Strength Parameter
Normalized measurement of the force required to break a saturated paper strip provides an evaluation of the performance of a material in moist environments. Wet tensile index is calculated by dividing the tensile strength of a water-soaked specimen by its basis weight, expressed in Newton meters per gram. This value isolates the contribution of chemical bonding and fibre entanglement from the effects of sheet thickness.
Packaging products such as grocery bags and liquid containers must maintain a specific threshold to prevent failure during use.
Comparative Analysis
Testing typically occurs after the sample has been immersed in distilled water for a period ranging from seconds to hours depending on the grade. The wet tensile index allows for a direct comparison between different paper weights and manufacturing runs. While dry strength relies heavily on hydrogen bonding, wet strength depends on the presence of crosslinking resins or insoluble binders.
A high ratio of wet to dry strength indicates an effective chemical treatment. Results are sensitive to the temperature of the soaking water and the presence of surfactants.
Quality Control
Mill operators use this index to monitor the dosage of wet-strength additives. Consistent values ensure that the finished product meets the rigorous demands of the supply chain.
