ABSTRACT Glassy polymer coatings on metal substrates rely on their mechanical, physical, and transport properties for corrosion protection. These properties are influenced by free volume between polymer chains that plays a critical role in coating performance. Free volume permits local segmental mobility that affects mechanical properties, such as yield and adhesion, and also permits diffusion of small molecules (water, ions, and oxygen) through the coating to the substrate. Fractional free volume is calculated from the specific volume and Bondi group contribution theory for the occupied volume. Free volume distribution (free volume element size and number) is measured by positron annihilation lifetime spectroscopy (PALS) using the ortho-positronium (oPs) probe, which detects free volume elements in glassy polymer coatings. The oPs probe is sensitive to phenomena that affect both the mechanical and barrier properties of coatings including physical ageing, water sorption, and plasticisation, making PALS a suitable allied testing method for corrosion-protective coatings.

中文翻译：

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自由体积在用于防腐涂层的玻璃态聚合物的分子迁移率和性能中的作用

摘要 金属基材上的玻璃状聚合物涂层依靠其机械、物理和传输特性来提供防腐蚀保护。这些特性受聚合物链之间自由体积的影响，而聚合物链对涂层性能起着关键作用。自由体积允许局部分段迁移，影响机械性能，例如产量和附着力，还允许小分子（水、离子和氧）通过涂层扩散到基材。分数自由体积是根据比体积和占据体积的邦迪群贡献理论计算的。自由体积分布（自由体积元素大小和数量）通过正电子湮没寿命光谱 (PALS) 使用正电子 (oPs) 探针进行测量，该探针可检测玻璃聚合物涂层中的自由体积元素。