EVA processing and molding method. Generally, EVA with ethylene acetate content below 5% is mainly used for film, wire and cable, LDPE modifier, adhesive, etc; EVA products with ethylene acetate content of 5%~10% are elastic films; EVA with 20~28% vinyl acetate is mainly used for hot-melt adhesives and coating products; The content of vinyl acetate is 5%~45%, and the main products are films (including agricultural films) and sheets, injection molding, molding products, foaming products, hot-melt adhesives, etc.
How to process EVA materials? The processing technologies of EVA products include: injection molding, extrusion, blow molding, calendering, rotational vacuum thermoforming, foaming, coating, heat sealing, welding, etc.
How to process EVA materials and what materials are required:
Main raw materials for EVA processing:
LDPE: It can be used to make foam products with large magnification, which are hard but not resilient, and mainly used for foam insulation materials, slippers, bags, etc;
EPDM: increase elasticity;
Natural rubber: increase skid resistance.
EVA processing color selection:
Color masterbatch: good dispersion and positive color
Toner: low price, poor dispersion, and polluted working environment;
Colored sand: good dispersion, less pollution.
EVA processing foaming agent:
Existing high, medium and low temperature
High temperature: it has good magnification, but it affects the color of products;
Medium temperature: for injection and small mode.
Generally speaking, EVA foaming has three processes: injection, traditional large plate foaming and small foam in mold.
1. Ejection
This process is relatively advanced. Only one process is needed to produce the product. It requires high precision of the mold and will be the mainstream in the future. Its principle is similar to the injection molding in the plastic industry. The difference is that the injection molding starts immediately, and the mold temperature is different. That is, the EVA injection process just adjusts the mold temperature and opening time of the plastic injection molding. Now most enterprises that make sports shoes have changed to this method.
2. Small foam in mold
It is mainly used for shoe materials. The first foaming of the second insole of sports shoes is to granulate the trained materials (7470M) and put them into the open mold after weighing. The general appearance of the shoes is the result of the foaming. The difficulty is the symmetry of the mold and the formula, and the magnification and hardness should be controlled at the same time. The foaming conditions of this process are relatively flexible, depending on the appearance and structure of the product. Of course, it is mainly the change of time and temperature.
The second molding is to grind off the skin of the previously foamed rough embryo, and press it into the finished mold. After heating and cooling, the product is formed. The heating temperature is 125-135 ℃, and the pressure is 50 kg/cm2. After heating for a certain period of time, water cooling will be done, and the second midsole will be taken out. The size of the compressed bottom is relatively stable, and its physical performance is relatively better.
3. Traditional flat large foam
Now most small factories in China use this process, and the equipment cost is relatively low. This process is to make plates, and also needs to make products through blanking, edging and other processes. The foaming condition is relatively fixed, and the time is determined by the mold thickness, generally 90-110 seconds/MM, the temperature is 160-170, and the pressure is 150KG/cm2.
This is all about EVA processing and molding method. BONITO company has been specialized in manufacturing EVA for more than ten years and has become an industry leader. We are an eva manufacturer focusing on eva processing, eva production and eva tool kit. If you have eva processing, please contact us.
