Water sensitivity of latex-based films

A series of polymer latices based on methyl methacrylate (MMA) and butyl acrylate (BA) incorporating electrosteric stabilizers containing acrylic acid (AA) and methacrylic acid (MAA) was prepared, and the water sensitivity of films formed from these latices was investigated by immersion tests. A number of variables were considered, including the concentration of the hydrophilic monomer, the presence/absence of a free-radical inhibitor, and the use of various chaser systems to remove residual monomer. Water sensitivity did not increase proportionally to the amount of hydrophilic monomer in the feed and was not directly related to the amount or molecular weight of ungrafted polyelectrolyte or to the length of the grafted polyelectrolyte chains. A model is advanced suggesting that the primary role of the electrosteric stabilizer in reducing water resistance is connected with its ability to prevent coherence of the polymer particles to form a continuous film. This ability should be related to a poor capacity to stabilize water-in-oil emulsions.