Which properties determine the strength and durability of a sheet of paper?

The strength and durability of a sheet of paper are determined by a combination of four primary factors:

• Individual fibre strength: The inherent physical properties of the raw material used.1
• Average fibre length: Longer fibres generally contribute to greater strength.1
• Interfibre bonding: This is the ability of fibres to adhere to one another, which is significantly enhanced through mechanical beating and refining processes that increase surface area and promote hydrogen bonding.12
• Sheet structure and formation: The way the fibres are randomly felted together during the manufacturing process.1

For applications requiring maximum strength, durability, and permanence, manufacturers often use rag fibres (such as cotton or linen) due to their superior length, fineness, and purity compared to most wood pulps.2

While these factors establish the base strength, other properties like tensile strength, bursting strength, and folding endurance are used to measure a paper's resistance to various stresses during use. Additionally, additives such as resins can be incorporated to provide wet strength, preventing the loss of coherence that typically occurs when paper is exposed to water.13