Environmental Storage Condition
The moisture content of paperboard adjusts continuously in response to the water vapor pressure of the surrounding atmosphere. Uncontrolled relative humidity exposure can lead to significant dimensional changes, curling, and warping of the sheet. This interaction is driven by the hydrophilic nature of the cellulose fibers that make up the paperboard.
Fiber Moisture Interaction
Cellulose fibers expand when they absorb water from humid air and contract when they release it into dry air. A relative humidity exposure that deviates from the standard fifty percent level alters the flat profile of the sheets, making them difficult to feed into high-speed printers. This expansion or contraction occurs unevenly across the sheet if the moisture distribution is not uniform, leading to wavy edges or twist warp.
Protecting the board with moisture-barrier wrapping during transport and storage prevents these rapid, damaging moisture exchanges.
Converting Line Impact
High or low moisture levels in the board directly affect its performance during the die-cutting and creasing operations. Dry board is stiff and prone to cracking along the crease lines, while overly damp board is soft and loses its folding stiffness. Printers and converters monitor the climate in their warehouses and production areas to ensure that the board remains within its optimal moisture range.
This environmental control ensures consistent feeding, precise register during printing, and reliable folding performance on the packaging line.
