Film formation stages for poly(vinyl acetate) latex particles: a photon transmission study

Abstract

Photon transmission technique was used to monitor the evolution of transparency during film formation from poly(vinyl acetate) (PVAc) latex particles. The latex films were prepared below the glass transition temperature (Tg) of PVAc. These films were annealed at elevated temperatures in various time intervals above the Tg of PVAc. It is observed that transmitted photon intensity (Itr) from these films increased as the annealing temperature is increased. It is seen from Itr curves that there are two film formation stages. These successive stages are named void closure (viscous flow) and interdiffusion. The activation energies for viscous flow (ΔH) and backbone motion (ΔEb) were obtained by using well-defined models. The averaged values of the backbone (ΔEb) and the viscous flow activation energies (ΔH) were found to be 188.6 and 5.6 kcal/mol, respectively. The minimum film formation (τM,TM) and healing points (τH,TH) were determined. Minimum film formation (ΔEM) and healing activation energies (ΔEH) were measured using these time–temperature pairs. ΔEM and ΔEH were found to be 32.5 and 28.3 kcal/mol, respectively.