Film formation from Pickering stabilized waterborne polymer dispersions

- Mechanisms involved in the formation of films from silica stabilized waterborne polymer dispersions studied.
- Silica delays the interdiffusion of polymer from different particles, but it does not avoid it.
- Capillarity forces are able to overcome the resistance of the hard shell formed around the particles.
- Silica has the remarkable effect of increasing at the same time the Young's modulus, and stress and elongation at break.
- Films absorbed less water than films containing PVOH, which is the workhorse for VAc-Veova10 latexe.

The mechanisms involved in the formation of films from high solids industrial-like - vinyl acetate - VeoVa10 (vinyl decanoate) waterborne dispersions Pickering stabilized with surface modified colloidal silica were studied using a combination of techniques including TEM, FRET, ESEM and SEM. It was found that Pickering stabilized dispersions yield films with the silica forming a honeycomb structure that partially hinders the interdiffusion of the polymers from different particles. Nevertheless, coherent films were formed only 9 °C above the Tg of the polymer, due to the strong capillarity forces developed in the compact array of particles formed during water evaporation in the film formation. These Pickering dispersions allowed achieving the remarkable effect of increasing at the same time the Young's modulus, the stress at break and the elongation at break by increasing the silica concentration. Water uptake of the films decreased with the silica concentration and with the surface modification of the silica. Films with >5 wt. % of the more hydrophobic silica absorbed less water than films stabilized with PVOH, which is the workhorse for VAc-VeoVa10 latexes.

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