B. Mesic
Karlstad University,
Sweden
Keywords: water absorption, dispersion coatings, paperboard
Summary:
Abstract This study explores water absorption by precoated paperboard under high hydrostatic pressure using a modified Cobb tester. The new modified tester, based on TAPPI standard T 414, features an extended water column (up to 550 mm). Evaluation involved measuring water absorption at different exposure Cobb times (Cobb 20s and Cobb 60s) and water column heights (10–500 mm), corresponding to hydrostatic pressures of 98 Pa and 4.9 kPa, respectively. Pre-coatings, comprising styrene acrylate and two ground calcium carbonates (GCC), formed open and closed pre-coating structures at 6 g/m² on 210 g/m² board. Uncoated 210 g/m² and 350 g/m² boards were also studied as reference. Coating characterization involved SEM, mercury intrusion, and roughness. Results indicate the new device effectively simulates Cobb tester conditions. The characterization of the coating also confirmed the presence of more open/larger pores of open coatings, confirming the desired coating structure. Absorption was primarily pressure-driven, noticeable even at shorter exposure times (5 s and 15 s). Open-coated boards exhibited slightly higher absorption. Despite limitations, the proposed tester offers an accessible method for studying high-pressure board exposure.