Abstract Packaging materials containing certain salts can regulate the humidity of packaged products. This study investigated whether thermoforming of foamed monolayer PP films with dispersed NaCl increases the water vapour sorption capacity and rate. Foamed monolayer PP-films (thickness 630 μm, porosity 0.28) with 6 (g/100 g) dispersed NaCl crystals were thermoformed to cups with depths up to 90 mm. By thermoforming the porosity increased up to 0.63 and the effective water vapour diffusion coefficient elevated by one order of magnitude from 10−11 to 10−10 cm²∙s−1. Therefore, such films absorb and desorb water vapour with a higher rate and they can bind more salt solution which is formed from solid salt crystals by water vapour absorption. Our results are important for packaging producers who thermoform films to cups and trays. This study addresses markets for fresh produce and other products with a high water activity.

中文翻译：

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用于湿度调节的分散氯化钠热成型发泡聚丙烯薄膜的孔隙率、厚度分布和水蒸气吸附

摘要 含有某些盐类的包装材料可以调节包装产品的湿度。本研究调查了分散有 NaCl 的发泡单层 PP 薄膜的热成型是否会增加水蒸气吸附能力和速率。具有 6 (g/100 g) 分散 NaCl 晶体的发泡单层 PP 薄膜（厚度 630 μm，孔隙率 0.28）被热成型为深度高达 90 mm 的杯子。通过热成型，孔隙率增加到 0.63，有效水蒸气扩散系数提高了一个数量级，从 10-11 到 10-10 cm²∙s-1。因此，这种薄膜以更高的速度吸收和解吸水蒸气，并且它们可以结合更多由固体盐晶体通过水蒸气吸收形成的盐溶液。我们的结果对于将薄膜热成型为杯子和托盘的包装生产商很重要。