EVA (Ethylene-Vinyl Acetate Copolymer) is widely used in foamed shoe materials due to its excellent flexibility, elasticity, surface gloss, and chemical stability. Its foamed blends are extensively applied in the midsoles and interior components of medium-to-high-grade sports shoes, hiking shoes, slippers, and sandals. Thanks to its outstanding cost-performance ratio, EVA is expected to remain the dominant material choice for mass-market athletic footwear for the foreseeable future.
Among various shoe material colors, white is by far the most common base color, and EVA foamed products are no exception. However, EVA itself does not possess a naturally bright white appearance. To enhance the whiteness of the finished product, manufacturers typically incorporate optical brighteners during the production process.
Given the wide variety of optical brighteners available, which one is the most suitable for EVA foamed shoe materials? The answer is Optical Brightener KCB. Its mechanism of action is as follows: KCB absorbs ultraviolet light and emits blue fluorescence. This blue light acts as a complementary color to the yellowish undertone inherent in the substrate, and the two combine to produce white light as perceived by the human eye, resulting in a visibly brighter and whiter product. Moreover, KCB is not limited to white products-it can also effectively enhance the color vividness of colored articles.
Specifically designed for foaming applications, KCB offers multiple advantages:
Heat Resistance Matching: The molding temperature for EVA ranges from approximately 210°C to 230°C, while KCB can withstand temperatures up to 210°C, making it highly compatible with EVA foaming processes.
Superior Color Shade: KCB exhibits a pure blue shade, delivering more pronounced whitening effects.
Excellent Stability: KCB is renowned for its outstanding stability among optical brighteners, making it particularly suitable for foamed shoe materials by effectively preventing or delaying yellowing during long-term storage.
In terms of processing, the current mainstream method for EVA foaming is injection molding. Manufacturers simply need to mix KCB evenly into the EVA raw material prior to the foaming stage. The recommended dosage is 200 to 500 grams per metric ton of EVA compound, which is sufficient to significantly improve the surface appearance and overall quality of the finished shoe material.