Microporous interconnected is called open-cell foam, and the interlocked is called closed-cell foam. There are two classification of foams: rigid and soft. According to the American Society for Experimentation and Information specifications, in the temperature of 18 ~ 29 ℃, in the time of 5s, around the diameter of 2.5cm round rod a week, such as from time to time crack, the test sample belongs to the soft foam; vice versa is a hard foam. Foam can also be divided into two categories: low foaming and high foaming. Usually the foam multiplier (foam than the volume increase before the foam multiplier) less than 5 is called low foam, more than 5 is called high foam.

First, rigid foam that is at room temperature, the composition of the foam polymer is crystalline or amorphous, their glass transition temperature is higher than room temperature, therefore, the texture of the foam at room temperature is harder.

Second, soft foam that constitute the foam polymer melting point is less than room temperature or amorphous polymer glass transition temperature is lower than room temperature, the material is soft at room temperature.

Third, semi-rigid (or semi-soft) foam is between the above two types of foam body.