Residual solvent minimization in polystyrene‐p‐xylene coatings using a nonvolatile additive

Abstract

AbstractThe use of plasticizer has been extensively studied for enhancing the flexibility, processability, solubility, and vapor permeability of polymeric materials. However, its use in enhancing drying of polymeric coatings has been scarcely studied. In the present work, the optimization of plasticizer loading for drying characteristics and residual solvent minimization in polystyrene‐p‐xylene polymeric coatings has been investigated. Coatings were prepared by solution casting technique at various triphenyl phosphate (TPP) loadings from 0 to 7.50 wt% for two cases of initial solution volumes of 75 and 125 μl. For these two cases, respectively, the minimum residual solvent values of 0.02% and 1.61% were obtained, both at 2.50 wt% TPP loading. However, the two cases exhibited residual solvent values of 2.32% and 4.45% at 0 wt% TPP. Further, the SEM results also showed that at 2.50 wt% TPP loading, the coatings developed a dense, smooth and defect‐free morphology attributed to their minimized residual solvent content. The coatings, however, had a porous and phase‐separated morphology originally at 0 wt% TPP. The variation of residual solvent, coating thickness and drying rate with plasticizer loading followed the same behavior for different initial solution volumes. All these parameters attained their peak values consistently at 2.50 wt% TPP. The study is first of its kind to indicate massive reduction in residual solvent attributed to the addition of a nonvolatile plasticizer. TPP also imparts flame retardance to inherently inflammable polystyrene thereby facilitating its implementation in electronic devices. The obtained coatings have possible applications in electronics, electro‐optics, and food packaging.