Dispersion Barrier Performance in Folding Boxboard Substrates
Aqueous dispersion barrier performance depends on wet coat weight uniformity, film drying coalescence, and creasing matrix geometry that prevents score line cracking.
Cobb 1800 Test
Moisture Measurement
Extended exposure to liquid water determines the absorption capacity of sizing agents in heavy duty linerboard or corrugated mediums. The cobb 1800 test measures the mass of water absorbed by one square metre of material over a duration of thirty minutes. This duration distinguishes it from standard shorter tests used for lighter folding boxboards.
It evaluates the durability of packaging intended for humid environments or direct weather contact.
Testing Protocol
Precise preparation of the sample ensures that only one side of the board contacts the water within the metal cylinder. After the cobb 1800 test concludes, the technician removes excess surface water using standardized blotting paper and a weighted roller. The difference in weight before and after the timed soak indicates the effectiveness of the internal or surface sizing.
Industrial Application
Boards used for export fruit crates or maritime shipping containers require high resistance to saturation to maintain structural integrity. A high result in the cobb 1800 test indicates a risk of delamination or compression failure when the carton becomes wet. Achieving a low value often requires the addition of specialized resins or waxes during the papermaking process.
This metric helps converters select materials that survive the rigors of cold storage and long distance transport. If the sizing is insufficient, the fibres swell and the board loses its ability to stack without buckling under the weight of the contents. Manufacturers utilize these results to guarantee the performance of secondary packaging in extreme humidity.