Effect of Li Halides on the Mechanical Properties and Thermoplasticity of Poly(vinyl alcohol) Molded by Hot Pressing

Abstract

The effect of lithium halide salts on the characteristics of poly(vinyl alcohol) (PVA) gels fabricated using the hot-press (HP) technique is investigated. The incorporation of lithium salts, such as lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), degrades the mechanical properties of the PVA gel and decreases its crystallinity, melting point, and glass transition temperature (T_g). Additionally, the melting point of PVA is lowered, resulting in the melting of PVA below its decomposition temperature, leading to thermoplasticity. Following thermoforming, the mechanical properties of the PVA gel are minimally altered compared with those before thermoforming, potentially enhancing the processability of PVA and diversifying the range of achievable shapes. Notably, the majority of the introduced lithium salts can be eliminated by washing. Notably, the most pronounced change in the PVA gel properties is obtained with LiCl addition than with LiBr or LiI addition, suggesting that LiCl imparts superior processing characteristics to PVA gels.