A Comprehensive Analysis of the Different Processes of EVA Foaming

Conventional flat slab stock foam

Product Form and Subsequent Processing: This process makes a sheet, which needs to be made into a product by punching, grinding, and other processes.
Foaming conditions: The foaming temperature is 160 – 170 ℃, the time is determined by the thickness of the mold, generally 90 – 110 seconds / mm, and the pressure is 150kg / sq. cm. Small factories generally use this process, and machinery and equipment costs are relatively low.

Application areas: This process is mainly used in footwear, specifically sports shoes, to create the first foam of the secondary midsole.
Process and Difficulties: According to the formula to practice good material granulation, weighing into the open mold, foam out is the general appearance of the shoes. The difficulty of this process is the symmetry of the mold and formula. Otherwise, it is difficult to control the multiplier and hardness simultaneously. Foaming conditions are more flexible, depending on the product shape and structure, mainly time changes and temperature changes that are not too big.

Development prospects and principles: This process should be mainstream in the future, a process is done out of the product, but the mold precision is higher. The principle is similar to the plastic industry injection molding, only injection molding is immediately open, and mold temperature is different, that is, the EVA injection but is the plastic injection mold temperature and the mold time to adjust it.

process route and environmental considerations: this process needs to solve the problem of how to lock the gas. From the patent literature and some of the enterprise information, the EVA supercritical foaming process is such a route: dense refining co-mingled cross-linking, granulation, molding to get pre-cured soles, the soles into the autoclave foaming device, to the kettle into the physical blowing agent, the use of decompression to get the microcellular foaming soles materials. If you want the whole process to be environmentally friendly and clean, you can replace chemical cross-linking with radiation cross-linking and other methods in the previous cross-linking process.