The absorption of liquid into a pore network structure depends on porosity, pore size distribution, surface free energy of the involved phases, and external pressure. In the case of ink setting on coated paper, significant decrease of accessible pore volume can take place due to swelling of latex binder particles when contacted with the vehicle of oil-based ink. The reduction in pore network connectivity can be detected by an optical reflectance measurement procedure based on the refractive index differences between the coating components and the surrounding medium present in the interparticle pores.
In this study, GCC model coatings with latices displaying differing oil uptake and swelling characteristics were exposed to liquid supersource imbibition without external pressure. Effects of both linseed oil and mineral oil were studied. In the case of free liquid propagation, i.e. in coatings with low content of binders, a linearly increasing trend of logarithmic reflectance gradient in the coating thickness is observed as a function of time, indicating deceleration of the wetting front propagation in consequence of the establishment of the flow resistive viscous factors at long timescales, and the subsequent approach of the saturation point at the wetting front. In contrast, in the case of restricted propagation, due to high binder content of swelling latex particles, a deviation of the logarithmic reflectance gradient from the linear trend is observed as saturation is approached. However, the relationship between spatial logarithmic reflectance gradient and liquid uptake per unit cross-sectional porosity continues to follow linear trends irrespective of the binder if the porosity is corrected for the loss due to swelling, thus enabling the effect of the binder on the structure to be studied in isolation.
|Number of pages||8|
|Journal||Nordic Pulp & Paper Research Journal|
|Publication status||Published - 2012|
|MoE publication type||A1 Journal article-refereed|
- Ink Setting
- Liquid Absorption into Porous Media
- Liquid Distribution in Porous Media
- Polymer Network-Liquid Interactions
- Latex Properties
- Latex Swelling
- Light Scattering
- Refractive Index
- IMBIBITION BEHAVIOR