EVA processing and molding methods, in general, EVA with a vinyl acetate content of less than 5%, its main products are films, wires and cables, LDPE modifiers, adhesives, etc.; EVA products with a vinyl acetate content of 5% to 10% are elastic Films, etc.; EVA with a vinyl acetate content of 20-28%, mainly used for hot-melt adhesives and coating products; with a vinyl acetate content of 5%-45%, the main products are films (including agricultural films) and sheets, Injection molding, molded products, foamed products, hot melt adhesives, etc.

How to process EVA materials, the processing technology of EVA products are: EVA can be injection molding, extrusion molding, blow molding, calendering, rotational molding vacuum thermoforming, foaming, coating, heat sealing, welding and other forming processes.

How to process EVA materials and what materials are required:

Main raw materials for EVA processing:

LDPE: It can be used to make foamed products with a large ratio, which is relatively hard and has no resilience. It is mainly used for foam insulation materials, slippers, bags, etc.;

EPDM: increased elasticity;

Natural Rubber: Increases anti-slip properties.

EVA processing color selection:

Masterbatch: good dispersibility, positive color

Toner: low price, poor dispersion, polluted working environment;

Colored sand: better dispersion and less pollution.

EVA processing foaming agent:

Existing high, medium and low temperature

High temperature: It has a good magnification, but it will affect the color of the product;

Medium temperature: for injection and small mold.

Generally speaking, there are three processes for EVA foaming, injection, traditional flat large foaming and in-mold small foaming.

1. Injection

This kind of technology is relatively advanced, and it only needs one process to make a product. It requires high mold precision and will be the mainstream in the future. Its principle is similar to injection molding in the plastic industry, the difference is that injection molding is to open the mold immediately, and the mold temperature is different, that is, the EVA injection process just adjusts the mold temperature and mold opening time of plastic injection molding. Now most companies that make sports shoes have switched to this method.

2. Small foaming in the mold

It is mainly used on shoe materials. The first foaming of the secondary midsole of sports shoes is to weigh the granulated material (7470M) and put it into the opened mold. The general shape of the shoe is the foaming . The difficulty is the symmetry of the mold and formula, and the magnification and hardness need to be controlled at the same time. The foaming conditions of this process are relatively flexible, depending on the shape and structure of the product. Of course, it is mainly the change of time, and the change of temperature is not large.

The second forming is to grind off the skin of the previously foamed rough embryo, press it into the finished product mold, and go through two steps of heating and cooling before the product is formed. The heating temperature is 125-135 degrees Celsius, and the pressure is 50 kg/cm2. After heating for a certain period of time, do water cooling, and take it out to be the secondary midsole. The bottom size of this kind of compression is relatively stable, and the physical properties are relatively better.

3. Traditional flat foaming

Most of the small factories in China now adopt this process, and the equipment cost is relatively low. This process produces plates, which also need to be punched, edged and other processes to make products. The foaming conditions are relatively fixed, the time is determined by the thickness of the mold, generally 90-110 seconds/MM, the temperature is 160-170, and the pressure is 150KG/square CM.