Svarcova Anna, Svoboda Petr
Department of Polymer Engineering, Faculty of Technology, Tomas Bata University in Zlin, Vavreckova 5669, 76001 Zlin, Czech Republic.
Molecules. 2025 Mar 27;30(7):1485. doi: 10.3390/molecules30071485.
The properties of EVA copolymers with various vinyl acetate (VA) contents were compared, with EVA 206 (6 wt.% VA) and EVA 212 (12 wt.% VA) having the same melt flow indices of 2 g/10 min. The impact of electron irradiation at levels of 60, 120, and 180 kGy was studied. Four testing methods were employed as follows: wide-angle X-ray diffraction (WAXD); differential scanning calorimetry (DSC); dynamic mechanical analysis (DMA), using a high-temperature frequency sweep at 150 °C; and gel content analysis. The amount of crystalline phase was determined by WAXD and DSC. Copolymers with a higher VA content (EVA 212) had lower crystallinity. The increase in the amorphous phase allows for the greater movement of radicals, enabling them to react and form cross-links. The effects of the VA content, radiation dose, and frequency on dynamic mechanical properties were investigated by DMA. The DMA analysis focused on the shear storage modulus G', damping factor tanδ, and complex viscosity η*. After irradiation, the damping factor tanδ decreased with an increasing VA content, indicating improved elasticity and a higher degree of cross-linking. A gel content analysis was used to calculate the parameters of the Charlesby-Pinner and Charlesby-Rosiak equations, which help with the determination of the relationship between cross-linking and chain scission. The ratio of cross-linking to scission G(X)/G(S) was higher for the EVA with a higher VA content (EVA 212). Due to a higher VA content (12 wt.%), EVA 212 exhibits more efficient network formation.
比较了具有不同醋酸乙烯酯（VA）含量的乙烯-醋酸乙烯酯共聚物（EVA）的性能，其中EVA 206（VA含量6 wt.%）和EVA 212（VA含量12 wt.%）具有相同的熔体流动指数，均为2 g/10 min。研究了60、120和180 kGy剂量的电子辐照的影响。采用了以下四种测试方法：广角X射线衍射（WAXD）；差示扫描量热法（DSC）；动态力学分析（DMA），在150°C下进行高温频率扫描；以及凝胶含量分析。通过WAXD和DSC测定结晶相的含量。具有较高VA含量的共聚物（EVA 212）结晶度较低。非晶相的增加使得自由基的运动更加自由，从而使它们能够反应并形成交联。通过DMA研究了VA含量、辐射剂量和频率对动态力学性能的影响。DMA分析聚焦于剪切储能模量G'、阻尼因子tanδ和复数粘度η*。辐照后，阻尼因子tanδ随着VA含量的增加而降低，表明弹性提高且交联程度更高。使用凝胶含量分析来计算查尔斯比-平纳方程和查尔斯比-罗西亚克方程的参数，这有助于确定交联与链断裂之间的关系。VA含量较高的EVA（EVA 212）的交联与断裂比G(X)/G(S)更高。由于VA含量较高（12 wt.%），EVA 212表现出更有效的网络形成。
