Li Yaozong, Jiang Junjie, Huang Hanyi, Wang Zelin, Wang Liang, Chen Bichi, Zhai Wentao
School of Materials Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China.
Materials (Basel). 2024 Jul 27;17(15):3719. doi: 10.3390/ma17153719.
Ethylene-vinyl acetate copolymer (EVA), a crucial elastomeric resin, finds extensive application in the footwear industry. Conventional chemical foaming agents, including azodicarbonamide and 4,4'-oxybis(benzenesulfonyl hydrazide), have been identified as environmentally problematic. Hence, this study explores the potential of physical foaming of EVA using supercritical nitrogen as a sustainable alternative, garnering considerable interest in both academia and industry. The EVA formulations and processing parameters were optimized and EVA foams with densities between 0.15 and 0.25 g/cm were produced. Key findings demonstrate that physical foaming not only reduces environmental impact but also enhances product quality by a uniform cell structure with small cell size (50-100 μm), a wide foaming temperature window (120-180 °C), and lower energy consumption. The research further elucidates the mechanisms of cell nucleation and growth within the crosslinked EVA network, highlighting the critical role of blowing agent dispersion and localized crosslinking around nucleated cells in defining the foam's cellular morphology. These findings offer valuable insights for producing EVA foams with a more controllable cellular structure, utilizing physical foaming techniques.
乙烯-醋酸乙烯酯共聚物（EVA）是一种关键的弹性体树脂，在制鞋工业中有着广泛应用。包括偶氮二甲酰胺和4,4'-氧双（苯磺酰肼）在内的传统化学发泡剂已被认定存在环境问题。因此，本研究探索了使用超临界氮气对EVA进行物理发泡作为一种可持续替代方法的潜力，这在学术界和工业界都引起了相当大的兴趣。对EVA配方和加工参数进行了优化，并制备出密度在0.15至0.25 g/cm之间的EVA泡沫。主要研究结果表明，物理发泡不仅减少了环境影响，还通过具有小泡孔尺寸（50 - 100μm）、宽发泡温度窗口（120 - 180°C）和较低能耗的均匀泡孔结构提高了产品质量。该研究进一步阐明了交联EVA网络中泡孔成核和生长的机制，强调了发泡剂分散以及成核泡孔周围局部交联在决定泡沫泡孔形态方面的关键作用。这些研究结果为利用物理发泡技术生产具有更可控泡孔结构的EVA泡沫提供了有价值的见解。
