The Use of Aqueous‐based Emulsion Polymers as Moisture Barrier Coatings for Carton Boards

Abstract

AbstractThe rate of moisture permeation through paper carton boards can be critical in high peformance packaging applications. Moisture barrier paperboards have been developed using aqueous‐based emulsion polymers, and the results obtained with these materials are presented. These polymers include polyethylene terephthalate (PET), polyvinylidene chloride (PVdC), and styrene‐based emulsions. A range of these coated carton boards were prepared using a hand coater to achieve a controlled range of barrier layer thickness (6–100 microns). Water vapour transmission rate (WVTR) analysis was carried out on these coated boards over a range of temperatures and relative humidities. In addition, some boards were precoated with a primer coat before the application of the barrier topcoat in order to investigate the effect of carton board topography on the moisture barrier properties. Low WVTRs in the range of 3–10 g/(m2 day) were achieved using several of the emulsion polymers. It is clearly shown that pre‐coating the surface of a board with aprimer before applying a barrier coat can lower the WVTR further even with a thinner overall layer of coating. Analysis also illustrated that boards coated on one side exhibited anisotropic characteristics, with lower WVTRs always being achieved when the coated side of the board is adjacent to the higher humidity.