Barrier properties created by dispersion coating

Abstract

The objective of this work was to gain insight into 1) how a coating layer with barrier properties is built up, 2) how different polymer dispersions and pigments function as a barrier against gases and fluids, and 3) how the thickness and evenness of the coating layer affect barrier properties. In addition to tests for permeability of water vapor, barrier properties required for functional applications (i.e., against solvents and acids) were studied. Permeability of an organic solvent (ortho-dichlorobenzene) and hydrochloric acid was studied as a function of barrier layer structure. Providing a barrier to these materials is important in the processing of printing functionality on paper. Pigment particle orientation and tortuosity were examined by infrared spectroscopy and by high-resolution, focused ion beam milling and imaging. The barrier properties were influenced by the thickness and evenness of the coating layer and the mass ratio between the pigment and latex. A barrier against water vapor did not always ensure a barrier against the organic solvent or the acid. In addition to barrier properties, the choice of coating materials affects coatability and may provide possibilities for cost savings.