ABSTRACT
Plastics containing many cells or bubbles are called foamed plastics or plastic foams. Plastic foams have many unique characteristics such as a light weight, shock absorption, and good insulation. Generally, the cell structures of plastic foams can be classi ed into either a closed-cell structure or an open-cell (porous) structure. A closed-cell structure, where a
large proportion of the cells are independent of each other, is easy to produce during foaming. However, an open-cell structure, where a large proportion of the cells are connected to other cells by open passage, can be more dif cult to achieve during foaming.
