Fibre Deformation
Molecular movement within the cellulose network allows paper to deform under mechanical stress without immediate structural failure. Physical scientists describe hydrogen bond slipping as the process where intermolecular bonds between cellulose chains break and reform at new positions when tension is applied. This continuous rearrangement of bonds provides paper sheets with essential ductility.
It prevents sudden ruptures during high-speed printing runs.
Creep Mechanism
Tensile load sustained over long periods causes paper sheets to stretch gradually as the polymer chains slide past each other. This progressive elongation occurs because hydrogen bond slipping allows the fibre network to relieve internal stresses. The rate of this deformation decreases over time under a constant load.
This decay in the creep rate occurs because the fibres align themselves closer together, which increases the density of the network.
Moisture Effect
High relative humidity accelerates this molecular relaxation by introducing water molecules that compete with cellulose for bonding sites. When water penetrates the amorphous regions of the fibre, it disrupts the existing bonds and increases the rate of hydrogen bond slipping by acting as a molecular lubricant. This disruption weakens the sheet and leads to severe sag in stored corrugated boxes.
Preventing this degradation requires moisture-resistant barriers or polymer coatings that keep water from reaching the fibre junctions, especially in high-humidity shipping containers.
