Enhancing paper extensibility through synergistic effect of low-consistency refining and drying conditions

The growing demand for sustainable packaging has driven research into paper as a renewable and biodegradable alternative to plastics. However, achieving high extensibility while maintaining sufficient tensile strength remains a challenge in paper-based materials. In particular, the coupled influence of low-consistency refining and different drying conditions on extensibility development remains insufficiently understood. Using bleached softwood kraft pulp, this study investigates how the synergistic interaction between low-consistency refining and drying conditions affects the extensibility and strength of paper. The novelty of this approach lies in demonstrating that the combination of refining and drying can enhance fibre-network extensibility while preserving tensile strength. While refining induces fibrillation and fibre swelling, increasing fibre conformability and shrinkage potential, the applied drying conditions governed the development of strain capacity within the fibre network. By coupling these processes, elongation values up to 21.1% were achieved without critical loss of tensile strength, partially overcoming the conventional strength-extensibility trade-off typically observed in paper materials. Multi-scale characterization combining water retention value, zeta potential, microscopy, limiting viscosity number, Fourier transform infrared spectroscopy, and mechanical testing revealed that extensibility development is associated not only with fibre surface fibrillation, but also with subtle modifications in cellulose supramolecular organization and enhanced network rearrangement during drying. The findings provide new insights into process-driven tailoring of stretchable fibre-based materials for sustainable packaging applications.