A real time study on drying and the mechano-optical behavior of polyvinyl alcohol films in solid and swollen state

In this paper, we investigate film drying followed by mechano-optical behavior of PVA films in solid and swollen state, respectively. During drying the real time evolution of thickness, weight, and birefringence (both in and out of plane) are captured using a highly instrumented measurement system. During drying, initially isotropic solution rapidly loses water and beyond a critical stage it develops optical anisotropy in the thickness direction as reflected in rapid development of out of plane birefringence while in-plane isotropy is maintained. Stretching the dried films in the solid state yields three regimes of non-linear stress and strain-optical behavior. The temperature shows a positive effect on the birefringence value at given true strain levels. Swelling the PVA films with water, facilitate room temperature stretchability, hence providing a route of stretching that avoids decomposition and discoloration that occurs at elevated temperatures. The effects of moisture content on mechano-optical properties of PVA films are mapped and opposite dependences of photolelastic and strain optical constants on moisture content are observed. [Display omitted] •We investigate film drying followed by mechano-optical behavior of PVA films in both solid and swollen state.•Aqueous PVA solution develops out of plane optical anisotropy while maintaining in-plane isotropy during drying.•Stretching of dried films lead to three regimes of stress and strain-optical behavior.•Photoelastic and strain optical constants depend on moisture level in the films.