Stability of latex paints during freezing and thawing cycles is an important performance criterion. Adding volatile organic compounds (VOCs) in the paint formulation depresses its freezing point and imparts stability. However, environmental concerns have increased the pressure to reduce the amount of VOCs in the paint. In order to design dispersions that are freeze-thaw (FT) stable we need to understand the mechanism of stabilization. We use propylene glycol additive to FT stabilize an acrylic paint formulation. The paint is frozen and thawed in a controlled rate freezer and the microstructure at various stages in the process is observed using cryogenic scanning electron microscopy (cryoSEM). We report the effect of freezing rate, thawing rate and the amount of additive on the frozen microstructure. The results are compared with the (FT unstable) acrylic paint without the additive. We observed that the size of ice crystals formed during freezing increases when either the cooling rate is reduced or the amount of glycol in the paint is increased. However, it is only during thawing that the particles aggregate. Similarly, we observed that the thawing rate also greatly affects the microstructure and eventually the stability of the paint. Finally, we elucidate the cryoSEM results reported here and propose a mechanism of FT stabilization of paint due to VOCs.

Cryo-microscopy study of freeze-thaw stabilization of paint

242nd National Meeting (2011)

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