Unheated Warehouse Storage Impact on Multi Ply Boxboard Moisture Equilibrium
Unheated storage alters multi-ply boxboard moisture equilibrium, swelling sheet edges, reducing internal bond strength, and causing severe converting curl.
Thermomechanical Pulp Hydration
Fiber Treatment
Absorption of wood fibers produced through the combination of heat and mechanical grinding increases the flexibility and bonding potential of the material. Thermomechanical pulp hydration occurs when the dry, stiff fibers are reintroduced to water during the stock preparation phase of papermaking. Fiber swelling allows the external surfaces to develop a greater area for hydrogen bonding during the drying of the paper web.
Unlike chemical pulps, these fibers retain much of their lignin, making them naturally more resistant to water penetration until treated.
Rotating Agitators
Rotating agitators in the pulper break down the dry bales and ensure that each fiber is fully wetted to achieve a uniform suspension. The degree of swelling is influenced by the water temperature and the presence of any residual chemicals from the original pulping process. Longer soaking times or additional mechanical refining can enhance the hydration, resulting in a sheet with higher tensile strength and better opacity.
If the hydration is insufficient, the paper will be brittle and have poor surface strength, leading to linting issues during high-speed printing. Over-hydration is also avoided as it slows the drainage of water on the forming wire and can lead to a translucent appearance.
Management of Hydration
Management of hydration is essential for producing newsprint and magazine papers that require a balance of bulk and smoothness. Properly hydrated fibers provide the necessary stiffness for high-speed web feeding. The final quality of the printing surface depends on the uniform distribution of these moisture-laden fibers.