Evaluation of moisture diffusion as a threat to polymer/inorganic nanoparticles composites properties: Polystyrene/calcium sulfate nanocomposite as a case study

The present study aims to investigate the water diffusivity into polystyrene/ calcium sulfate (PS/CaSO ₄ ) nanocomposite samples as a threat to the intended reinforcing properties. For this purpose, CaSO ₄ nanoparticles were synthesized through a chemical reaction using polyethylene glycol as the stabilizing agent. The polystyrene/calcium sulfate nanocomposites were fabricated through in situ polymerization of styrene monomer and stearic acid coated CaSO ₄ nanoparticles. SEM analysis was applied to determine the size and shape of the produced nanoparticles. In addition, TEM analysis was applied to study the general morphology and structure of the nanocomposites in order to confirm the PS/CaSO ₄ nanocomposites formation. FTIR analysis was employed to study the surface functions and bonds formation in both the surface treatment and nanocomposite preparation steps. Water diffusivity into the nanocomposites was evaluated through samples water exposure followed by calculation of the effective diffusion coefficients (D _eff ) using the diffusion equation given by Fick’s 2nd law. The calculation results have revealed that the obtained D _eff values for water diffusivity in PS/CaSO ₄ (1.5 wt.%) and pure PS samples were 8.73 × 10 ⁻²⁰ and 11.1 × 10 ⁻²⁰ m ² /s, respectively.