Water-dispersible paper for packaging applications – balancing material strength and dispersibility

Abstract Water-dispersible paper is useful for packaging applications as it disintegrates into its fibers after usage, and also is a fully biodegradable material. Here, we first introduce a laboratory testing method for the disintegration performance of different paper grades under low agitation in water. Then a quantitative analysis on the technological and physical mechanisms responsible for dispersibility of paper is performed. We identify lignin content, degree of refining and addition of starch as relevant factors reducing paper dispersibility. Addition of a debonding agent, a non-ionic surfactant, was not found to be effective here. We found a strong correlation of both, wet- and dry tensile strength to dispersibility. From all water absorption related paper properties only ultrasonic liquid penetration measurements were correlated to paper dispersibility. Principal component analysis revealed that paper strength and water penetration speed are not governed by different latent variables but instead are all strongly associated with the first principal component. This suggests that the same mechanisms are responsible for reduction of water penetration speed and wet/dry strength. Hence we suggest to decouple network strength and water penetration, e.g. by identifying suitable additives imparting bonding strength without reducing the access of water which is required to break the fiber–fiber bonds.