap powder to the aqueous resin solution. After stirring, they become foams, which are then heated to harden the foams and become foamed plastics.