When the foam is formed, the foaming agent releases a large amount of gas at the decomposition temperature to form the foam core. After sudden pressure relief, the foam core releases pressure, which causes EVA and other materials to expand and form foam materials. The ratio of the increase of raw material particle volume is the EVA foaming ratio.

EVA foam material is widely used in footwear industry. Molding technology, mold shape and size all have effects on the foaming ratio, while the shape of shoe mold is generally a complex curved surface, the shape and size are more complicated, and the corresponding foaming ratio is also more complicated. The foaming ratio of different sections or different positions of the same section of the shoe mold is different. At present, the shoe mold adopts experimental method to study the technological parameters and the shape of foamed products, which have the most direct influence on EVA foaming ratio.

1. The process parameters include mold temperature, molding time, injection pressure and molding pressure, and the factors affecting EVA foaming ratio are analyzed. Mold temperature has a significant influence on foaming ratio, followed by molding time, and injection pressure and molding pressure have little influence. With the increase of mold temperature, the foaming ratio gradually increases and eventually tends to a stable value, and with the increase of molding time, the foaming ratio gradually reaches the maximum and finally tends to a stable value. In addition, the foaming ratio of large-size sheet is large. With the increase of foaming pressure holding time, the foaming ratio gradually reaches the maximum value and finally tends to a stable value.

2. The sheet with large foamed product size has large foaming ratio; With the increase of the side length of foamed products, the foaming ratio also increases to some extent.

To sum up, we get the following two conclusions:

1, mold temperature has a significant effect on the rate of EVA foam, followed by molding time, injection pressure and molding pressure have little effect.

2. The foaming ratio in the cylinder diameter direction is greater than that in the sphere diameter direction; The foaming ratio of quadrangular prism side length is greater than that of triangular prism side length; The foaming ratio of non-porous sheet is similar to that of porous sheet in thickness direction; With the increase of particle size, the foaming ratio of EVA increased.