Film formation and barrier performance of latex based coating: Impact of drying temperature in a flexographic process

The post-application behaviour of aqueous dispersion barrier coatings is investigated. We have adapted a dispersion formulation initially optimised for rod coating, for application to linerboard by a flexographic press. The clay/talc/wax/poly(styrene-butadiene) latex dispersion coatings demonstrated a 60% reduction in water vapour transport rate across the barrier, and a 75% reduction in direct water uptake when the applied film was dried at 75 degrees C. Multi-layer coatings with a combined application rate of 7 g m(-2) exhibited Cobb(120) direct water uptake of 16.3 +/- 3.7g m(-2) (120s water contact duration) and a water vapour transport rate of 140 +/- 12g m(-2) d(-1) (23 degrees C, 50% RH). Investigation of the post-coating curing regime demonstrated a decrease in the prevalence of crack defects within the cured film, and corresponding improvement in barrier properties when higher drying temperatures were employed. Dynamic mechanical analysis of the cured films indicated improvements in homogeneity and a greater extent of intermolecular interactions in the coating formulations cured at elevated temperatures.